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Sample records for visual cortex induces

  1. Monocular Visual Deprivation Suppresses Excitability in Adult Human Visual Cortex

    DEFF Research Database (Denmark)

    Lou, Astrid Rosenstand; Madsen, Kristoffer Hougaard; Paulson, Olaf Bjarne

    2011-01-01

    The adult visual cortex maintains a substantial potential for plasticity in response to a change in visual input. For instance, transcranial magnetic stimulation (TMS) studies have shown that binocular deprivation (BD) increases the cortical excitability for inducing phosphenes with TMS. Here, we...... employed TMS to trace plastic changes in adult visual cortex before, during, and after 48 h of monocular deprivation (MD) of the right dominant eye. In healthy adult volunteers, MD-induced changes in visual cortex excitability were probed with paired-pulse TMS applied to the left and right occipital cortex...... of visual deprivation has a substantial impact on experience-dependent plasticity of the human visual cortex....

  2. Locomotion Induces Stimulus-Specific Response Enhancement in Adult Visual Cortex.

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    Kaneko, Megumi; Fu, Yu; Stryker, Michael P

    2017-03-29

    The responses of neurons in the visual cortex (V1) of adult mammals have long been thought to be stable over long periods. Here, we investigated whether repeated exposure to specific stimuli would enhance V1 visual responses in mice using intrinsic signal imaging through the intact skull and two-photon imaging of calcium signals in single neurons. Mice ran on Styrofoam balls floating on air while viewing one of three different, high-contrast visual stimuli. V1 responses to the stimuli that were viewed by the animal were specifically enhanced, while responses to other stimuli were unaffected. Similar exposure in stationary mice or in mice in which NMDA receptors were partially blocked did not significantly enhance responses. These findings indicate that stimulus-specific plasticity in the adult visual cortex depends on concurrent locomotion, presumably as a result of the high-gain state of the visual cortex induced by locomotion. SIGNIFICANCE STATEMENT We report a rapid and persistent increase in visual cortical responses to visual stimuli presented during locomotion in intact mice. We first used a method that is completely noninvasive to image intrinsic signals through the intact skull. We then measured the same effects on single neurons using two-photon calcium imaging and found that the increase in response to a particular stimulus produced by locomotion depends on how well the neuron is initially driven by the stimulus. To our knowledge, this is the first time such enhancement has been described in single neurons or using noninvasive measurements. Copyright © 2017 the authors 0270-6474/17/373532-12$15.00/0.

  3. L-dopa methyl ester attenuates amblyopia-induced neuronal injury in visual cortex of amblyopic cat.

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    Li, Rong; Liang, Tao; Chen, Zhaoni; Zhang, Shijun; Lin, Xing; Huang, Renbin

    2013-09-15

    In the present study, we aimed to assess the potential anti-amblyopic effects of L-dopa methyl ester (LDME) on visual cortex area 17 in an amblyopic feline model induced by monocular vision deprivation. After LDME administration, pathophysiologic and ultrastructural observations were utilized to examine the morphological changes of nerve cells in visual cortex area 17. Dopamine (DA) and its metabolite contents in visual cortex area 17 were investigated through HPLC analysis. Apoptotic cells in visual cortex area 17 were evaluated by TUNEL assay. Additionally, the c-fos expression both at gene and protein levels was assessed using RT-PCR and immunohistochemistry analyses, respectively. The contents of DA and its metabolites were elevated in visual cortex area 17. Neuronal rejuvenation which occurred in visual cortex area 17 was observed through anatomical and physiological assessments. Similarly, TUNEL results showed that neuronal apoptosis was inhibited in the visual cortex of amblyopic cats by both L-dopa and LDME therapies. Meanwhile, the c-fos expression was notably up-regulated at both the mRNA and protein levels by the treatments. These findings suggested that LDME treatment could effectively increase DA and its metabolite contents, and restrain the apoptotic process, as well as elevate the c-fos expression in nerve cells of visual cortex area 17. Taken together, LDME might ameliorate the functional cytoarchitecture in visual cortex area 17 through mechanisms that elevate DA content and increase endogenous c-fos expression, as well as inhibit neuronal lesion in visual cortex tissue. Copyright © 2013 Elsevier B.V. All rights reserved.

  4. Transcranial magnetic stimulation-induced 'visual echoes' are generated in early visual cortex

    NARCIS (Netherlands)

    Jolij, Jacob; Lamme, Victor A. F.

    2010-01-01

    Transcranial magnetic stimulation (TMS) of the early visual areas can trigger perception of a flash of light, a so-called phosphene. Here we show that a very brief presentation of a stimulus can modulate features of a subsequent TMS-induced phosphene, to a level that participants mistake phosphenes

  5. Brain-derived Neurotrophic Factor Overexpression Induces Precocious Critical Period in Mouse Visual Cortex

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    Hanover, Jessica L.; Huang, Z. Josh; Tonegawa, Susumu; Stryker, Michael P.

    2008-01-01

    Brain-derived neurotrophic factor (BDNF) is a candidate molecule for regulating activity-dependent synaptic plasticity on the grounds of its expression pattern in developing visual cortex and that of its receptor, trkB (Castrén et al., 1992; Bozzi et al., 1995; Schoups et al., 1995; Cabelli et al., 1996), as well as the modulation of these patterns by activity (Castrén et al., 1992; Bozzi et al., 1995; Schoups et al., 1995). Infusing trkB ligands or their neutralizing agents, the trkB-IgG fusion proteins, into visual cortex alters the development and plasticity of ocular dominance columns (Cabelli et al., 1995; Riddle et al., 1995; Galuske et al., 1996; Gillespie et al., 1996; Cabelli et al., 1997). To test further the physiological role of BDNF, we studied a transgenic mouse that expresses elevated levels of BDNF in primary visual cortex (V1) postnatally (Huang et al., 1999). We found that unlike the infusion experiments, excess BDNF expressed in mouse visual cortex did not block ocular dominance plasticity. Instead, single neurons in V1 of the BDNF transgenic mice were as susceptible to the effects of monocular deprivation (MD) as neurons in wild-type mice, but only during a precocious critical period. At a time when V1 in the wild-type mouse responded maximally to a 4 d MD with a reduction in its response to deprived eye visual stimulation, the transgenic mouse V1 had already passed the peak of its precocious critical period and no longer responded maximally. This finding suggests a role for BDNF in promoting the postnatal maturation of cortical circuitry. PMID:10559430

  6. Refractive surgery in anisometropic adult patients induce plastic changes in primary visual cortex.

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    Vuori, Elisa; Vanni, Simo; Henriksson, Linda; Tervo, Timo M T; Holopainen, Juha M

    2012-11-01

    To prospectively study the effect of refractive surgery in the primary visual cortex of adult anisometropic and isometropic myopic patients. Two anisometropic and two isometropic myopic patients were examined with multifocal functional magnetic resonance imaging technique (mffMRI) before refractive surgery and at 3, 6, 9 and 12 months postoperatively. Two controls without refractive surgery were also examined with mffMRI in the beginning and in the end of the study. Anisometropic patients had only their more myopic eye operated to correct the anisometropia. The myopic isometropic patients had their both eyes operated. Operated anisometropic eyes showed 65% reduced amount of active voxels in foveal data at 12 months postoperatively compared with the preoperative situation. In unoperated anisometropic eyes, the corresponding value was 86% and in myopic patients and controls 31% and 1%, respectively. To confirm this finding, the number of activated voxels representing the innermost ring of the stimulus was also calculated, and an exactly similar phenomenon was encountered in the anisometropic patients. Both anisometropic patients improved the best-spectacle-corrected visual acuity in the operated eye after refractive surgery. Our results suggest that plastic changes may take place in the primary visual cortex of anisometropic adult patients after refractive surgery. © 2011 The Authors. Acta Ophthalmologica © 2011 Acta Ophthalmologica Scandinavica Foundation.

  7. Brain-derived Neurotrophic Factor Overexpression Induces Precocious Critical Period in Mouse Visual Cortex

    OpenAIRE

    Hanover, Jessica L.; Huang, Z. Josh; Tonegawa, Susumu; Stryker, Michael P.

    1999-01-01

    Brain-derived neurotrophic factor (BDNF) is a candidate molecule for regulating activity-dependent synaptic plasticity on the grounds of its expression pattern in developing visual cortex and that of its receptor, trkB (Castrén et al., 1992; Bozzi et al., 1995; Schoups et al., 1995; Cabelli et al., 1996), as well as the modulation of these patterns by activity (Castrén et al., 1992; Bozzi et al., 1995; Schoups et al., 1995). Infusing trkB ligands or their neutralizing agents, the trkB-IgG fus...

  8. Preparatory attention in visual cortex.

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    Battistoni, Elisa; Stein, Timo; Peelen, Marius V

    2017-05-01

    Top-down attention is the mechanism that allows us to selectively process goal-relevant aspects of a scene while ignoring irrelevant aspects. A large body of research has characterized the effects of attention on neural activity evoked by a visual stimulus. However, attention also includes a preparatory phase before stimulus onset in which the attended dimension is internally represented. Here, we review neurophysiological, functional magnetic resonance imaging, magnetoencephalography, electroencephalography, and transcranial magnetic stimulation (TMS) studies investigating the neural basis of preparatory attention, both when attention is directed to a location in space and when it is directed to nonspatial stimulus attributes (content-based attention) ranging from low-level features to object categories. Results show that both spatial and content-based attention lead to increased baseline activity in neural populations that selectively code for the attended attribute. TMS studies provide evidence that this preparatory activity is causally related to subsequent attentional selection and behavioral performance. Attention thus acts by preactivating selective neurons in the visual cortex before stimulus onset. This appears to be a general mechanism that can operate on multiple levels of representation. We discuss the functional relevance of this mechanism, its limitations, and its relation to working memory, imagery, and expectation. We conclude by outlining open questions and future directions. © 2017 New York Academy of Sciences.

  9. Visual Categorization and the Parietal Cortex

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    Jamie K Fitzgerald

    2012-05-01

    Full Text Available The primate brain is adept at rapidly grouping items and events into functional classes, or categories, in order to recognize the significance of stimuli and guide behavior. Higher cognitive functions have traditionally been considered the domain of frontal areas. However, increasing evidence suggests that parietal cortex is also involved in categorical and associative processes. Previous work showed that the parietal cortex is highly involved in spatial processing, attention and saccadic eye movement planning, and more recent studies have found decision-making signals in LIP. We recently found that a subdivision of parietal cortex, the lateral intraparietal area (LIP, reflects learned categories for multiple types of visual stimuli. Additionally, a comparison of categorization signals in parietal and frontal areas found stronger and earlier categorization signals in parietal cortex, arguing that parietal abstract association or category signals are unlikely to arise via feedback from prefrontal cortex (PFC.

  10. Category selectivity in human visual cortex: Beyond visual object recognition

    NARCIS (Netherlands)

    Peelen, M.V.; Downing, P.E.

    2017-01-01

    Human ventral temporal cortex shows a categorical organization, with regions responding selectively to faces, bodies, tools, scenes, words, and other categories. Why is this? Traditional accounts explain category selectivity as arising within a hierarchical system dedicated to visual object

  11. Conceptual size representation in ventral visual cortex.

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    Gabay, Shai; Kalanthroff, Eyal; Henik, Avishai; Gronau, Nurit

    2016-01-29

    Recent findings suggest that visual objects may be mapped along the ventral occipitotemporal cortex according to their real-world size (Konkle and Oliva, 2012). It has been argued that such mapping does not reflect an abstract, conceptual size representation, but rather the visual or functional properties associated with small versus big real-world objects. To determine whether a more abstract conceptual size representation may affect visual cortical activation we used meaningless geometrical shapes, devoid of semantic or functional associations, which were associated with specific size representations by virtue of extensive training. Following training, participants underwent functional magnetic resonance imaging (fMRI) scanning while performing a conceptual size comparison task on the geometrical shapes. In addition, a size comparison task was conducted for numeral digits denoting small and big numbers. A region-of-interest analysis revealed larger blood oxygenation level dependent (BOLD) responses for conceptually 'big' than for conceptually 'small' shapes, as well as for big versus small numbers, within medial (parahippocampal place area, PPA) and lateral (occipital place area, OPA) place-selective regions. Processing of the 'big' visual shapes further elicited enhanced activation in early visual cortex, possibly reflecting top-down projections from PPA. By using arbitrary shapes and numbers we minimized visual, categorical, or functional influences on fMRI measurement, providing evidence for a possible neural mechanism underlying the representation of abstract conceptual size within the ventral visual stream. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. Visual cortex entrains to sign language.

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    Brookshire, Geoffrey; Lu, Jenny; Nusbaum, Howard C; Goldin-Meadow, Susan; Casasanto, Daniel

    2017-06-13

    Despite immense variability across languages, people can learn to understand any human language, spoken or signed. What neural mechanisms allow people to comprehend language across sensory modalities? When people listen to speech, electrophysiological oscillations in auditory cortex entrain to slow ([Formula: see text]8 Hz) fluctuations in the acoustic envelope. Entrainment to the speech envelope may reflect mechanisms specialized for auditory perception. Alternatively, flexible entrainment may be a general-purpose cortical mechanism that optimizes sensitivity to rhythmic information regardless of modality. Here, we test these proposals by examining cortical coherence to visual information in sign language. First, we develop a metric to quantify visual change over time. We find quasiperiodic fluctuations in sign language, characterized by lower frequencies than fluctuations in speech. Next, we test for entrainment of neural oscillations to visual change in sign language, using electroencephalography (EEG) in fluent speakers of American Sign Language (ASL) as they watch videos in ASL. We find significant cortical entrainment to visual oscillations in sign language sign is strongest over occipital and parietal cortex, in contrast to speech, where coherence is strongest over the auditory cortex. Nonsigners also show coherence to sign language, but entrainment at frontal sites is reduced relative to fluent signers. These results demonstrate that flexible cortical entrainment to language does not depend on neural processes that are specific to auditory speech perception. Low-frequency oscillatory entrainment may reflect a general cortical mechanism that maximizes sensitivity to informational peaks in time-varying signals.

  13. Numerosity processing in early visual cortex.

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    Fornaciai, Michele; Brannon, Elizabeth M; Woldorff, Marty G; Park, Joonkoo

    2017-08-15

    While parietal cortex is thought to be critical for representing numerical magnitudes, we recently reported an event-related potential (ERP) study demonstrating selective neural sensitivity to numerosity over midline occipital sites very early in the time course, suggesting the involvement of early visual cortex in numerosity processing. However, which specific brain area underlies such early activation is not known. Here, we tested whether numerosity-sensitive neural signatures arise specifically from the initial stages of visual cortex, aiming to localize the generator of these signals by taking advantage of the distinctive folding pattern of early occipital cortices around the calcarine sulcus, which predicts an inversion of polarity of ERPs arising from these areas when stimuli are presented in the upper versus lower visual field. Dot arrays, including 8-32dots constructed systematically across various numerical and non-numerical visual attributes, were presented randomly in either the upper or lower visual hemifields. Our results show that neural responses at about 90ms post-stimulus were robustly sensitive to numerosity. Moreover, the peculiar pattern of polarity inversion of numerosity-sensitive activity at this stage suggested its generation primarily in V2 and V3. In contrast, numerosity-sensitive ERP activity at occipito-parietal channels later in the time course (210-230ms) did not show polarity inversion, indicating a subsequent processing stage in the dorsal stream. Overall, these results demonstrate that numerosity processing begins in one of the earliest stages of the cortical visual stream. Copyright © 2017 Elsevier Inc. All rights reserved.

  14. Deep Hierarchies in the Primate Visual Cortex

    DEFF Research Database (Denmark)

    Krüger, Norbert; Jannsen, Per; Kalkan, S.

    2013-01-01

    Computational modeling of the primate visual system yields insights of potential relevance to some of the challenges that computer vision is facing, such as object recognition and categorization, motion detection and activity recognition or vision-based navigation and manipulation. This article...... reviews some functional principles and structures that are generally thought to underlie the primate visual cortex, and attempts to extract biological principles that could further advance computer vision research. Organized for a computer vision audience, we present functional principles...... of the processing hierarchies present in the primate visual system considering recent discoveries in neurophysiology. The hierarchal processing in the primate visual system is characterized by a sequence of different levels of processing (in the order of ten) that constitute a deep hierarchy in contrast to the flat...

  15. Microstimulation of visual cortex to restore vision.

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    Tehovnik, Edward J; Slocum, Warren M; Smirnakis, Stelios M; Tolias, Andreas S

    2009-01-01

    This review argues that one reason why a functional visuo-cortical prosthetic device has not been developed to restore even minimal vision to blind individuals is because there is no animal model to guide the design and development of such a device. Over the past 8 years we have been conducting electrical microstimulation experiments on alert behaving monkeys with the aim of better understanding how electrical stimulation of the striate cortex (area V1) affects oculo- and skeleto-motor behaviors. Based on this work and upon review of the literature, we arrive at several conclusions: (1) As with the development of the cochlear implant, the development of a visuo-cortical prosthesis can be accelerated by using animals to test the perceptual effects of microstimulating V1 in intact and blind monkeys. (2) Although a saccade-based paradigm is very convenient for studying the effectiveness of delivering stimulation to V1 to elicit saccadic eye movements, it is less ideal for probing the volitional state of monkeys, as they perceive electrically induced phosphenes. (3) Electrical stimulation of V1 can delay visually guided saccades generated to a punctate target positioned in the receptive field of the stimulated neurons. We call the region of visual space affected by the stimulation a delay field. The study of delay fields has proven to be an efficient way to study the size and shape of phosphenes generated by stimulation of macaque V1. (4) An alternative approach to ascertain what monkeys see during electrical stimulation of V1 is to have them signal the detection of current with a lever press. Monkeys can readily detect currents of 1-2 microA delivered to V1. In order to evoke featured phosphenes currents of under 5 microA will be necessary. (5) Partially lesioning the retinae of monkeys is superior to completely lesioning the retinae when determining how blindness affects phosphene induction. We finish by proposing a future experimental paradigm designed to determine

  16. Compressive Temporal Summation in Human Visual Cortex.

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    Zhou, Jingyang; Benson, Noah C; Kay, Kendrick N; Winawer, Jonathan

    2018-01-17

    Combining sensory inputs over space and time is fundamental to vision. Population receptive field models have been successful in characterizing spatial encoding throughout the human visual pathways. A parallel question, how visual areas in the human brain process information distributed over time, has received less attention. One challenge is that the most widely used neuroimaging method, fMRI, has coarse temporal resolution compared with the time-scale of neural dynamics. Here, via carefully controlled temporally modulated stimuli, we show that information about temporal processing can be readily derived from fMRI signal amplitudes in male and female subjects. We find that all visual areas exhibit subadditive summation, whereby responses to longer stimuli are less than the linear prediction from briefer stimuli. We also find fMRI evidence that the neural response to two stimuli is reduced for brief interstimulus intervals (indicating adaptation). These effects are more pronounced in visual areas anterior to V1-V3. Finally, we develop a general model that shows how these effects can be captured with two simple operations: temporal summation followed by a compressive nonlinearity. This model operates for arbitrary temporal stimulation patterns and provides a simple and interpretable set of computations that can be used to characterize neural response properties across the visual hierarchy. Importantly, compressive temporal summation directly parallels earlier findings of compressive spatial summation in visual cortex describing responses to stimuli distributed across space. This indicates that, for space and time, cortex uses a similar processing strategy to achieve higher-level and increasingly invariant representations of the visual world. SIGNIFICANCE STATEMENT Combining sensory inputs over time is fundamental to seeing. Two important temporal phenomena are summation, the accumulation of sensory inputs over time, and adaptation, a response reduction for repeated

  17. Connectivity Changes Underlying Neurofeedback Training of Visual Cortex Activity

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    Scharnowski, Frank; Rosa, Maria Joao; Golestani, Narly; Hutton, Chloe; Josephs, Oliver

    2014-01-01

    Neurofeedback based on real-time functional magnetic resonance imaging (fMRI) is a new approach that allows training of voluntary control over regionally specific brain activity. However, the neural basis of successful neurofeedback learning remains poorly understood. Here, we assessed changes in effective brain connectivity associated with neurofeedback training of visual cortex activity. Using dynamic causal modeling (DCM), we found that training participants to increase visual cortex activity was associated with increased effective connectivity between the visual cortex and the superior parietal lobe. Specifically, participants who learned to control activity in their visual cortex showed increased top-down control of the superior parietal lobe over the visual cortex, and at the same time reduced bottom-up processing. These results are consistent with efficient employment of top-down visual attention and imagery, which were the cognitive strategies used by participants to increase their visual cortex activity. PMID:24609065

  18. Connectivity changes underlying neurofeedback training of visual cortex activity.

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    Frank Scharnowski

    Full Text Available Neurofeedback based on real-time functional magnetic resonance imaging (fMRI is a new approach that allows training of voluntary control over regionally specific brain activity. However, the neural basis of successful neurofeedback learning remains poorly understood. Here, we assessed changes in effective brain connectivity associated with neurofeedback training of visual cortex activity. Using dynamic causal modeling (DCM, we found that training participants to increase visual cortex activity was associated with increased effective connectivity between the visual cortex and the superior parietal lobe. Specifically, participants who learned to control activity in their visual cortex showed increased top-down control of the superior parietal lobe over the visual cortex, and at the same time reduced bottom-up processing. These results are consistent with efficient employment of top-down visual attention and imagery, which were the cognitive strategies used by participants to increase their visual cortex activity.

  19. Migraine with visual aura associated with thicker visual cortex

    DEFF Research Database (Denmark)

    Gaist, David; Hougaard, Anders; Garde, Ellen

    2018-01-01

    Until recent years it was believed that migraine with aura was a disorder causing intermittent neurological symptoms, with no impact on brain structure. However, recent MRI studies have reported increased cortical thickness of visual and somatosensory areas in patients with migraine with aura...... the regions of interest and active migraine, or number of lifetime aura attacks. Migraine with aura discordant twin pairs (n = 30) only differed in mean thickness of V2 (0.039 mm, 95% CI 0.005 to 0.074). In conclusion, females with migraine with aura have a thicker cortex corresponding to visual areas and our...

  20. Neural Anatomy of Primary Visual Cortex Limits Visual Working Memory.

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    Bergmann, Johanna; Genç, Erhan; Kohler, Axel; Singer, Wolf; Pearson, Joel

    2016-01-01

    Despite the immense processing power of the human brain, working memory storage is severely limited, and the neuroanatomical basis of these limitations has remained elusive. Here, we show that the stable storage limits of visual working memory for over 9 s are bound by the precise gray matter volume of primary visual cortex (V1), defined by fMRI retinotopic mapping. Individuals with a bigger V1 tended to have greater visual working memory storage. This relationship was present independently for both surface size and thickness of V1 but absent in V2, V3 and for non-visual working memory measures. Additional whole-brain analyses confirmed the specificity of the relationship to V1. Our findings indicate that the size of primary visual cortex plays a critical role in limiting what we can hold in mind, acting like a gatekeeper in constraining the richness of working mental function. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  1. The spatiotopic 'visual' cortex of the blind

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    Likova, Lora

    2012-03-01

    Visual cortex activity in the blind has been shown in sensory tasks. Can it be activated in memory tasks? If so, are inherent features of its organization meaningfully employed? Our recent results in short-term blindfolded subjects imply that human primary visual cortex (V1) may operate as a modality-independent 'sketchpad' for working memory (Likova, 2010a). Interestingly, the spread of the V1 activation approximately corresponded to the spatial extent of the images in terms of their angle of projection to the subject. We now raise the questions of whether under long-term visual deprivation V1 is also employed in non-visual memory task, in particular in congenitally blind individuals, who have never had visual stimulation to guide the development of the visual area organization, and whether such spatial organization is still valid for the same paradigm that was used in blindfolded individuals. The outcome has implications for an emerging reconceptualization of the principles of brain architecture and its reorganization under sensory deprivation. Methods: We used a novel fMRI drawing paradigm in congenitally and late-onset blind, compared with sighted and blindfolded subjects in three conditions of 20s duration, separated by 20s rest-intervals, (i) Tactile Exploration: raised-line images explored and memorized; (ii) Tactile Memory Drawing: drawing the explored image from memory; (iii) Scribble: mindless drawing movements with no memory component. Results and Conclusions: V1 was strongly activated for Tactile Memory Drawing and Tactile Exploration in these totally blind subjects. Remarkably, after training, even in the memory task, the mapping of V1 activation largely corresponded to the angular projection of the tactile stimuli relative to the ego-center (i.e., the effective visual angle at the head); beyond this projective boundary, peripheral V1 signals were dramatically reduced or even suppressed. The matching extent of the activation in the congenitally blind

  2. GABAA receptors in visual and auditory cortex and neural activity changes during basic visual stimulation

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    Qin, Pengmin; Duncan, Niall W.; Wiebking, Christine; Gravel, Paul; Lyttelton, Oliver; Hayes, Dave J.; Verhaeghe, Jeroen; Kostikov, Alexey; Schirrmacher, Ralf; Reader, Andrew J.; Northoff, Georg

    2012-01-01

    Recent imaging studies have demonstrated that levels of resting γ-aminobutyric acid (GABA) in the visual cortex predict the degree of stimulus-induced activity in the same region. These studies have used the presentation of discrete visual stimulus; the change from closed eyes to open also represents a simple visual stimulus, however, and has been shown to induce changes in local brain activity and in functional connectivity between regions. We thus aimed to investigate the role of the GABA system, specifically GABAA receptors, in the changes in brain activity between the eyes closed (EC) and eyes open (EO) state in order to provide detail at the receptor level to complement previous studies of GABA concentrations. We conducted an fMRI study involving two different modes of the change from EC to EO: an EO and EC block design, allowing the modeling of the haemodynamic response, followed by longer periods of EC and EO to allow the measuring of functional connectivity. The same subjects also underwent [18F]Flumazenil PET to measure GABAA receptor binding potentials. It was demonstrated that the local-to-global ratio of GABAA receptor binding potential in the visual cortex predicted the degree of changes in neural activity from EC to EO. This same relationship was also shown in the auditory cortex. Furthermore, the local-to-global ratio of GABAA receptor binding potential in the visual cortex also predicted the change in functional connectivity between the visual and auditory cortex from EC to EO. These findings contribute to our understanding of the role of GABAA receptors in stimulus-induced neural activity in local regions and in inter-regional functional connectivity. PMID:23293594

  3. GABAA receptors in visual and auditory cortex and neural activity changes during basic visual stimulation

    Directory of Open Access Journals (Sweden)

    Pengmin eQin

    2012-12-01

    Full Text Available Recent imaging studies have demonstrated that levels of resting GABA in the visual cortex predict the degree of stimulus-induced activity in the same region. These studies have used the presentation of discrete visual stimulus; the change from closed eyes to open also represents a simple visual stimulus, however, and has been shown to induce changes in local brain activity and in functional connectivity between regions. We thus aimed to investigate the role of the GABA system, specifically GABAA receptors, in the changes in brain activity between the eyes closed (EC and eyes open (EO state in order to provide detail at the receptor level to complement previous studies of GABA concentrations. We conducted an fMRI study involving two different modes of the change from EC to EO: An EO and EC block design, allowing the modelling of the haemodynamic response, followed by longer periods of EC and EO to allow the measuring of functional connectivity. The same subjects also underwent [18F]Flumazenil PET measure GABAA receptor binding potentials. It was demonstrated that the local-to-global ratio of GABAA receptor binding potential in the visual cortex predicted the degree of changes in neural activity from EC to EO. This same relationship was also shown in the auditory cortex. Furthermore, the local-to-global ratio of GABAA receptor binding potential in the visual cortex also predicts the change of functional connectivity between visual and auditory cortex from EC to EO. These findings contribute to our understanding of the role of GABAA receptors in stimulus-induced neural activity in local regions and in inter-regional functional connectivity.

  4. Is theta burst stimulation applied to visual cortex able to modulate peripheral visual acuity?

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    Sabrina Brückner

    Full Text Available Repetitive transcranial magnetic stimulation is usually applied to visual cortex to explore the effects on cortical excitability. Most researchers therefore concentrate on changes of phosphene threshold, rarely on consequences for visual performance. Thus, we investigated peripheral visual acuity in the four quadrants of the visual field using Landolt C optotypes before and after repetitive stimulation of the visual cortex. We applied continuous and intermittend theta burst stimulation with various stimulation intensities (60%, 80%, 100%, 120% of individual phosphene threshold as well as monophasic and biphasic 1 Hz stimulation, respectively. As an important result, no serious adverse effects were observed. In particular, no seizure was induced, even with theta burst stimulation applied with 120% of individual phosphene threshold. In only one case stimulation was ceased because the subject reported intolerable pain. Baseline visual acuity decreased over sessions, indicating a continuous training effect. Unexpectedly, none of the applied transcranial magnetic stimulation protocols had an effect on performance: no change in visual acuity was found in any of the four quadrants of the visual field. Binocular viewing as well as the use of peripheral instead of foveal presentation of the stimuli might have contributed to this result. Furthermore, intraindividual variability could have masked the TMS- induced effects on visual acuity.

  5. Metabolic profile of visual cortex in diabetic rats measured with in vivo proton MRS.

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    Li, Shuang; Wang, Xinghua; Yang, Junjie; Lei, Hao; Wang, Xuxia; Xiang, Yi

    2017-11-01

    The purpose of the present study was to characterize the metabolic profile of the visual cortex in streptozotocin-induced Type 1 diabetic rats by means of in vivo proton MRS. Several metabolite concentration ratios in the visual cortex were calculated. In addition, postmortem histologic analyses for retinal ganglion cell (RGC) loss, optic nerve injury and visual cortex alterations were monitored. The results showed that diabetes induced several changes in visual cortex metabolites, such as reduced N-acetylaspartate, glutamate, γ-aminobutyric acid, taurine and choline-containing compound levels. Nevertheless, myo-inositol levels increased significantly as compared with controls. Remarkable RGC loss and optic nerve degeneration were observed by morphological analysis. Moreover, the results showed significant neuronal loss and glial activation in the visual cortex. These findings indicated that, besides vascular abnormalities, neuronal loss and degeneration in the visual pathway were induced due to disrupted glucose homeostasis in diabetes. Metabolic or functional abnormalities were induced in cerebral neurons of the visual cortex by diabetes. Copyright © 2017 John Wiley & Sons, Ltd.

  6. Brief Novel Visual Experience Fundamentally Changes Synaptic Plasticity in the Mouse Visual Cortex.

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    Li, Shuo; Wang, Laijian; Tie, Xiaoxiu; Sohya, Kazuhiro; Lin, Xian; Kirkwood, Alfredo; Jiang, Bin

    2017-09-27

    LTP has been known to be a mechanism by which experience modifies synaptic responses in the neocortex. Visual deprivation in the form of dark exposure or dark rearing from birth enhances NMDAR-dependent LTP in layer 2/3 of visual cortex, a process often termed metaplasticity, which may involve changes in NMDAR subunit composition and function. However, the effects of reexposure to light after dark rearing from birth on LTP induction have not been explored. Here, we showed that the light exposure after dark rearing revealed a novel NMDAR independent form of LTP in the layer 2/3 pyramidal cells in visual cortex of mice of both sexes, which is dependent on mGluR5 activation and is associated with intracellular Ca 2+ rise, CaMKII activity, PKC activity, and intact protein synthesis. Moreover, the capacity to induce mGluR-dependent LTP is transient: it only occurs when mice of both sexes reared in the dark from birth are exposed to light for 10-12 h, and it does not occur in vision-experienced, male mice, even after prolonged exposure to dark. Thus, the mGluR5-LTP unmasked by short visual experience can only be observed after dark rearing but not after dark exposure. These results suggested that, as in hippocampus, in layer 2/3 of visual cortex, there is coexistence of two distinct activity-dependent systems of synaptic plasticity, NMDAR-LTP, and mGluR5-LTP. The mGluR5-LTP unmasked by short visual experience may play a critical role in the faster establishment of normal receptive field properties. SIGNIFICANCE STATEMENT LTP has been known to be a mechanism by which experience modifies synaptic responses in the neocortex. Visual deprivation in the form of dark exposure or dark rearing from birth enhances NMDAR-dependent LTP in layer 2/3 of visual cortex, a process often termed metaplasticity. NMDAR-dependent form of LTP in visual cortex has been well characterized. Here, we report that an NMDAR-independent form of LTP can be promoted by novel visual experience on dark

  7. Population Dynamics of Early Visual Cortex during Working Memory.

    Science.gov (United States)

    Rahmati, Masih; Saber, Golbarg T; Curtis, Clayton E

    2018-02-01

    Although the content of working memory (WM) can be decoded from the spatial patterns of brain activity in early visual cortex, how populations encode WM representations remains unclear. Here, we address this limitation by using a model-based approach that reconstructs the feature encoded by population activity measured with fMRI. Using this approach, we could successfully reconstruct the locations of memory-guided saccade goals based on the pattern of activity in visual cortex during a memory delay. We could reconstruct the saccade goal even when we dissociated the visual stimulus from the saccade goal using a memory-guided antisaccade procedure. By comparing the spatiotemporal population dynamics, we find that the representations in visual cortex are stable but can also evolve from a representation of a remembered visual stimulus to a prospective goal. Moreover, because the representation of the antisaccade goal cannot be the result of bottom-up visual stimulation, it must be evoked by top-down signals presumably originating from frontal and/or parietal cortex. Indeed, we find that trial-by-trial fluctuations in delay period activity in frontal and parietal cortex correlate with the precision with which our model reconstructed the maintained saccade goal based on the pattern of activity in visual cortex. Therefore, the population dynamics in visual cortex encode WM representations, and these representations can be sculpted by top-down signals from frontal and parietal cortex.

  8. Retinal oscillations carry visual information to cortex

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    Kilian Koepsell

    2009-04-01

    Full Text Available Thalamic relay cells fire action potentials that transmit information from retina to cortex. The amount of information that spike trains encode is usually estimated from the precision of spike timing with respect to the stimulus. Sensory input, however, is only one factor that influences neural activity. For example, intrinsic dynamics, such as oscillations of networks of neurons, also modulate firing pattern. Here, we asked if retinal oscillations might help to convey information to neurons downstream. Specifically, we made whole-cell recordings from relay cells to reveal retinal inputs (EPSPs and thalamic outputs (spikes and then analyzed these events with information theory. Our results show that thalamic spike trains operate as two multiplexed channels. One channel, which occupies a low frequency band (<30 Hz, is encoded by average firing rate with respect to the stimulus and carries information about local changes in the visual field over time. The other operates in the gamma frequency band (40-80 Hz and is encoded by spike timing relative to retinal oscillations. At times, the second channel conveyed even more information than the first. Because retinal oscillations involve extensive networks of ganglion cells, it is likely that the second channel transmits information about global features of the visual scene.

  9. Verbal memory retrieval engages visual cortex in musicians.

    Science.gov (United States)

    Huang, Z; Zhang, J X; Yang, Z; Dong, G; Wu, J; Chan, A S; Weng, X

    2010-06-16

    As one major line of research on brain plasticity, many imaging studies have been conducted to identify the functional and structural reorganization associated with musical expertise. Based on previous behavioral research, the present study used functional magnetic resonance imaging to identify the neural correlates of superior verbal memory performance in musicians. Participants with and without musical training performed a verbal memory task to first encode a list of words auditorily delivered and then silently recall as many words as possible. They performed in separate blocks a control task involving pure tone pitch judgment. Post-scan recognition test showed better memory performance in musicians than non-musicians. During memory retrieval, the musicians showed significantly greater activations in bilateral though left-lateralized visual cortex relative to the pitch judgment baseline. In comparison, no such visual cortical activations were found in the non-musicians. No group differences were observed during the encoding stage. The results echo a previous report of visual cortical activation during verbal memory retrieval in the absence of any visual sensory stimulation in the blind population, who are also known to possess superior verbal memory. It is suggested that the visual cortex can be recruited to serve as extra memory resources and contributes to the superior verbal memory in special situations. While in the blind population, such cross-modal functional reorganization may be induced by sensory deprivation; in the musicians it may be induced by the long-term and demanding nature of musical training to use as much available neural resources as possible. 2010 IBRO. Published by Elsevier Ltd. All rights reserved.

  10. Migraine with visual aura associated with thicker visual cortex.

    Science.gov (United States)

    Gaist, David; Hougaard, Anders; Garde, Ellen; Reislev, Nina Linde; Wiwie, Rikke; Iversen, Pernille; Madsen, Camilla Gøbel; Blaabjerg, Morten; Nielsen, Helle Hvilsted; Krøigård, Thomas; Østergaard, Kamilla; Kyvik, Kirsten Ohm; Hjelmborg, Jacob; Madsen, Kristoffer; Siebner, Hartwig Roman; Ashina, Messoud

    2018-01-18

    Until recent years it was believed that migraine with aura was a disorder causing intermittent neurological symptoms, with no impact on brain structure. However, recent MRI studies have reported increased cortical thickness of visual and somatosensory areas in patients with migraine with aura, suggesting that such structural alterations were either due to increased neuronal density in the areas involved, or a result of multiple episodes of cortical spreading depression as part of aura attacks. Subsequent studies have yielded conflicting results, possibly due to methodological reasons, e.g. small number of subjects. In this cross-sectional study, we recruited females aged 30-60 years from the nationwide Danish Twin Registry. Brain MRI of females with migraine with aura (patients), their co-twins, and unrelated migraine-free twins (controls) were performed at a single centre and assessed for cortical thickness in predefined cortical areas (V1, V2, V3A, MT, somatosensory cortex), blinded to headache diagnoses. The difference in cortical thickness between patients and controls adjusted for age, and other potential confounders was assessed. Comparisons of twin pairs discordant for migraine with aura were also performed. Comparisons were based on 166 patients, 30 co-twins, and 137 controls. Compared with controls, patients had a thicker cortex in areas V2 [adjusted mean difference 0.032 mm (95% confidence interval 0.003 to 0.061), V3A [adjusted mean difference 0.037 mm (95% confidence interval 0.008 to 0.067)], while differences in the remaining areas examined were not statistically significant [adjusted mean difference (95% confidence interval): V1 0.022 (-0.007 to 0.052); MT: 0.018 (-0.011 to 0.047); somatosensory cortex: 0.020 (-0.009 to 0.049)]. We found no association between the regions of interest and active migraine, or number of lifetime aura attacks. Migraine with aura discordant twin pairs (n = 30) only differed in mean thickness of V2 (0.039 mm, 95% CI 0

  11. Reorganization of early visual cortex functional connectivity following selective peripheral and central visual loss.

    Science.gov (United States)

    Sabbah, Norman; Sanda, Nicolae; Authié, Colas N; Mohand-Saïd, Saddek; Sahel, José-Alain; Habas, Christophe; Amedi, Amir; Safran, Avinoam B

    2017-02-24

    Behavioral alterations emerging after central or peripheral vision loss suggest that cerebral reorganization occurs for both the afferented and deafferented early visual cortex (EVC). We explored the functional reorganization of the central and peripheral EVC following visual field defects specifically affecting central or peripheral vision. Compared to normally sighted, afferented central and peripheral EVC enhance their functional connectivity with areas involved in visual processing, whereas deafferented central and peripheral EVC increase their functional connectivity with more remote regions. The connectivity pattern of afferented EVC suggests adaptive changes that might enhance the visual processing capacity whereas the connectivity pattern of deafferented EVC may reflect the involvement of these regions in high-order mechanisms. Characterizing and understanding the plastic changes induced by these visual defects is essential for any attempt to develop efficient rehabilitation strategies.

  12. Preprocessing of emotional visual information in the human piriform cortex.

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    Schulze, Patrick; Bestgen, Anne-Kathrin; Lech, Robert K; Kuchinke, Lars; Suchan, Boris

    2017-08-23

    This study examines the processing of visual information by the olfactory system in humans. Recent data point to the processing of visual stimuli by the piriform cortex, a region mainly known as part of the primary olfactory cortex. Moreover, the piriform cortex generates predictive templates of olfactory stimuli to facilitate olfactory processing. This study fills the gap relating to the question whether this region is also capable of preprocessing emotional visual information. To gain insight into the preprocessing and transfer of emotional visual information into olfactory processing, we recorded hemodynamic responses during affective priming using functional magnetic resonance imaging (fMRI). Odors of different valence (pleasant, neutral and unpleasant) were primed by images of emotional facial expressions (happy, neutral and disgust). Our findings are the first to demonstrate that the piriform cortex preprocesses emotional visual information prior to any olfactory stimulation and that the emotional connotation of this preprocessing is subsequently transferred and integrated into an extended olfactory network for olfactory processing.

  13. H3 and H4 Lysine Acetylation Correlates with Developmental and Experimentally Induced Adult Experience-Dependent Plasticity in the Mouse Visual Cortex

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    Gabriela Vierci

    2016-01-01

    Full Text Available Histone posttranslational modifications play a fundamental role in orchestrating gene expression. In this work, we analyzed the acetylation of H3 and H4 histones (AcH3-AcH4 and its modulation by visual experience in the mouse visual cortex (VC during normal development and in two experimental conditions that restore juvenile-like plasticity levels in adults (fluoxetine treatment and enriched environment. We found that AcH3-AcH4 declines with age and is upregulated by treatments restoring plasticity in the adult. We also found that visual experience modulates AcH3-AcH4 in young and adult plasticity-restored mice but not in untreated ones. Finally, we showed that the transporter vGAT is downregulated in adult plasticity-restored models. In summary, we identified a dynamic regulation of AcH3-AcH4, which is associated with high plasticity levels and enhanced by visual experience. These data, along with recent ones, indicate H3-H4 acetylation as a central hub in the control of experience-dependent plasticity in the VC.

  14. Decoding sound and imagery content in early visual cortex.

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    Vetter, Petra; Smith, Fraser W; Muckli, Lars

    2014-06-02

    Human early visual cortex was traditionally thought to process simple visual features such as orientation, contrast, and spatial frequency via feedforward input from the lateral geniculate nucleus (e.g., [1]). However, the role of nonretinal influence on early visual cortex is so far insufficiently investigated despite much evidence that feedback connections greatly outnumber feedforward connections [2-5]. Here, we explored in five fMRI experiments how information originating from audition and imagery affects the brain activity patterns in early visual cortex in the absence of any feedforward visual stimulation. We show that category-specific information from both complex natural sounds and imagery can be read out from early visual cortex activity in blindfolded participants. The coding of nonretinal information in the activity patterns of early visual cortex is common across actual auditory perception and imagery and may be mediated by higher-level multisensory areas. Furthermore, this coding is robust to mild manipulations of attention and working memory but affected by orthogonal, cognitively demanding visuospatial processing. Crucially, the information fed down to early visual cortex is category specific and generalizes to sound exemplars of the same category, providing evidence for abstract information feedback rather than precise pictorial feedback. Our results suggest that early visual cortex receives nonretinal input from other brain areas when it is generated by auditory perception and/or imagery, and this input carries common abstract information. Our findings are compatible with feedback of predictive information to the earliest visual input level (e.g., [6]), in line with predictive coding models [7-10]. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

  15. Timing-dependent LTP and LTD in mouse primary visual cortex following different visual deprivation models

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    Chen, Xia; Fu, Junhong; Cheng, Wenbo; Song, Desheng; Qu, Xiaolei; Yang, Zhuo; Zhao, Kanxing

    2017-01-01

    Visual deprivation during the critical period induces long-lasting changes in cortical circuitry by adaptively modifying neuro-transmission and synaptic connectivity at synapses. Spike timing-dependent plasticity (STDP) is considered a strong candidate for experience-dependent changes. However, the visual deprivation forms that affect timing-dependent long-term potentiation(LTP) and long-term depression(LTD) remain unclear. Here, we demonstrated the temporal window changes of tLTP and tLTD, elicited by coincidental pre- and post-synaptic firing, following different modes of 6-day visual deprivation. Markedly broader temporal windows were found in robust tLTP and tLTD in the V1M of the deprived visual cortex in mice after 6-day MD and DE. The underlying mechanism for the changes seen with visual deprivation in juvenile mice using 6 days of dark exposure or monocular lid suture involves an increased fraction of NR2b-containing NMDAR and the consequent prolongation of NMDAR-mediated response duration. Moreover, a decrease in NR2A protein expression at the synapse is attributable to the reduction of the NR2A/2B ratio in the deprived cortex. PMID:28520739

  16. "Visual" Cortex Responds to Spoken Language in Blind Children.

    Science.gov (United States)

    Bedny, Marina; Richardson, Hilary; Saxe, Rebecca

    2015-08-19

    Plasticity in the visual cortex of blind individuals provides a rare window into the mechanisms of cortical specialization. In the absence of visual input, occipital ("visual") brain regions respond to sound and spoken language. Here, we examined the time course and developmental mechanism of this plasticity in blind children. Nineteen blind and 40 sighted children and adolescents (4-17 years old) listened to stories and two auditory control conditions (unfamiliar foreign speech, and music). We find that "visual" cortices of young blind (but not sighted) children respond to sound. Responses to nonlanguage sounds increased between the ages of 4 and 17. By contrast, occipital responses to spoken language were maximal by age 4 and were not related to Braille learning. These findings suggest that occipital plasticity for spoken language is independent of plasticity for Braille and for sound. We conclude that in the absence of visual input, spoken language colonizes the visual system during brain development. Our findings suggest that early in life, human cortex has a remarkably broad computational capacity. The same cortical tissue can take on visual perception and language functions. Studies of plasticity provide key insights into how experience shapes the human brain. The "visual" cortex of adults who are blind from birth responds to touch, sound, and spoken language. To date, all existing studies have been conducted with adults, so little is known about the developmental trajectory of plasticity. We used fMRI to study the emergence of "visual" cortex responses to sound and spoken language in blind children and adolescents. We find that "visual" cortex responses to sound increase between 4 and 17 years of age. By contrast, responses to spoken language are present by 4 years of age and are not related to Braille-learning. These findings suggest that, early in development, human cortex can take on a strikingly wide range of functions. Copyright © 2015 the authors 0270-6474/15/3511674-08$15.00/0.

  17. From motor cortex to visual cortex: the application of noninvasive brain stimulation to amblyopia.

    Science.gov (United States)

    Thompson, Benjamin; Mansouri, Behzad; Koski, Lisa; Hess, Robert F

    2012-04-01

    Noninvasive brain stimulation is a technique for inducing changes in the excitability of discrete neural populations in the human brain. A current model of the underlying pathological processes contributing to the loss of motor function after stroke has motivated a number of research groups to investigate the potential therapeutic application of brain stimulation to stroke rehabilitation. The loss of motor function is modeled as resulting from a combination of reduced excitability in the lesioned motor cortex and an increased inhibitory drive from the nonlesioned hemisphere over the lesioned hemisphere. This combination of impaired neural function and pathological suppression resonates with current views on the cause of the visual impairment in amblyopia. Here, we discuss how the rationale for using noninvasive brain stimulation in stroke rehabilitation can be applied to amblyopia, review a proof-of-principle study demonstrating that brain stimulation can temporarily improve amblyopic eye function, and propose future research avenues. Copyright © 2010 Wiley Periodicals, Inc.

  18. Rapid and reversible recruitment of early visual cortex for touch.

    Directory of Open Access Journals (Sweden)

    Lotfi B Merabet

    2008-08-01

    Full Text Available The loss of vision has been associated with enhanced performance in non-visual tasks such as tactile discrimination and sound localization. Current evidence suggests that these functional gains are linked to the recruitment of the occipital visual cortex for non-visual processing, but the neurophysiological mechanisms underlying these crossmodal changes remain uncertain. One possible explanation is that visual deprivation is associated with an unmasking of non-visual input into visual cortex.We investigated the effect of sudden, complete and prolonged visual deprivation (five days in normally sighted adult individuals while they were immersed in an intensive tactile training program. Following the five-day period, blindfolded subjects performed better on a Braille character discrimination task. In the blindfold group, serial fMRI scans revealed an increase in BOLD signal within the occipital cortex in response to tactile stimulation after five days of complete visual deprivation. This increase in signal was no longer present 24 hours after blindfold removal. Finally, reversible disruption of occipital cortex function on the fifth day (by repetitive transcranial magnetic stimulation; rTMS impaired Braille character recognition ability in the blindfold group but not in non-blindfolded controls. This disruptive effect was no longer evident once the blindfold had been removed for 24 hours.Overall, our findings suggest that sudden and complete visual deprivation in normally sighted individuals can lead to profound, but rapidly reversible, neuroplastic changes by which the occipital cortex becomes engaged in processing of non-visual information. The speed and dynamic nature of the observed changes suggests that normally inhibited or masked functions in the sighted are revealed by visual loss. The unmasking of pre-existing connections and shifts in connectivity represent rapid, early plastic changes, which presumably can lead, if sustained and

  19. Attentional Modulation in Visual Cortex Is Modified during Perceptual Learning

    Science.gov (United States)

    Bartolucci, Marco; Smith, Andrew T.

    2011-01-01

    Practicing a visual task commonly results in improved performance. Often the improvement does not transfer well to a new retinal location, suggesting that it is mediated by changes occurring in early visual cortex, and indeed neuroimaging and neurophysiological studies both demonstrate that perceptual learning is associated with altered activity…

  20. Spatial Working Memory Effects in Early Visual Cortex

    Science.gov (United States)

    Munneke, Jaap; Heslenfeld, Dirk J.; Theeuwes, Jan

    2010-01-01

    The present study investigated how spatial working memory recruits early visual cortex. Participants were required to maintain a location in working memory while changes in blood oxygen level dependent (BOLD) signals were measured during the retention interval in which no visual stimulation was present. We show working memory effects during the…

  1. Spatial working memory effects in early visual cortex

    NARCIS (Netherlands)

    Munneke, J.; Heslenfeld, D.J.; Theeuwes, J.

    2010-01-01

    The present study investigated how spatial working memory recruits early visual cortex. Participants were required to maintain a location in working memory while changes in blood oxygen level dependent (BOLD) signals were measured during the retention interval in which no visual stimulation was

  2. High-intensity Erotic Visual Stimuli De-activate the Primary Visual Cortex in Women

    NARCIS (Netherlands)

    Huynh, Hieu K.; Beers, Caroline; Willemsen, Antoon; Lont, Erna; Laan, Ellen; Dierckx, Rudi; Jansen, Monique; Sand, Michael; Schultz, Willibrord Weijmar; Holstege, Gert

    Introduction. The primary visual cortex, Brodmann's area (BA 17), plays a vital role in basic survival mechanisms in humans. In most neuro-imaging studies in which the volunteers have to watch pictures or movies, the primary visual cortex is similarly activated independent of the content of the

  3. High-intensity Erotic Visual Stimuli De-activate the Primary Visual Cortex in Women

    NARCIS (Netherlands)

    Huynh, Hieu K.; Beers, Caroline; Willemsen, Antoon; Lont, Erna; Laan, Ellen; Dierckx, Rudi; Jansen, Monique; Sand, Michael; Weijmar Schultz, Willibrord; Holstege, Gert

    2012-01-01

    Introduction. The primary visual cortex, Brodmann's area (BA 17), plays a vital role in basic survival mechanisms in humans. In most neuro-imaging studies in which the volunteers have to watch pictures or movies, the primary visual cortex is similarly activated independent of the content of the

  4. Enhanced alpha-oscillations in visual cortex during anticipation of self-generated visual stimulation.

    Science.gov (United States)

    Stenner, Max-Philipp; Bauer, Markus; Haggard, Patrick; Heinze, Hans-Jochen; Dolan, Ray

    2014-11-01

    The perceived intensity of sensory stimuli is reduced when these stimuli are caused by the observer's actions. This phenomenon is traditionally explained by forward models of sensory action-outcome, which arise from motor processing. Although these forward models critically predict anticipatory modulation of sensory neural processing, neurophysiological evidence for anticipatory modulation is sparse and has not been linked to perceptual data showing sensory attenuation. By combining a psychophysical task involving contrast discrimination with source-level time-frequency analysis of MEG data, we demonstrate that the amplitude of alpha-oscillations in visual cortex is enhanced before the onset of a visual stimulus when the identity and onset of the stimulus are controlled by participants' motor actions. Critically, this prestimulus enhancement of alpha-amplitude is paralleled by psychophysical judgments of a reduced contrast for this stimulus. We suggest that alpha-oscillations in visual cortex preceding self-generated visual stimulation are a likely neurophysiological signature of motor-induced sensory anticipation and mediate sensory attenuation. We discuss our results in relation to proposals that attribute generic inhibitory functions to alpha-oscillations in prioritizing and gating sensory information via top-down control.

  5. In Vivo Voltage-Sensitive Dye Study of Lateral Spreading of Cortical Activity in Mouse Primary Visual Cortex Induced by a Current Impulse.

    Science.gov (United States)

    Fehérvári, Tamás Dávid; Okazaki, Yuka; Sawai, Hajime; Yagi, Tetsuya

    2015-01-01

    In the mammalian primary visual cortex (V1), lateral spreading of excitatory potentials is believed to be involved in spatial integrative functions, but the underlying cortical mechanism is not well understood. Visually-evoked population-level responses have been shown to propagate beyond the V1 initial activation site in mouse, similar to higher mammals. Visually-evoked responses are, however, affected by neuronal circuits prior to V1 (retina, LGN), making the separate analysis of V1 difficult. Intracortical stimulation eliminates these initial processing steps. We used in vivo RH1691 voltage-sensitive dye (VSD) imaging and intracortical microstimulation in adult C57BL/6 mice to elucidate the spatiotemporal properties of population-level signal spreading in V1 cortical circuits. The evoked response was qualitatively similar to that measured in single-cell electrophysiological experiments in rodents: a fast transient fluorescence peak followed by a fast and a slow decrease or hyperpolarization, similar to EPSP and fast and slow IPSPs in single cells. The early cortical response expanded at speeds commensurate with long horizontal projections (at 5% of the peak maximum, 0.08-0.15 m/s) however, the bulk of the VSD signal propagated slowly (at half-peak maximum, 0.05-0.08 m/s) suggesting an important role of regenerative multisynaptic transmission through short horizontal connections in V1 spatial integrative functions. We also found a tendency for a widespread and fast cortical response suppression in V1, which was eliminated by GABAA-antagonists gabazine and bicuculline methiodide. Our results help understand the neuronal circuitry involved in lateral spreading in V1.

  6. In Vivo Voltage-Sensitive Dye Study of Lateral Spreading of Cortical Activity in Mouse Primary Visual Cortex Induced by a Current Impulse.

    Directory of Open Access Journals (Sweden)

    Tamás Dávid Fehérvári

    Full Text Available In the mammalian primary visual cortex (V1, lateral spreading of excitatory potentials is believed to be involved in spatial integrative functions, but the underlying cortical mechanism is not well understood. Visually-evoked population-level responses have been shown to propagate beyond the V1 initial activation site in mouse, similar to higher mammals. Visually-evoked responses are, however, affected by neuronal circuits prior to V1 (retina, LGN, making the separate analysis of V1 difficult. Intracortical stimulation eliminates these initial processing steps. We used in vivo RH1691 voltage-sensitive dye (VSD imaging and intracortical microstimulation in adult C57BL/6 mice to elucidate the spatiotemporal properties of population-level signal spreading in V1 cortical circuits. The evoked response was qualitatively similar to that measured in single-cell electrophysiological experiments in rodents: a fast transient fluorescence peak followed by a fast and a slow decrease or hyperpolarization, similar to EPSP and fast and slow IPSPs in single cells. The early cortical response expanded at speeds commensurate with long horizontal projections (at 5% of the peak maximum, 0.08-0.15 m/s however, the bulk of the VSD signal propagated slowly (at half-peak maximum, 0.05-0.08 m/s suggesting an important role of regenerative multisynaptic transmission through short horizontal connections in V1 spatial integrative functions. We also found a tendency for a widespread and fast cortical response suppression in V1, which was eliminated by GABAA-antagonists gabazine and bicuculline methiodide. Our results help understand the neuronal circuitry involved in lateral spreading in V1.

  7. Visual cortex activation decrement following cochlear implantation in prelingual deafened children.

    Science.gov (United States)

    Liu, Jiahao; Liang, Maojin; Chen, Yuebo; Wang, Yajing; Cai, Yuexin; Chen, Suijun; Chen, Ling; Li, Xianghui; Qiu, Zeheng; Jiang, Jiajia; Wang, Junbo; Zheng, Yiqing

    2017-08-01

    Visual take-over of the auditory cortex in prelingual deaf children has been widely reported. However, there have been few studies on visual cortex plasticity after cochlear implantation (CI). In this study, we investigated the hypothesis that extrinsic auditory stimulation following CI in prelingual deafened children can induce visual cortex plasticity. Visual evoked potentials (VEPs) were recorded in 37 CI children (4 groups with different use times) and 8 control subjects, in response to sound and nonsound stimuli. Latency and amplitude were analyzed for the P1, N1 and P2 components on the Oz electrode. Comparisons of VEP were conducted between the sound and nonsound stimuli and among different groups in order to view evidence of visual cortex reorganization. The latency of the P2 component was significantly longer at the occipital site (Oz) in CI 0M than those in the other four groups. After the effect of age was excluded, a significant negative correlation was found between CI usage and P2 latency of nonsound stimuli. Occipital P1N1 latency and P1 amplitude were not affected by group or stimulus category. However, the N1 and P2 amplitudes were significantly larger in response to a sound stimulus than to a nonsound stimulus. Our findings suggest that P2 latency develops with CI usage and may be a biomarker of visual cortex plasticity. Copyright © 2017. Published by Elsevier B.V.

  8. Top-down influence on the visual cortex of the blind during sensory substitution

    Science.gov (United States)

    Murphy, Matthew C.; Nau, Amy C.; Fisher, Christopher; Kim, Seong-Gi; Schuman, Joel S.; Chan, Kevin C.

    2017-01-01

    Visual sensory substitution devices provide a non-surgical and flexible approach to vision rehabilitation in the blind. These devices convert images taken by a camera into cross-modal sensory signals that are presented as a surrogate for direct visual input. While previous work has demonstrated that the visual cortex of blind subjects is recruited during sensory substitution, the cognitive basis of this activation remains incompletely understood. To test the hypothesis that top-down input provides a significant contribution to this activation, we performed functional MRI scanning in 11 blind (7 acquired and 4 congenital) and 11 sighted subjects under two conditions: passive listening of image-encoded soundscapes before sensory substitution training and active interpretation of the same auditory sensory substitution signals after a 10-minute training session. We found that the modulation of visual cortex activity due to active interpretation was significantly stronger in the blind over sighted subjects. In addition, congenitally blind subjects showed stronger task-induced modulation in the visual cortex than acquired blind subjects. In a parallel experiment, we scanned 18 blind (11 acquired and 7 congenital) and 18 sighted subjects at rest to investigate alterations in functional connectivity due to visual deprivation. The results demonstrated that visual cortex connectivity of the blind shifted away from sensory networks and toward known areas of top-down input. Taken together, our data support the model of the brain, including the visual system, as a highly flexible task-based and not sensory-based machine. PMID:26584776

  9. GABA(A) receptors in visual and auditory cortex and neural activity changes during basic visual stimulation.

    Science.gov (United States)

    Qin, Pengmin; Duncan, Niall W; Wiebking, Christine; Gravel, Paul; Lyttelton, Oliver; Hayes, Dave J; Verhaeghe, Jeroen; Kostikov, Alexey; Schirrmacher, Ralf; Reader, Andrew J; Northoff, Georg

    2012-01-01

    Recent imaging studies have demonstrated that levels of resting γ-aminobutyric acid (GABA) in the visual cortex predict the degree of stimulus-induced activity in the same region. These studies have used the presentation of discrete visual stimulus; the change from closed eyes to open also represents a simple visual stimulus, however, and has been shown to induce changes in local brain activity and in functional connectivity between regions. We thus aimed to investigate the role of the GABA system, specifically GABA(A) receptors, in the changes in brain activity between the eyes closed (EC) and eyes open (EO) state in order to provide detail at the receptor level to complement previous studies of GABA concentrations. We conducted an fMRI study involving two different modes of the change from EC to EO: an EO and EC block design, allowing the modeling of the haemodynamic response, followed by longer periods of EC and EO to allow the measuring of functional connectivity. The same subjects also underwent [(18)F]Flumazenil PET to measure GABA(A) receptor binding potentials. It was demonstrated that the local-to-global ratio of GABA(A) receptor binding potential in the visual cortex predicted the degree of changes in neural activity from EC to EO. This same relationship was also shown in the auditory cortex. Furthermore, the local-to-global ratio of GABA(A) receptor binding potential in the visual cortex also predicted the change in functional connectivity between the visual and auditory cortex from EC to EO. These findings contribute to our understanding of the role of GABA(A) receptors in stimulus-induced neural activity in local regions and in inter-regional functional connectivity.

  10. "Visual" Cortex Responds to Spoken Language in Blind Children

    OpenAIRE

    Bedny, Marina; Richardson, Hilary; Saxe, Rebecca R.

    2015-01-01

    Plasticity in the visual cortex of blind individuals provides a rare window into the mechanisms of cortical specialization. In the absence of visual input, occipital (“visual”) brain regions respond to sound and spoken language. Here, we examined the time course and developmental mechanism of this plasticity in blind children. Nineteen blind and 40 sighted children and adolescents (4–17 years old) listened to stories and two auditory control conditions (unfamiliar foreign speech, and music). ...

  11. Adaptation to sensory input tunes visual cortex to criticality

    Science.gov (United States)

    Shew, Woodrow L.; Clawson, Wesley P.; Pobst, Jeff; Karimipanah, Yahya; Wright, Nathaniel C.; Wessel, Ralf

    2015-08-01

    A long-standing hypothesis at the interface of physics and neuroscience is that neural networks self-organize to the critical point of a phase transition, thereby optimizing aspects of sensory information processing. This idea is partially supported by strong evidence for critical dynamics observed in the cerebral cortex, but the impact of sensory input on these dynamics is largely unknown. Thus, the foundations of this hypothesis--the self-organization process and how it manifests during strong sensory input--remain unstudied experimentally. Here we show in visual cortex and in a computational model that strong sensory input initially elicits cortical network dynamics that are not critical, but adaptive changes in the network rapidly tune the system to criticality. This conclusion is based on observations of multifaceted scaling laws predicted to occur at criticality. Our findings establish sensory adaptation as a self-organizing mechanism that maintains criticality in visual cortex during sensory information processing.

  12. Two distinct neural mechanisms in early visual cortex determine subsequent visual processing.

    Science.gov (United States)

    Jacobs, Christianne; de Graaf, Tom A; Sack, Alexander T

    2014-10-01

    Neuroscience research has conventionally focused on how the brain processes sensory information, after the information has been received. Recently, increased interest focuses on how the state of the brain upon receiving inputs determines and biases their subsequent processing and interpretation. Here, we investigated such 'pre-stimulus' brain mechanisms and their relevance for objective and subjective visual processing. Using non-invasive focal brain stimulation [transcranial magnetic stimulation (TMS)] we disrupted spontaneous brain state activity within early visual cortex (EVC) before onset of visual stimulation, at two different pre-stimulus-onset-asynchronies (pSOAs). We found that TMS pulses applied to EVC at either 20 msec or 50 msec before onset of a simple orientation stimulus both prevented this stimulus from reaching visual awareness. Interestingly, only the TMS-induced visual suppression following TMS at a pSOA of ?20 msec was retinotopically specific, while TMS at a pSOA of ?50 msec was not. In a second experiment, we used more complex symbolic arrow stimuli, and found TMS-induced suppression only when disrupting EVC at a pSOA of ? ?60 msec, which, in line with Experiment 1, was not retinotopically specific. Despite this topographic unspecificity of the ?50 msec effect, the additional control measurements as well as tracking and removal of eye blinks, suggested that also this effect was not the result of an unspecific artifact, and thus neural in origin. We therefore obtained evidence of two distinct neural mechanisms taking place in EVC, both determining whether or not subsequent visual inputs are successfully processed by the human visual system.

  13. Semantics of the Visual Environment Encoded in Parahippocampal Cortex.

    Science.gov (United States)

    Bonner, Michael F; Price, Amy Rose; Peelle, Jonathan E; Grossman, Murray

    2016-03-01

    Semantic representations capture the statistics of experience and store this information in memory. A fundamental component of this memory system is knowledge of the visual environment, including knowledge of objects and their associations. Visual semantic information underlies a range of behaviors, from perceptual categorization to cognitive processes such as language and reasoning. Here we examine the neuroanatomic system that encodes visual semantics. Across three experiments, we found converging evidence indicating that knowledge of verbally mediated visual concepts relies on information encoded in a region of the ventral-medial temporal lobe centered on parahippocampal cortex. In an fMRI study, this region was strongly engaged by the processing of concepts relying on visual knowledge but not by concepts relying on other sensory modalities. In a study of patients with the semantic variant of primary progressive aphasia (semantic dementia), atrophy that encompassed this region was associated with a specific impairment in verbally mediated visual semantic knowledge. Finally, in a structural study of healthy adults from the fMRI experiment, gray matter density in this region related to individual variability in the processing of visual concepts. The anatomic location of these findings aligns with recent work linking the ventral-medial temporal lobe with high-level visual representation, contextual associations, and reasoning through imagination. Together, this work suggests a critical role for parahippocampal cortex in linking the visual environment with knowledge systems in the human brain.

  14. Electrical Stimulation of Visual Cortex: Relevance for the Development of Visual Cortical Prosthetics.

    Science.gov (United States)

    Bosking, William H; Beauchamp, Michael S; Yoshor, Daniel

    2017-09-15

    Electrical stimulation of the cerebral cortex is a powerful tool for exploring cortical function. Stimulation of early visual cortical areas is easily detected by subjects and produces simple visual percepts known as phosphenes. A device implanted in visual cortex that generates patterns of phosphenes could be used as a substitute for natural vision in blind patients. We review the possibilities and limitations of such a device, termed a visual cortical prosthetic. Currently, we can predict the location and size of phosphenes produced by stimulation of single electrodes. A functional prosthetic, however, must produce spatial temporal patterns of activity that will result in the perception of complex visual objects. Although stimulation of later visual cortical areas alone usually does not lead to a visual percept, it can alter visual perception and the performance of visual behaviors, and training subjects to use signals injected into these areas may be possible.

  15. A direct demonstration of functional specialization in human visual cortex.

    Science.gov (United States)

    Zeki, S; Watson, J D; Lueck, C J; Friston, K J; Kennard, C; Frackowiak, R S

    1991-03-01

    We have used positron emission tomography (PET), which measures regional cerebral blood flow (rCBF), to demonstrate directly the specialization of function in the normal human visual cortex. A novel technique, statistical parametric mapping, was used to detect foci of significant change in cerebral blood flow within the prestriate cortex, in order to localize those parts involved in the perception of color and visual motion. For color, we stimulated the subjects with a multicolored abstract display containing no recognizable objects (Land color Mondrian) and contrasted the resulting blood flow maps with those obtained when subjects viewed an identical display consisting of equiluminous shades of gray. The comparison identified a unique area (area V4) located in the lingual and fusiform gyri of the prestriate cortex. For motion, blood flow maps when subjects viewed moving or stationary black and white random-square patterns were contrasted. The comparison identified a unique area located in the region of the temporo-parieto-occipital junction (area V5). We thus provide direct evidence to show that, just as in the macaque monkey, different areas of the human prestriate visual cortex are specialized for different attributes of vision. The striate cortex (V1) and the contiguous visual area (V2), which in the monkey brain feed both the homologous areas, were active in all 4 conditions. This pattern of activity allowed us to use an extension of the approach to assess the functional relationship between the 3 areas during color and motion stimulation. This is based on an hypothesis-led analysis of the covariance structure of the blood flow maps and promises to be a powerful tool for inferring anatomical pathways in the normal human brain.(ABSTRACT TRUNCATED AT 250 WORDS)

  16. Visual cortex in aging and Alzheimer's disease: changes in visual field maps and population receptive fields

    Science.gov (United States)

    Brewer, Alyssa A.; Barton, Brian

    2012-01-01

    Although several studies have suggested that cortical alterations underlie such age-related visual deficits as decreased acuity, little is known about what changes actually occur in visual cortex during healthy aging. Two recent studies showed changes in primary visual cortex (V1) during normal aging; however, no studies have characterized the effects of aging on visual cortex beyond V1, important measurements both for understanding the aging process and for comparison to changes in age-related diseases. Similarly, there is almost no information about changes in visual cortex in Alzheimer's disease (AD), the most common form of dementia. Because visual deficits are often reported as one of the first symptoms of AD, measurements of such changes in the visual cortex of AD patients might improve our understanding of how the visual system is affected by neurodegeneration as well as aid early detection, accurate diagnosis and timely treatment of AD. Here we use fMRI to first compare the visual field map (VFM) organization and population receptive fields (pRFs) between young adults and healthy aging subjects for occipital VFMs V1, V2, V3, and hV4. Healthy aging subjects do not show major VFM organizational deficits, but do have reduced surface area and increased pRF sizes in the foveal representations of V1, V2, and hV4 relative to healthy young control subjects. These measurements are consistent with behavioral deficits seen in healthy aging. We then demonstrate the feasibility and first characterization of these measurements in two patients with mild AD, which reveal potential changes in visual cortex as part of the pathophysiology of AD. Our data aid in our understanding of the changes in the visual processing pathways in normal aging and provide the foundation for future research into earlier and more definitive detection of AD. PMID:24570669

  17. Phosphene Perception Relates to Visual Cortex Glutamate Levels and Covaries with Atypical Visuospatial Awareness

    Science.gov (United States)

    Terhune, Devin B.; Murray, Elizabeth; Near, Jamie; Stagg, Charlotte J.; Cowey, Alan; Cohen Kadosh, Roi

    2015-01-01

    Phosphenes are illusory visual percepts produced by the application of transcranial magnetic stimulation to occipital cortex. Phosphene thresholds, the minimum stimulation intensity required to reliably produce phosphenes, are widely used as an index of cortical excitability. However, the neural basis of phosphene thresholds and their relationship to individual differences in visual cognition are poorly understood. Here, we investigated the neurochemical basis of phosphene perception by measuring basal GABA and glutamate levels in primary visual cortex using magnetic resonance spectroscopy. We further examined whether phosphene thresholds would relate to the visuospatial phenomenology of grapheme-color synesthesia, a condition characterized by atypical binding and involuntary color photisms. Phosphene thresholds negatively correlated with glutamate concentrations in visual cortex, with lower thresholds associated with elevated glutamate. This relationship was robust, present in both controls and synesthetes, and exhibited neurochemical, topographic, and threshold specificity. Projector synesthetes, who experience color photisms as spatially colocalized with inducing graphemes, displayed lower phosphene thresholds than associator synesthetes, who experience photisms as internal images, with both exhibiting lower thresholds than controls. These results suggest that phosphene perception is driven by interindividual variation in glutamatergic activity in primary visual cortex and relates to cortical processes underlying individual differences in visuospatial awareness. PMID:25725043

  18. Adult visual experience promotes recovery of primary visual cortex from long-term monocular deprivation

    OpenAIRE

    Fischer, Quentin S.; Aleem, Salman; Zhou, Hongyi; Pham, Tony A.

    2007-01-01

    Prolonged visual deprivation from early childhood to maturity is believed to cause permanent visual impairment. However, there have been case reports of substantial improvement of binocular vision in human adults following lifelong visual impairment or deprivation. These observations, together with recent findings of adult ocular dominance plasticity in rodents, led us to re-examine whether adult primary visual cortex (V1) is capable of any recovery following long-term monocular deprivation s...

  19. Visual Map Shifts based on Whisker-Guided Cues in the Young Mouse Visual Cortex

    Directory of Open Access Journals (Sweden)

    Kohei Yoshitake

    2013-12-01

    Full Text Available Mice navigate nearby space using their vision and whiskers, and young mice learn to integrate these heterogeneous inputs in perceptual space. We found that cortical responses were depressed in the primary visual cortex of young mice after wearing a monocular prism. This depression was uniformly observed in the primary visual cortex and was eliminated by whisker trimming or lesions in the posterior parietal cortex. Compensatory visual map shifts of responses elicited via the eye that had worn the prism were also observed. As a result, cortical responses elicited via each eye were clearly separated when a visual stimulus was placed in front of the mice. A comparison of response areas before and after prism wearing indicated that the map shifts were produced by depression with spatial eccentricity. Visual map shifts based on whisker-guided cues may serve as a model for investigating the cellular and molecular mechanisms underlying higher sensory integration in the mammalian brain.

  20. Visual short-term memory: activity supporting encoding and maintenance in retinotopic visual cortex.

    Science.gov (United States)

    Sneve, Markus H; Alnæs, Dag; Endestad, Tor; Greenlee, Mark W; Magnussen, Svein

    2012-10-15

    Recent studies have demonstrated that retinotopic cortex maintains information about visual stimuli during retention intervals. However, the process by which transient stimulus-evoked sensory responses are transformed into enduring memory representations is unknown. Here, using fMRI and short-term visual memory tasks optimized for univariate and multivariate analysis approaches, we report differential involvement of human retinotopic areas during memory encoding of the low-level visual feature orientation. All visual areas show weaker responses when memory encoding processes are interrupted, possibly due to effects in orientation-sensitive primary visual cortex (V1) propagating across extrastriate areas. Furthermore, intermediate areas in both dorsal (V3a/b) and ventral (LO1/2) streams are significantly more active during memory encoding compared with non-memory (active and passive) processing of the same stimulus material. These effects in intermediate visual cortex are also observed during memory encoding of a different stimulus feature (spatial frequency), suggesting that these areas are involved in encoding processes on a higher level of representation. Using pattern-classification techniques to probe the representational content in visual cortex during delay periods, we further demonstrate that simply initiating memory encoding is not sufficient to produce long-lasting memory traces. Rather, active maintenance appears to underlie the observed memory-specific patterns of information in retinotopic cortex. Copyright © 2012 Elsevier Inc. All rights reserved.

  1. Vestibular Activation Differentially Modulates Human Early Visual Cortex and V5/MT Excitability and Response Entropy

    Science.gov (United States)

    Guzman-Lopez, Jessica; Arshad, Qadeer; Schultz, Simon R; Walsh, Vincent; Yousif, Nada

    2013-01-01

    Head movement imposes the additional burdens on the visual system of maintaining visual acuity and determining the origin of retinal image motion (i.e., self-motion vs. object-motion). Although maintaining visual acuity during self-motion is effected by minimizing retinal slip via the brainstem vestibular-ocular reflex, higher order visuovestibular mechanisms also contribute. Disambiguating self-motion versus object-motion also invokes higher order mechanisms, and a cortical visuovestibular reciprocal antagonism is propounded. Hence, one prediction is of a vestibular modulation of visual cortical excitability and indirect measures have variously suggested none, focal or global effects of activation or suppression in human visual cortex. Using transcranial magnetic stimulation-induced phosphenes to probe cortical excitability, we observed decreased V5/MT excitability versus increased early visual cortex (EVC) excitability, during vestibular activation. In order to exclude nonspecific effects (e.g., arousal) on cortical excitability, response specificity was assessed using information theory, specifically response entropy. Vestibular activation significantly modulated phosphene response entropy for V5/MT but not EVC, implying a specific vestibular effect on V5/MT responses. This is the first demonstration that vestibular activation modulates human visual cortex excitability. Furthermore, using information theory, not previously used in phosphene response analysis, we could distinguish between a specific vestibular modulation of V5/MT excitability from a nonspecific effect at EVC. PMID:22291031

  2. Ventromedial prefrontal cortex mediates visual attention during facial emotion recognition.

    Science.gov (United States)

    Wolf, Richard C; Philippi, Carissa L; Motzkin, Julian C; Baskaya, Mustafa K; Koenigs, Michael

    2014-06-01

    The ventromedial prefrontal cortex is known to play a crucial role in regulating human social and emotional behaviour, yet the precise mechanisms by which it subserves this broad function remain unclear. Whereas previous neuropsychological studies have largely focused on the role of the ventromedial prefrontal cortex in higher-order deliberative processes related to valuation and decision-making, here we test whether ventromedial prefrontal cortex may also be critical for more basic aspects of orienting attention to socially and emotionally meaningful stimuli. Using eye tracking during a test of facial emotion recognition in a sample of lesion patients, we show that bilateral ventromedial prefrontal cortex damage impairs visual attention to the eye regions of faces, particularly for fearful faces. This finding demonstrates a heretofore unrecognized function of the ventromedial prefrontal cortex-the basic attentional process of controlling eye movements to faces expressing emotion. © The Author (2014). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  3. Plasticity of the visual cortex and treatment of amblyopia.

    Science.gov (United States)

    Sengpiel, Frank

    2014-09-22

    Over the last 50 years, research into the developmental plasticity of the visual cortex has led to a growing understanding of first the causes and then of the underlying cellular mechanisms of amblyopia or 'lazy eye', the commonest childhood disorder of vision. While it is widely believed that amblyopia cannot be treated successfully after the age of about 7, recent animal studies have demonstrated that visual cortex plasticity can be restored or enhanced later in life, paving the way for new strategies for the treatment of amblyopia that attempt to remove molecular brakes on plasticity. In addition, both animal and human work has established that amblyopia is not simply a monocular deficit, and therefore the most promising new non-invasive approaches force the two eyes to cooperate as opposed to conventional procedures that severely penalise the good eye. Copyright © 2014 Elsevier Ltd. All rights reserved.

  4. High-intensity erotic visual stimuli de-activate the primary visual cortex in women.

    Science.gov (United States)

    Huynh, Hieu K; Beers, Caroline; Willemsen, Antoon; Lont, Erna; Laan, Ellen; Dierckx, Rudi; Jansen, Monique; Sand, Michael; Weijmar Schultz, Willibrord; Holstege, Gert

    2012-06-01

    The primary visual cortex, Brodmann's area (BA 17), plays a vital role in basic survival mechanisms in humans. In most neuro-imaging studies in which the volunteers have to watch pictures or movies, the primary visual cortex is similarly activated independent of the content of the pictures or movies. However, in case the volunteers perform demanding non-visual tasks, the primary visual cortex becomes de-activated, although the amount of incoming visual sensory information is the same. Do low- and high-intensity erotic movies, compared to neutral movies, produce similar de-activation of the primary visual cortex? Brain activation/de-activation was studied by Positron Emission Tomography scanning of the brains of 12 healthy heterosexual premenopausal women, aged 18-47, who watched neutral, low- and high-intensity erotic film segments. We measured differences in regional cerebral blood flow (rCBF) in the primary visual cortex during watching neutral, low-intensity erotic, and high-intensity erotic film segments. Watching high-intensity erotic, but not low-intensity erotic movies, compared to neutral movies resulted in strong de-activation of the primary (BA 17) and adjoining parts of the secondary visual cortex. The strong de-activation during watching high-intensity erotic film might represent compensation for the increased blood supply in the brain regions involved in sexual arousal, also because high-intensity erotic movies do not require precise scanning of the visual field, because the impact is clear to the observer. © 2012 International Society for Sexual Medicine.

  5. NrCAM deletion causes topographic mistargeting of thalamocortical axons to the visual cortex and disrupts visual acuity.

    Science.gov (United States)

    Demyanenko, Galina P; Riday, Thorfinn T; Tran, Tracy S; Dalal, Jasbir; Darnell, Eli P; Brennaman, Leann H; Sakurai, Takeshi; Grumet, Martin; Philpot, Benjamin D; Maness, Patricia F

    2011-01-26

    NrCAM is a neural cell adhesion molecule of the L1 family that has been linked to autism spectrum disorders, a disease spectrum in which abnormal thalamocortical connectivity may contribute to visual processing defects. Here we show that NrCAM interaction with neuropilin-2 (Npn-2) is critical for semaphorin 3F (Sema3F)-induced guidance of thalamocortical axon subpopulations at the ventral telencephalon (VTe), an intermediate target for thalamic axon sorting. Genetic deletion of NrCAM or Npn-2 caused contingents of embryonic thalamic axons to misproject caudally in the VTe. The resultant thalamocortical map of NrCAM-null mutants showed striking mistargeting of motor and somatosensory thalamic axon contingents to the primary visual cortex, but retinogeniculate targeting and segregation were normal. NrCAM formed a molecular complex with Npn-2 in brain and neural cells, and was required for Sema3F-induced growth cone collapse in thalamic neuron cultures, consistent with a vital function for NrCAM in Sema3F-induced axon repulsion. NrCAM-null mice displayed reduced responses to visual evoked potentials recorded from layer IV in the binocular zone of primary visual cortex (V1), particularly when evoked from the ipsilateral eye, indicating abnormal visual acuity and ocularity. These results demonstrate that NrCAM is required for normal maturation of cortical visual acuity, and suggest that the aberrant projection of thalamic motor and somatosensory axons to the visual cortex in NrCAM-null mutant mice impairs cortical functions.

  6. The role of human ventral visual cortex in motion perception

    Science.gov (United States)

    Saygin, Ayse P.; Lorenzi, Lauren J.; Egan, Ryan; Rees, Geraint; Behrmann, Marlene

    2013-01-01

    Visual motion perception is fundamental to many aspects of visual perception. Visual motion perception has long been associated with the dorsal (parietal) pathway and the involvement of the ventral ‘form’ (temporal) visual pathway has not been considered critical for normal motion perception. Here, we evaluated this view by examining whether circumscribed damage to ventral visual cortex impaired motion perception. The perception of motion in basic, non-form tasks (motion coherence and motion detection) and complex structure-from-motion, for a wide range of motion speeds, all centrally displayed, was assessed in five patients with a circumscribed lesion to either the right or left ventral visual pathway. Patients with a right, but not with a left, ventral visual lesion displayed widespread impairments in central motion perception even for non-form motion, for both slow and for fast speeds, and this held true independent of the integrity of areas MT/V5, V3A or parietal regions. In contrast with the traditional view in which only the dorsal visual stream is critical for motion perception, these novel findings implicate a more distributed circuit in which the integrity of the right ventral visual pathway is also necessary even for the perception of non-form motion. PMID:23983030

  7. Neural computation of visual imaging based on Kronecker product in the primary visual cortex

    Directory of Open Access Journals (Sweden)

    Guozheng Yao

    2010-03-01

    Full Text Available Abstract Background What kind of neural computation is actually performed by the primary visual cortex and how is this represented mathematically at the system level? It is an important problem in the visual information processing, but has not been well answered. In this paper, according to our understanding of retinal organization and parallel multi-channel topographical mapping between retina and primary visual cortex V1, we divide an image into orthogonal and orderly array of image primitives (or patches, in which each patch will evoke activities of simple cells in V1. From viewpoint of information processing, this activated process, essentially, involves optimal detection and optimal matching of receptive fields of simple cells with features contained in image patches. For the reconstruction of the visual image in the visual cortex V1 based on the principle of minimum mean squares error, it is natural to use the inner product expression in neural computation, which then is transformed into matrix form. Results The inner product is carried out by using Kronecker product between patches and function architecture (or functional column in localized and oriented neural computing. Compared with Fourier Transform, the mathematical description of Kronecker product is simple and intuitive, so is the algorithm more suitable for neural computation of visual cortex V1. Results of computer simulation based on two-dimensional Gabor pyramid wavelets show that the theoretical analysis and the proposed model are reasonable. Conclusions Our results are: 1. The neural computation of the retinal image in cortex V1 can be expressed to Kronecker product operation and its matrix form, this algorithm is implemented by the inner operation between retinal image primitives and primary visual cortex's column. It has simple, efficient and robust features, which is, therefore, such a neural algorithm, which can be completed by biological vision. 2. It is more suitable

  8. Remodeling of inhibitory synaptic connections in developing ferret visual cortex

    Directory of Open Access Journals (Sweden)

    Dalva Matthew B

    2010-02-01

    Full Text Available Abstract Background In the visual cortex, as in many other regions of the developing brain, excitatory synaptic connections undergo substantial remodeling during development. While evidence suggests that local inhibitory synapses may behave similarly, the extent and mechanisms that mediate remodeling of inhibitory connections are not well understood. Results Using scanning laser photostimulation in slices of developing ferret visual cortex, we assessed the overall patterns of developing inhibitory and excitatory synaptic connections converging onto individual neurons. Inhibitory synaptic inputs onto pyramidal neurons in cortical layers 2 and 3 were already present as early as postnatal day 20, well before eye opening, and originated from regions close to the recorded neurons. During the ensuing 2 weeks, the numbers of synaptic inputs increased, with the numbers of inhibitory (and excitatory synaptic inputs peaking near the time of eye opening. The pattern of inhibitory inputs refined rapidly prior to the refinement of excitatory inputs. By uncaging the neurotransmtter GABA in brain slices from animals of different ages, we find that this rapid refinement correlated with a loss of excitatory activity by GABA. Conclusion Inhibitory synapses, like excitatory synapses, undergo significant postnatal remodeling. The time course of the remodeling of inhibitory connections correlates with the emergence of orientation tuning in the visual cortex, implicating these rearrangements in the genesis of adult cortical response properties.

  9. Saccadic modulation of stimulus processing in primary visual cortex

    Science.gov (United States)

    McFarland, James M.; Bondy, Adrian G.; Saunders, Richard C.; Cumming, Bruce G.; Butts, Daniel A.

    2015-01-01

    Saccadic eye movements play a central role in primate vision. Yet, relatively little is known about their effects on the neural processing of visual inputs. Here we examine this question in primary visual cortex (V1) using receptive-field-based models, combined with an experimental design that leaves the retinal stimulus unaffected by saccades. This approach allows us to analyse V1 stimulus processing during saccades with unprecedented detail, revealing robust perisaccadic modulation. In particular, saccades produce biphasic firing rate changes that are composed of divisive gain suppression followed by an additive rate increase. Microsaccades produce similar, though smaller, modulations. We furthermore demonstrate that this modulation is likely inherited from the LGN, and is driven largely by extra-retinal signals. These results establish a foundation for integrating saccades into existing models of visual cortical stimulus processing, and highlight the importance of studying visual neuron function in the context of eye movements. PMID:26370359

  10. Markers of Alzheimer’s Disease in Primary Visual Cortex in Normal Aging in Mice

    Directory of Open Access Journals (Sweden)

    Luis Fernando Hernández-Zimbrón

    2017-01-01

    Full Text Available Aging is the principal risk factor for the development of Alzheimer’s disease (AD. The hallmarks of AD are accumulation of the amyloid-β peptide 1–42 (Aβ42 and abnormal hyperphosphorylation of Tau (p-Tau protein in different areas of the brain and, more recently reported, in the visual cortex. Recently, Aβ42 peptide overproduction has been involved in visual loss. Similar to AD, in normal aging, there is a significant amyloid deposition related to the overactivation of the aforementioned mechanisms. However, the mechanisms associated with visual loss secondary to age-induced visual cortex affectation are not completely understood. Young and aged mice were used as model to analyze the presence of Aβ42, p-Tau, glial-acidic fibrillary protein (GFAP, and presenilin-2, one of the main enzymes involved in Aβ42 production. Our results show a significant increase of Aβ42 deposition in aged mice in the following cells and/or tissues: endothelial cells and blood vessels and neurons of the visual cortex; they also show an increase of the expression of GFAP and presenilin-2 in this region. These results provide a comprehensive framework for the role of Aβ42 in visual loss due to inflammation present with aging and offer some clues for fruitful avenues for the study of healthy aging.

  11. Visual cortex is rescued from the effects of dark rearing by overexpression of BDNF

    OpenAIRE

    Gianfranceschi, Laura; Siciliano, Rosita; Walls, Jennifer; Morales, Bernardo; Kirkwood, Alfredo; Huang, Z. Josh; Tonegawa, Susumu; Maffei, Lamberto

    2003-01-01

    Visual deprivation such as dark rearing (DR) prolongs the critical period for ocular dominance plasticity and retards the maturation of γ-aminobutyric acid (GABA)ergic inhibition in visual cortex. The molecular signals that mediate the effects of DR on the development of visual cortex are not well defined. To test the role of brain-derived neurotrophic factor (BDNF), we examined the effects of DR in transgenic mice in which BDNF expression in visual cortex was uncoupled from visual experience...

  12. Differential Sampling of Visual Space in Ventral and Dorsal Early Visual Cortex.

    Science.gov (United States)

    Silson, Edward H; Reynolds, Richard C; Kravitz, Dwight J; Baker, Chris I

    2018-02-28

    A fundamental feature of cortical visual processing is the separation of visual processing for the upper and lower visual fields. In early visual cortex (EVC), the upper visual field is processed ventrally, with the lower visual field processed dorsally. This distinction persists into several category-selective regions of occipitotemporal cortex, with ventral and lateral scene-, face-, and object-selective regions biased for the upper and lower visual fields, respectively. Here, using an elliptical population receptive field (pRF) model, we systematically tested the sampling of visual space within ventral and dorsal divisions of human EVC in both male and female participants. We found that (1) pRFs tend to be elliptical and oriented toward the fovea with distinct angular distributions for ventral and dorsal divisions of EVC, potentially reflecting a radial bias; and (2) pRFs in ventral areas were larger (∼1.5×) and more elliptical (∼1.2×) than those in dorsal areas. These differences potentially reflect a tendency for receptive fields in ventral temporal cortex to overlap the fovea with less emphasis on precise localization and isotropic representation of space compared with dorsal areas. Collectively, these findings suggest that ventral and dorsal divisions of EVC sample visual space differently, likely contributing to and/or stemming from the functional differentiation of visual processing observed in higher-level regions of the ventral and dorsal cortical visual pathways. SIGNIFICANCE STATEMENT The processing of visual information from the upper and lower visual fields is separated in visual cortex. Although ventral and dorsal divisions of early visual cortex (EVC) are commonly assumed to sample visual space equivalently, we demonstrate systematic differences using an elliptical population receptive field (pRF) model. Specifically, we demonstrate that (1) ventral and dorsal divisions of EVC exhibit diverging distributions of pRF angle, which are biased

  13. Visual cortex is rescued from the effects of dark rearing by overexpression of BDNF.

    Science.gov (United States)

    Gianfranceschi, Laura; Siciliano, Rosita; Walls, Jennifer; Morales, Bernardo; Kirkwood, Alfredo; Huang, Z Josh; Tonegawa, Susumu; Maffei, Lamberto

    2003-10-14

    Visual deprivation such as dark rearing (DR) prolongs the critical period for ocular dominance plasticity and retards the maturation of gamma-aminobutyric acid (GABA)ergic inhibition in visual cortex. The molecular signals that mediate the effects of DR on the development of visual cortex are not well defined. To test the role of brain-derived neurotrophic factor (BDNF), we examined the effects of DR in transgenic mice in which BDNF expression in visual cortex was uncoupled from visual experience and remained elevated during DR. In dark-reared transgenic mice, visual acuity, receptive field size of visual cortical neurons, critical period for ocular dominance plasticity, and intracortical inhibition were indistinguishable from those observed in light-reared mice. Therefore, BDNF overexpression is sufficient for the development of aspects of visual cortex in the absence of visual experience. These results suggest that reduced BDNF expression contributes to retarded maturation of GABAergic inhibition and delayed development of visual cortex during visual deprivation.

  14. Retinotopic coding of extraretinal pursuit signals in early visual cortex.

    Science.gov (United States)

    Lebranchu, Pierre; Bastin, J; Pelegrini-Issac, M; Lehericy, S; Berthoz, A; Orban, G A

    2010-09-01

    During smooth pursuit, the image of the target is stabilized on the fovea, implying that speed judgments made during pursuit must rely on an extraretinal signal providing precise eye speed information. To characterize the introduction of such extraretinal signal into the human visual system, we performed a factorial, functional magnetic resonance imaging experiment, in which we manipulated the factor eye movement, with "fixation" and "pursuit" as levels, and the factor task, with "speed" and "form" judgments as levels. We hypothesized that the extraretinal speed signal is reflected as an interaction between speed judgments and pursuit. Random effects analysis yielded an interaction only in dorsal early visual cortex. Retinotopic mapping localized this interaction on the horizontal meridian (HM) between dorsal areas visual 2 and 3 (V2/V3) at 1-2 degrees azimuth. This corresponded to the position the pursuit target would have reached, if moving retinotopically, at the time of the subject's speed judgment. Because the 2 V2/V3 HMs are redundant, both may be involved in speed judgments, the ventral one involving judgments based on retinal motion and the dorsal one judgments requiring an internal signal. These results indicate that an extraretinal speed signal is injected into early visual cortex during pursuit.

  15. Visual predictions in the orbitofrontal cortex rely on associative content.

    Science.gov (United States)

    Chaumon, Maximilien; Kveraga, Kestutis; Barrett, Lisa Feldman; Bar, Moshe

    2014-11-01

    Predicting upcoming events from incomplete information is an essential brain function. The orbitofrontal cortex (OFC) plays a critical role in this process by facilitating recognition of sensory inputs via predictive feedback to sensory cortices. In the visual domain, the OFC is engaged by low spatial frequency (LSF) and magnocellular-biased inputs, but beyond this, we know little about the information content required to activate it. Is the OFC automatically engaged to analyze any LSF information for meaning? Or is it engaged only when LSF information matches preexisting memory associations? We tested these hypotheses and show that only LSF information that could be linked to memory associations engages the OFC. Specifically, LSF stimuli activated the OFC in 2 distinct medial and lateral regions only if they resembled known visual objects. More identifiable objects increased activity in the medial OFC, known for its function in affective responses. Furthermore, these objects also increased the connectivity of the lateral OFC with the ventral visual cortex, a crucial region for object identification. At the interface between sensory, memory, and affective processing, the OFC thus appears to be attuned to the associative content of visual information and to play a central role in visuo-affective prediction. © The Author 2013. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  16. Large-scale Contextual Effects in Early Human Visual Cortex

    Directory of Open Access Journals (Sweden)

    Sung Jun Joo

    2012-10-01

    Full Text Available A commonly held view about neurons in early visual cortex is that they serve as localized feature detectors. Here, however, we demonstrate that the responses of neurons in early visual cortex are sensitive to global visual patterns. Using multiple methodologies–psychophysics, fMRI, and EEG–we measured neural responses to an oriented Gabor (“target” embedded in various orientation patterns. Specifically, we varied whether a central target deviated from its context by changing distant orientations while leaving the immediately neighboring flankers unchanged. The results of psychophysical contrast adaptation and fMRI experiments show that a target that deviates from its context results in more neural activity compared to a target that is grouped into an alternating pattern. For example, the neural response to a vertically oriented target was greater when it deviated from the orientation of flankers (HHVHH compared to when it was grouped into an alternating pattern (VHVHV. We then found that this pattern-sensitive response manifests in the earliest sensory component of the event-related potential to the target. Finally, in a forced-choice classification task of “noise” stimuli, perceptions are biased to “see” an orientation that deviates from its context. Our results show that neurons in early visual cortex are sensitive to large-scale global patterns in images in a way that is more sophisticated than localized feature detection. Our results showing a reduced neural response to statistical redundancies in images is not only optimal from an information theory perspective but also takes into account known energy constraints in neural processing.

  17. Structural and functional changes across the visual cortex of a patient with visual form agnosia.

    Science.gov (United States)

    Bridge, Holly; Thomas, Owen M; Minini, Loredana; Cavina-Pratesi, Cristiana; Milner, A David; Parker, Andrew J

    2013-07-31

    Loss of shape recognition in visual-form agnosia occurs without equivalent losses in the use of vision to guide actions, providing support for the hypothesis of two visual systems (for "perception" and "action"). The human individual DF received a toxic exposure to carbon monoxide some years ago, which resulted in a persisting visual-form agnosia that has been extensively characterized at the behavioral level. We conducted a detailed high-resolution MRI study of DF's cortex, combining structural and functional measurements. We present the first accurate quantification of the changes in thickness across DF's occipital cortex, finding the most substantial loss in the lateral occipital cortex (LOC). There are reduced white matter connections between LOC and other areas. Functional measures show pockets of activity that survive within structurally damaged areas. The topographic mapping of visual areas showed that ordered retinotopic maps were evident for DF in the ventral portions of visual cortical areas V1, V2, V3, and hV4. Although V1 shows evidence of topographic order in its dorsal portion, such maps could not be found in the dorsal parts of V2 and V3. We conclude that it is not possible to understand fully the deficits in object perception in visual-form agnosia without the exploitation of both structural and functional measurements. Our results also highlight for DF the cortical routes through which visual information is able to pass to support her well-documented abilities to use visual information to guide actions.

  18. Spontaneous activity in the visual cortex is organized by visual streams.

    Science.gov (United States)

    Lu, Kun-Han; Jeong, Jun Young; Wen, Haiguang; Liu, Zhongming

    2017-09-01

    Large-scale functional networks have been extensively studied using resting state functional magnetic resonance imaging (fMRI). However, the pattern, organization, and function of fine-scale network activity remain largely unknown. Here, we characterized the spontaneously emerging visual cortical activity by applying independent component (IC) analysis to resting state fMRI signals exclusively within the visual cortex. In this subsystem scale, we observed about 50 spatially ICs that were reproducible within and across subjects, and analyzed their spatial patterns and temporal relationships to reveal the intrinsic parcellation and organization of the visual cortex. The resulting visual cortical parcels were aligned with the steepest gradient of cortical myelination, and were organized into functional modules segregated along the dorsal/ventral pathways and foveal/peripheral early visual areas. Cortical distance could partly explain intra-hemispherical functional connectivity, but not interhemispherical connectivity; after discounting the effect of anatomical affinity, the fine-scale functional connectivity still preserved a similar visual-stream-specific modular organization. Moreover, cortical retinotopy, folding, and cytoarchitecture impose limited constraints to the organization of resting state activity. Given these findings, we conclude that spontaneous activity patterns in the visual cortex are primarily organized by visual streams, likely reflecting feedback network interactions. Hum Brain Mapp 38:4613-4630, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  19. Robustness of traveling waves in ongoing activity of visual cortex.

    Science.gov (United States)

    Nauhaus, Ian; Busse, Laura; Ringach, Dario L; Carandini, Matteo

    2012-02-29

    Numerous studies have revealed traveling waves of activity in sensory cortex, both following sensory stimulation and during ongoing activity. We contributed to this body of work by measuring the spike-triggered average of the local field potential (stLFP) at multiple concurrent locations (Nauhaus et al., 2009) in the visual cortex of anesthetized cats and macaques. We found the stLFP to be progressively delayed at increasing distances from the site of the triggering spikes, and interpreted this as a traveling wave of depolarization originating from that site. Our results were criticized, however, on two grounds. First, a study using the same recording techniques in the visual cortex of awake macaques reported an apparent lack of traveling waves, and proposed that traveling waves could arise artifactually from excessive filtering of the field potentials (Ray and Maunsell, 2011). Second, the interpretability of the stLFP was questioned (Kenneth Miller, personal communication), as the stLFP must reflect not only interactions between spike trains and field potentials, but also correlations within and across the spike trains. Here, we show that our data and interpretation are not imperiled by these criticisms. We reanalyzed our field potentials to remove any possible artifact due to filtering and to discount the effects of correlations within and across the triggering spike trains. In both cases, we found that the traveling waves were still present. In fact, closer inspection of Ray and Maunsell's (2011) data from awake cortex shows that they do agree with ours, as they contain clear evidence for traveling waves.

  20. The temporal dynamics of early visual cortex involvement in behavioral priming.

    Directory of Open Access Journals (Sweden)

    Christianne Jacobs

    Full Text Available Transcranial magnetic stimulation (TMS allows for non-invasive interference with ongoing neural processing. Applied in a chronometric design over early visual cortex (EVC, TMS has proved valuable in indicating at which particular time point EVC must remain unperturbed for (conscious vision to be established. In the current study, we set out to examine the effect of EVC TMS across a broad range of time points, both before (pre-stimulus and after (post-stimulus the onset of symbolic visual stimuli. Behavioral priming studies have shown that the behavioral impact of a visual stimulus can be independent from its conscious perception, suggesting two independent neural signatures. To assess whether TMS-induced suppression of visual awareness can be dissociated from behavioral priming in the temporal domain, we thus implemented three different measures of visual processing, namely performance on a standard visual discrimination task, a subjective rating of stimulus visibility, and a visual priming task. To control for non-neural TMS effects, we performed electrooculographical recordings, placebo TMS (sham, and control site TMS (vertex. Our results suggest that, when considering the appropriate control data, the temporal pattern of EVC TMS disruption on visual discrimination, subjective awareness and behavioral priming are not dissociable. Instead, TMS to EVC disrupts visual perception holistically, both when applied before and after the onset of a visual stimulus. The current findings are discussed in light of their implications on models of visual awareness and (subliminal priming.

  1. The temporal dynamics of early visual cortex involvement in behavioral priming.

    Science.gov (United States)

    Jacobs, Christianne; de Graaf, Tom A; Goebel, Rainer; Sack, Alexander T

    2012-01-01

    Transcranial magnetic stimulation (TMS) allows for non-invasive interference with ongoing neural processing. Applied in a chronometric design over early visual cortex (EVC), TMS has proved valuable in indicating at which particular time point EVC must remain unperturbed for (conscious) vision to be established. In the current study, we set out to examine the effect of EVC TMS across a broad range of time points, both before (pre-stimulus) and after (post-stimulus) the onset of symbolic visual stimuli. Behavioral priming studies have shown that the behavioral impact of a visual stimulus can be independent from its conscious perception, suggesting two independent neural signatures. To assess whether TMS-induced suppression of visual awareness can be dissociated from behavioral priming in the temporal domain, we thus implemented three different measures of visual processing, namely performance on a standard visual discrimination task, a subjective rating of stimulus visibility, and a visual priming task. To control for non-neural TMS effects, we performed electrooculographical recordings, placebo TMS (sham), and control site TMS (vertex). Our results suggest that, when considering the appropriate control data, the temporal pattern of EVC TMS disruption on visual discrimination, subjective awareness and behavioral priming are not dissociable. Instead, TMS to EVC disrupts visual perception holistically, both when applied before and after the onset of a visual stimulus. The current findings are discussed in light of their implications on models of visual awareness and (subliminal) priming.

  2. Coding of Border Ownership in Monkey Visual Cortex

    OpenAIRE

    Zhou, Hong; Friedman, Howard S.; von der Heydt, Rüdiger

    2000-01-01

    Areas V1 and V2 of the visual cortex have traditionally been conceived as stages of local feature representations. We investigated whether neural responses carry information about how local features belong to objects. Single-cell activity was recorded in areas V1, V2, and V4 of awake behaving monkeys. Displays were used in which the same local feature (contrast edge or line) could be presented as part of different figures. For example, the same light–dark edge could be the left side of a dark...

  3. Neural discriminability in rat lateral extrastriate cortex and deep but not superficial primary visual cortex linearly correlates with shape discriminability

    Directory of Open Access Journals (Sweden)

    Ben eVermaercke

    2015-05-01

    Full Text Available Recent studies have revealed a surprising degree of functional specialization in rodent visual cortex. It is unknown to what degree this functional organization is related to the well-known hierarchical organization of the visual system in primates. We designed a study in rats that targets one of the hallmarks of the hierarchical object vision pathway in primates: selectivity for behaviorally relevant dimensions. We compared behavioral performance in a visual water maze with neural discriminability in five visual cortical areas. We tested behavioral discrimination in two independent batches of six rats using six pairs of shapes used previously to probe shape selectivity in monkey cortex (Lehky and Sereno, 2007. The relative difficulty (error rate of shape pairs was strongly correlated between the two batches, indicating that some shape pairs were more difficult to discriminate than others. Then, we recorded in naive rats from five visual areas from primary visual cortex (V1 over areas LM, LI, LL, up to lateral occipito-temporal cortex (TO. Shape selectivity in the upper layers of V1, where the information enters cortex, correlated mostly with physical stimulus dissimilarity and not with behavioral performance. In contrast, neural discriminability in lower layers of all areas was strongly correlated with behavioral performance. These findings, in combination with the results from Vermaercke et al 2014, suggest that the functional specialization in rodent lateral visual cortex reflects a processing hierarchy resulting in the emergence of complex selectivity for behaviorally relevant stimulus differences.

  4. LSD alters eyes-closed functional connectivity within the early visual cortex in a retinotopic fashion.

    Science.gov (United States)

    Roseman, Leor; Sereno, Martin I; Leech, Robert; Kaelen, Mendel; Orban, Csaba; McGonigle, John; Feilding, Amanda; Nutt, David J; Carhart-Harris, Robin L

    2016-08-01

    The question of how spatially organized activity in the visual cortex behaves during eyes-closed, lysergic acid diethylamide (LSD)-induced "psychedelic imagery" (e.g., visions of geometric patterns and more complex phenomena) has never been empirically addressed, although it has been proposed that under psychedelics, with eyes-closed, the brain may function "as if" there is visual input when there is none. In this work, resting-state functional connectivity (RSFC) data was analyzed from 10 healthy subjects under the influence of LSD and, separately, placebo. It was suspected that eyes-closed psychedelic imagery might involve transient local retinotopic activation, of the sort typically associated with visual stimulation. To test this, it was hypothesized that, under LSD, patches of the visual cortex with congruent retinotopic representations would show greater RSFC than incongruent patches. Using a retinotopic localizer performed during a nondrug baseline condition, nonadjacent patches of V1 and V3 that represent the vertical or the horizontal meridians of the visual field were identified. Subsequently, RSFC between V1 and V3 was measured with respect to these a priori identified patches. Consistent with our prior hypothesis, the difference between RSFC of patches with congruent retinotopic specificity (horizontal-horizontal and vertical-vertical) and those with incongruent specificity (horizontal-vertical and vertical-horizontal) increased significantly under LSD relative to placebo, suggesting that activity within the visual cortex becomes more dependent on its intrinsic retinotopic organization in the drug condition. This result may indicate that under LSD, with eyes-closed, the early visual system behaves as if it were seeing spatially localized visual inputs. Hum Brain Mapp 37:3031-3040, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  5. Statistical learning of visual transitions in monkey inferotemporal cortex.

    Science.gov (United States)

    Meyer, Travis; Olson, Carl R

    2011-11-29

    One of the most fundamental functions of the brain is to predict upcoming events on the basis of the recent past. A closely related function is to signal when a prediction has been violated. The identity of the brain regions that mediate these functions is not known. We set out to determine whether they are implemented at the level of single neurons in the visual system. We gave monkeys prolonged exposure to pairs of images presented in fixed sequence so that each leading image became a strong predictor for the corresponding trailing image. We then monitored the responses of neurons in the inferotemporal cortex to image sequences that obeyed or violated the transitional rules imposed during training. Inferotemporal neurons exhibited a transitional surprise effect, responding much more strongly to unpredicted transitions than to predicted transitions. Thus, neurons even in the visual system make experience-based predictions and react when they fail.

  6. Building maps from maps in primary visual cortex.

    Science.gov (United States)

    Nauhaus, Ian; Nielsen, Kristina J

    2014-02-01

    Neurons in the visual system respond to more complex and holistic features at each new stage of processing. Often, these features are organized into continuous maps. Could there be a fundamental link between continuous maps and functional hierarchies? Here, we review recent studies regarding V1 maps providing some of the most noteworthy advances in our understanding of how and why maps exist. In particular, we focus on the common theme that some maps are inherited from the input of parallel pathways, which are then intimately linked to the emergence of new functional properties and their corresponding maps. These results on V1 maps may prove to be a unifying framework for hierarchical representations in the visual cortex. Copyright © 2013 Elsevier Ltd. All rights reserved.

  7. Systematic variation of population receptive field properties across cortical depth in human visual cortex

    NARCIS (Netherlands)

    Fracasso, Alessio; Petridou, N; Dumoulin, Serge O

    2016-01-01

    Receptive fields (RFs) in visual cortex are organized in antagonistic, center-surround, configurations. RF properties change systematically across eccentricity and between visual field maps. However, it is unknown how center-surround configurations are organized in human visual cortex across lamina.

  8. Functionally Specific Oscillatory Activity Correlates between Visual and Auditory Cortex in the Blind

    Science.gov (United States)

    Schepers, Inga M.; Hipp, Joerg F.; Schneider, Till R.; Roder, Brigitte; Engel, Andreas K.

    2012-01-01

    Many studies have shown that the visual cortex of blind humans is activated in non-visual tasks. However, the electrophysiological signals underlying this cross-modal plasticity are largely unknown. Here, we characterize the neuronal population activity in the visual and auditory cortex of congenitally blind humans and sighted controls in a…

  9. Postoperative increase in grey matter volume in visual cortex after unilateral cataract surgery

    DEFF Research Database (Denmark)

    Lou, Astrid R.; Madsen, Kristoffer Hougaard; Julian, Hanne O.

    2013-01-01

    surgery induces a regional increase in grey matter in areas V1 and V2 of the visual cortex. Results:  In all patients, cataract surgery immediately improved visual acuity, contrast sensitivity and mean sensitivity in the visual field of the operated eye. The improvement in vision was stable throughout...... the 6 weeks after operation. VBM revealed a regional expansion of grey matter volume in area V2 contralateral to the operated eye during the 6-week period after surgery. Individual increases in grey matter were predicted by the symmetry in visual acuity between the operated eye and nonoperated eye...... by restoring vision. Methods:  Twelve patients aged 50–85 years underwent structural high-resolution T1-weighted MRI of the whole brain 2 days and 6 weeks after unilateral cataract surgery. Voxel-based morphometry (VBM) based on T1-weighted magnetic resonance imaging (MRI) was employed to test whether cataract...

  10. Music and words in the visual cortex: The impact of musical expertise.

    Science.gov (United States)

    Mongelli, Valeria; Dehaene, Stanislas; Vinckier, Fabien; Peretz, Isabelle; Bartolomeo, Paolo; Cohen, Laurent

    2017-01-01

    How does the human visual system accommodate expertise for two simultaneously acquired symbolic systems? We used fMRI to compare activations induced in the visual cortex by musical notation, written words and other classes of objects, in professional musicians and in musically naïve controls. First, irrespective of expertise, selective activations for music were posterior and lateral to activations for words in the left occipitotemporal cortex. This indicates that symbols characterized by different visual features engage distinct cortical areas. Second, musical expertise increased the volume of activations for music and led to an anterolateral displacement of word-related activations. In musicians, there was also a dramatic increase of the brain-scale networks connected to the music-selective visual areas. Those findings reveal that acquiring a double visual expertise involves an expansion of category-selective areas, the development of novel long-distance functional connectivity, and possibly some competition between categories for the colonization of cortical space. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Disparity-tuned population responses from human visual cortex.

    Science.gov (United States)

    Cottereau, Benoit R; McKee, Suzanne P; Ales, Justin M; Norcia, Anthony M

    2011-01-19

    We used source imaging of visual evoked potentials to measure neural population responses over a wide range of horizontal disparities (0.5-64 arcmin). The stimulus was a central disk that moved back and forth across the fixation plane at 2 Hz, surrounded either by binocularly uncorrelated dots (disparity noise) or by correlated dots presented in the fixation plane. Both disk and surround were composed of dynamic random dots to remove coherent monocular information. Disparity tuning was measured in five visual regions of interest (ROIs) [V1, human middle temporal area (hMT+), V4, lateral occipital complex (LOC), and V3A], defined in separate functional magnetic resonance imaging scans. The disparity tuning functions peaked between 2 and 16 arcmin for both types of surround in each ROI. Disparity tuning in the V1 ROI was unaffected by the type of surround, but surround correlation altered both the amplitude and phase of the disparity responses in the other ROIs. Response amplitude increased when the disk was in front of the surround in the V3A and LOC ROIs, indicating that these areas encode figure-ground relationships and object convexity. The correlated surround produced a consistent phase lag at the second harmonic in the hMT+ and V4 ROIs without a change in amplitude, while in the V3A ROI, both phase and amplitude effects were observed. Sensitivity to disparity context is thus widespread in visual cortex, but the dynamics of these contextual interactions differ across regions.

  12. Aversive learning shapes neuronal orientation tuning in human visual cortex.

    Science.gov (United States)

    McTeague, Lisa M; Gruss, L Forest; Keil, Andreas

    2015-07-28

    The responses of sensory cortical neurons are shaped by experience. As a result perceptual biases evolve, selectively facilitating the detection and identification of sensory events that are relevant for adaptive behaviour. Here we examine the involvement of human visual cortex in the formation of learned perceptual biases. We use classical aversive conditioning to associate one out of a series of oriented gratings with a noxious sound stimulus. After as few as two grating-sound pairings, visual cortical responses to the sound-paired grating show selective amplification. Furthermore, as learning progresses, responses to the orientations with greatest similarity to the sound-paired grating are increasingly suppressed, suggesting inhibitory interactions between orientation-selective neuronal populations. Changes in cortical connectivity between occipital and fronto-temporal regions mirror the changes in visuo-cortical response amplitudes. These findings suggest that short-term behaviourally driven retuning of human visual cortical neurons involves distal top-down projections as well as local inhibitory interactions.

  13. Reactivation of ocular dominance plasticity in the adult visual cortex.

    Science.gov (United States)

    Pizzorusso, Tommaso; Medini, Paolo; Berardi, Nicoletta; Chierzi, Sabrina; Fawcett, James W; Maffei, Lamberto

    2002-11-08

    In young animals, monocular deprivation leads to an ocular dominance shift, whereas in adults after the critical period there is no such shift. Chondroitin sulphate proteoglycans (CSPGs) are components of the extracellular matrix (ECM) inhibitory for axonal sprouting. We tested whether the developmental maturation of the ECM is inhibitory for experience-dependent plasticity in the visual cortex. The organization of CSPGs into perineuronal nets coincided with the end of the critical period and was delayed by dark rearing. After CSPG degradation with chondroitinase-ABC in adult rats, monocular deprivation caused an ocular dominance shift toward the nondeprived eye. The mature ECM is thus inhibitory for experience-dependent plasticity, and degradation of CSPGs reactivates cortical plasticity.

  14. Fluctuations of extracellular glucose and lactate in the mouse primary visual cortex during visual stimulation.

    Science.gov (United States)

    Béland-Millar, Alexandria; Messier, Claude

    2018-02-16

    We measured the extracellular glucose and lactate in the primary visual cortex in the CD-1 mouse using electrochemical electrodes. To gain some additional information on brain metabolism, we examined the impact of systemic injections of lactate and fructose on the brain extracellular glucose and lactate changes observed during visual stimulation. We found that simple stimulation using a flashlight produced a decrease in visual cortex extracellular glucose and an increase in extracellular lactate. Similar results were observed following visual stimulation with an animated movie without soundtrack or the presentation of a novel object. Specificity of these observations was confirmed by the absence of extracellular glucose and lactate changes when the mice were presented a second time with the same object. Previous experiments have shown that systemic injections of fructose and lactate lead to an increase in blood lactate but no change in blood glucose while they both increase brain extracellular glucose but they do not increase brain extracellular lactate. When mice were visually stimulated after they had received these injections, we found that lactate, and to a slightly lesser degree fructose, both reduced the amplitude of the changes in extracellular glucose and lactate that accompanied visual stimulation. Thus, neural activation leads to an increase in extracellular lactate and a decrease in extracellular glucose. Novelty, attentional resources and availability of metabolic fuels modulate these fluctuations. The observations are consistent with a modified view of brain metabolism that takes into account the blood and brain glucose availability. Copyright © 2018. Published by Elsevier B.V.

  15. Anisotropy of ongoing neural activity in the primate visual cortex

    Directory of Open Access Journals (Sweden)

    Maier A

    2014-09-01

    Full Text Available Alexander Maier,1 Michele A Cox,1 Kacie Dougherty,1 Brandon Moore,1 David A Leopold2 1Department of Psychology, College of Arts and Science, Vanderbilt University, Nashville, TN, USA; 2Section on Cognitive Neurophysiology and Imaging, National Institute of Mental Health, National Institute of Health, Bethesda, MD, USA Abstract: The mammalian neocortex features distinct anatomical variation in its tangential and radial extents. This review consolidates previously published findings from our group in order to compare and contrast the spatial profile of neural activity coherence across these distinct cortical dimensions. We focus on studies of ongoing local field potential (LFP data obtained simultaneously from multiple sites in the primary visual cortex in two types of experiments in which electrode contacts were spaced either along the cortical surface or at different laminar positions. These studies demonstrate that across both dimensions the coherence of ongoing LFP fluctuations diminishes as a function of interelectrode distance, although the nature and spatial scale of this falloff is very different. Along the cortical surface, the overall LFP coherence declines gradually and continuously away from a given position. In contrast, across the cortical layers, LFP coherence is discontinuous and compartmentalized as a function of depth. Specifically, regions of high LFP coherence fall into discrete superficial and deep laminar zones, with an abrupt discontinuity between the granular and infragranular layers. This spatial pattern of ongoing LFP coherence is similar when animals are at rest and when they are engaged in a behavioral task. These results point to the existence of partially segregated laminar zones of cortical processing that extend tangentially within the laminar compartments and are thus oriented orthogonal to the cortical columns. We interpret these electrophysiological observations in light of the known anatomical organization of

  16. TMS of the occipital cortex induces tactile sensations in the fingers of blind Braille readers.

    Science.gov (United States)

    Ptito, M; Fumal, A; de Noordhout, A Martens; Schoenen, J; Gjedde, A; Kupers, R

    2008-01-01

    Various non-visual inputs produce cross-modal responses in the visual cortex of early blind subjects. In order to determine the qualitative experience associated with these occipital activations, we systematically stimulated the entire occipital cortex using single pulse transcranial magnetic stimulation (TMS) in early blind subjects and in blindfolded seeing controls. Whereas blindfolded seeing controls reported only phosphenes following occipital cortex stimulation, some of the blind subjects reported tactile sensations in the fingers that were somatotopically organized onto the visual cortex. The number of cortical sites inducing tactile sensations appeared to be related to the number of hours of Braille reading per day, Braille reading speed and dexterity. These data, taken in conjunction with previous anatomical, behavioural and functional imaging results, suggest the presence of a polysynaptic cortical pathway between the somatosensory cortex and the visual cortex in early blind subjects. These results also add new evidence that the activity of the occipital lobe in the blind takes its qualitative expression from the character of its new input source, therefore supporting the cortical deference hypothesis.

  17. Visual cortex and auditory cortex activation in early binocularly blind macaques: A BOLD-fMRI study using auditory stimuli.

    Science.gov (United States)

    Wang, Rong; Wu, Lingjie; Tang, Zuohua; Sun, Xinghuai; Feng, Xiaoyuan; Tang, Weijun; Qian, Wen; Wang, Jie; Jin, Lixin; Zhong, Yufeng; Xiao, Zebin

    2017-04-15

    Cross-modal plasticity within the visual and auditory cortices of early binocularly blind macaques is not well studied. In this study, four healthy neonatal macaques were assigned to group A (control group) or group B (binocularly blind group). Sixteen months later, blood oxygenation level-dependent functional imaging (BOLD-fMRI) was conducted to examine the activation in the visual and auditory cortices of each macaque while being tested using pure tones as auditory stimuli. The changes in the BOLD response in the visual and auditory cortices of all macaques were compared with immunofluorescence staining findings. Compared with group A, greater BOLD activity was observed in the bilateral visual cortices of group B, and this effect was particularly obvious in the right visual cortex. In addition, more activated volumes were found in the bilateral auditory cortices of group B than of group A, especially in the right auditory cortex. These findings were consistent with the fact that there were more c-Fos-positive cells in the bilateral visual and auditory cortices of group B compared with group A (p visual cortices of binocularly blind macaques can be reorganized to process auditory stimuli after visual deprivation, and this effect is more obvious in the right than the left visual cortex. These results indicate the establishment of cross-modal plasticity within the visual and auditory cortices. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  18. The primary visual cortex in the neural circuit for visual orienting

    Science.gov (United States)

    Zhaoping, Li

    The primary visual cortex (V1) is traditionally viewed as remote from influencing brain's motor outputs. However, V1 provides the most abundant cortical inputs directly to the sensory layers of superior colliculus (SC), a midbrain structure to command visual orienting such as shifting gaze and turning heads. I will show physiological, anatomical, and behavioral data suggesting that V1 transforms visual input into a saliency map to guide a class of visual orienting that is reflexive or involuntary. In particular, V1 receives a retinotopic map of visual features, such as orientation, color, and motion direction of local visual inputs; local interactions between V1 neurons perform a local-to-global computation to arrive at a saliency map that highlights conspicuous visual locations by higher V1 responses. The conspicuous location are usually, but not always, where visual input statistics changes. The population V1 outputs to SC, which is also retinotopic, enables SC to locate, by lateral inhibition between SC neurons, the most salient location as the saccadic target. Experimental tests of this hypothesis will be shown. Variations of the neural circuit for visual orienting across animal species, with more or less V1 involvement, will be discussed. Supported by the Gatsby Charitable Foundation.

  19. Direct tactile stimulation of dorsal occipito-temporal cortex in a visual agnosic

    OpenAIRE

    Allen, Harriet A.; Humphreys, Glyn W.

    2009-01-01

    The human occipito-temporal cortex is preferentially activated by images of objects as opposed to scrambled images [1]. Touching objects (versus textures) also activates this region [2–10]. We used neuropsychological fMRI to probe whether dorsal regions of the lateral occipital cortex (LO) are activated in tactile recognition without mediation through visual recognition. We tested a patient (HJA) with visual agnosia due to bilateral lesions of the ventral occipito-temporal cortex but spared d...

  20. Primary visual cortex activity along the apparent-motion trace reflects illusory perception.

    Directory of Open Access Journals (Sweden)

    Lars Muckli

    2005-08-01

    Full Text Available The illusion of apparent motion can be induced when visual stimuli are successively presented at different locations. It has been shown in previous studies that motion-sensitive regions in extrastriate cortex are relevant for the processing of apparent motion, but it is unclear whether primary visual cortex (V1 is also involved in the representation of the illusory motion path. We investigated, in human subjects, apparent-motion-related activity in patches of V1 representing locations along the path of illusory stimulus motion using functional magnetic resonance imaging. Here we show that apparent motion caused a blood-oxygenation-level-dependent response along the V1 representations of the apparent-motion path, including regions that were not directly activated by the apparent-motion-inducing stimuli. This response was unaltered when participants had to perform an attention-demanding task that diverted their attention away from the stimulus. With a bistable motion quartet, we confirmed that the activity was related to the conscious perception of movement. Our data suggest that V1 is part of the network that represents the illusory path of apparent motion. The activation in V1 can be explained either by lateral interactions within V1 or by feedback mechanisms from higher visual areas, especially the motion-sensitive human MT/V5 complex.

  1. Transcranial magnetic stimulation of visual cortex in memory: cortical state, interference and reactivation of visual content in memory.

    Science.gov (United States)

    van de Ven, Vincent; Sack, Alexander T

    2013-01-01

    Memory for perceptual events includes the neural representation of the sensory information at short or longer time scales. Recent transcranial magnetic stimulation (TMS) studies of human visual cortex provided evidence that sensory cortex contributes to memory functions. In this review, we provide an exhaustive overview of these studies and ascertain how well the available evidence supports the idea of a causal role of sensory cortex in memory retention and retrieval. We discuss the validity and implications of the studies using a number of methodological and theoretical criteria that are relevant for brain stimulation of visual cortex. While most studies applied TMS to visual cortex to interfere with memory functions, a handful of pioneering studies used TMS to 'reactivate' memories in visual cortex. Interestingly, similar effects of TMS on memory were found in different memory tasks, which suggests that different memory systems share a neural mechanism of memory in visual cortex. At the same time, this neural mechanism likely interacts with higher order brain areas. Based on this overview and evaluation, we provide a first attempt to an integrative framework that describes how sensory processes contribute to memory in visual cortex, and how higher order areas contribute to this mechanism. Copyright © 2012 Elsevier B.V. All rights reserved.

  2. Functional MRI of the visual cortex and visual testing in patients with previous optic neuritis

    DEFF Research Database (Denmark)

    Langkilde, Annika Reynberg; Frederiksen, J.L.; Rostrup, Egill

    2002-01-01

    The volume of cortical activation as detected by functional magnetic resonance imaging (fMRI) in the visual cortex has previously been shown to be reduced following optic neuritis (ON). In order to understand the cause of this change, we studied the cortical activation, both the size of the activ......The volume of cortical activation as detected by functional magnetic resonance imaging (fMRI) in the visual cortex has previously been shown to be reduced following optic neuritis (ON). In order to understand the cause of this change, we studied the cortical activation, both the size...... of the activated area and the signal change following ON, and compared the results with results of neuroophthalmological testing. We studied nine patients with previous acute ON and 10 healthy persons served as controls using fMRI with visual stimulation. In addition to a reduced activated volume, patients showed...... to both the results of the contrast sensitivity test and to the Snellen visual acuity. Our results indicate that fMRI is a useful method for the study of ON, even in cases where the visual acuity is severely impaired. The reduction in activated volume could be explained as a reduced neuronal input...

  3. Functional MRI of the visual cortex and visual testing in patients with previous optic neuritis

    DEFF Research Database (Denmark)

    Langkilde, Annika Reynberg; Frederiksen, J.L.; Rostrup, Egill

    2002-01-01

    of the activated area and the signal change following ON, and compared the results with results of neuroophthalmological testing. We studied nine patients with previous acute ON and 10 healthy persons served as controls using fMRI with visual stimulation. In addition to a reduced activated volume, patients showed...... to both the results of the contrast sensitivity test and to the Snellen visual acuity. Our results indicate that fMRI is a useful method for the study of ON, even in cases where the visual acuity is severely impaired. The reduction in activated volume could be explained as a reduced neuronal input......The volume of cortical activation as detected by functional magnetic resonance imaging (fMRI) in the visual cortex has previously been shown to be reduced following optic neuritis (ON). In order to understand the cause of this change, we studied the cortical activation, both the size...

  4. Functional implications of orientation maps in primary visual cortex

    Science.gov (United States)

    Koch, Erin; Jin, Jianzhong; Alonso, Jose M.; Zaidi, Qasim

    2016-11-01

    Stimulus orientation in the primary visual cortex of primates and carnivores is mapped as iso-orientation domains radiating from pinwheel centres, where orientation preferences of neighbouring cells change circularly. Whether this orientation map has a function is currently debated, because many mammals, such as rodents, do not have such maps. Here we show that two fundamental properties of visual cortical responses, contrast saturation and cross-orientation suppression, are stronger within cat iso-orientation domains than at pinwheel centres. These differences develop when excitation (not normalization) from neighbouring oriented neurons is applied to different cortical orientation domains and then balanced by inhibition from un-oriented neurons. The functions of the pinwheel mosaic emerge from these local intra-cortical computations: Narrower tuning, greater cross-orientation suppression and higher contrast gain of iso-orientation cells facilitate extraction of object contours from images, whereas broader tuning, greater linearity and less suppression of pinwheel cells generate selectivity for surface patterns and textures.

  5. Anodal transcranial direct current stimulation reduces psychophysically measured surround suppression in the human visual cortex.

    Directory of Open Access Journals (Sweden)

    Daniel P Spiegel

    Full Text Available Transcranial direct current stimulation (tDCS is a safe, non-invasive technique for transiently modulating the balance of excitation and inhibition within the human brain. It has been reported that anodal tDCS can reduce both GABA mediated inhibition and GABA concentration within the human motor cortex. As GABA mediated inhibition is thought to be a key modulator of plasticity within the adult brain, these findings have broad implications for the future use of tDCS. It is important, therefore, to establish whether tDCS can exert similar effects within non-motor brain areas. The aim of this study was to assess whether anodal tDCS could reduce inhibitory interactions within the human visual cortex. Psychophysical measures of surround suppression were used as an index of inhibition within V1. Overlay suppression, which is thought to originate within the lateral geniculate nucleus (LGN, was also measured as a control. Anodal stimulation of the occipital poles significantly reduced psychophysical surround suppression, but had no effect on overlay suppression. This effect was specific to anodal stimulation as cathodal stimulation had no effect on either measure. These psychophysical results provide the first evidence for tDCS-induced reductions of intracortical inhibition within the human visual cortex.

  6. Fluctuation scaling in the visual cortex at threshold

    Science.gov (United States)

    Medina, José M.; Díaz, José A.

    2016-05-01

    Fluctuation scaling relates trial-to-trial variability to the average response by a power function in many physical processes. Here we address whether fluctuation scaling holds in sensory psychophysics and its functional role in visual processing. We report experimental evidence of fluctuation scaling in human color vision and form perception at threshold. Subjects detected thresholds in a psychophysical masking experiment that is considered a standard reference for studying suppression between neurons in the visual cortex. For all subjects, the analysis of threshold variability that results from the masking task indicates that fluctuation scaling is a global property that modulates detection thresholds with a scaling exponent that departs from 2, β =2.48 ±0.07 . We also examine a generalized version of fluctuation scaling between the sample kurtosis K and the sample skewness S of threshold distributions. We find that K and S are related and follow a unique quadratic form K =(1.19 ±0.04 ) S2+(2.68 ±0.06 ) that departs from the expected 4/3 power function regime. A random multiplicative process with weak additive noise is proposed based on a Langevin-type equation. The multiplicative process provides a unifying description of fluctuation scaling and the quadratic S -K relation and is related to on-off intermittency in sensory perception. Our findings provide an insight into how the human visual system interacts with the external environment. The theoretical methods open perspectives for investigating fluctuation scaling and intermittency effects in a wide variety of natural, economic, and cognitive phenomena.

  7. Layer-specific endocannabinoid-mediated long-term depression of GABAergic neurotransmission onto principal neurons in mouse visual cortex.

    Science.gov (United States)

    Sun, Wenjuan; Wang, Laijian; Li, Shuo; Tie, Xiaoxiu; Jiang, Bin

    2015-08-01

    Visually induced endocannabinoid-mediated long-term depression of GABAergic neurotransmission (iLTD) mediates the maturation of GABAergic release in layer 2/3 of visual cortex. Here we examined whether the maturation of GABAergic transmission in other layers of visual cortex also requires endocannabinoids. The developmental plasticity of GABAergic neurotransmission onto the principal neurons in different layers of mouse visual cortex was examined in cortical slices by whole-cell recordings of inhibitory postsynaptic currents evoked by presynaptic inhibitory inputs. Theta burst stimulation of GABAergic inputs induced an endocannabinoid-mediated long-term depression of GABAergic neurotransmission onto pyramidal cells in layer 2/3 from postnatal day (P)10 to 30 and in layer 5 from P10 to 40, whereas that of GABAergic inputs did not induce iLTD onto star pyramidal neurons in layer 4 at any time postnatally, indicating that this plasticity is laminar-specific. The developmental loss of iLTD paralleled the maturation of GABAergic inhibition in both layer 2/3 and layer 5. Visual deprivation delayed the developmental loss of iLTD in layers 3 and 5 during a critical period, while 2 days of light exposure eliminated iLTD in both layers. Furthermore, the GABAergic synapses in layers 2/3 and 5 did not normally mature in the type 1 cannabinoid receptor knock-out mice, whereas those in layer 4 did not require endocannabinoid receptor for maturation. These results suggest that visually induced endocannabinoid-dependent iLTD mediates the maturation of GABAergic release in extragranular layer rather than in granular layer of mouse visual cortex. © 2015 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

  8. Functional organization and visual representations in human ventral lateral prefrontal cortex

    Directory of Open Access Journals (Sweden)

    Annie Wai Yiu Chan

    2013-07-01

    Full Text Available Recent neuroimaging studies in both human and non-human primates have identified face selective activation in the ventral lateral prefrontal cortex even in the absence of working memory demands. Further, research has suggested that this face-selective response is largely driven by the presence of the eyes. However, the nature and origin of visual category responses in the ventral lateral prefrontal cortex remain unclear. Further, in a broader sense, how do these findings relate to our current understandings of lateral prefrontal cortex? What do these findings tell us about the underlying function and organization principles of the ventral lateral prefrontal cortex? What is the future direction for investigating visual representations in this cortex? This review focuses on the function, topography, and circuitry of the ventral lateral prefrontal cortex to enhance our understanding of the evolution and development of this cortex.

  9. Representation of visual scenes by local neuronal populations in layer 2/3 of mouse visual cortex

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    Bjorn M Kampa

    2011-12-01

    Full Text Available How are visual scenes encoded in local neural networks of visual cortex? In rodents, visual cortex lacks a columnar organization so that processing of diverse features from a spot in visual space could be performed locally by populations of neighboring neurons. To examine how complex visual scenes are represented by local microcircuits in mouse visual cortex we measured visually-evoked responses of layer 2/3 neuronal populations using 3D two-photon calcium imaging. Both natural and artificial movie scenes (10-s duration evoked distributed and sparsely organized responses in local populations of 70 to 150 neurons within the sampled volumes. About 50% of neurons showed calcium transients during visual scene presentation, of which about half displayed reliable temporal activation patterns. The majority of the reliably responding neurons were activated primarily by one of the four visual scenes applied. Consequently, single neurons performed poorly in decoding, which visual scene had been presented. In contrast, high levels of decoding performance (>80% were reached when considering population responses, requiring about 80 randomly picked cells or 20 reliable responders. Furthermore, reliable responding neurons tended to have neighbors sharing the same stimulus preference. Because of this local redundancy, it was beneficial for efficient scene decoding to read out activity from spatially distributed rather than locally clustered neurons. Our results suggest a population code in layer 2/3 of visual cortex, where the visual environment is dynamically represented in the activation of distinct functional sub-networks.

  10. Top-down modulation in human visual cortex predicts the stability of a perceptual illusion

    Science.gov (United States)

    Meindertsma, Thomas; Hillebrand, Arjan; van Dijk, Bob W.; Lamme, Victor A. F.; Donner, Tobias H.

    2014-01-01

    Conscious perception sometimes fluctuates strongly, even when the sensory input is constant. For example, in motion-induced blindness (MIB), a salient visual target surrounded by a moving pattern suddenly disappears from perception, only to reappear after some variable time. Whereas such changes of perception result from fluctuations of neural activity, mounting evidence suggests that the perceptual changes, in turn, may also cause modulations of activity in several brain areas, including visual cortex. In this study, we asked whether these latter modulations might affect the subsequent dynamics of perception. We used magnetoencephalography (MEG) to measure modulations in cortical population activity during MIB. We observed a transient, retinotopically widespread modulation of beta (12–30 Hz)-frequency power over visual cortex that was closely linked to the time of subjects' behavioral report of the target disappearance. This beta modulation was a top-down signal, decoupled from both the physical stimulus properties and the motor response but contingent on the behavioral relevance of the perceptual change. Critically, the modulation amplitude predicted the duration of the subsequent target disappearance. We propose that the transformation of the perceptual change into a report triggers a top-down mechanism that stabilizes the newly selected perceptual interpretation. PMID:25411458

  11. Spatial organization of astrocytes in ferret visual cortex

    Science.gov (United States)

    López‐Hidalgo, Mónica; Hoover, Walter B.

    2016-01-01

    ABSTRACT Astrocytes form an intricate partnership with neural circuits to influence numerous cellular and synaptic processes. One prominent organizational feature of astrocytes is the “tiling” of the brain with non‐overlapping territories. There are some documented species and brain region–specific astrocyte specializations, but the extent of astrocyte diversity and circuit specificity are still unknown. We quantitatively defined the rules that govern the spatial arrangement of astrocyte somata and territory overlap in ferret visual cortex using a combination of in vivo two‐photon imaging, morphological reconstruction, immunostaining, and model simulations. We found that ferret astrocytes share, on average, half of their territory with other astrocytes. However, a specific class of astrocytes, abundant in thalamo‐recipient cortical layers (“kissing” astrocytes), overlap markedly less. Together, these results demonstrate novel features of astrocyte organization indicating that different classes of astrocytes are arranged in a circuit‐specific manner and that tiling does not apply universally across brain regions and species. J. Comp. Neurol. 524:3561–3576, 2016. © 2016 The Authors The Journal of Comparative Neurology Published by Wiley Periodicals, Inc. PMID:27072916

  12. Spatiotemporal specificity of contrast adaptation in mouse primary visual cortex

    Directory of Open Access Journals (Sweden)

    Emily Elizabeth LeDue

    2013-10-01

    Full Text Available Prolonged viewing of high contrast gratings alters perceived stimulus contrast, and produces characteristic changes in the contrast response functions of neurons in the primary visual cortex (V1. This is referred to as contrast adaptation. Although contrast adaptation has been well studied, its underlying neural mechanisms are not well understood. Therefore, we investigated contrast adaptation in mouse V1 with the goal of establishing a quantitative description of this phenomenon in a genetically manipulable animal model. One interesting aspect of contrast adaptation that has been observed both perceptually and in single unit studies is its specificity for the spatial and temporal characteristics of the stimulus. Therefore in the present work we determined if the magnitude of contrast adaptation in mouse V1 neurons was dependent on the spatial frequency and temporal frequency of the adapting grating. We used protocols that were readily comparable with previous studies in cats and primates, and also a novel contrast ramp stimulus that characterized the spatial and temporal specificity of contrast adaptation simultaneously. Similar to previous work in higher mammals, we found that contrast adaptation was strongest when the spatial frequency and temporal frequency of the adapting grating matched the test stimulus. This suggests similar mechanisms underlying contrast adaptation across animal models and indicates that the rapidly advancing genetic tools available in mice could be used to provide insights into this phenomenon.

  13. Information tuning of populations of neurons in primary visual cortex.

    Science.gov (United States)

    Kang, Kukjin; Shapley, Robert M; Sompolinsky, Haim

    2004-04-14

    Neurons in macaque primary visual cortex (V1) show a diversity of orientation tuning properties, exhibiting a broad distribution of tuning width, baseline activity, peak response, and circular variance (CV). Here, we studied how the different tuning features affect the performance of these cells in discriminating between stimuli with different orientations. Previous studies of the orientation discrimination power of neurons in V1 focused on resolving two nearby orientations close to the psychophysical threshold of orientation discrimination. Here, we developed a theoretical framework, the information tuning curve, that measures the discrimination power of cells as a function of the orientation difference, deltatheta, of the two stimuli. This tuning curve also represents the mutual information between the neuronal responses and the stimulus orientation. We studied theoretically the dependence of the information tuning curve on the orientation tuning width, baseline, and peak responses. Of main interest is the finding that narrow orientation tuning is not necessarily optimal for all angular discrimination tasks. Instead, the optimal tuning width depends linearly on deltatheta. We applied our theory to study the discrimination performance of a population of 490 neurons in macaque V1. We found that a significant fraction of the neuronal population exhibits favorable tuning properties for large deltatheta. We also studied how the discrimination capability of neurons is distributed and compared several other measures of the orientation tuning such as CV with Chernoff distances for normalized tuning curves.

  14. Top-down modulation of lateral interactions in visual cortex.

    Science.gov (United States)

    Ramalingam, Nirmala; McManus, Justin N J; Li, Wu; Gilbert, Charles D

    2013-01-30

    The primary visual cortex (V1) changes its computation according to the perceptual task being performed. We propose that this cognitive modulation results from gating of V1 intrinsic connections. To test this idea, using behavioral paradigms that engage top-down modulation of V1 contextual interactions, we recorded from chronically implanted electrode arrays in macaques. We observed task-dependent changes in interactions between V1 sites measured both by correlation between spike trains and by coherence between local field potentials (LFP-LFP coherence). The direction of the changes in aggregate activity, as measured by LFPs, depended on perceptual strategy: perceptual grouping increased LFP coherence between sites crucial for the task, whereas perceptual segregation lowered the LFP coherence. Using spiking activity as a measure, we found that the behaviorally driven changes in correlation structure between neurons dramatically increased the stimulus-related information that they convey; this additional increase in encoded information at the level of neuronal ensembles equals that obtained from task-driven reconfigurations of neural tuning curves. The improvements in information encoding were strongest for stimuli with greatest discrimination difficulty.

  15. Age-dependent cortical thinning of peripheral visual field representations in primary visual cortex

    Directory of Open Access Journals (Sweden)

    Joseph Caleb Griffis

    2016-10-01

    Full Text Available The cerebral cortex changes throughout the lifespan, and the cortical grey matter in many brain regions becomes thinner with advancing age. Effects of aging on cortical thickness have been observed in many brain regions, including areas involved in basic perceptual functions such as processing visual inputs. An important property of early visual cortices is their topographic organization – the cortical structure of early visual areas forms a topographic map of retinal inputs. Primary visual cortex (V1 is considered to be the most basic cortical area in the visual processing hierarchy, and is topographically organized from posterior (central visual representation to anterior (peripheral visual representation along the calcarine sulcus. Some studies have reported strong age-dependent cortical thinning in portions of V1 that likely correspond to peripheral visual representations, while there is less evidence of substantial cortical thinning in central V1. However, the effect of aging on cortical thickness in V1 as a function of its topography has not been directly investigated. To address this gap in the literature, we estimated the cortical thickness of different eccentricity sectors in V1 using T1-weighted MRI scans acquired from groups of healthy younger and older adults, and then assessed whether between-group differences in V1 cortical thickness depended on cortical eccentricity. These analyses revealed age-dependent cortical thinning specific to peripheral visual field representations in anterior portions of V1, but did not provide evidence for age-dependent cortical thinning in other portions of V1. Additional analyses found similar effects when analyses were restricted to the gyral crown, sulcul depth, and sulcul wall, indicating that these effects are not likely due to differences in gyral/sulcul contributions to our regions of interest. Importantly, this finding indicates that age-dependent changes in cortical structure may differ among

  16. Detailed illustration of the visual field representation along the visual pathway to the primary visual cortex: a graphical summary.

    Science.gov (United States)

    Wärntges, Simone; Michelson, Georg

    2014-01-01

    In the literature, different graphic illustrations are available, which depict different parts of the visual pathway in relation to visual field sectors, to retinal sectors, the layers of the lateral geniculate nucleus (LGN), or sections of the primary visual cortex (V1). However, a complete overview is missing, which may be useful for a more precise differentiation of predominantly ophthalmological from intracerebral diseases. It may also be of interest to investigate additional intracerebral reasons that are involved in impaired vision of largely unknown pathophysiology. This work combines the scientific knowledge of partial graphics in one detailed illustration that allows exact follow-up of the neuronal connections from individual visual field sectors to the V1 areas. A selective search for peer-reviewed graphics of the visual pathway was performed in PubMed and Google Pictures. Sixteen different visual field sectors and their 16 corresponding retinal sectors were set in relation to 64 LGN sections and 20 areas of V1. Segmented cross-sectional areas of the optic nerve supplemented the graphical representation of the fiber orientation in relation to the visual field. The detailed illustration of the visual field projection along the visual pathway structures may facilitate a more precise calculation of correlations between morphological and functional measurements of ophthalmological and neuroradiological examinations. © 2013 S. Karger AG, Basel.

  17. Visual Prediction Error Spreads Across Object Features in Human Visual Cortex.

    Science.gov (United States)

    Jiang, Jiefeng; Summerfield, Christopher; Egner, Tobias

    2016-12-14

    Visual cognition is thought to rely heavily on contextual expectations. Accordingly, previous studies have revealed distinct neural signatures for expected versus unexpected stimuli in visual cortex. However, it is presently unknown how the brain combines multiple concurrent stimulus expectations such as those we have for different features of a familiar object. To understand how an unexpected object feature affects the simultaneous processing of other expected feature(s), we combined human fMRI with a task that independently manipulated expectations for color and motion features of moving-dot stimuli. Behavioral data and neural signals from visual cortex were then interrogated to adjudicate between three possible ways in which prediction error (surprise) in the processing of one feature might affect the concurrent processing of another, expected feature: (1) feature processing may be independent; (2) surprise might "spread" from the unexpected to the expected feature, rendering the entire object unexpected; or (3) pairing a surprising feature with an expected feature might promote the inference that the two features are not in fact part of the same object. To formalize these rival hypotheses, we implemented them in a simple computational model of multifeature expectations. Across a range of analyses, behavior and visual neural signals consistently supported a model that assumes a mixing of prediction error signals across features: surprise in one object feature spreads to its other feature(s), thus rendering the entire object unexpected. These results reveal neurocomputational principles of multifeature expectations and indicate that objects are the unit of selection for predictive vision. We address a key question in predictive visual cognition: how does the brain combine multiple concurrent expectations for different features of a single object such as its color and motion trajectory? By combining a behavioral protocol that independently varies expectation of

  18. A mouse model of visual perceptual learning reveals alterations in neuronal coding and dendritic spine density in the visual cortex

    Directory of Open Access Journals (Sweden)

    Yan eWang

    2016-03-01

    Full Text Available Visual perceptual learning (VPL can improve spatial vision in normally sighted and visually impaired individuals. Although previous studies of humans and large animals have explored the neural basis of VPL, elucidation of the underlying cellular and molecular mechanisms remains a challenge. Owing to the advantages of molecular genetic and optogenetic manipulations, the mouse is a promising model for providing a mechanistic understanding of VPL. Here, we thoroughly evaluated the effects and properties of VPL on spatial vision in C57BL/6J mice using a two-alternative, forced-choice visual water task. Briefly, the mice underwent prolonged training at near the individual threshold of contrast or spatial frequency (SF for pattern discrimination or visual detection for 35 consecutive days. Following training, the contrast-threshold trained mice showed an 87% improvement in contrast sensitivity (CS and a 55% gain in visual acuity (VA. Similarly, the SF-threshold trained mice exhibited comparable and long-lasting improvements in VA and significant gains in CS over a wide range of SFs. Furthermore, learning largely transferred across eyes and stimulus orientations. Interestingly, learning could transfer from a pattern discrimination task to a visual detection task, but not vice versa. We validated that this VPL fully restored VA in adult amblyopic mice and old mice. Taken together, these data indicate that mice, as a species, exhibit reliable VPL. Intrinsic signal optical imaging revealed that mice with perceptual training had higher cut-off SFs in primary visual cortex (V1 than those without perceptual training. Moreover, perceptual training induced an increase in the dendritic spine density in layer 2/3 pyramidal neurons of V1. These results indicated functional and structural alterations in V1 during VPL. Overall, our VPL mouse model will provide a platform for investigating the neurobiological basis of VPL.

  19. Visual cortex in aging and Alzheimer’s disease: Changes in visual field maps and population receptive fields

    Directory of Open Access Journals (Sweden)

    Alyssa A. Brewer

    2014-02-01

    Full Text Available Although several studies have suggested that cortical alterations underlie such age-related visual deficits as decreased acuity, little is known about what changes actually occur in visual cortex during healthy aging. Two recent studies showed changes in primary visual cortex (V1 during normal aging; however, no studies have characterized the effects of aging on visual cortex beyond V1, important measurements both for understanding the aging process and for comparison to changes in age-related diseases. Similarly, there is almost no information about changes in visual cortex in Alzheimer’s disease (AD, the most common form of dementia. Because visual deficits are often reported as one of the first symptoms of AD, measurements of such changes in the visual cortex of AD patients might improve our understanding of how the visual system is affected by neurodegeneration as well as aid early detection, accurate diagnosis and timely treatment of AD. Here we use fMRI to first compare the visual field map (VFM organization and population receptive fields (pRFs between young adults and healthy aging subjects for occipital VFMs V1, V2, V3, and hV4. Healthy aging subjects do not show major VFM organizational deficits, but do have reduced surface area and increased pRF sizes in the foveal representations of V1, V2, and hV4 relative to healthy young control subjects. These measurements are consistent with behavioral deficits seen in healthy aging. We then demonstrate the feasibility and first characterization of these measurements in two patients with mild AD, which reveal potential changes in visual cortex as part of the pathophysiology of AD. Our data aid in our understanding of the changes in the visual processing pathways in normal aging and provide the foundation for future research into earlier and more definitive detection of AD.

  20. Computational Model of Primary Visual Cortex Combining Visual Attention for Action Recognition.

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    Na Shu

    Full Text Available Humans can easily understand other people's actions through visual systems, while computers cannot. Therefore, a new bio-inspired computational model is proposed in this paper aiming for automatic action recognition. The model focuses on dynamic properties of neurons and neural networks in the primary visual cortex (V1, and simulates the procedure of information processing in V1, which consists of visual perception, visual attention and representation of human action. In our model, a family of the three-dimensional spatial-temporal correlative Gabor filters is used to model the dynamic properties of the classical receptive field of V1 simple cell tuned to different speeds and orientations in time for detection of spatiotemporal information from video sequences. Based on the inhibitory effect of stimuli outside the classical receptive field caused by lateral connections of spiking neuron networks in V1, we propose surround suppressive operator to further process spatiotemporal information. Visual attention model based on perceptual grouping is integrated into our model to filter and group different regions. Moreover, in order to represent the human action, we consider the characteristic of the neural code: mean motion map based on analysis of spike trains generated by spiking neurons. The experimental evaluation on some publicly available action datasets and comparison with the state-of-the-art approaches demonstrate the superior performance of the proposed model.

  1. Temporal sequence of visuo-auditory interaction in multiple areas of the guinea pig visual cortex.

    Directory of Open Access Journals (Sweden)

    Masataka Nishimura

    Full Text Available Recent studies in humans and monkeys have reported that acoustic stimulation influences visual responses in the primary visual cortex (V1. Such influences can be generated in V1, either by direct auditory projections or by feedback projections from extrastriate cortices. To test these hypotheses, cortical activities were recorded using optical imaging at a high spatiotemporal resolution from multiple areas of the guinea pig visual cortex, to visual and/or acoustic stimulations. Visuo-auditory interactions were evaluated according to differences between responses evoked by combined auditory and visual stimulation, and the sum of responses evoked by separate visual and auditory stimulations. Simultaneous presentation of visual and acoustic stimulations resulted in significant interactions in V1, which occurred earlier than in other visual areas. When acoustic stimulation preceded visual stimulation, significant visuo-auditory interactions were detected only in V1. These results suggest that V1 is a cortical origin of visuo-auditory interaction.

  2. Cross-Modal Functional Reorganization of Visual and Auditory Cortex in Adult Cochlear Implant Users Identified with fNIRS

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    Ling-Chia Chen

    2016-01-01

    Full Text Available Cochlear implant (CI users show higher auditory-evoked activations in visual cortex and higher visual-evoked activation in auditory cortex compared to normal hearing (NH controls, reflecting functional reorganization of both visual and auditory modalities. Visual-evoked activation in auditory cortex is a maladaptive functional reorganization whereas auditory-evoked activation in visual cortex is beneficial for speech recognition in CI users. We investigated their joint influence on CI users’ speech recognition, by testing 20 postlingually deafened CI users and 20 NH controls with functional near-infrared spectroscopy (fNIRS. Optodes were placed over occipital and temporal areas to measure visual and auditory responses when presenting visual checkerboard and auditory word stimuli. Higher cross-modal activations were confirmed in both auditory and visual cortex for CI users compared to NH controls, demonstrating that functional reorganization of both auditory and visual cortex can be identified with fNIRS. Additionally, the combined reorganization of auditory and visual cortex was found to be associated with speech recognition performance. Speech performance was good as long as the beneficial auditory-evoked activation in visual cortex was higher than the visual-evoked activation in the auditory cortex. These results indicate the importance of considering cross-modal activations in both visual and auditory cortex for potential clinical outcome estimation.

  3. Frequency spectrum might act as communication code between retina and visual cortex I.

    Science.gov (United States)

    Yang, Xu; Gong, Bo; Lu, Jian-Wei

    2015-01-01

    To explore changes and possible communication relationship of local potential signals recorded simultaneously from retina and visual cortex I (V1). Fourteen C57BL/6J mice were measured with pattern electroretinogram (PERG) and pattern visually evoked potential (PVEP) and fast Fourier transform has been used to analyze the frequency components of those signals. The amplitude of PERG and PVEP was measured at about 36.7 µV and 112.5 µV respectively and the dominant frequency of PERG and PVEP, however, stay unchanged and both signals do not have second, or otherwise, harmonic generation. The results suggested that retina encodes visual information in the way of frequency spectrum and then transfers it to primary visual cortex. The primary visual cortex accepts and deciphers the input visual information coded from retina. Frequency spectrum may act as communication code between retina and V1.

  4. On spike-timing-dependent-plasticity, memristive devices, and building a self-learning visual cortex

    National Research Council Canada - National Science Library

    Zamarreño-Ramos, Carlos; Camuñas-Mesa, Luis A; Pérez-Carrasco, Jose A; Masquelier, Timothée; Serrano-Gotarredona, Teresa; Linares-Barranco, Bernabé

    2011-01-01

    ...) found in real biological synapses. Understanding this link allows neuromorphic engineers to develop circuit architectures that use this type of memristors to artificially emulate parts of the visual cortex...

  5. Multisensory and Modality Specific Processing of Visual Speech in Different Regions of the Premotor Cortex

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    Daniel eCallan

    2014-05-01

    Full Text Available Behavioral and neuroimaging studies have demonstrated that brain regions involved with speech production also support speech perception, especially under degraded conditions. The premotor cortex has been shown to be active during both observation and execution of action (‘Mirror System’ properties, and may facilitate speech perception by mapping unimodal and multimodal sensory features onto articulatory speech gestures. For this functional magnetic resonance imaging (fMRI study, participants identified vowels produced by a speaker in audio-visual (saw the speaker’s articulating face and heard her voice, visual only (only saw the speaker’s articulating face, and audio only (only heard the speaker’s voice conditions with varying audio signal-to-noise ratios in order to determine the regions of the premotor cortex involved with multisensory and modality specific processing of visual speech gestures. The task was designed so that identification could be made with a high level of accuracy from visual only stimuli to control for task difficulty and differences in intelligibility. The results of the fMRI analysis for visual only and audio-visual conditions showed overlapping activity in inferior frontal gyrus and premotor cortex. The left ventral inferior premotor cortex showed properties of multimodal (audio-visual enhancement with a degraded auditory signal. The left inferior parietal lobule and right cerebellum also showed these properties. The left ventral superior and dorsal premotor cortex did not show this multisensory enhancement effect, but there was greater activity for the visual only over audio-visual conditions in these areas. The results suggest that the inferior regions of the ventral premotor cortex are involved with integrating multisensory information, whereas, more superior and dorsal regions of the premotor cortex are involved with mapping unimodal (in this case visual sensory features of the speech signal with

  6. Evidence for unlimited capacity processing of simple features in visual cortex.

    Science.gov (United States)

    White, Alex L; Runeson, Erik; Palmer, John; Ernst, Zachary R; Boynton, Geoffrey M

    2017-06-01

    Performance in many visual tasks is impaired when observers attempt to divide spatial attention across multiple visual field locations. Correspondingly, neuronal response magnitudes in visual cortex are often reduced during divided compared with focused spatial attention. This suggests that early visual cortex is the site of capacity limits, where finite processing resources must be divided among attended stimuli. However, behavioral research demonstrates that not all visual tasks suffer such capacity limits: The costs of divided attention are minimal when the task and stimulus are simple, such as when searching for a target defined by orientation or contrast. To date, however, every neuroimaging study of divided attention has used more complex tasks and found large reductions in response magnitude. We bridged that gap by using functional magnetic resonance imaging to measure responses in the human visual cortex during simple feature detection. The first experiment used a visual search task: Observers detected a low-contrast Gabor patch within one or four potentially relevant locations. The second experiment used a dual-task design, in which observers made independent judgments of Gabor presence in patches of dynamic noise at two locations. In both experiments, blood-oxygen level-dependent (BOLD) signals in the retinotopic cortex were significantly lower for ignored than attended stimuli. However, when observers divided attention between multiple stimuli, BOLD signals were not reliably reduced and behavioral performance was unimpaired. These results suggest that processing of simple features in early visual cortex has unlimited capacity.

  7. Analysis of primary visual cortex in dementia with Lewy bodies indicates GABAergic involvement associated with recurrent complex visual hallucinations.

    Science.gov (United States)

    Khundakar, Ahmad A; Hanson, Peter S; Erskine, Daniel; Lax, Nichola Z; Roscamp, Joseph; Karyka, Evangelia; Tsefou, Eliona; Singh, Preeti; Cockell, Simon J; Gribben, Andrew; Ramsay, Lynne; Blain, Peter G; Mosimann, Urs P; Lett, Deborah J; Elstner, Matthias; Turnbull, Douglass M; Xiang, Charles C; Brownstein, Michael J; O'Brien, John T; Taylor, John-Paul; Attems, Johannes; Thomas, Alan J; McKeith, Ian G; Morris, Christopher M

    2016-06-30

    Dementia with Lewy bodies (DLB) patients frequently experience well formed recurrent complex visual hallucinations (RCVH). This is associated with reduced blood flow or hypometabolism on imaging of the primary visual cortex. To understand these associations in DLB we used pathological and biochemical analysis of the primary visual cortex to identify changes that could underpin RCVH. Alpha-synuclein or neurofibrillary tangle pathology in primary visual cortex was essentially absent. Neurone density or volume within the primary visual cortex in DLB was also unchanged using unbiased stereology. Microarray analysis, however, demonstrated changes in neuropeptide gene expression and other markers, indicating altered GABAergic neuronal function. Calcium binding protein and GAD65/67 immunohistochemistry showed preserved interneurone populations indicating possible interneurone dysfunction. This was demonstrated by loss of post synaptic GABA receptor markers including gephyrin, GABARAP, and Kif5A, indicating reduced GABAergic synaptic activity. Glutamatergic neuronal signalling was also altered with vesicular glutamate transporter protein and PSD-95 expression being reduced. Changes to the primary visual cortex in DLB indicate that reduced GABAergic transmission may contribute to RCVH in DLB and treatment using targeted GABAergic modulation or similar approaches using glutamatergic modification may be beneficial.

  8. Spontaneous Activity Patterns in Primary Visual Cortex Predispose to Visual Hallucinations.

    Science.gov (United States)

    Pajani, Auréliane; Kok, Peter; Kouider, Sid; de Lange, Floris P

    2015-09-16

    According to theoretical frameworks casting perception as inference, vision results from the integration of bottom-up visual input with top-down expectations. Under conditions of strongly degraded sensory input, this may occasionally result in false perceptions in the absence of a sensory signal, also termed "hallucinations." Here, we investigated whether spontaneous prestimulus activity patterns in sensory circuits, which may embody a participant's prior expectations, predispose the observer toward false perceptions. Specifically, we used fMRI to investigate whether the representational content of prestimulus activity in early visual cortex is linked to subsequent perception during a challenging detection task. Human participants were asked to detect oriented gratings of a particular orientation that were embedded in noise. We found two characteristics of prestimulus activity that predisposed participants to hallucinations: overall lower prestimulus activity and a bias in the prestimulus activity patterns toward the to-be-detected (expected) grating. These results suggest that perceptual hallucinations may be due to an imprecise and biased state of sensory circuits preceding sensory evidence collection. When sensory stimulation is strongly degraded, we occasionally misperceive a stimulus when only noise is present: a perceptual hallucination. Using fMRI in healthy participants, we investigated whether the state of early visual cortex preceding stimulus onset predisposes an observer to hallucinations. We found two characteristics of prestimulus activity that predisposed participants to hallucinations: overall lower prestimulus activity and a bias in the prestimulus activity patterns toward the expected grating. These results suggest that perceptual hallucinations are due to an imprecise and biased state of sensory circuits preceding sensation. Copyright © 2015 the authors 0270-6474/15/3512947-07$15.00/0.

  9. Interactions of top-down and bottom-up mechanisms in human visual cortex.

    Science.gov (United States)

    McMains, Stephanie; Kastner, Sabine

    2011-01-12

    Multiple stimuli present in the visual field at the same time compete for neural representation by mutually suppressing their evoked activity throughout visual cortex, providing a neural correlate for the limited processing capacity of the visual system. Competitive interactions among stimuli can be counteracted by top-down, goal-directed mechanisms such as attention, and by bottom-up, stimulus-driven mechanisms. Because these two processes cooperate in everyday life to bias processing toward behaviorally relevant or particularly salient stimuli, it has proven difficult to study interactions between top-down and bottom-up mechanisms. Here, we used an experimental paradigm in which we first isolated the effects of a bottom-up influence on neural competition by parametrically varying the degree of perceptual grouping in displays that were not attended. Second, we probed the effects of directed attention on the competitive interactions induced with the parametric design. We found that the amount of attentional modulation varied linearly with the degree of competition left unresolved by bottom-up processes, such that attentional modulation was greatest when neural competition was little influenced by bottom-up mechanisms and smallest when competition was strongly influenced by bottom-up mechanisms. These findings suggest that the strength of attentional modulation in the visual system is constrained by the degree to which competitive interactions have been resolved by bottom-up processes related to the segmentation of scenes into candidate objects.

  10. Image Statistics and the Representation of Material Properties in the Visual Cortex.

    Science.gov (United States)

    Baumgartner, Elisabeth; Gegenfurtner, Karl R

    2016-01-01

    We explored perceived material properties (roughness, texturedness, and hardness) with a novel approach that compares perception, image statistics and brain activation, as measured with fMRI. We initially asked participants to rate 84 material images with respect to the above mentioned properties, and then scanned 15 of the participants with fMRI while they viewed the material images. The images were analyzed with a set of image statistics capturing their spatial frequency and texture properties. Linear classifiers were then applied to the image statistics as well as the voxel patterns of visually responsive voxels and early visual areas to discriminate between images with high and low perceptual ratings. Roughness and texturedness could be classified above chance level based on image statistics. Roughness and texturedness could also be classified based on the brain activation patterns in visual cortex, whereas hardness could not. Importantly, the agreement in classification based on image statistics and brain activation was also above chance level. Our results show that information about visual material properties is to a large degree contained in low-level image statistics, and that these image statistics are also partially reflected in brain activity patterns induced by the perception of material images.

  11. Visual illusion induced by sound.

    Science.gov (United States)

    Shams, Ladan; Kamitani, Yukiyasu; Shimojo, Shinsuke

    2002-06-01

    We present the first cross-modal modification of visual perception which involves a phenomenological change in the quality-as opposed to a small, gradual, or quantitative change-of the percept of a non-ambiguous visual stimulus. We report a visual illusion which is induced by sound: when a single flash of light is accompanied by multiple auditory beeps, the single flash is perceived as multiple flashes. We present two experiments as well as several observations which establish that this alteration of the visual percept is due to cross-modal perceptual interactions as opposed to cognitive, attentional, or other origins. The results of the second experiment also reveal that the temporal window of these audio-visual interactions is approximately 100 ms.

  12. Disgust and Suppression of the Visual Cortex: Lateralization Effects?

    Directory of Open Access Journals (Sweden)

    Moon Wilton

    2012-05-01

    Full Text Available Research has shown that unlike other threat emotions, disgust does not evoke a typical sympathetic fight or flight response. Rather, disgust induces a parasympathetic response. A recent EEG study has demonstrated that this inhibitory reaction is also present in neuronal systems. Disgust stimuli elicited diminished Visual Event Related Potential (VERP amplitude in comparison to neutral and fear stimuli at P1 in the posterior Oz electrode (Kruesmark and Li, 2011 J Neurosci 31 (9, 3429–3434. In order to investigate whether VERPs were sensitive to different domains of disgust, we presented participants with random sequence of neutral, sociomoral, mutilation, and contamination images derived from the IAPS database. EEG results indicated no significant effect at Oz contrary to prior research. The results did, however, demonstrate lateralization effects. Whilst no differences were found between the disgust conditions themselves, the left P1 potential for all the disgust conditions was significantly attenuated compared to neutral. Conversely, this effect did not occur in the right posterior electrodes. In a second study, we presented the different disgust images in blocks in order to investigate the role of anticipation. Again, the left sided P1 was attenuated compared to neutral; however, on the right, mutilation elicited significantly greater P1 amplitude than did all other conditions. The results suggest suppressed visual processing for disgust elicitors in the left posterior regions and heightened activity for mutilation stimuli in the right, when mutilation was expected. These results may reflect a lateralized approach-avoidance mechanism, which begins as early as 125 ms after stimulus onset.

  13. Effects of Visual Cortex Activation on the Nociceptive Blink Reflex in Healthy Subjects

    Science.gov (United States)

    Sava, Simona L.; de Pasqua, Victor; Magis, Delphine; Schoenen, Jean

    2014-01-01

    Bright light can cause excessive visual discomfort, referred to as photophobia. The precise mechanisms linking luminance to the trigeminal nociceptive system supposed to mediate this discomfort are not known. To address this issue in healthy human subjects we modulated differentially visual cortex activity by repetitive transcranial magnetic stimulation (rTMS) or flash light stimulation, and studied the effect on supraorbital pain thresholds and the nociceptive-specific blink reflex (nBR). Low frequency rTMS that inhibits the underlying cortex, significantly decreased pain thresholds, increased the 1st nBR block ipsi- and contralaterally and potentiated habituation contralaterally. After high frequency or sham rTMS over the visual cortex, and rMS over the right greater occipital nerve we found no significant change. By contrast, excitatory flash light stimulation increased pain thresholds, decreased the 1st nBR block of ipsi- and contralaterally and increased habituation contralaterally. Our data demonstrate in healthy subjects a functional relation between the visual cortex and the trigeminal nociceptive system, as assessed by the nociceptive blink reflex. The results argue in favour of a top-down inhibitory pathway from the visual areas to trigemino-cervical nociceptors. We postulate that in normal conditions this visuo-trigeminal inhibitory pathway may avoid disturbance of vision by too frequent blinking and that hypoactivity of the visual cortex for pathological reasons may promote headache and photophobia. PMID:24936654

  14. The Corpus Callosum and the Visual Cortex: Plasticity Is a Game for Two

    Directory of Open Access Journals (Sweden)

    Marta Pietrasanta

    2012-01-01

    Full Text Available Throughout life, experience shapes and selects the most appropriate brain functional connectivity to adapt to a changing environment. An ideal system to study experience-dependent plasticity is the visual cortex, because visual experience can be easily manipulated. In this paper, we focus on the role of interhemispheric, transcallosal projections in experience-dependent plasticity of the visual cortex. We review data showing that deprivation of sensory experience can modify the morphology of callosal fibres, thus altering the communication between the two hemispheres. More importantly, manipulation of callosal input activity during an early critical period alters developmental maturation of functional properties in visual cortex and modifies its ability to remodel in response to experience. We also discuss recent data in rat visual cortex, demonstrating that the corpus callosum plays a role in binocularity of cortical neurons and is involved in the plastic shift of eye preference that follows a period of monocular eyelid suture (monocular deprivation in early age. Thus, experience can modify the fine connectivity of the corpus callosum, and callosal connections represent a major pathway through which experience can mediate functional maturation and plastic rearrangements in the visual cortex.

  15. Wakefulness suppresses retinal wave-related neural activity in visual cortex.

    Science.gov (United States)

    Mukherjee, Didhiti; Yonk, Alex J; Sokoloff, Greta; Blumberg, Mark S

    2017-08-01

    In the developing visual system before eye opening, spontaneous retinal waves trigger bursts of neural activity in downstream structures, including visual cortex. At the same ages when retinal waves provide the predominant input to the visual system, sleep is the predominant behavioral state. However, the interactions between behavioral state and retinal wave-driven activity have never been explicitly examined. Here we characterized unit activity in visual cortex during spontaneous sleep-wake cycles in 9- and 12-day-old rats. At both ages, cortical activity occurred in discrete rhythmic bursts, ~30-60 s apart, mirroring the timing of retinal waves. Interestingly, when pups spontaneously woke up and moved their limbs in the midst of a cortical burst, the activity was suppressed. Finally, experimentally evoked arousals also suppressed intraburst cortical activity. All together, these results indicate that active wake interferes with the activation of the developing visual cortex by retinal waves. They also suggest that sleep-wake processes can modulate visual cortical plasticity at earlier ages than has been previously considered.NEW & NOTEWORTHY By recording in visual cortex in unanesthetized infant rats, we show that neural activity attributable to retinal waves is specifically suppressed when pups spontaneously awaken or are experimentally aroused. These findings suggest that the relatively abundant sleep of early development plays a permissive functional role for the visual system. It follows, then, that biological or environmental factors that disrupt sleep may interfere with the development of these neural networks. Copyright © 2017 the American Physiological Society.

  16. Predictions to motion stimuli in human early visual cortex : Effects of motion displacement on motion predictability

    NARCIS (Netherlands)

    Schellekens, W.|info:eu-repo/dai/nl/413971309; Ramsey, N. F.|info:eu-repo/dai/nl/07313774X; Raemaekers, M.|info:eu-repo/dai/nl/31370709X

    2015-01-01

    Recently, several studies showed that fMRI BOLD responses to moving random dot stimuli are enhanced at the location of dot appearance, i.e., the motion trailing edge. Possibly, BOLD activity in human visual cortex reflects predictability of visual motion input. In the current study, we investigate

  17. Task alters category representations in prefrontal but not high-level visual cortex.

    Science.gov (United States)

    Bugatus, Lior; Weiner, Kevin S; Grill-Spector, Kalanit

    2017-07-15

    A central question in neuroscience is how cognitive tasks affect category representations across the human brain. Regions in lateral occipito-temporal cortex (LOTC), ventral temporal cortex (VTC), and ventro-lateral prefrontal cortex (VLFPC) constitute the extended "what" pathway, which is considered instrumental for visual category processing. However, it is unknown (1) whether distributed responses across LOTC, VTC, and VLPFC explicitly represent category, task, or some combination of both, and (2) in what way representations across these subdivisions of the extended 'what' pathway may differ. To fill these gaps in knowledge, we scanned 12 participants using fMRI to test the effect of category and task on distributed responses across LOTC, VTC, and VLPFC. Results reveal that task and category modulate responses in both high-level visual regions, as well as prefrontal cortex. However, we found fundamentally different types of representations across the brain. Distributed responses in high-level visual regions are more strongly driven by category than task, and exhibit task-independent category representations. In contrast, distributed responses in prefrontal cortex are more strongly driven by task than category, and contain task-dependent category representations. Together, these findings of differential representations across the brain support a new idea that LOTC and VTC maintain stable category representations allowing efficient processing of visual information, while prefrontal cortex contains flexible representations in which category information may emerge only when relevant to the task. Copyright © 2017 Elsevier Inc. All rights reserved.

  18. Heterogenous migraine aura symptoms correlate with visual cortex functional magnetic resonance imaging responses.

    Science.gov (United States)

    Arngrim, Nanna; Hougaard, Anders; Ahmadi, Khazar; Vestergaard, Mark Bitsch; Schytz, Henrik Winther; Amin, Faisal Mohammad; Larsson, Henrik Bo Wiberg; Olesen, Jes; Hoffmann, Michael B; Ashina, Messoud

    2017-12-01

    Migraine aura is sparsely studied due to the highly challenging task of capturing patients during aura. Cortical spreading depression (CSD) is likely the underlying phenomenon of aura. The possible correlation between the multifaceted phenomenology of aura symptoms and the effects of CSD on the brain has not been ascertained. Five migraine patients were studied during various forms of aura symptoms induced by hypoxia, sham hypoxia, or physical exercise with concurrent photostimulation. The blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) signal response to visual stimulation was measured in retinotopic mapping-defined visual cortex areas V1 to V4. We found reduced BOLD response in patients reporting scotoma and increased response in patients who only experienced positive symptoms. Furthermore, patients with bilateral visual symptoms had corresponding bihemispherical changes in BOLD response. These findings suggest that different aura symptoms reflect different types of cerebral dysfunction, which correspond to specific changes in BOLD signal reactivity. Furthermore, we provide evidence of bilateral CSD recorded by fMRI during bilateral aura symptoms. Ann Neurol 2017;82:925-939. © 2017 American Neurological Association.

  19. IGF-1 Restores Visual Cortex Plasticity in Adult Life by Reducing Local GABA Levels

    Directory of Open Access Journals (Sweden)

    José Fernando Maya-Vetencourt

    2012-01-01

    Full Text Available The central nervous system architecture is markedly modified by sensory experience during early life, but a decline of plasticity occurs with age. Recent studies have challenged this dogma providing evidence that both pharmacological treatments and paradigms based on the manipulation of environmental stimulation levels can be successfully employed as strategies for enhancing plasticity in the adult nervous system. Insulin-like growth factor 1 (IGF-1 is a peptide implicated in prenatal and postnatal phases of brain development such as neurogenesis, neuronal differentiation, synaptogenesis, and experience-dependent plasticity. Here, using the visual system as a paradigmatic model, we report that IGF-1 reactivates neural plasticity in the adult brain. Exogenous administration of IGF-1 in the adult visual cortex, indeed, restores the susceptibility of cortical neurons to monocular deprivation and promotes the recovery of normal visual functions in adult amblyopic animals. These effects were accompanied by a marked reduction of intracortical GABA levels. Moreover, we show that a transitory increase of IGF-1 expression is associated to the plasticity reinstatement induced by environmental enrichment (EE and that blocking IGF-1 action by means of the IGF-1 receptor antagonist JB1 prevents EE effects on plasticity processes.

  20. A Comparison of Visual Response Properties in the Lateral Geniculate Nucleus and Primary Visual Cortex of Awake and Anesthetized Mice

    OpenAIRE

    Durand, Séverine; Iyer, Ramakrishnan; Mizuseki, Kenji; de Vries, Saskia; Mihalas, Stefan; Reid, R. Clay

    2016-01-01

    The cerebral cortex of the mouse has become one of the most important systems for studying information processing and the neural correlates of behavior. Multiple studies have examined the first stages of visual cortical processing: primary visual cortex (V1) and its thalamic inputs from the dorsal lateral geniculate nucleus (dLGN), but more rarely in the lateral posterior nucleus (LP) in mice. Multiple single-unit surveys of dLGN and V1, both with electrophysiology and two-photon calcium imag...

  1. Feature-coding transitions to conjunction-coding with progression through human visual cortex.

    Science.gov (United States)

    Cowell, Rosemary A; Leger, Krystal R; Serences, John T

    2017-12-01

    Identifying an object and distinguishing it from similar items depends upon the ability to perceive its component parts as conjoined into a cohesive whole, but the brain mechanisms underlying this ability remain elusive. The ventral visual processing pathway in primates is organized hierarchically: Neuronal responses in early stages are sensitive to the manipulation of simple visual features, whereas neuronal responses in subsequent stages are tuned to increasingly complex stimulus attributes. It is widely assumed that feature-coding dominates in early visual cortex whereas later visual regions employ conjunction-coding in which object representations are different from the sum of their simple feature parts. However, no study in humans has demonstrated that putative object-level codes in higher visual cortex cannot be accounted for by feature-coding and that putative feature codes in regions prior to ventral temporal cortex are not equally well characterized as object-level codes. Thus the existence of a transition from feature- to conjunction-coding in human visual cortex remains unconfirmed, and if a transition does occur its location remains unknown. By employing multivariate analysis of functional imaging data, we measure both feature-coding and conjunction-coding directly, using the same set of visual stimuli, and pit them against each other to reveal the relative dominance of one vs. the other throughout cortex. Our results reveal a transition from feature-coding in early visual cortex to conjunction-coding in both inferior temporal and posterior parietal cortices. This novel method enables the use of experimentally controlled stimulus features to investigate population-level feature and conjunction codes throughout human cortex. NEW & NOTEWORTHY We use a novel analysis of neuroimaging data to assess representations throughout visual cortex, revealing a transition from feature-coding to conjunction-coding along both ventral and dorsal pathways. Occipital

  2. Functional organization and visual representations of human ventral lateral prefrontal cortex

    Science.gov (United States)

    Chan, Annie W.-Y.

    2013-01-01

    Recent neuroimaging studies in both human and non-human primates have identified face selective activation in the ventral lateral prefrontal cortex (VLPFC) even in the absence of working memory (WM) demands. Further, research has suggested that this face-selective response is largely driven by the presence of the eyes. However, the nature and origin of visual category responses in the VLPFC remain unclear. In a broader sense, how do these findings relate to our current understandings of lateral prefrontal cortex? What do these findings tell us about the underlying function and organization principles of the VLPFC? What is the future direction for investigating visual representations in this cortex? This review focuses on the function, topography, and circuitry of the VLPFC to enhance our understanding of the evolution and development of this cortex. PMID:23847558

  3. Altered glial gene expression, density, and architecture in the visual cortex upon retinal degeneration.

    Science.gov (United States)

    Cornett, Ashley; Sucic, Joseph F; Hillsburg, Dylan; Cyr, Lindsay; Johnson, Catherine; Polanco, Anthony; Figuereo, Joe; Cabine, Kenneth; Russo, Nickole; Sturtevant, Ann; Jarvinen, Michael K

    2011-11-08

    Genes encoding the proteins of cytoskeletal intermediate filaments (IF) are tightly regulated, and they are important for establishing neural connections. However, it remains uncertain to what extent neurological disease alters IF gene expression or impacts cells that express IFs. In this study, we determined the onset of visual deficits in a mouse model of progressive retinal degeneration (Pde6b(-) mice; Pde6b(+) mice have normal vision) by observing murine responses to a visual task throughout development, from postnatal day (PND) 21 to adult (N=174 reliable observations). Using Q-PCR, we evaluated whether expression of the genes encoding two Type III IF proteins, glial fibrillary acidic protein (GFAP) and vimentin was altered in the visual cortex before, during, and after the onset of visual deficits. Using immunohistochemical techniques, we investigated the impact of vision loss on the density and morphology of astrocytes that expressed GFAP and vimentin in the visual cortex. We found that Pde6b(-) mice displayed 1) evidence of blindness at PND 49, with visual deficits detected at PND 35, 2) reduced GFAP mRNA expression in the visual cortex between PND 28 and PND 49, and 3) an increased ratio of vimentin:GFAP-labeled astrocytes at PND 49 with reduced GFAP cell body area. Together, these findings demonstrate that retinal degeneration modifies cellular and molecular indices of glial plasticity in a visual system with drastically reduced visual input. The functional consequences of these structural changes remain uncertain. Copyright © 2011 Elsevier B.V. All rights reserved.

  4. Early Visual Cortex as a Multiscale Cognitive Blackboard

    NARCIS (Netherlands)

    Roelfsema, Pieter R.; de Lange, Floris P.

    2016-01-01

    Neurons in early visual cortical areas not only represent incoming visual information but are also engaged by higher level cognitive processes, including attention, working memory, imagery, and decision-making. Are these cognitive effects an epiphenomenon or are they functionally relevant for these

  5. Early visual cortex as a multiscale cognitive blackboard.

    NARCIS (Netherlands)

    Roelfsema, P.R.; De Lange, Floris

    2016-01-01

    Neurons in early visual cortical areas not only represent incoming visual information but are also engaged by higher level cognitive processes, including attention, working memory, imagery, and decision-making. Are these cognitive effects an epiphenomenon or are they functionally relevant for these

  6. Saturation in Phosphene Size with Increasing Current Levels Delivered to Human Visual Cortex.

    Science.gov (United States)

    Bosking, William H; Sun, Ping; Ozker, Muge; Pei, Xiaomei; Foster, Brett L; Beauchamp, Michael S; Yoshor, Daniel

    2017-07-26

    Electrically stimulating early visual cortex results in a visual percept known as a phosphene. Although phosphenes can be evoked by a wide range of electrode sizes and current amplitudes, they are invariably described as small. To better understand this observation, we electrically stimulated 93 electrodes implanted in the visual cortex of 13 human subjects who reported phosphene size while stimulation current was varied. Phosphene size increased as the stimulation current was initially raised above threshold, but then rapidly reached saturation. Phosphene size also depended on the location of the stimulated site, with size increasing with distance from the foveal representation. We developed a model relating phosphene size to the amount of activated cortex and its location within the retinotopic map. First, a sigmoidal curve was used to predict the amount of activated cortex at a given current. Second, the amount of active cortex was converted to degrees of visual angle by multiplying by the inverse cortical magnification factor for that retinotopic location. This simple model accurately predicted phosphene size for a broad range of stimulation currents and cortical locations. The unexpected saturation in phosphene sizes suggests that the functional architecture of cerebral cortex may impose fundamental restrictions on the spread of artificially evoked activity and this may be an important consideration in the design of cortical prosthetic devices.SIGNIFICANCE STATEMENT Understanding the neural basis for phosphenes, the visual percepts created by electrical stimulation of visual cortex, is fundamental to the development of a visual cortical prosthetic. Our experiments in human subjects implanted with electrodes over visual cortex show that it is the activity of a large population of cells spread out across several millimeters of tissue that supports the perception of a phosphene. In addition, we describe an important feature of the production of phosphenes by

  7. Images of Illusory Motion in Primary Visual Cortex

    DEFF Research Database (Denmark)

    Larsen, Axel; Madsen, Kristoffer; Ellegaard Lund, Torben

    2006-01-01

    Illusory motion can be generated by successively flashing a stationary visual stimulus in two spatial locations separated by several degrees of visual angle. In appropriate conditions, the apparent motion is indistinguishable from real motion: The observer experiences a luminous object traversing...... a continuous path from one stimulus location to the other through intervening positions where no physical stimuli exist. The phenomenon has been extensively investigated for nearly a century but little is known about its neurophysiological foundation. Here we present images of activations in the primary visual...

  8. Multisensory and modality specific processing of visual speech in different regions of the premotor cortex.

    Science.gov (United States)

    Callan, Daniel E; Jones, Jeffery A; Callan, Akiko

    2014-01-01

    Behavioral and neuroimaging studies have demonstrated that brain regions involved with speech production also support speech perception, especially under degraded conditions. The premotor cortex (PMC) has been shown to be active during both observation and execution of action ("Mirror System" properties), and may facilitate speech perception by mapping unimodal and multimodal sensory features onto articulatory speech gestures. For this functional magnetic resonance imaging (fMRI) study, participants identified vowels produced by a speaker in audio-visual (saw the speaker's articulating face and heard her voice), visual only (only saw the speaker's articulating face), and audio only (only heard the speaker's voice) conditions with varying audio signal-to-noise ratios in order to determine the regions of the PMC involved with multisensory and modality specific processing of visual speech gestures. The task was designed so that identification could be made with a high level of accuracy from visual only stimuli to control for task difficulty and differences in intelligibility. The results of the functional magnetic resonance imaging (fMRI) analysis for visual only and audio-visual conditions showed overlapping activity in inferior frontal gyrus and PMC. The left ventral inferior premotor cortex (PMvi) showed properties of multimodal (audio-visual) enhancement with a degraded auditory signal. The left inferior parietal lobule and right cerebellum also showed these properties. The left ventral superior and dorsal premotor cortex (PMvs/PMd) did not show this multisensory enhancement effect, but there was greater activity for the visual only over audio-visual conditions in these areas. The results suggest that the inferior regions of the ventral premotor cortex are involved with integrating multisensory information, whereas, more superior and dorsal regions of the PMC are involved with mapping unimodal (in this case visual) sensory features of the speech signal with

  9. Visual search for object categories is predicted by the representational architecture of high-level visual cortex.

    Science.gov (United States)

    Cohen, Michael A; Alvarez, George A; Nakayama, Ken; Konkle, Talia

    2017-01-01

    Visual search is a ubiquitous visual behavior, and efficient search is essential for survival. Different cognitive models have explained the speed and accuracy of search based either on the dynamics of attention or on similarity of item representations. Here, we examined the extent to which performance on a visual search task can be predicted from the stable representational architecture of the visual system, independent of attentional dynamics. Participants performed a visual search task with 28 conditions reflecting different pairs of categories (e.g., searching for a face among cars, body among hammers, etc.). The time it took participants to find the target item varied as a function of category combination. In a separate group of participants, we measured the neural responses to these object categories when items were presented in isolation. Using representational similarity analysis, we then examined whether the similarity of neural responses across different subdivisions of the visual system had the requisite structure needed to predict visual search performance. Overall, we found strong brain/behavior correlations across most of the higher-level visual system, including both the ventral and dorsal pathways when considering both macroscale sectors as well as smaller mesoscale regions. These results suggest that visual search for real-world object categories is well predicted by the stable, task-independent architecture of the visual system. Here, we ask which neural regions have neural response patterns that correlate with behavioral performance in a visual processing task. We found that the representational structure across all of high-level visual cortex has the requisite structure to predict behavior. Furthermore, when directly comparing different neural regions, we found that they all had highly similar category-level representational structures. These results point to a ubiquitous and uniform representational structure in high-level visual cortex

  10. Modeling and Simulation. II. Specificity Models for Visual Cortex Development.

    Science.gov (United States)

    1986-12-12

    interactions contributing to the (ci’lar d(,nwin:33(’e of i4)noctil:rly dominated (-ells in the normal cat striate cortex, Brain ’es. 41, 1-10; 1980. 82. Sjllii...responses. The dashed line shows the response to the left eye stimulus alone, which was fixed for this curve. The right eye stimulus was advanced or delayed...A more complex diagram from Silito (1985) which uses the scheme in A (upper left ). In the upper right , three of these channels interact to produce a

  11. Organization of texture segregation processing in primate visual cortex.

    NARCIS (Netherlands)

    Lamme, V.A.F.; van Dijk, B.W.; Spekreijse, H.

    1993-01-01

    Investigated which cortical areas and layers are involved in global feature interactions underlying texture segregation in humans and monkeys. Visual stimulation was assessed with an electrostatic monitor, and scalp or intracortical recordings with electrodes were made. Signal processing and

  12. Developmental alcohol exposure impairs synaptic plasticity without overtly altering microglial function in mouse visual cortex.

    Science.gov (United States)

    Wong, Elissa L; Lutz, Nina M; Hogan, Victoria A; Lamantia, Cassandra E; McMurray, Helene R; Myers, Jason R; Ashton, John M; Majewska, Ania K

    2018-01-01

    Fetal alcohol spectrum disorder (FASD), caused by gestational ethanol (EtOH) exposure, is one of the most common causes of non-heritable and life-long mental disability worldwide, with no standard treatment or therapy available. While EtOH exposure can alter the function of both neurons and glia, it is still unclear how EtOH influences brain development to cause deficits in sensory and cognitive processing later in life. Microglia play an important role in shaping synaptic function and plasticity during neural circuit development and have been shown to mount an acute immunological response to EtOH exposure in certain brain regions. Therefore, we hypothesized that microglial roles in the healthy brain could be permanently altered by early EtOH exposure leading to deficits in experience-dependent plasticity. We used a mouse model of human third trimester high binge EtOH exposure, administering EtOH twice daily by subcutaneous injections from postnatal day 4 through postnatal day 9 (P4-:P9). Using a monocular deprivation model to assess ocular dominance plasticity, we found an EtOH-induced deficit in this type of visually driven experience-dependent plasticity. However, using a combination of immunohistochemistry, confocal microscopy, and in vivo two-photon microscopy to assay microglial morphology and dynamics, as well as fluorescence activated cell sorting (FACS) and RNA-seq to examine the microglial transcriptome, we found no evidence of microglial dysfunction in early adolescence. We also found no evidence of microglial activation in visual cortex acutely after early ethanol exposure, possibly because we also did not observe EtOH-induced neuronal cell death in this brain region. We conclude that early EtOH exposure caused a deficit in experience-dependent synaptic plasticity in the visual cortex that was independent of changes in microglial phenotype or function. This demonstrates that neural plasticity can remain impaired by developmental ethanol exposure even in

  13. [Responses of rabbit's visual cortex neurons to changes in intensity and orientation of visual stimuli].

    Science.gov (United States)

    Polianskiĭ, V B; Alymkulov, D E; Evtikhin, D V; Sokolov, E N; Chernyshev, B V

    2010-01-01

    Changes in the number of spikes in the early phasic discharge (50-90 ms from stimuli replacement) of neurons in the rabbit's primary visual cortex were studied under conditions of an instant change in a flashing-line pattern. We used three type of stimulation: lines with different orientations (0-90 degrees) but constant intensity; lines with constant orientation but different intensities; complex stimuli with different intensities and different orientations of lines. Factor analysis made it possible to reconstruct two-dimensional sensory spaces of orientations in 13 of 43 analyzed neurons (30%). In 5 of 30 analyzed neurons (16.6%), both two-dimensional spaces of orientations and two-dimensional spaces of intensities were revealed. Achromatic spaces were reconstructed during changes in the lines of varying intensities but constant orientation. In experiments with complex stimuli, the intensity of lines with orientations varying from 0 to 38.58 degree was 5 cd/m2. The intensity of lines with orientations varying from 51.44 to 90 degrees was 15 cd/m2. In the sensorial space, stimuli with different intensities were located on the plane formed by the first and second significant factors in opposite quadrants, whereas within each quadrant, the stimuli were arranged closely to their orientation from minimum to maximum. We suggest that this type of sensory space reflects the interaction between intensity and orientation attributes of visual stimuli with the factor of intensity prevailing over the factor of orientation. Only 7 (12%) neurons with such complex spaces were found.

  14. Activation in left primary visual cortex representing parafoveal visual field during reading Japanese texts.

    Science.gov (United States)

    Shimada, Yoichi; Hirayama, Kazumi; Nakadomari, Satoshi; Furuta, Ayumu; Misaki, Masaya; Kan, Shigeyuki; Koike, Takahiko; Miyauchi, Satoru; Mori, Etsuro

    2011-08-23

    Activation in the left primary visual cortex (V1) representing the parafoveal field during text reading has been interpreted as attentional modulation in the process of deciding saccadic target for reading ahead. Kanji words serve the main cue to decide the goal of saccades in Japanese. We aimed to determine the exact location of this modulation in the V1 and to determine whether the area of the modulation changes according to the location where the next Kanji word appears or it is fixed on a certain region in V1. Using functional magnetic resonance imaging, we determined the area in V1 representing each eccentricity on the horizontal meridian of the visual field for each participant. Then we investigated brain activation while they were reading two sets of Japanese texts that scrolled leftward as the participants. In set 1, the distance between the heads of adjacent Kanji words was about 3°. In set 2, the distance was about 5°. From the results of these experiments, we obtained activation amplitude of the area corresponding to each eccentricity. We recorded eye movements simultaneously with the acquisition of fMRI data. The maximum peak of the activation was found in the region representing about 4.5° of eccentricity on the horizontal meridian in the left V1 for each participant. The activation pattern did not essentially differ between the two text conditions, although the location of the saccades made for reading next section of the text corresponds to the head of the next Kanji word. The activation modulation during reading Japanese texts occurs in the parafoveal V1 of the left hemisphere. The attentional modulation did not change with the distance to the next goal of saccade but was fixed on the area representing about 4.5° of eccentricity. Copyright © 2011 Elsevier B.V. All rights reserved.

  15. Surround modulation characteristics of local field potential and spiking activity in primary visual cortex of cat.

    Science.gov (United States)

    Zhang, Li; Li, Bing

    2013-01-01

    In primary visual cortex, spiking activity that evoked by stimulus confined in receptive field can be modulated by surround stimulus. This center-surround interaction is hypothesized to be the basis of visual feature integration and segregation. Spiking output has been extensively reported to be surround suppressive. However, less is known about the modulation properties of the local field potential (LFP), which generally reflects synaptic inputs. We simultaneously recorded spiking activity and LFP in the area 17 of anesthetized cats to examine and compare their modulation characteristics. When the stimulus went beyond the classical receptive field, LFP exhibited decreased power along the gamma band (30-100 Hz) in most of our recording sites. Further investigation revealed that suppression of the LFP gamma mean power (gLFP) depended on the angle between the center and surround orientations. The strongest suppression was induced when center and surround orientations were parallel. Moreover, the surround influence of the gLFP exhibited an asymmetric spatial organization. These results demonstrate that the gLFP has similar but not identical surround modulation properties, as compared to the spiking activity. The spatiotemporal integration of LFP implies that the oscillation and synchronization of local synaptic inputs may have important functions in surround modulation.

  16. Peripheral nerve injury induces glial activation in primary motor cortex

    Directory of Open Access Journals (Sweden)

    Julieta Troncoso

    2015-02-01

    Full Text Available Preliminary evidence suggests that peripheral facial nerve injuries are associated with sensorimotor cortex reorganization. We have characterized facial nerve lesion-induced structural changes in primary motor cortex layer 5 pyramidal neurons and their relationship with glial cell density using a rodent facial paralysis model. First, we used adult transgenic mice expressing green fluorescent protein in microglia and yellow fluorescent protein in pyramidal neurons which were subjected to either unilateral lesion of the facial nerve or sham surgery. Two-photon excitation microscopy was then used for evaluating both layer 5 pyramidal neurons and microglia in vibrissal primary motor cortex (vM1. It was found that facial nerve lesion induced long-lasting changes in dendritic morphology of vM1 layer 5 pyramidal neurons and in their surrounding microglia. Pyramidal cells’ dendritic arborization underwent overall shrinkage and transient spine pruning. Moreover, microglial cell density surrounding vM1 layer 5 pyramidal neurons was significantly increased with morphological bias towards the activated phenotype. Additionally, we induced facial nerve lesion in Wistar rats to evaluate the degree and extension of facial nerve lesion-induced reorganization processes in central nervous system using neuronal and glial markers. Immunoreactivity to NeuN (neuronal nuclei antigen, GAP-43 (growth-associated protein 43, GFAP (glial fibrillary acidic protein, and Iba 1 (Ionized calcium binding adaptor molecule 1 were evaluated 1, 3, 7, 14, 28 and 35 days after either unilateral facial nerve lesion or sham surgery. Patches of decreased NeuN immunoreactivity were found bilaterally in vM1 as well as in primary somatosensory cortex (CxS1. Significantly increased GAP-43 immunoreactivity was found bilaterally after the lesion in hippocampus, striatum, and sensorimotor cortex. One day after lesion GFAP immunoreactivity increased bilaterally in hippocampus, subcortical white

  17. Primary Generators of Visually Evoked Field Potentials Recorded in the Macaque Auditory Cortex.

    Science.gov (United States)

    Kajikawa, Yoshinao; Smiley, John F; Schroeder, Charles E

    2017-10-18

    Prior studies have reported "local" field potential (LFP) responses to faces in the macaque auditory cortex and have suggested that such face-LFPs may be substrates of audiovisual integration. However, although field potentials (FPs) may reflect the synaptic currents of neurons near the recording electrode, due to the use of a distant reference electrode, they often reflect those of synaptic activity occurring in distant sites as well. Thus, FP recordings within a given brain region (e.g., auditory cortex) may be "contaminated" by activity generated elsewhere in the brain. To determine whether face responses are indeed generated within macaque auditory cortex, we recorded FPs and concomitant multiunit activity with linear array multielectrodes across auditory cortex in three macaques (one female), and applied current source density (CSD) analysis to the laminar FP profile. CSD analysis revealed no appreciable local generator contribution to the visual FP in auditory cortex, although we did note an increase in the amplitude of visual FP with cortical depth, suggesting that their generators are located below auditory cortex. In the underlying inferotemporal cortex, we found polarity inversions of the main visual FP components accompanied by robust CSD responses and large-amplitude multiunit activity. These results indicate that face-evoked FP responses in auditory cortex are not generated locally but are volume-conducted from other face-responsive regions. In broader terms, our results underscore the caution that, unless far-field contamination is removed, LFPs in general may reflect such "far-field" activity, in addition to, or in absence of, local synaptic responses.SIGNIFICANCE STATEMENT Field potentials (FPs) can index neuronal population activity that is not evident in action potentials. However, due to volume conduction, FPs may reflect activity in distant neurons superimposed upon that of neurons close to the recording electrode. This is problematic as the

  18. Experience-dependent spatial expectations in mouse visual cortex

    DEFF Research Database (Denmark)

    Fiser, Aris; Mahringer, David; Oyibo, Hassana K.

    2016-01-01

    In generative models of brain function, internal representations are used to generate predictions of sensory input, yet little is known about how internal models influence sensory processing. Here we show that, with experience in a virtual environment, the activity of neurons in layer 2/3 of mous...... scene based on spatial location and compares this representation with feed-forward visual input....

  19. Decoding of faces and face components in face-sensitive human visual cortex

    Directory of Open Access Journals (Sweden)

    David F Nichols

    2010-07-01

    Full Text Available A great challenge to the field of visual neuroscience is to understand how faces are encoded and represented within the human brain. Here we show evidence from functional magnetic resonance imaging (fMRI for spatially distributed processing of the whole face and its components in face-sensitive human visual cortex. We used multi-class linear pattern classifiers constructed with a leave-one-scan-out verification procedure to discriminate brain activation patterns elicited by whole faces, the internal features alone, and the external head outline alone. Furthermore, our results suggest that whole faces are represented disproportionately in the fusiform cortex (FFA whereas the building blocks of faces are represented disproportionately in occipitotemporal cortex (OFA. Faces and face components may therefore be organized with functional clustering within both the FFA and OFA, but with specialization for face components in the OFA and the whole face in the FFA.

  20. Layer-specificity in the effects of attention and working memory on activity in primary visual cortex.

    NARCIS (Netherlands)

    Van Kerkoerle, Timo; Self, M.W.; Roelfsema, P.R.

    2017-01-01

    Neuronal activity in early visual cortex depends on attention shifts but the contribution to working memory has remained unclear. Here, we examine neuronal activity in the different layers of the primary visual cortex (V1) in an attention-demanding and a working memory task. A current-source density

  1. Layer-specificity in the effects of attention and working memory on activity in primary visual cortex

    NARCIS (Netherlands)

    van Kerkoerle, Timo; Self, Matthew W.; Roelfsema, Pieter R.

    2017-01-01

    Neuronal activity in early visual cortex depends on attention shifts but the contribution to working memory has remained unclear. Here, we examine neuronal activity in the different layers of the primary visual cortex (V1) in an attention-demanding and a working memory task. A current-source density

  2. Visual cortex activation range of color vision with BOLD-fMRI in anisometropia amblyopia children

    Directory of Open Access Journals (Sweden)

    Hui-Fang Zhang

    2014-08-01

    Full Text Available AIM: To analyze the recovery of visual cortex activation range of color vision in anisometropia amblyopia children after treatment by using blood oxygen level dependence-functional magnetic resonance imaging(BOLD-fMRIand SPM8 software.METHODS: Self-control study. This fMRI study directly compared activity in visual cortex produced by color monocular stimulation in 13 monocular anisometropia amblyopia children. The project of study was blocked design. The data of functions and anatomical MRI was stimulated by three-primary colors and was preprocessed and analyzed by SPM8 that based on MATLAB software. According to the data, we compared the change of the central area of color vision when first visit and 1, 2,4wk after treatment. RESULTS: The BA17, BA18, BA19 and BA37 of amblyopia children were different activated after they accepted the three-primary colors stimulation(Pt value were 3.5210, 3.2716, 3.1534(Pt value were 3.7345, 3.2701(PCONCLUSION: After 4wk treatment, visual cortex activation of color vision of anisometropia amblyopic children is expanded, but with low extent, after the short-term treatment of amblyopia, visual cortex activation of color vision has a certain degree of recovery but not obvious.

  3. Visual cortex activation recorded by dynamic emission computed tomography of inhaled xenon 133

    DEFF Research Database (Denmark)

    Henriksen, L; Paulson, O B; Lassen, N A

    1981-01-01

    % respectively. Looking at different pictures displayed on a screen raised regional CBF by 26%. The most complex task, reading and copying a text, increased blood flow by 45%. Averaging the different tasks resulted in a mean regional CBF increase in the visual cortex of 35%. The result is comparable...

  4. Medial Prefrontal Cortex Is Selectively Involved in Response Selection Using Visual Context in the Background

    Science.gov (United States)

    Lee, Inah; Shin, Ji Yun

    2012-01-01

    The exact roles of the medial prefrontal cortex (mPFC) in conditional choice behavior are unknown and a visual contextual response selection task was used for examining the issue. Inactivation of the mPFC severely disrupted performance in the task. mPFC inactivations, however, did not disrupt the capability of perceptual discrimination for visual…

  5. Neuroimaging Weighs In: Humans Meet Macaques in “Primate” Visual Cortex

    OpenAIRE

    Tootell, Roger B.H.; Tsao, Doris; Vanduffel, Wim

    2003-01-01

    It has been only a decade since functional magnetic resonance imaging (fMRI) was introduced, but approximately four fMRI papers are now published every working day. Here we review this progress in a well studied system: primate visual cortex.

  6. Higher Brain Functions Served by the Lowly Rodent Primary Visual Cortex

    Science.gov (United States)

    Gavornik, Jeffrey P.; Bear, Mark F.

    2014-01-01

    It has been more than 50 years since the first description of ocular dominance plasticity--the profound modification of primary visual cortex (V1) following temporary monocular deprivation. This discovery immediately attracted the intense interest of neurobiologists focused on the general question of how experience and deprivation modify the brain…

  7. Irrelevant Auditory and Visual Events Induce a Visual Attentional Blink

    NARCIS (Netherlands)

    Van der Burg, Erik; Nieuwenstein, Mark R.; Theeuwes, Jan; Olivers, Christian N. L.

    2013-01-01

    In the present study we investigated whether a task-irrelevant distractor can induce a visual attentional blink pattern. Participants were asked to detect only a visual target letter (A, B, or C) and to ignore the preceding auditory, visual, or audiovisual distractor. An attentional blink was

  8. Temporal Processing Capacity in High-Level Visual Cortex Is Domain Specific.

    Science.gov (United States)

    Stigliani, Anthony; Weiner, Kevin S; Grill-Spector, Kalanit

    2015-09-09

    Prevailing hierarchical models propose that temporal processing capacity--the amount of information that a brain region processes in a unit time--decreases at higher stages in the ventral stream regardless of domain. However, it is unknown if temporal processing capacities are domain general or domain specific in human high-level visual cortex. Using a novel fMRI paradigm, we measured temporal capacities of functional regions in high-level visual cortex. Contrary to hierarchical models, our data reveal domain-specific processing capacities as follows: (1) regions processing information from different domains have differential temporal capacities within each stage of the visual hierarchy and (2) domain-specific regions display the same temporal capacity regardless of their position in the processing hierarchy. In general, character-selective regions have the lowest capacity, face- and place-selective regions have an intermediate capacity, and body-selective regions have the highest capacity. Notably, domain-specific temporal processing capacities are not apparent in V1 and have perceptual implications. Behavioral testing revealed that the encoding capacity of body images is higher than that of characters, faces, and places, and there is a correspondence between peak encoding rates and cortical capacities for characters and bodies. The present evidence supports a model in which the natural statistics of temporal information in the visual world may affect domain-specific temporal processing and encoding capacities. These findings suggest that the functional organization of high-level visual cortex may be constrained by temporal characteristics of stimuli in the natural world, and this temporal capacity is a characteristic of domain-specific networks in high-level visual cortex. Significance statement: Visual stimuli bombard us at different rates every day. For example, words and scenes are typically stationary and vary at slow rates. In contrast, bodies are dynamic

  9. Contralateral Bias of High Spatial Frequency Tuning and Cardinal Direction Selectivity in Mouse Visual Cortex.

    Science.gov (United States)

    Salinas, Kirstie J; Figueroa Velez, Dario X; Zeitoun, Jack H; Kim, Hyungtae; Gandhi, Sunil P

    2017-10-18

    Binocular mechanisms for visual processing are thought to enhance spatial acuity by combining matched input from the two eyes. Studies in the primary visual cortex of carnivores and primates have confirmed that eye-specific neuronal response properties are largely matched. In recent years, the mouse has emerged as a prominent model for binocular visual processing, yet little is known about the spatial frequency tuning of binocular responses in mouse visual cortex. Using calcium imaging in awake mice of both sexes, we show that the spatial frequency preference of cortical responses to the contralateral eye is ∼35% higher than responses to the ipsilateral eye. Furthermore, we find that neurons in binocular visual cortex that respond only to the contralateral eye are tuned to higher spatial frequencies. Binocular neurons that are well matched in spatial frequency preference are also matched in orientation preference. In contrast, we observe that binocularly mismatched cells are more mismatched in orientation tuning. Furthermore, we find that contralateral responses are more direction-selective than ipsilateral responses and are strongly biased to the cardinal directions. The contralateral bias of high spatial frequency tuning was found in both awake and anesthetized recordings. The distinct properties of contralateral cortical responses may reflect the functional segregation of direction-selective, high spatial frequency-preferring neurons in earlier stages of the central visual pathway. Moreover, these results suggest that the development of binocularity and visual acuity may engage distinct circuits in the mouse visual system.SIGNIFICANCE STATEMENT Seeing through two eyes is thought to improve visual acuity by enhancing sensitivity to fine edges. Using calcium imaging of cellular responses in awake mice, we find surprising asymmetries in the spatial processing of eye-specific visual input in binocular primary visual cortex. The contralateral visual pathway is

  10. Reduced visual cortex grey matter volume in children and adolescents with reactive attachment disorder

    Directory of Open Access Journals (Sweden)

    Koji Shimada

    2015-01-01

    Full Text Available Child maltreatment increases the risk for psychiatric disorders throughout childhood and into adulthood. One negative outcome of child maltreatment can be a disorder of emotional functioning, reactive attachment disorder (RAD, where the child displays wary, watchful, and emotionally withdrawn behaviours. Despite its clinical importance, little is known about the potential neurobiological consequences of RAD. The aim of this study was to elucidate whether RAD was associated with alterations in grey matter volume (GMV. High-resolution magnetic resonance imaging datasets were obtained for children and adolescents with RAD (n = 21; mean age = 12.76 years and typically developing (TD control subjects (n = 22; mean age = 12.95 years. Using a whole-brain voxel-based morphometry approach, structural images were analysed controlling for age, gender, full scale intelligence quotient, and total brain volume. The GMV was significantly reduced by 20.6% in the left primary visual cortex (Brodmann area 17 of the RAD group compared to the TD group (p = .038, family-wise error-corrected cluster level. This GMV reduction was related to an internalising problem measure of the Strength and Difficulties Questionnaire. The visual cortex has been viewed as part of the neurocircuit regulating the stress response to emotional visual images. Combined with previous studies of adults with childhood maltreatment, early adverse experience (e.g. sensory deprivation may affect the development of the primary visual system, reflecting in the size of the visual cortex in children and adolescents with RAD. These visual cortex GMV abnormalities may also be associated with the visual emotion regulation impairments of RAD, leading to an increased risk for later psychopathology.

  11. Connectivity Reveals Sources of Predictive Coding Signals in Early Visual Cortex During Processing of Visual Optic Flow.

    Science.gov (United States)

    Schindler, Andreas; Bartels, Andreas

    2017-05-01

    Superimposed on the visual feed-forward pathway, feedback connections convey higher level information to cortical areas lower in the hierarchy. A prominent framework for these connections is the theory of predictive coding where high-level areas send stimulus interpretations to lower level areas that compare them with sensory input. Along these lines, a growing body of neuroimaging studies shows that predictable stimuli lead to reduced blood oxygen level-dependent (BOLD) responses compared with matched nonpredictable counterparts, especially in early visual cortex (EVC) including areas V1-V3. The sources of these modulatory feedback signals are largely unknown. Here, we re-examined the robust finding of relative BOLD suppression in EVC evident during processing of coherent compared with random motion. Using functional connectivity analysis, we show an optic flow-dependent increase of functional connectivity between BOLD suppressed EVC and a network of visual motion areas including MST, V3A, V6, the cingulate sulcus visual area (CSv), and precuneus (Pc). Connectivity decreased between EVC and 2 areas known to encode heading direction: entorhinal cortex (EC) and retrosplenial cortex (RSC). Our results provide first evidence that BOLD suppression in EVC for predictable stimuli is indeed mediated by specific high-level areas, in accord with the theory of predictive coding. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  12. Transcranial magnetic stimulation reveals the content of visual short-term memory in the visual cortex.

    Science.gov (United States)

    Silvanto, Juha; Cattaneo, Zaira

    2010-05-01

    Cortical areas involved in sensory analysis are also believed to be involved in short-term storage of that sensory information. Here we investigated whether transcranial magnetic stimulation (TMS) can reveal the content of visual short-term memory (VSTM) by bringing this information to visual awareness. Subjects were presented with two random-dot displays (moving either to the left or to the right) and they were required to maintain one of these in VSTM. In Experiment 1, TMS was applied over the motion-selective area V5/MT+ above phosphene threshold during the maintenance phase. The reported phosphene contained motion features of the memory item, when the phosphene spatially overlapped with memory item. Specifically, phosphene motion was enhanced when the memory item moved in the same direction as the subjects' V5/MT+ baseline phosphene, whereas it was reduced when the motion direction of the memory item was incongruent with that of the baseline V5/MT+ phosphene. There was no effect on phosphene reports when there was no spatial overlap between the phosphene and the memory item. In Experiment 2, VSTM maintenance did not influence the appearance of phosphenes induced from the lateral occipital region. These interactions between VSTM maintenance and phosphene appearance demonstrate that activity in V5/MT+ reflects the motion qualities of items maintained in VSTM. Furthermore, these results also demonstrate that information in VSTM can modulate the pattern of visual activation reaching awareness, providing evidence for the view that overlapping neuronal populations are involved in conscious visual perception and VSTM. 2010. Published by Elsevier Inc.

  13. TMS of the occipital cortex induces tactile sensations in the fingers of blind Braille readers

    DEFF Research Database (Denmark)

    Ptito, M; Fumal, A; de Noordhout, A Martens

    2008-01-01

    Various non-visual inputs produce cross-modal responses in the visual cortex of early blind subjects. In order to determine the qualitative experience associated with these occipital activations, we systematically stimulated the entire occipital cortex using single pulse transcranial magnetic...... stimulation (TMS) in early blind subjects and in blindfolded seeing controls. Whereas blindfolded seeing controls reported only phosphenes following occipital cortex stimulation, some of the blind subjects reported tactile sensations in the fingers that were somatotopically organized onto the visual cortex...... cortical pathway between the somatosensory cortex and the visual cortex in early blind subjects. These results also add new evidence that the activity of the occipital lobe in the blind takes its qualitative expression from the character of its new input source, therefore supporting the cortical deference...

  14. Prior auditory information shapes visual category-selectivity in ventral occipito-temporal cortex.

    Science.gov (United States)

    Adam, Ruth; Noppeney, Uta

    2010-10-01

    Objects in our natural environment generate signals in multiple sensory modalities. This fMRI study investigated the influence of prior task-irrelevant auditory information on visually-evoked category-selective activations in the ventral occipito-temporal cortex. Subjects categorized pictures as landmarks or animal faces, while ignoring the preceding congruent or incongruent sound. Behaviorally, subjects responded slower to incongruent than congruent stimuli. At the neural level, the lateral and medial prefrontal cortices showed increased activations for incongruent relative to congruent stimuli consistent with their role in response selection. In contrast, the parahippocampal gyri combined visual and auditory information additively: activation was greater for visual landmarks than animal faces and landmark-related sounds than animal vocalizations resulting in increased parahippocampal selectivity for congruent audiovisual landmarks. Effective connectivity analyses showed that this amplification of visual landmark-selectivity was mediated by increased negative coupling of the parahippocampal gyrus with the superior temporal sulcus for congruent stimuli. Thus, task-irrelevant auditory information influences visual object categorization at two stages. In the ventral occipito-temporal cortex auditory and visual category information are combined additively to sharpen visual category-selective responses. In the left inferior frontal sulcus, as indexed by a significant incongruency effect, visual and auditory category information are integrated interactively for response selection. Copyright 2010 Elsevier Inc. All rights reserved.

  15. Visual maps in the adult primate cerebral cortex: some implications for brain development and evolution

    Directory of Open Access Journals (Sweden)

    M.G.P. Rosa

    2002-12-01

    Full Text Available In this paper, the topology of cortical visuotopic maps in adult primates is reviewed, with emphasis on recent studies. The observed visuotopic organisation can be summarised with reference to two basic rules. First, adjacent radial columns in the cortex represent partially overlapping regions of the visual field, irrespective of whether these columns are part of the same or different cortical areas. This primary rule is seldom, if ever, violated. Second, adjacent regions of the visual field tend to be represented in adjacent radial columns of a same area. This rule is not as rigid as the first, as many cortical areas form discontinuous, second-order representations of the visual field. A developmental model based on these physiological observations, and on comparative studies of cortical organisation, is then proposed, in order to explain how a combination of molecular specification steps and activity-driven processes can generate the variety of visuotopic organisations observed in adult cortex.

  16. Time-compressed preplay of anticipated events in human primary visual cortex.

    Science.gov (United States)

    Ekman, Matthias; Kok, Peter; de Lange, Floris P

    2017-05-23

    Perception is guided by the anticipation of future events. It has been hypothesized that this process may be implemented by pattern completion in early visual cortex, in which a stimulus sequence is recreated after only a subset of the visual input is provided. Here we test this hypothesis using ultra-fast functional magnetic resonance imaging to measure BOLD activity at precisely defined receptive field locations in visual cortex (V1) of human volunteers. We find that after familiarizing subjects with a spatial sequence, flashing only the starting point of the sequence triggers an activity wave in V1 that resembles the full stimulus sequence. This preplay activity is temporally compressed compared to the actual stimulus sequence and remains present even when attention is diverted from the stimulus sequence. Preplay might therefore constitute an automatic prediction mechanism for temporal sequences in V1.

  17. Neuronal correlates of amblyopia in the visual cortex of macaque monkeys with experimental strabismus and anisometropia.

    Science.gov (United States)

    Kiorpes, L; Kiper, D C; O'Keefe, L P; Cavanaugh, J R; Movshon, J A

    1998-08-15

    Amblyopia is a developmental disorder of pattern vision. After surgical creation of esotropic strabismus in the first weeks of life or after wearing -10 diopter contact lenses in one eye to simulate anisometropia during the first months of life, macaques often develop amblyopia. We studied the response properties of visual cortex neurons in six amblyopic macaques; three monkeys were anisometropic, and three were strabismic. In all monkeys, cortical binocularity was reduced. In anisometropes, the amblyopic eye influenced a relatively small proportion of cortical neurons; in strabismics, the influence of the two eyes was more nearly equal. The severity of amblyopia was related to the relative strength of the input of the amblyopic eye to the cortex only for the more seriously affected amblyopes. Measurements of the spatial frequency tuning and contrast sensitivity of cortical neurons showed few differences between the eyes for the three less severe amblyopes (two strabismic and one anisometropic). In the three more severely affected animals (one strabismic and two anisometropic), the optimal spatial frequency and spatial resolution of cortical neurons driven by the amblyopic eye were substantially and significantly lower than for neurons driven by the nonamblyopic eye. There were no reliable differences in neuronal contrast sensitivity between the eyes. A sample of neurons recorded from cortex representing the peripheral visual field showed no interocular differences, suggesting that the effects of amblyopia were more pronounced in portions of the cortex subserving foveal vision. Qualitatively, abnormalities in both the eye dominance and spatial properties of visual cortex neurons were related on a case-by-case basis to the depth of amblyopia. Quantitative analysis suggests, however, that these abnormalities alone do not explain the full range of visual deficits in amblyopia. Studies of extrastriate cortical areas may uncover further abnormalities that explain these

  18. Reward- and attention-related biasing of sensory selection in visual cortex.

    Science.gov (United States)

    Buschschulte, Antje; Boehler, Carsten N; Strumpf, Hendrik; Stoppel, Christian; Heinze, Hans-Jochen; Schoenfeld, Mircea A; Hopf, Jens-Max

    2014-05-01

    Attention to task-relevant features leads to a biasing of sensory selection in extrastriate cortex. Features signaling reward seem to produce a similar bias, but how modulatory effects due to reward and attention relate to each other is largely unexplored. To address this issue, it is critical to separate top-down settings defining reward relevance from those defining attention. To this end, we used a visual search paradigm in which the target's definition (attention to color) was dissociated from reward relevance by delivering monetary reward on search frames where a certain task-irrelevant color was combined with the target-defining color to form the target object. We assessed the state of neural biasing for the attended and reward-relevant color by analyzing the neuromagnetic brain response to asynchronously presented irrelevant distractor probes drawn in the target-defining color, the reward-relevant color, and a completely irrelevant color as a reference. We observed that for the prospect of moderate rewards, the target-defining color but not the reward-relevant color produced a selective enhancement of the neuromagnetic response between 180 and 280 msec in ventral extrastriate visual cortex. Increasing reward prospect caused a delayed attenuation (220-250 msec) of the response to reward probes, which followed a prior (160-180 msec) response enhancement in dorsal ACC. Notably, shorter latency responses in dorsal ACC were associated with stronger attenuation in extrastriate visual cortex. Finally, an analysis of the brain response to the search frames revealed that the presence of the reward-relevant color in search distractors elicited an enhanced response that was abolished after increasing reward size. The present data together indicate that when top-down definitions of reward relevance and attention are separated, the behavioral significance of reward-associated features is still rapidly coded in higher-level cortex areas, thereby commanding effective top

  19. Response properties of local field potentials and multiunit activity in the mouse visual cortex.

    Science.gov (United States)

    Land, R; Engler, G; Kral, A; Engel, A K

    2013-12-19

    Extracellular local field potentials (LFPs) and multiunit activity (MUA) reflect the spatially integrated activity of multiple neurons in a given cortical structure. In the cat and primate visual cortices, these signals exhibit selectivity for visual stimulus features, such as orientation, direction of motion or spatial frequency. In the mouse visual cortex, a model which has been increasingly used in visual neuroscience, the visual stimulus selectivity of population signals has not been examined in detail. We recorded LFPs and MUA using multielectrode arrays and two derived measures, the high-pass filtered continuous MUA and the bipolar first spatial derivative of the LFP, in the visual cortex of isoflurane-anesthetized C57Bl/6 mice. We analyzed the onset latency and characterized the receptive fields in addition to the direction, orientation, and spatial and temporal frequency preferences of these signals. Population signals exhibited onset latencies as short as ∼30ms and possessed receptive fields as large as ∼38° with MUA receptive fields smaller than those of LFPs. All four population signals exhibited similar spatial frequency preferences (∼0.1 cycles per degree) and temporal frequency preferences (∼1 cycle per second). However, for all population signals, spatial and frequency tunings were broad and orientation and direction of motion preferences were absent. The characterization of the visual stimulus selectivity of LFPs and MUA in the mouse visual cortex should provide information regarding their usability in characterizing stimulus properties and disclose possible limitations. Copyright © 2013 The Authors. Published by Elsevier Ltd.. All rights reserved.

  20. Attention Priority Map of Face Images in Human Early Visual Cortex.

    Science.gov (United States)

    Mo, Ce; He, Dongjun; Fang, Fang

    2018-01-03

    Attention priority maps are topographic representations that are used for attention selection and guidance of task-related behavior during visual processing. Previous studies have identified attention priority maps of simple artificial stimuli in multiple cortical and subcortical areas, but investigating neural correlates of priority maps of natural stimuli is complicated by the complexity of their spatial structure and the difficulty of behaviorally characterizing their priority map. To overcome these challenges, we reconstructed the topographic representations of upright/inverted face images from fMRI BOLD signals in human early visual areas primary visual cortex (V1) and the extrastriate cortex (V2 and V3) based on a voxelwise population receptive field model. We characterized the priority map behaviorally as the first saccadic eye movement pattern when subjects performed a face-matching task relative to the condition in which subjects performed a phase-scrambled face-matching task. We found that the differential first saccadic eye movement pattern between upright/inverted and scrambled faces could be predicted from the reconstructed topographic representations in V1-V3 in humans of either sex. The coupling between the reconstructed representation and the eye movement pattern increased from V1 to V2/3 for the upright faces, whereas no such effect was found for the inverted faces. Moreover, face inversion modulated the coupling in V2/3, but not in V1. Our findings provide new evidence for priority maps of natural stimuli in early visual areas and extend traditional attention priority map theories by revealing another critical factor that affects priority maps in extrastriate cortex in addition to physical salience and task goal relevance: image configuration. SIGNIFICANCE STATEMENT Prominent theories of attention posit that attention sampling of visual information is mediated by a series of interacting topographic representations of visual space known as

  1. Retinotopic mapping of the human visual cortex at a magnetic field strength of 7T.

    Science.gov (United States)

    Hoffmann, Michael B; Stadler, Jörg; Kanowski, Martin; Speck, Oliver

    2009-01-01

    fMRI-based retinotopic mapping data obtained at a magnetic field strength of 7T are evaluated and compared to 3T acquisitions. With established techniques retinotopic mapping data were obtained in four subjects for 25 slices parallel to the calcarine sulcus at 7 and 3T for three voxel sizes (2.5(3), 1.4(3), and 1.1(3)mm(3)) and in two subjects for 49 slices at 7T for 2.5(3)mm(3) voxels. The data were projected to the flattened representation of T1 weighted images acquired at 3T. The obtained retinotopic maps allowed for the identification of visual areas in the occipito-parietal cortex. The mean coherence increased with magnetic field strength and with voxel size. At 7T, the occipital cortex could be sampled with high sensitivity in a short single session at high resolution. Alternatively, at lower resolution simultaneous mapping of a great expanse of occipito-parietal cortex was possible. Retinotopic mapping at 7T aids a detailed description of the visual areas. Here, recent findings of multiple stimulus-driven retinotopic maps along the intraparietal sulcus are supported. Retinotopic mapping at 7T opens the possibility to detail our understanding of the cortical visual field representations in general and of their plasticity in visual system pathologies.

  2. Drive for Consumption, Craving, and Connectivity in the Visual Cortex during the Imagery of Desired Food

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    Jessica eBullins

    2013-11-01

    Full Text Available There is considerable interest in understanding food cravings given the obesogenic environment of Western Society. In this paper we examine how the imagery of palatable foods affects cravings and functional connectivity in the visual cortex for people who differ on the power of food scale (PFS. Fourteen older, overweight/obese adults came to our laboratory on two different occasions. Both times they ate a controlled breakfast meal and then were restricted from eating for 2.5 hours prior to scanning. On one day they consumed a BOOST® liquid meal after the period of food restriction, whereas on the other day they only consumed water (NO BOOST® condition. After these manipulations, they had an fMRI scan in which they were asked to image both neutral objects and their favorite snack foods; they also completed visual analogue scales for craving, hunger, and the vividness of the imagery experiences. Irrespective of the BOOST® manipulation, we observed marked increases in food cravings when older, overweight/obese adults created images of favorite foods in their minds as opposed to creating an image of neutral objects; however, the increase in food craving following the imagery of desired food was more pronounced among those scoring high than low on the PFS. Furthermore, local efficiency within the visual cortex when imaging desired food was higher for those scoring high as compared to low on the PFS. The active imagery of desired foods seemed to have overpowered the BOOST® manipulation when evaluating connectivity in the visual cortex.

  3. Direct tactile stimulation of dorsal occipito-temporal cortex in a visual agnosic.

    Science.gov (United States)

    Allen, Harriet A; Humphreys, Glyn W

    2009-06-23

    The human occipito-temporal cortex is preferentially activated by images of objects as opposed to scrambled images. Touching objects (versus textures) also activates this region. We used neuropsychological fMRI to probe whether dorsal regions of the lateral occipital cortex (LO) are activated in tactile recognition without mediation through visual recognition. We tested a patient (HJA) with visual agnosia due to bilateral lesions of the ventral occipito-temporal cortex but spared dorsal LO. HJA's recognition of visual objects was impaired. Nevertheless, his tactile recognition was preserved. We measured brain activity while participants viewed and touched objects and textures. There was overlapping activity in regions including LO and cerebellum for both stimuli for control participants, including new regions not before considered bimodal. For HJA, there were overlapping regions in the intact dorsal LO. Within a subset of the regions found in control participants, HJA showed activity only for tactile objects, suggesting that these regions are specifically involved in successful multimodal recognition. Activation of dorsal LO by tactile input is not secondary to visual recognition but can operate directly through tactile input.

  4. Model-based analysis of patterned motion processing in mouse primary visual cortex

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    Dylan Richard Muir

    2015-08-01

    Full Text Available Neurons in sensory areas of neocortex show responses tuned to specific features of the environment. In visual cortex, information about features such as edges or textures with particular orientations must be integrated to recognize a visual scene or object. Connectivity studies in rodent cortex have revealed that neurons make specific connections within sub-networks sharing common input tuning. In principle, this sub-network architecture enables local cortical circuits to integrate sensory information. However, whether feature integration indeed occurs locally in rodent primary sensory areas has not been examined directly. We studied local integration of sensory features in primary visual cortex (V1 of the mouse by presenting drifting grating and plaid stimuli, while recording the activity of neuronal populations with two-photon calcium imaging. Using a Bayesian model-based analysis framework, we classified single-cell responses as being selective for either individual grating components or for moving plaid patterns. Rather than relying on trial-averaged responses, our model-based framework takes into account single-trial responses and can easily be extended to consider any number of arbitrary predictive models. Our analysis method was able to successfully classify significantly more responses than traditional partial correlation analysis, and provides a rigorous statistical framework to rank any number of models and reject poorly performing models. We also found large a proportion of cells that respond strongly to only one stimulus class. In addition, a quarter of selectively responding neurons had more complex responses that could not be explained by any simple integration model. Our results show that a broad range of pattern integration processes takes place already at the level of primary visual cortex. This diversity of integration is consistent with processing of visual inputs by local sub-networks within V1 that are tuned to combinations

  5. Decorrelated Input Dissociates Narrow Band γ Power and BOLD in Human Visual Cortex.

    Science.gov (United States)

    Butler, Russell; Bernier, Pierre-Michel; Lefebvre, Jérémie; Gilbert, Guillaume; Whittingstall, Kevin

    2017-05-31

    Although fMRI using the BOLD contrast is widely used for noninvasively mapping hemodynamic brain activity in humans, its exact link to underlying neural processing is poorly understood. Whereas some studies have reported that BOLD signals measured in visual cortex are tightly linked to neural activity in the narrow band γ (NBG) range, others have found a weak correlation between the two. To elucidate the mechanisms behind these conflicting findings, we hypothesized that BOLD reflects the strength of synaptic inputs to cortex, whereas NBG is more dependent on how well these inputs are correlated. To test this, we measured NBG, BOLD, and cerebral blood flow responses to stimuli that either correlate or decorrelate neural activity in human visual cortex. Next, we simulated a recurrent network model of excitatory and inhibitory neurons that reproduced in detail the experimental NBG and BOLD data. Results show that the visually evoked BOLD response was solely predicted by the sum of local inputs, whereas NBG was critically dependent on how well these inputs were correlated. In summary, the NBG-BOLD relationship strongly depends on the nature of sensory input to cortex: stimuli that increase the number of correlated inputs to visual cortex will increase NBG and BOLD in a similar manner, whereas stimuli that increase the number of decorrelated inputs will dissociate the two. The NBG-BOLD relationship is therefore not fixed but is rather highly dependent on input correlations that are both stimulus- and state-dependent. SIGNIFICANCE STATEMENT It is widely believed that γ oscillations in cortex are tightly linked to local hemodynamic activity. Here, we present experimental evidence showing how a stimulus can increase local blood flow to the brain despite suppressing γ power. Moreover, using a sophisticated model of cortical neurons, it is proposed that this occurs when synaptic input to cortex is strong yet decorrelated. Because input correlations are largely determined

  6. Brief daily binocular vision prevents monocular deprivation effects in visual cortex.

    Science.gov (United States)

    Schwarzkopf, D Samuel; Vorobyov, Vasily; Mitchell, Donald E; Sengpiel, Frank

    2007-01-01

    Even short periods of early monocular deprivation result in reduced cortical representation and visual acuity of the deprived eye. However, we have shown recently that the dramatic deprivation effects on vision can be prevented entirely if the animal receives a brief period of concordant binocular vision each day. We examine here the extent to which the cortical deprivation effects can be counteracted by daily periods of normal experience. Cats received variable daily regimens of monocular deprivation (by wearing a mask) and binocular vision. We subsequently assessed visual cortex function with optical imaging of intrinsic signals and visually evoked potential recordings. Regardless of the overall length of visual experience, daily binocular vision for as little as 30 min, but no less, allowed normal ocular dominance and visual responses to be maintained despite several times longer periods of deprivation. Thus, the absolute amount of daily binocular vision rather than its relative share of the daily exposure determined the outcome. When 30 min of binocular exposure was broken up into two 15-min blocks flanking the deprivation period, ocular dominance resembled that of animals with only 15 min of binocular vision, suggesting that binocular experience must be continuous to be most effective. Our results demonstrate that normal experience is clearly more efficacious in maintaining normal functional architecture of the visual cortex than abnormal experience is in altering it. The beneficial effects of very short periods of binocular vision may prevent any long-term effects (amblyopia) from brief periods of compromised vision through injury or infection during development.

  7. Category Selectivity of Human Visual Cortex in Perception of Rubin Face–Vase Illusion

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    Xiaogang Wang

    2017-09-01

    Full Text Available When viewing the Rubin face–vase illusion, our conscious perception spontaneously alternates between the face and the vase; this illusion has been widely used to explore bistable perception. Previous functional magnetic resonance imaging (fMRI studies have studied the neural mechanisms underlying bistable perception through univariate and multivariate pattern analyses; however, no studies have investigated the issue of category selectivity. Here, we used fMRI to investigate the neural mechanisms underlying the Rubin face–vase illusion by introducing univariate amplitude and multivariate pattern analyses. The results from the amplitude analysis suggested that the activity in the fusiform face area was likely related to the subjective face perception. Furthermore, the pattern analysis results showed that the early visual cortex (EVC and the face-selective cortex could discriminate the activity patterns of the face and vase perceptions. However, further analysis of the activity patterns showed that only the face-selective cortex contains the face information. These findings indicated that although the EVC and face-selective cortex activities could discriminate the visual information, only the activity and activity pattern in the face-selective areas contained the category information of face perception in the Rubin face–vase illusion.

  8. Wireless data and power transfer of an optogenetic implantable visual cortex stimulator.

    Science.gov (United States)

    Fattah, Nabeel; Laha, Soumyasanta; Sokolov, Danil; Chester, Graeme; Degenaar, Patrick

    2015-08-01

    In this paper, the wireless data and power transfer for a novel optogenetic visual cortex implant system was demonstrated by using pork tissue mimic in-vitro at the ISM 2.4 GHz and 13.5 MHz frequency band respectively. The observed data rate was 120 kbps with no loss in data for up to a thickness of 35 mm in both water & pork. To increase the power level of the implant a Class E power amplifier is separately designed and simulated for the transmitter end and has an output power of around 223 mW with an efficiency of 81.83%. The transferred power at the receiver was measured to be 66.80 mW for the pork tissue medium considering a distance of 5 mm between the transmitter and the receiver coils, with a coupling coefficient of ~0.8. This serves the power requirement of the visual cortex implant.

  9. Director field model of the primary visual cortex for contour detection.

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    Vijay Singh

    Full Text Available We aim to build the simplest possible model capable of detecting long, noisy contours in a cluttered visual scene. For this, we model the neural dynamics in the primate primary visual cortex in terms of a continuous director field that describes the average rate and the average orientational preference of active neurons at a particular point in the cortex. We then use a linear-nonlinear dynamical model with long range connectivity patterns to enforce long-range statistical context present in the analyzed images. The resulting model has substantially fewer degrees of freedom than traditional models, and yet it can distinguish large contiguous objects from the background clutter by suppressing the clutter and by filling-in occluded elements of object contours. This results in high-precision, high-recall detection of large objects in cluttered scenes. Parenthetically, our model has a direct correspondence with the Landau-de Gennes theory of nematic liquid crystal in two dimensions.

  10. Radial asymmetries in population receptive field size and cortical magnification factor in early visual cortex.

    Science.gov (United States)

    Silva, Maria Fatima; Brascamp, Jan W; Ferreira, Sónia; Castelo-Branco, Miguel; Dumoulin, Serge O; Harvey, Ben M

    2017-11-14

    Human visual cortex does not represent the whole visual field with the same detail. Changes in receptive field size, population receptive field (pRF) size and cortical magnification factor (CMF) with eccentricity are well established, and associated with changes in visual acuity with eccentricity. Visual acuity also changes across polar angle. However, it remains unclear how RF size, pRF size and CMF change across polar angle. Here, we examine differences in pRF size and CMF across polar angle in V1, V2 and V3 using pRF modeling of human fMRI data. In these visual field maps, we find smaller pRFs and larger CMFs in horizontal (left and right) than vertical (upper and lower) visual field quadrants. Differences increase with eccentricity, approximately in proportion to average pRF size and CMF. Similarly, we find larger CMFs in the lower than upper quadrant, and again differences increase with eccentricity. However, pRF size differences between lower and upper quadrants change direction with eccentricity. Finally, we find slightly smaller pRFs in the left than right quadrants of V2 and V3, though this difference is very small, and we find no differences in V1 and no differences in CMF. Moreover, differences in pRF size and CMF vary gradually with polar angle and are not limited to the meridians or visual field map discontinuities. PRF size and CMF differences do not consistently follow patterns of cortical curvature, despite the link between cortical curvature and polar angle in V1. Thus, the early human visual cortex has a radially asymmetric representation of the visual field. These asymmetries may underlie consistent reports of asymmetries in perceptual abilities. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. Receptive field properties of neurons in the primary visual cortex under photopic and scotopic lighting conditions

    OpenAIRE

    Duffy, Kevin R.; Hubel, David H.

    2007-01-01

    Knowledge of the physiology of the primate visual cortex (area V-1) comes mostly from studies done in photopic conditions, in which retinal cones are active and rods play little or no part. Conflicting results have come from research into the effects of dark adaptation on receptive field organization of cells in the retina and the lateral geniculate nucleus. These studies claim either that the effect of the surround disappears with dark adaptation or that it does not. The current study has as...

  12. Random Wiring, Ganglion Cell Mosaics, and the Functional Architecture of the Visual Cortex.

    OpenAIRE

    Manuel Schottdorf; Wolfgang Keil; David Coppola; White, Leonard E.; Fred Wolf

    2015-01-01

    The architecture of iso-orientation domains in the primary visual cortex (V1) of placental carnivores and primates apparently follows species invariant quantitative laws. Dynamical optimization models assuming that neurons coordinate their stimulus preferences throughout cortical circuits linking millions of cells specifically predict these invariants. This might indicate that V1's intrinsic connectome and its functional architecture adhere to a single optimization principle with high precisi...

  13. Neural correlates of visual motion processing without awareness in patients with striate cortex and pulvinar lesions.

    Science.gov (United States)

    Barleben, Maria; Stoppel, Christian M; Kaufmann, Jörn; Merkel, Christian; Wecke, Thoralf; Goertler, Michael; Heinze, Hans-Jochen; Hopf, Jens-Max; Schoenfeld, Mircea A

    2015-04-01

    Patients with striate cortex lesions experience visual perception loss in the contralateral visual field. In few patients, however, stimuli within the blind field can lead to unconscious (blindsight) or even conscious perception when the stimuli are moving (Riddoch syndrome). Using functional magnetic resonance imaging (fMRI), we investigated the neural responses elicited by motion stimulation in the sighted and blind visual fields of eight patients with lesions of the striate cortex. Importantly, repeated testing ensured that none of the patients exhibited blindsight or a Riddoch syndrome. Three patients had additional lesions in the ipsilesional pulvinar. For blind visual field stimulation, great care was given that the moving stimulus was precisely presented within the borders of the scotoma. In six of eight patients, the stimulation within the scotoma elicited hemodynamic activity in area human middle temporal (hMT) while no activity was observed within the ipsilateral lesioned area of the striate cortex. One of the two patients in whom no ipsilesional activity was observed had an extensive lesion including massive subcortical damage. The other patient had an additional focal lesion within the lateral inferior pulvinar. Fiber-tracking based on anatomical and functional markers (hMT and Pulvinar) on individual diffusion tensor imaging (DTI) data from each patient revealed the structural integrity of subcortical pathways in all but the patient with the extensive subcortical lesion. These results provide clear evidence for the robustness of direct subcortical pathways from the pulvinar to area hMT in patients with striate cortex lesions and demonstrate that ipsilesional activity in area hMT is completely independent of conscious perception. © 2014 Wiley Periodicals, Inc.

  14. Adult Visual Experience Promotes Recovery of Primary Visual Cortex from Long-Term Monocular Deprivation

    Science.gov (United States)

    Fischer, Quentin S.; Aleem, Salman; Zhou, Hongyi; Pham, Tony A.

    2007-01-01

    Prolonged visual deprivation from early childhood to maturity is believed to cause permanent visual impairment. However, there have been case reports of substantial improvement of binocular vision in human adults following lifelong visual impairment or deprivation. These observations, together with recent findings of adult ocular dominance…

  15. Large-scale functional models of visual cortex for remote sensing

    Energy Technology Data Exchange (ETDEWEB)

    Brumby, Steven P [Los Alamos National Laboratory; Kenyon, Garrett [Los Alamos National Laboratory; Rasmussen, Craig E [Los Alamos National Laboratory; Swaminarayan, Sriram [Los Alamos National Laboratory; Bettencourt, Luis [Los Alamos National Laboratory; Landecker, Will [PORTLAND STATE UNIV.

    2009-01-01

    Neuroscience has revealed many properties of neurons and of the functional organization of visual cortex that are believed to be essential to human vision, but are missing in standard artificial neural networks. Equally important may be the sheer scale of visual cortex requiring {approx}1 petaflop of computation. In a year, the retina delivers {approx}1 petapixel to the brain, leading to massively large opportunities for learning at many levels of the cortical system. We describe work at Los Alamos National Laboratory (LANL) to develop large-scale functional models of visual cortex on LANL's Roadrunner petaflop supercomputer. An initial run of a simple region VI code achieved 1.144 petaflops during trials at the IBM facility in Poughkeepsie, NY (June 2008). Here, we present criteria for assessing when a set of learned local representations is 'complete' along with general criteria for assessing computer vision models based on their projected scaling behavior. Finally, we extend one class of biologically-inspired learning models to problems of remote sensing imagery.

  16. Asymmetric multisensory interactions of visual and somatosensory responses in a region of the rat parietal cortex.

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    Michael T Lippert

    Full Text Available Perception greatly benefits from integrating multiple sensory cues into a unified percept. To study the neural mechanisms of sensory integration, model systems are required that allow the simultaneous assessment of activity and the use of techniques to affect individual neural processes in behaving animals. While rodents qualify for these requirements, little is known about multisensory integration and areas involved for this purpose in the rodent. Using optical imaging combined with laminar electrophysiological recordings, the rat parietal cortex was identified as an area where visual and somatosensory inputs converge and interact. Our results reveal similar response patterns to visual and somatosensory stimuli at the level of current source density (CSD responses and multi-unit responses within a strip in parietal cortex. Surprisingly, a selective asymmetry was observed in multisensory interactions: when the somatosensory response preceded the visual response, supra-linear summation of CSD was observed, but the reverse stimulus order resulted in sub-linear effects in the CSD. This asymmetry was not present in multi-unit activity however, which showed consistently sub-linear interactions. These interactions were restricted to a specific temporal window, and pharmacological tests revealed significant local intra-cortical contributions to this phenomenon. Our results highlight the rodent parietal cortex as a system to model the neural underpinnings of multisensory processing in behaving animals and at the cellular level.

  17. Independent effects of motivation and spatial attention in the human visual cortex.

    Science.gov (United States)

    Bayer, Mareike; Rossi, Valentina; Vanlessen, Naomi; Grass, Annika; Schacht, Annekathrin; Pourtois, Gilles

    2017-01-01

    Motivation and attention constitute major determinants of human perception and action. Nonetheless, it remains a matter of debate whether motivation effects on the visual cortex depend on the spatial attention system, or rely on independent pathways. This study investigated the impact of motivation and spatial attention on the activity of the human primary and extrastriate visual cortex by employing a factorial manipulation of the two factors in a cued pattern discrimination task. During stimulus presentation, we recorded event-related potentials and pupillary responses. Motivational relevance increased the amplitudes of the C1 component at ∼70 ms after stimulus onset. This modulation occurred independently of spatial attention effects, which were evident at the P1 level. Furthermore, motivation and spatial attention had independent effects on preparatory activation as measured by the contingent negative variation; and pupil data showed increased activation in response to incentive targets. Taken together, these findings suggest independent pathways for the influence of motivation and spatial attention on the activity of the human visual cortex. © The Author (2016). Published by Oxford University Press.

  18. HDAC2 expression in parvalbumin interneurons regulates synaptic plasticity in the mouse visual cortex

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    Alexi Nott

    2015-01-01

    Full Text Available An experience-dependent postnatal increase in GABAergic inhibition in the visual cortex is important for the closure of a critical period of enhanced synaptic plasticity. Although maturation of the subclass of parvalbumin (Pv–expressing GABAergic interneurons is known to contribute to critical period closure, the role of epigenetics on cortical inhibition and synaptic plasticity has not been explored. The transcription regulator, histone deacetylase 2 (HDAC2, has been shown to modulate synaptic plasticity and learning processes in hippocampal excitatory neurons. We found that genetic deletion of HDAC2 specifically from Pv interneurons reduces inhibitory input in the visual cortex of adult mice and coincides with enhanced long-term depression that is more typical of young mice. These findings show that HDAC2 loss in Pv interneurons leads to a delayed closure of the critical period in the visual cortex and supports the hypothesis that HDAC2 is a key negative regulator of synaptic plasticity in the adult brain.

  19. HDAC2 expression in parvalbumin interneurons regulates synaptic plasticity in the mouse visual cortex.

    Science.gov (United States)

    Nott, Alexi; Cho, Sukhee; Seo, Jinsoo; Tsai, Li-Huei

    2015-01-01

    An experience-dependent postnatal increase in GABAergic inhibition in the visual cortex is important for the closure of a critical period of enhanced synaptic plasticity. Although maturation of the subclass of Parvalbumin (Pv)-expressing GABAergic interneurons is known to contribute to critical period closure, the role of epigenetics on cortical inhibition and synaptic plasticity has not been explored. The transcription regulator, histone deacetylase 2 (HDAC2), has been shown to modulate synaptic plasticity and learning processes in hippocampal excitatory neurons. We found that genetic deletion of HDAC2 specifically from Pv-interneurons reduces inhibitory input in the visual cortex of adult mice, and coincides with enhanced long-term depression (LTD) that is more typical of young mice. These findings show that HDAC2 loss in Pv-interneurons leads to a delayed closure of the critical period in the visual cortex and supports the hypothesis that HDAC2 is a key negative regulator of synaptic plasticity in the adult brain.

  20. Morphology of primary visual cortex predicts individual differences in fixation duration during text reading.

    Science.gov (United States)

    Henderson, John M; Choi, Wonil; Luke, Steven G

    2014-12-01

    In skilled reading, fixations are brief periods of time in which the eyes settle on words. E-Z Reader, a computational model of dynamic reading, posits that fixation durations are under real-time control of lexical processing. Lexical processing, in turn, requires efficient visual encoding. Here we tested the hypothesis that individual differences in fixation durations are related to individual differences in the efficiency of early visual encoding. To test this hypothesis, we recorded participants' eye movements during reading. We then examined individual differences in fixation duration distributions as a function of individual differences in the morphology of primary visual cortex measured from MRI scans. The results showed that greater gray matter surface area and volume in visual cortex predicted shorter and less variable fixation durations in reading. These results suggest that individual differences in eye movements during skilled reading are related to initial visual encoding, consistent with models such as E-Z Reader that emphasize lexical control over fixation time.

  1. Attention to Color Sharpens Neural Population Tuning via Feedback Processing in the Human Visual Cortex Hierarchy.

    Science.gov (United States)

    Bartsch, Mandy V; Loewe, Kristian; Merkel, Christian; Heinze, Hans-Jochen; Schoenfeld, Mircea A; Tsotsos, John K; Hopf, Jens-Max

    2017-10-25

    Attention can facilitate the selection of elementary object features such as color, orientation, or motion. This is referred to as feature-based attention and it is commonly attributed to a modulation of the gain and tuning of feature-selective units in visual cortex. Although gain mechanisms are well characterized, little is known about the cortical processes underlying the sharpening of feature selectivity. Here, we show with high-resolution magnetoencephalography in human observers (men and women) that sharpened selectivity for a particular color arises from feedback processing in the human visual cortex hierarchy. To assess color selectivity, we analyze the response to a color probe that varies in color distance from an attended color target. We find that attention causes an initial gain enhancement in anterior ventral extrastriate cortex that is coarsely selective for the target color and transitions within ∼100 ms into a sharper tuned profile in more posterior ventral occipital cortex. We conclude that attention sharpens selectivity over time by attenuating the response at lower levels of the cortical hierarchy to color values neighboring the target in color space. These observations support computational models proposing that attention tunes feature selectivity in visual cortex through backward-propagating attenuation of units less tuned to the target.SIGNIFICANCE STATEMENT Whether searching for your car, a particular item of clothing, or just obeying traffic lights, in everyday life, we must select items based on color. But how does attention allow us to select a specific color? Here, we use high spatiotemporal resolution neuromagnetic recordings to examine how color selectivity emerges in the human brain. We find that color selectivity evolves as a coarse to fine process from higher to lower levels within the visual cortex hierarchy. Our observations support computational models proposing that feature selectivity increases over time by attenuating the

  2. Mapping arealisation of the visual cortex of non-primate species: lessons for development and evolution

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    Jihane eHomman-Ludiye

    2014-07-01

    Full Text Available In order to integrate and interpret visual stimuli and build a representation of the surrounding environment, the visual cortex is organised in anatomically distinct and functionally unique areas. Each area processes a particular aspect of the visual scene, with the signal flowing from one area to the next in a bottom-up processing sequence. Areal borders can be demarcated both functionally by systematic electrophysiology mapping, and anatomically by sharp changes in cellular distribution and molecular expression profiles. Primates, including humans, are heavily dependent on vision, with approximately 50% of their neocortical surface dedicated to visual processing and possess many more visual areas than any other mammal, making them often the model of choice to study visual arealisation. However, the recent identification of differential gene expression profiles between cortices in a number of species has allowed for the introduction of non-primate animal models in the field to better understand development and evolution. Profiling the mosaic of visual areas in less complex species was pivotal in understanding the mechanisms responsible for patterning the developing neocortex, specifying area identity as well as the evolutionary events that have allowed for primates to develop more areas. In addition, species with fewer areas provide a simpler system in which to study and map cortical connectivity. In this review we focus on non-primate species that have contributed to elucidating the evolution and development of the visual cortex, including small nocturnal species and carnivores. We present the current understanding of the mechanisms supporting the establishment of areal borders during development and the limitations of the predominant mouse model and the need for alternate species.

  3. Widespread correlation patterns of fMRI signal across visual cortex reflect eccentricity organization

    Science.gov (United States)

    Arcaro, Michael J; Honey, Christopher J; Mruczek, Ryan EB; Kastner, Sabine; Hasson, Uri

    2015-01-01

    The human visual system can be divided into over two-dozen distinct areas, each of which contains a topographic map of the visual field. A fundamental question in vision neuroscience is how the visual system integrates information from the environment across different areas. Using neuroimaging, we investigated the spatial pattern of correlated BOLD signal across eight visual areas on data collected during rest conditions and during naturalistic movie viewing. The correlation pattern between areas reflected the underlying receptive field organization with higher correlations between cortical sites containing overlapping representations of visual space. In addition, the correlation pattern reflected the underlying widespread eccentricity organization of visual cortex, in which the highest correlations were observed for cortical sites with iso-eccentricity representations including regions with non-overlapping representations of visual space. This eccentricity-based correlation pattern appears to be part of an intrinsic functional architecture that supports the integration of information across functionally specialized visual areas. DOI: http://dx.doi.org/10.7554/eLife.03952.001 PMID:25695154

  4. Contextual Learning Induces Dendritic Spine Clustering in Retrosplenial Cortex

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    Adam C Frank

    2014-03-01

    Full Text Available Molecular and electrophysiological studies find convergent evidence suggesting that plasticity within a dendritic tree is not randomly dispersed, but rather clustered into functional groups. Further, results from in silico neuronal modeling show that clustered plasticity is able to increase storage capacity 45 times compared to dispersed plasticity. Recent in vivo work utilizing chronic 2-photon microscopy tested the clustering hypothesis and showed that repetitive motor learning is able to induce clustered addition of new dendritic spines on apical dendrites of L5 neurons in primary motor cortex; moreover, clustered spines were found to be more stable than non-clustered spines, suggesting a physiological role for spine clustering. To further test this hypothesis we used in vivo 2-photon imaging in Thy1-YFP-H mice to chronically examine dendritic spine dynamics in retrosplenial cortex (RSC during spatial learning. RSC is a key component of an extended spatial learning and memory circuit that includes hippocampus and entorhinal cortex. Importantly, RSC is known from both lesion and immediate early gene studies to be critically involved in spatial learning and more specifically in contextual fear conditioning. We utilized a modified contextual fear conditioning protocol wherein animals received a mild foot shock each day for five days; this protocol induces gradual increases in context freezing over several days before the animals reach a behavioral plateau. We coupled behavioral training with four separate in vivo imaging sessions, two before training begins, one early in training, and a final session after training is complete. This allowed us to image spine dynamics before training as well as early in learning and after animals had reached behavioral asymptote. We find that this contextual learning protocol induces a statistically significant increase in the formation of clusters of new dendritic spines in trained animals when compared to home

  5. Visual Input Enhances Selective Speech Envelope Tracking in Auditory Cortex at a ‘Cocktail Party’

    Science.gov (United States)

    Golumbic, Elana Zion; Cogan, Gregory B.; Schroeder, Charles E.; Poeppel, David

    2013-01-01

    Our ability to selectively attend to one auditory signal amidst competing input streams, epitomized by the ‘Cocktail Party’ problem, continues to stimulate research from various approaches. How this demanding perceptual feat is achieved from a neural systems perspective remains unclear and controversial. It is well established that neural responses to attended stimuli are enhanced compared to responses to ignored ones, but responses to ignored stimuli are nonetheless highly significant, leading to interference in performance. We investigated whether congruent visual input of an attended speaker enhances cortical selectivity in auditory cortex, leading to diminished representation of ignored stimuli. We recorded magnetoencephalographic (MEG) signals from human participants as they attended to segments of natural continuous speech. Using two complementary methods of quantifying the neural response to speech, we found that viewing a speaker’s face enhances the capacity of auditory cortex to track the temporal speech envelope of that speaker. This mechanism was most effective in a ‘Cocktail Party’ setting, promoting preferential tracking of the attended speaker, whereas without visual input no significant attentional modulation was observed. These neurophysiological results underscore the importance of visual input in resolving perceptual ambiguity in a noisy environment. Since visual cues in speech precede the associated auditory signals, they likely serve a predictive role in facilitating auditory processing of speech, perhaps by directing attentional resources to appropriate points in time when to-be-attended acoustic input is expected to arrive. PMID:23345218

  6. Laminar imaging of positive and negative BOLD in human visual cortex at 7T.

    Science.gov (United States)

    Fracasso, Alessio; Luijten, Peter R; Dumoulin, Serge O; Petridou, Natalia

    2017-02-14

    Deciphering the direction of information flow is critical to understand the brain. Data from non-human primate histology shows that connections between lower to higher areas (e.g. retina→V1), and between higher to lower areas (e.g. V1←V2) can be dissociated based upon the distribution of afferent synapses at the laminar level. Ultra-high field scanners opened up the possibility to image brain structure and function at an unprecedented level of detail. Taking advantage of the increased spatial resolution available, it could theoretically be possible to disentangle activity from different cortical depths from human cerebral cortex, separately studying different compartments across depth. Here we use half-millimeter human functional and structural magnetic resonance imaging (fMRI, MRI) to derive laminar profiles in early visual cortex using a paradigm known to elicit two separate responses originating from an excitatory and a suppressive source, avoiding any contamination due to blood-stealing. We report the shape of laminar blood level oxygenation level dependent (BOLD) profiles from the excitatory and suppressive conditions. We analyse positive and negative %BOLD laminar profiles with respect to the dominating linear trend towards the pial surface, a confounding feature of gradient echo BOLD fMRI, and examine the correspondence with the anatomical landmark of input-related signals in primary visual cortex, the stria of Gennari. Copyright © 2017. Published by Elsevier Inc.

  7. Golgi-like staining of visual cortex cells obtained by extracellular biocytin application in vitro.

    Science.gov (United States)

    Kenan-Vaknin, G; Katz, H; Malach, R

    1992-02-07

    We report here the application of biocytin (a biotin-lysine complex) as an extracellular tracer in vitro. Biocytin was applied extracellularly, revealing Golgi-like staining of cells in the adult in vitro rat visual cortex. Micropipettes were filled with a solution of 2.3-2.6% biocytin dissolved in 0.05 M Tris buffer, pH 7.4. Biocytin was applied by one of 3 methods: diffusion, pressure injection or drop application. Cell bodies and dendrites around the application site and their efferent axonal processes were stained; dendritic spines were often visible. The injection sites varied in size from a single cell to a diameter of 400 microns. When applied in layer I-III, few filled cells were also seen in layers IV and V, outside the application site. The drop application (5-10 microliters) of biocytin resulted in filling of cells throughout the cortex. The combination of biocytin and the slice preparation was found to be very useful in revealing cell morphology and tracing interlaminar connections in the visual cortex. The advantages of this technique are its ease of application, the precise and restricted injection sites, and Golgi-like morphological detail.

  8. Non-uniform phase sensitivity in spatial frequency maps of the human visual cortex.

    Science.gov (United States)

    Farivar, Reza; Clavagnier, Simon; Hansen, Bruce C; Thompson, Ben; Hess, Robert F

    2017-02-15

    Just as a portrait painting can come from a collection of coarse and fine details, natural vision can be decomposed into coarse and fine components. Previous studies have shown that the early visual areas in the brain represent these components in a map-like fashion. Other studies have shown that these same visual areas can be sensitive to how coarse and fine features line up in space. We found that the brain actually jointly represents both the scale of the feature (fine, medium, or coarse) and the alignment of these features in space. The results suggest that the visual cortex has an optimized representation particularly for the alignment of fine details, which are crucial in understanding the visual scene. Complex natural scenes can be decomposed into their oriented spatial frequency (SF) and phase relationships, both of which are represented locally at the earliest stages of cortical visual processing. The SF preference map in the human cortex, obtained using synthetic stimuli, is orderly and correlates strongly with eccentricity. In addition, early visual areas show sensitivity to the phase information that describes the relationship between SFs and thereby dictates the structure of the image. Taken together, two possibilities arise for the joint representation of SF and phase: either the entirety of the cortical SF map is uniformly sensitive to phase, or a particular set of SFs is selectively phase sensitive - for example, greater phase sensitivity for higher SFs that define fine-scale edges in a complex scene. To test between these two possibilities, we constructed a novel continuous natural scene video whereby phase information was maintained in one SF band but scrambled elsewhere. By shifting the central frequency of the phase-aligned band in time, we mapped the phase-sensitive SF preference of the visual cortex. Using functional magnetic resonance imaging, we found that phase sensitivity in early visual areas is biased toward higher SFs. Compared to a SF

  9. Altered Balance of Receptive Field Excitation and Suppression in Visual Cortex of Amblyopic Macaque Monkeys.

    Science.gov (United States)

    Hallum, Luke E; Shooner, Christopher; Kumbhani, Romesh D; Kelly, Jenna G; García-Marín, Virginia; Majaj, Najib J; Movshon, J Anthony; Kiorpes, Lynne

    2017-08-23

    In amblyopia, a visual disorder caused by abnormal visual experience during development, the amblyopic eye (AE) loses visual sensitivity whereas the fellow eye (FE) is largely unaffected. Binocular vision in amblyopes is often disrupted by interocular suppression. We used 96-electrode arrays to record neurons and neuronal groups in areas V1 and V2 of six female macaque monkeys ( Macaca nemestrina ) made amblyopic by artificial strabismus or anisometropia in early life, as well as two visually normal female controls. To measure suppressive binocular interactions directly, we recorded neuronal responses to dichoptic stimulation. We stimulated both eyes simultaneously with large sinusoidal gratings, controlling their contrast independently with raised-cosine modulators of different orientations and spatial frequencies. We modeled each eye's receptive field at each cortical site using a difference of Gaussian envelopes and derived estimates of the strength of central excitation and surround suppression. We used these estimates to calculate ocular dominance separately for excitation and suppression. Excitatory drive from the FE dominated amblyopic visual cortex, especially in more severe amblyopes, but suppression from both the FE and AEs was prevalent in all animals. This imbalance created strong interocular suppression in deep amblyopes: increasing contrast in the AE decreased responses at binocular cortical sites. These response patterns reveal mechanisms that likely contribute to the interocular suppression that disrupts vision in amblyopes. SIGNIFICANCE STATEMENT Amblyopia is a developmental visual disorder that alters both monocular vision and binocular interaction. Using microelectrode arrays, we examined binocular interaction in primary visual cortex and V2 of six amblyopic macaque monkeys ( Macaca nemestrina ) and two visually normal controls. By stimulating the eyes dichoptically, we showed that, in amblyopic cortex, the binocular combination of signals is

  10. Reward modulation of prefrontal and visual association cortex during an incentive working memory task.

    Science.gov (United States)

    Krawczyk, Daniel C; Gazzaley, Adam; D'Esposito, Mark

    2007-04-13

    Cognitive performance differs with motivation, but little direct evidence exists regarding the neural mechanisms of the influence of reward motivation on working memory (WM). We tested the effects of motivation on the top-down control in visual WM. Encoding relevant stimuli for maintenance, while suppressing inappropriate inputs is considered a core process in cognition. Prior functional magnetic resonance imaging (fMRI) results demonstrated that stimulus-specific visual association cortex serves as a marker of activation differences for task-relevant and task-irrelevant inputs, such that enhanced activity occurs when attention is directed to relevant stimuli and suppressed activity occurs when attention is directed away from irrelevant stimuli [Gazzaley, A., Cooney, J., McEvoy, K., Knight, R.T., and D'Esposito, M. J. Cogn. Neurosci. 17, 507-517]. We used fMRI to test whether differential WM performance, indexed by lowered response times on a delayed-recognition task, was associated with amplification of enhancement and suppression effects during stimulus encoding within visual association cortex. Our results indicate that enhancement and suppression are amplified for trials with the highest reward level relative to non-rewarded trials for a scene-selective cortical region. In a face-selective region, similar modulation of enhancement for the highest reward level relative to non-rewarded trials was found. Prefrontal cortex also showed enhanced activity during high reward trials. Overall these results reveal that reward motivation can play a pivotal role in driving performance through top-down signaling in frontal regions involved in WM, as well as visual association regions selective to processing the perceptual inputs of the items to be remembered.

  11. Adaptation in the visual cortex: influence of membrane trajectory and neuronal firing pattern on slow afterpotentials.

    Directory of Open Access Journals (Sweden)

    Vanessa F Descalzo

    Full Text Available The input/output relationship in primary visual cortex neurons is influenced by the history of the preceding activity. To understand the impact that membrane potential trajectory and firing pattern has on the activation of slow conductances in cortical neurons we compared the afterpotentials that followed responses to different stimuli evoking similar numbers of action potentials. In particular, we compared afterpotentials following the intracellular injection of either square or sinusoidal currents lasting 20 seconds. Both stimuli were intracellular surrogates of different neuronal responses to prolonged visual stimulation. Recordings from 99 neurons in slices of visual cortex revealed that for stimuli evoking an equivalent number of spikes, sinusoidal current injection activated a slow afterhyperpolarization of significantly larger amplitude (8.5 ± 3.3 mV and duration (33 ± 17 s than that evoked by a square pulse (6.4 ± 3.7 mV, 28 ± 17 s; p<0.05. Spike frequency adaptation had a faster time course and was larger during plateau (square pulse than during intermittent (sinusoidal depolarizations. Similar results were obtained in 17 neurons intracellularly recorded from the visual cortex in vivo. The differences in the afterpotentials evoked with both protocols were abolished by removing calcium from the extracellular medium or by application of the L-type calcium channel blocker nifedipine, suggesting that the activation of a calcium-dependent current is at the base of this afterpotential difference. These findings suggest that not only the spikes, but the membrane potential values and firing patterns evoked by a particular stimulation protocol determine the responses to any subsequent incoming input in a time window that spans for tens of seconds to even minutes.

  12. Experience-dependent emergence of beta and gamma band oscillations in the primary visual cortex during the critical period.

    Science.gov (United States)

    Chen, Guang; Rasch, Malte J; Wang, Ran; Zhang, Xiao-hui

    2015-12-09

    Neural oscillatory activities have been shown to play important roles in neural information processing and the shaping of circuit connections during development. However, it remains unknown whether and how specific neural oscillations emerge during a postnatal critical period (CP), in which neuronal connections are most substantially modified by neural activity and experience. By recording local field potentials (LFPs) and single unit activity in developing primary visual cortex (V1) of head-fixed awake mice, we here demonstrate an emergence of characteristic oscillatory activities during the CP. From the pre-CP to CP, the peak frequency of spontaneous fast oscillatory activities shifts from the beta band (15-35 Hz) to the gamma band (40-70 Hz), accompanied by a decrease of cross-frequency coupling (CFC) and broadband spike-field coherence (SFC). Moreover, visual stimulation induced a large increase of beta-band activity but a reduction of gamma-band activity specifically from the CP onwards. Dark rearing of animals from the birth delayed this emergence of oscillatory activities during the CP, suggesting its dependence on early visual experience. These findings suggest that the characteristic neuronal oscillatory activities emerged specifically during the CP may represent as neural activity trait markers for the experience-dependent maturation of developing visual cortical circuits.

  13. The local and non-local components of the local field potential in awake primate visual cortex.

    Science.gov (United States)

    Gawne, Timothy J

    2010-12-01

    The Local Field Potential (LFP) is the analog signal recorded from a microelectrode inserted into cortex, typically in the frequency band of approximately 1 to 200 Hz. Here visual stimuli were flashed on in the receptive fields of primary visual cortical neurons in awake behaving macaques, and both isolated single units (neurons) and the LFP signal were recorded from the same unipolar microelectrode. The fall-off of single unit activity as a visual stimulus was moved from near the center to near the edge of the receptive field paralleled the fall-off of the stimulus-locked (evoked) LFP response. This suggests that the evoked LFP strongly reflects local neuronal activity. However, the evoked LFP could be significant even when the visual stimulus was completely outside the receptive field and the single unit response had fallen to zero, although this phenomenon was variable. Some of the non-local components of the LFP may be related to the slow distributed, or non-retinotopic, LFP signal previously observed in anesthetized animals. The induced (not time-locked to stimulus onset) component of the LFP showed significant increases only for stimuli within the receptive field of the single units. While the LFP primarily reflects local neuronal activity, it can also reflect neuronal activity at more distant sites, although these non-local components are typically more variable, slower, and weaker than the local components.

  14. Circuit Mechanisms Governing Local vs. Global Motion Processing in Mouse Visual Cortex

    DEFF Research Database (Denmark)

    Rasmussen, Rune; Yonehara, Keisuke

    2017-01-01

    literature on global motion processing based on works in primates and mice. Lastly, we propose what types of experiments could illuminate what circuit mechanisms are governing cortical global visual motion processing. We propose that PDS cells in mouse visual cortex appear as the perfect arena...... for delineating and solving how individual sensory features extracted by neural circuits in peripheral brain areas are integrated to build our rich cohesive sensory experiences.......A withstanding question in neuroscience is how neural circuits encode representations and perceptions of the external world. A particularly well-defined visual computation is the representation of global object motion by pattern direction-selective (PDS) cells from convergence of motion of local...

  15. Multichannel surface recordings on the visual cortex: implications for a neuroprosthesis

    Science.gov (United States)

    Chelvanayagam, D. K.; Vickery, R. M.; Kirkcaldie, M. T. K.; Coroneo, M. T.; Morley, J. W.

    2008-06-01

    Using a multi-channel platinum surface electrode array, recordings from cat primary visual cortex were obtained in response to visual stimuli, and electrical stimuli delivered using the elements of the array itself. Neural responses to electrical stimuli were consistent, regardless of stimulus polarity or leading phase (biphasic), although thresholds were lower for monophasic than biphasic pulses. Both visual and electrical stimuli reliably evoked responses with characteristic components, which interacted with each other in a nonlinear summation showing first facilitation then suppression during the window of interaction. The chronaxie for eliciting threshold cortical responses was about 100 µs, and the charge density with a pulse width of 50-100 µs was around 55 µC cm-2. These data form the basis of understanding the types of cortical responses to stimuli delivered by devices suitable for chronic implantation.

  16. Visual Deprivation Causes Refinement of Intracortical Circuits in the Auditory Cortex

    Directory of Open Access Journals (Sweden)

    Xiangying Meng

    2015-08-01

    Full Text Available Loss of a sensory modality can lead to functional enhancement of the remaining senses. For example, short-term visual deprivations, or dark exposure (DE, can enhance neuronal responses in the auditory cortex to sounds. These enhancements encompass increased spiking rates and frequency selectivity as well as increased spiking reliability. Although we previously demonstrated enhanced thalamocortical transmission after DE, increased synaptic strength cannot account for increased frequency selectivity or reliability. We thus investigated whether other changes in the underlying circuitry contributed to improved neuronal responses. We show that DE can lead to refinement of intra- and inter-laminar connections in the mouse auditory cortex. Moreover, we use a computational model to show that the combination of increased transmission and circuit refinement can lead to increased firing reliability. Thus cross-modal influences can alter the spectral and temporal processing of sensory stimuli by refinement of thalamocortical and intracortical circuits.

  17. A Comparison of Visual Response Properties in the Lateral Geniculate Nucleus and Primary Visual Cortex of Awake and Anesthetized Mice.

    Science.gov (United States)

    Durand, Séverine; Iyer, Ramakrishnan; Mizuseki, Kenji; de Vries, Saskia; Mihalas, Stefan; Reid, R Clay

    2016-11-30

    The cerebral cortex of the mouse has become one of the most important systems for studying information processing and the neural correlates of behavior. Multiple studies have examined the first stages of visual cortical processing: primary visual cortex (V1) and its thalamic inputs from the dorsal lateral geniculate nucleus (dLGN), but more rarely in the lateral posterior nucleus (LP) in mice. Multiple single-unit surveys of dLGN and V1, both with electrophysiology and two-photon calcium imaging, have described receptive fields in anesthetized animals. Increasingly, awake animals are being used in physiological studies, so it is important to compare neuronal responses between awake and anesthetized state. We have performed a comprehensive survey of spatial and temporal response properties in V1, dLGN, and lateral posterior nucleus of both anesthetized and awake animals, using a common set of stimuli: drifting sine-wave gratings spanning a broad range of spatial and temporal parameters, and sparse noise stimuli consisting of flashed light and dark squares. Most qualitative receptive field parameters were found to be unchanged between the two states, such as most aspects of spatial processing, but there were significant differences in several parameters, most notably in temporal processing. Compared with anesthetized animals, the temporal frequency that evoked the peak response was shifted toward higher values in the dLGN of awake mice and responses were more sustained. Further, the peak response to a flashed stimulus was earlier in all three areas. Overall, however, receptive field properties in the anesthetized animal remain a good model for those in the awake animal. The primary visual cortex (V1) of the mouse and its inputs from visual thalamus (dLGN), have become a dominant model for studying information processing in the brain. Early surveys of visual response properties (receptive fields) were performed in anesthetized animals. Although most recent studies of

  18. Attention modulates the responses of simple cells in monkey primary visual cortex.

    Science.gov (United States)

    McAdams, Carrie J; Reid, R Clay

    2005-11-23

    Spatial attention has long been postulated to act as a spotlight that increases the salience of visual stimuli at the attended location. We examined the effects of attention on the receptive fields of simple cells in primary visual cortex (V1) by training macaque monkeys to perform a task with two modes. In the attended mode, the stimuli relevant to the animal's task overlay the receptive field of the neuron being recorded. In the unattended mode, the animal was cued to attend to stimuli outside the receptive field of that neuron. The relevant stimulus, a colored pixel, was briefly presented within a white-noise stimulus, a flickering grid of black and white pixels. The receptive fields of the neurons were mapped by correlating spikes with the white-noise stimulus in both attended and unattended modes. We found that attention could cause significant modulation of the visually evoked response despite an absence of significant effects on the overall firing rates. On further examination of the relationship between the strength of the visual stimulation and the firing rate, we found that attention appears to cause multiplicative scaling of the visually evoked responses of simple cells, demonstrating that attention reaches back to the initial stages of visual cortical processing.

  19. Repetition Enhancement of Amygdala and Visual Cortex Functional Connectivity Reflects Nonconscious Memory for Negative Visual Stimuli.

    Science.gov (United States)

    Kark, Sarah M; Slotnick, Scott D; Kensinger, Elizabeth A

    2016-12-01

    Most studies using a recognition memory paradigm examine the neural processes that support the ability to consciously recognize past events. However, there can also be nonconscious influences from the prior study episode that reflect repetition suppression effects-a reduction in the magnitude of activity for repeated presentations of stimuli-that are revealed by comparing neural activity associated with forgotten items to correctly rejected novel items. The present fMRI study examined the effect of emotional valence (positive vs. negative) on repetition suppression effects. Using a standard recognition memory task, 24 participants viewed line drawings of previously studied negative, positive, and neutral photos intermixed with novel line drawings. For each item, participants made an old-new recognition judgment and a sure-unsure confidence rating. Collapsed across valence, repetition suppression effects were found in ventral occipital-temporal cortex and frontal regions. Activity levels in the majority of these regions were not modulated by valence. However, repetition enhancement of the amygdala and ventral occipital-temporal cortex functional connectivity reflected nonconscious memory for negative items. In this study, valence had little effect on activation patterns but had a larger effect on functional connectivity patterns that were markers of nonconscious memory. Beyond memory and emotion, these findings are relevant to other cognitive and social neuroscientists that utilize fMRI repetition effects to investigate perception, attention, social cognition, and other forms of learning and memory.

  20. Repetition enhancement of amygdala and visual cortex functional connectivity reflects nonconscious memory for negative visual stimuli

    Science.gov (United States)

    Kark, Sarah M.; Slotnick, Scott D.; Kensinger, Elizabeth A.

    2017-01-01

    Most studies using a recognition memory paradigm examine the neural processes that support the ability to consciously recognize past events. However, there can also be nonconscious influences from the prior study episode that reflect repetition suppression effects—a reduction in the magnitude of activity for repeated presentations of stimuli—that are revealed by comparing neural activity associated with forgotten items to correctly rejected novel items. The present fMRI study examined the effect of emotional valence (positive vs. negative) on repetition suppression effects. Using a standard recognition memory task, 24 participants viewed line drawings of previously studied negative, positive, and neutral photos intermixed with novel line drawings. For each item, participants made an old–new recognition judgment and a sure–unsure confidence rating. Collapsed across valence, repetition suppression effects were found in ventral occipital-temporal cortex and frontal regions. Activity levels in the majority of these regions were not modulated by valence. However, repetition enhancement of the amygdala and ventral occipital-temporal cortex functional connectivity reflected nonconscious memory for negative items. In this study, valence had little effect on activation patterns but had a larger effect on functional connectivity patterns that were markers of nonconscious memory. Beyond memory and emotion, these findings are relevant to other cognitive and social neuroscientists that utilize fMRI repetition effects to investigate perception, attention, social cognition, and other forms of learning and memory. PMID:27676616

  1. Neuronal correlate of visual associative long-term memory in the primate temporal cortex

    Science.gov (United States)

    Miyashita, Yasushi

    1988-10-01

    In human long-term memory, ideas and concepts become associated in the learning process1. No neuronal correlate for this cognitive function has so far been described, except that memory traces are thought to be localized in the cerebral cortex; the temporal lobe has been assigned as the site for visual experience because electric stimulation of this area results in imagery recall,2 and lesions produce deficits in visual recognition of objects3-9. We previously reported that in the anterior ventral temporal cortex of monkeys, individual neurons have a sustained activity that is highly selective for a few of the 100 coloured fractal patterns used in a visual working-memory task10. Here I report the development of this selectivity through repeated trials involving the working memory. The few patterns for which a neuron was conjointly selective were frequently related to each other through stimulus-stimulus association imposed during training. The results indicate that the selectivity acquired by these cells represents a neuronal correlate of the associative long-term memory of pictures.

  2. The Development and Activity-Dependent Expression of Aggrecan in the Cat Visual Cortex

    Science.gov (United States)

    Sengpiel, F.; Beaver, C. J.; Crocker-Buque, A.; Kelly, G. M.; Matthews, R. T.; Mitchell, D. E.

    2013-01-01

    The Cat-301 monoclonal antibody identifies aggrecan, a chondroitin sulfate proteoglycan in the cat visual cortex and dorsal lateral geniculate nucleus (dLGN). During development, aggrecan expression increases in the dLGN with a time course that matches the decline in plasticity. Moreover, examination of tissue from selectively visually deprived cats shows that expression is activity dependent, suggesting a role for aggrecan in the termination of the sensitive period. Here, we demonstrate for the first time that the onset of aggrecan expression in area 17 also correlates with the decline in experience-dependent plasticity in visual cortex and that this expression is experience dependent. Dark rearing until 15 weeks of age dramatically reduced the density of aggrecan-positive neurons in the extragranular layers, but not in layer IV. This effect was reversible as dark-reared animals that were subsequently exposed to light showed normal numbers of Cat-301-positive cells. The reduction in aggrecan following certain early deprivation regimens is the first biochemical correlate of the functional changes to the γ-aminobutyric acidergic system that have been reported following early deprivation in cats. PMID:22368089

  3. Feature-Specific Organization of Feedback Pathways in Mouse Visual Cortex.

    Science.gov (United States)

    Huh, Carey Y L; Peach, John P; Bennett, Corbett; Vega, Roxana M; Hestrin, Shaul

    2018-01-08

    Higher and lower cortical areas in the visual hierarchy are reciprocally connected [1]. Although much is known about how feedforward pathways shape receptive field properties of visual neurons, relatively little is known about the role of feedback pathways in visual processing. Feedback pathways are thought to carry top-down signals, including information about context (e.g., figure-ground segmentation and surround suppression) [2-5], and feedback has been demonstrated to sharpen orientation tuning of neurons in the primary visual cortex (V1) [6, 7]. However, the response characteristics of feedback neurons themselves and how feedback shapes V1 neurons' tuning for other features, such as spatial frequency (SF), remain largely unknown. Here, using a retrograde virus, targeted electrophysiological recordings, and optogenetic manipulations, we show that putatively feedback neurons in layer 5 (hereafter "L5 feedback") in higher visual areas, AL (anterolateral area) and PM (posteromedial area), display distinct visual properties in awake head-fixed mice. AL L5 feedback neurons prefer significantly lower SF (mean: 0.04 cycles per degree [cpd]) compared to PM L5 feedback neurons (0.15 cpd). Importantly, silencing AL L5 feedback reduced visual responses of V1 neurons preferring low SF (mean change in firing rate: -8.0%), whereas silencing PM L5 feedback suppressed responses of high-SF-preferring V1 neurons (-20.4%). These findings suggest that feedback connections from higher visual areas convey distinctly tuned visual inputs to V1 that serve to boost V1 neurons' responses to SF. Such like-to-like functional organization may represent an important feature of feedback pathways in sensory systems and in the nervous system in general. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Hearing suppression induced by electrical stimulation of human auditory cortex.

    Science.gov (United States)

    Fenoy, Albert J; Severson, Meryl A; Volkov, Igor O; Brugge, John F; Howard, Matthew A

    2006-11-06

    In the course of performing electrical stimulation functional mapping (ESFM) in neurosurgery patients, we identified three subjects who experienced hearing suppression during stimulation of sites within the superior temporal gyrus (STG). One of these patients had long standing tinnitus that affected both ears. In all subjects, auditory event related potentials (ERPs) were recorded from chronically implanted intracranial electrodes and the results were used to localize auditory cortical fields within the STG. Hearing suppression sites were identified within anterior lateral Heschl's gyrus (HG) and posterior lateral STG, in what may be auditory belt and parabelt fields. Cortical stimulation suppressed hearing in both ears, which persisted beyond the period of electrical stimulation. Subjects experienced other stimulation-evoked perceptions at some of these same sites, including symptoms of vestibular activation and alteration of audio-visual speech processing. In contrast, stimulation of presumed core auditory cortex within posterior medial HG evoked sound perceptions, or in one case an increase in tinnitus intensity, that affected the contralateral ear and did not persist beyond the period of stimulation. The current results confirm a rarely reported experimental observation, and correlate the cortical sites associated with hearing suppression with physiologically identified auditory cortical fields.

  5. Deep neural networks rival the representation of primate IT cortex for core visual object recognition.

    Directory of Open Access Journals (Sweden)

    Charles F Cadieu

    2014-12-01

    Full Text Available The primate visual system achieves remarkable visual object recognition performance even in brief presentations, and under changes to object exemplar, geometric transformations, and background variation (a.k.a. core visual object recognition. This remarkable performance is mediated by the representation formed in inferior temporal (IT cortex. In parallel, recent advances in machine learning have led to ever higher performing models of object recognition using artificial deep neural networks (DNNs. It remains unclear, however, whether the representational performance of DNNs rivals that of the brain. To accurately produce such a comparison, a major difficulty has been a unifying metric that accounts for experimental limitations, such as the amount of noise, the number of neural recording sites, and the number of trials, and computational limitations, such as the complexity of the decoding classifier and the number of classifier training examples. In this work, we perform a direct comparison that corrects for these experimental limitations and computational considerations. As part of our methodology, we propose an extension of "kernel analysis" that measures the generalization accuracy as a function of representational complexity. Our evaluations show that, unlike previous bio-inspired models, the latest DNNs rival the representational performance of IT cortex on this visual object recognition task. Furthermore, we show that models that perform well on measures of representational performance also perform well on measures of representational similarity to IT, and on measures of predicting individual IT multi-unit responses. Whether these DNNs rely on computational mechanisms similar to the primate visual system is yet to be determined, but, unlike all previous bio-inspired models, that possibility cannot be ruled out merely on representational performance grounds.

  6. Single Prazosin Infusion in Prelimbic Cortex Fosters Extinction of Amphetamine-Induced Conditioned Place Preference

    OpenAIRE

    Latagliata, Emanuele C.; Luisa Lo Iacono; Giulia Chiacchierini; Marco Sancandi; Alessandro Rava; Valeria Oliva; Stefano Puglisi-Allegra

    2017-01-01

    Exposure to drug-associated cues to induce extinction is a useful strategy to contrast cue-induced drug seeking. Norepinephrine (NE) transmission in medial prefrontal cortex has a role in the acquisition and extinction of conditioned place preference induced by amphetamine. We have reported recently that NE in prelimbic cortex delays extinction of amphetamine-induced conditioned place preference (CPP). A potential involvement of α1-adrenergic receptors in the extinction of appetitive conditio...

  7. A switch from inter-ocular to inter-hemispheric suppression following monocular deprivation in the rat visual cortex

    NARCIS (Netherlands)

    Pietrasanta, M.; Restani, L.; Cerri, C.; Olcese, U.; Medini, P.; Caleo, M.

    2014-01-01

    Binocularity is a key property of primary visual cortex (V1) neurons that is widely used to study synaptic integration in the brain and plastic mechanisms following an altered visual experience. However, it is not clear how the inputs from the two eyes converge onto binocular neurons, and how their

  8. Activation of lateral geniculate nucleus and primary visual cortex as detected by functional magnetic resonance imaging in normal subjects and in patients with visual disturbance

    Energy Technology Data Exchange (ETDEWEB)

    Miki, Atsushi [Niigata Univ. (Japan). Graduate School of Medical and Dental Sciences

    2002-12-01

    Functional magnetic resonance imaging (fMRI) during visual stimulation can detect regional cerebral blood flow changes that reflect neural activity in the lateral geniculate nucleus and primary visual cortex, which are major relay points in the human afferent visual system. FMRI has been used in the clinical evaluation of visual disorders such as homonymous hemianopia and unilateral eye diseases (optic neuritis, amblyopia, and so on). Future development in the data acquisition and data analysis may facilitate the use of fMRI for the management of patients with visual deficits and understanding of the visual disorders. (author)

  9. Neural associations of the early retinotopic cortex with the lateral occipital complex during visual perception.

    Directory of Open Access Journals (Sweden)

    Delong Zhang

    Full Text Available Previous studies have demonstrated that the early retinotopic cortex (ERC, i.e., V1/V2/V3 is highly associated with the lateral occipital complex (LOC during visual perception. However, it remains largely unclear how to evaluate their associations in quantitative way. The present study tried to apply a multivariate pattern analysis (MVPA to quantify the neural activity in ERC and its association with that of the LOC when participants saw visual images. To this end, we assessed whether low-level visual features (Gabor features could predict the neural activity in the ERC and LOC according to a voxel-based encoding model (VBEM, and then quantified the association of the neural activity between these regions by using an analogical VBEM. We found that the Gabor features remarkably predicted the activity of the ERC (e.g., the predicted accuracy was 52.5% for a participant instead of that of the LOC (4.2%. Moreover, the MVPA approach can also be used to establish corresponding relationships between the activity patterns in the LOC and those in the ERC (64.2%. In particular, we found that the integration of the Gabor features and LOC visual information could dramatically improve the 'prediction' of ERC activity (88.3%. Overall, the present study provides new evidences for the possibility of quantifying the association of the neural activity between the regions of ERC and LOC. This approach will help to provide further insights into the neural substrates of the visual processing.

  10. Deep hierarchies in the primate visual cortex: what can we learn for computer vision?

    Science.gov (United States)

    Krüger, Norbert; Janssen, Peter; Kalkan, Sinan; Lappe, Markus; Leonardis, Ales; Piater, Justus; Rodríguez-Sánchez, Antonio J; Wiskott, Laurenz

    2013-08-01

    Computational modeling of the primate visual system yields insights of potential relevance to some of the challenges that computer vision is facing, such as object recognition and categorization, motion detection and activity recognition, or vision-based navigation and manipulation. This paper reviews some functional principles and structures that are generally thought to underlie the primate visual cortex, and attempts to extract biological principles that could further advance computer vision research. Organized for a computer vision audience, we present functional principles of the processing hierarchies present in the primate visual system considering recent discoveries in neurophysiology. The hierarchical processing in the primate visual system is characterized by a sequence of different levels of processing (on the order of 10) that constitute a deep hierarchy in contrast to the flat vision architectures predominantly used in today's mainstream computer vision. We hope that the functional description of the deep hierarchies realized in the primate visual system provides valuable insights for the design of computer vision algorithms, fostering increasingly productive interaction between biological and computer vision research.

  11. Responses in posterior parietal cortex to movement intention task with visual and tactile cues.

    Science.gov (United States)

    Kamikawa, Yusuke; Tanaka, Toshihisa

    2015-01-01

    Posterior parietal cortex (PPC) is considered to be related to forming of motor intention. The detection of the direction intended movements and the type of intended movement is a challenging goal in neuroscience and engineering applications such as brain-computer interfacing (BCI). In previous studies, it has been reported that EEG signals extracted from PPC can be used to decode intended movement direction. However, it is not clear whether extracted EEG signals are related to motor intention, because visually evoked potential (VEP) which evoked by visual cue in their experiment may be included in their extracted EEG signals. The purpose of this study is to investigate the possibility of VEP mixed into extracted EEG signals. Therefore experiments with not only visual but also tactile cues were conducted. EEG components that could be related to PPC were extracted by using independent component analysis (ICA). We compared event related potential (ERP) waveforms between two experiments. In the result, ERP waveforms of the experiment with tactile cue were significantly different from that of the experiment with visual cue. This result suggests that VEP was included in the EEG signals extracted from PPC in the experiment with visual cue.

  12. Distributed Neural Plasticity for Shape Learning in the Human Visual Cortex

    Science.gov (United States)

    Betts, Lisa R; Sarkheil, Pegah; Welchman, Andrew E

    2005-01-01

    Expertise in recognizing objects in cluttered scenes is a critical skill for our interactions in complex environments and is thought to develop with learning. However, the neural implementation of object learning across stages of visual analysis in the human brain remains largely unknown. Using combined psychophysics and functional magnetic resonance imaging (fMRI), we show a link between shape-specific learning in cluttered scenes and distributed neuronal plasticity in the human visual cortex. We report stronger fMRI responses for trained than untrained shapes across early and higher visual areas when observers learned to detect low-salience shapes in noisy backgrounds. However, training with high-salience pop-out targets resulted in lower fMRI responses for trained than untrained shapes in higher occipitotemporal areas. These findings suggest that learning of camouflaged shapes is mediated by increasing neural sensitivity across visual areas to bolster target segmentation and feature integration. In contrast, learning of prominent pop-out shapes is mediated by associations at higher occipitotemporal areas that support sparser coding of the critical features for target recognition. We propose that the human brain learns novel objects in complex scenes by reorganizing shape processing across visual areas, while taking advantage of natural image correlations that determine the distinctiveness of target shapes. PMID:15934786

  13. A Survey of Architecture and Function of the Primary Visual Cortex (V1

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    Zhaoping Li

    2007-01-01

    Full Text Available The largest visual area, known as the primary visual cortex or V1, has greatly contributed to the current understanding of mammalian and human visual pathways and their role in visual perception. The initial discovery of orientation-sensitive neurons in V1, arranged according to a retinotopic mapping, suggested an analogy to its function as a low-level feature analyzer. Subsequent discoveries of phase, spatial frequency, color, ocular origin, and direction-of-motion-sensitive neurons, arranged into overlapping maps, further lent support to the view that it performs a rich decomposition, similar to signal processing transforms, of the retinal output. Like the other cortical areas, V1 has a laminar organization with specialization for input from the relayed retinal afferents, output to the higher visual areas, and the segregation of the magno (motion and parvo (form pathways. Spatially lateral connections that exist between neurons of similar and varying properties have also been proposed to give rise to a computation of a bottom-up saliency map in V1. We provide a review of the selectivity of neurons in V1, laminar specialization and analogies to signal processing techniques, a model of V1 saliency computation, and higher-area feedback that may mediate perception.

  14. Multiple distinct subtypes of GABAergic neurons in mouse visual cortex identified by triple immunostaining

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    Yuri Gonchar

    2008-03-01

    Full Text Available The majority of cortical interneurons use GABA (gamma amino butyric acid as inhibitory neurotransmitter. GABAergic neurons are morphologically, connectionally, electrically and chemically heterogeneous. In rat cerebral cortex three distinct groups of GABAergic interneurons have been identifi ed by the expression of parvalbumin (PV, calretinin (CR and somatostatin (SOM. Recent studies in mouse cerebral cortex have revealed a different organization in which the CR and SOM populations are partially overlapping. Because CR and SOM neurons derive from different progenitors located in different embryonic structures, the coexpression of CR + SOM suggests that the chemical differentiation of interneurons is regulated postmitotically. Here, we have taken an important fi rst step towards understanding this process by triple immunostaining mouse visual cortex with a panel of antibodies, which has been used extensively for classifying developing interneurons. We have found at least 13 distinct groups of GABAergic neurons which include PV, CR, SOM, CCK (cholecystokinin, CR + SOM, CR + NPY (neuropeptide Y, CR + VIP (vasointestinal polypeptide, SOM + NPY, SOM + VIP, VIP + ChAT (choline acetyltransferase, CCK + NPY, CR + SOM + NPY and CR + SOM + VIP expressing cells. Triple immunostaining with PV, CR and SOM antibodies during postnatal development further showed that PV is never colocalized with CR and SOM. Importantly, expression of SOM and CR + SOM developed after the percentage of CR cells that do not express SOM has reached the mature level, suggesting that the chemical differentiation of SOM and CR + SOM neurons is a postnatal event, which may be controlled by transcriptional regulation.

  15. BOLD responses to tactile stimuli in visual and auditory cortex depend on the frequency content of stimulation.

    Science.gov (United States)

    Nordmark, Per F; Pruszynski, J Andrew; Johansson, Roland S

    2012-10-01

    Although some brain areas preferentially process information from a particular sensory modality, these areas can also respond to other modalities. Here we used fMRI to show that such responsiveness to tactile stimuli depends on the temporal frequency of stimulation. Participants performed a tactile threshold-tracking task where the tip of either their left or right middle finger was stimulated at 3, 20, or 100 Hz. Whole-brain analysis revealed an effect of stimulus frequency in two regions: the auditory cortex and the visual cortex. The BOLD response in the auditory cortex was stronger during stimulation at hearable frequencies (20 and 100 Hz) whereas the response in the visual cortex was suppressed at infrasonic frequencies (3 Hz). Regardless of which hand was stimulated, the frequency-dependent effects were lateralized to the left auditory cortex and the right visual cortex. Furthermore, the frequency-dependent effects in both areas were abolished when the participants performed a visual task while receiving identical tactile stimulation as in the tactile threshold-tracking task. We interpret these findings in the context of the metamodal theory of brain function, which posits that brain areas contribute to sensory processing by performing specific computations regardless of input modality.

  16. Functional mapping of the human visual cortex with intravoxel incoherent motion MRI.

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    Christian Federau

    Full Text Available Functional imaging with intravoxel incoherent motion (IVIM magnetic resonance imaging (MRI is demonstrated. Images were acquired at 3 Tesla using a standard Stejskal-Tanner diffusion-weighted echo-planar imaging sequence with multiple b-values. Cerebro-spinal fluid signal, which is highly incoherent, was suppressed with an inversion recovery preparation pulse. IVIM microvascular perfusion parameters were calculated according to a two-compartment (vascular and non-vascular diffusion model. The results obtained in 8 healthy human volunteers during visual stimulation are presented. The IVIM blood flow related parameter fD* increased 170% during stimulation in the visual cortex, and 70% in the underlying white matter.

  17. The Second Spiking Threshold: Dynamics of Laminar Network Spiking in the Visual Cortex

    DEFF Research Database (Denmark)

    Forsberg, Lars E.; Bonde, Lars H.; Harvey, Michael A.

    2016-01-01

    Most neurons have a threshold separating the silent non-spiking state and the state of producing temporal sequences of spikes. But neurons in vivo also have a second threshold, found recently in granular layer neurons of the primary visual cortex, separating spontaneous ongoing spiking from...... were slow, frequently changing direction. In single trials, sharp as well as smooth and slow transients transform the trajectories to be outward directed, fast and crossing the threshold to become evoked. Although the speeds of the evolution of the evoked states differ, the same domain of the state...... space is explored indicating uniformity of the evoked states. All evoked states return to the spontaneous evoked spiking state as in a typical mono-stable dynamical system. In single trials, neither the original spiking rates, nor the temporal evolution in state space could distinguish simple visual...

  18. Primary visual cortex volume and total neuron number are reduced in schizophrenia

    DEFF Research Database (Denmark)

    Dorph-Petersen, Karl-Anton; Pierri, Joseph H.; Wu, Qiang

    2007-01-01

    with schizophrenia reported an increased density of neurons in the primary visual cortex (Brodmann's area 17, BA17). The observed changes in visual processing may thus be reflected in structural changes in the circuitry of BA17. To characterize the structural changes further we used stereological methods based...... on unbiased principles of sampling (Cavalieri's principle and the optical fractionator) to estimate the total volume and neuron number of BA17 in postmortem brains from 10 subjects with schizophrenia and 10 matched normal comparison subjects. In addition, we assessed cortical thickness. We found a marked...... and significant reduction in total neuron number (25%) and volume (22%) of BA17 in the schizophrenia group relative to the normal comparison subjects. In contrast, we found no changes in neuronal density or cortical thickness between the two groups. Subjects with schizophrenia therefore have a smaller cortical...

  19. Neuronal integration in visual cortex elevates face category tuning to conscious face perception.

    Science.gov (United States)

    Fahrenfort, Johannes J; Snijders, Tineke M; Heinen, Klaartje; van Gaal, Simon; Scholte, H Steven; Lamme, Victor A F

    2012-12-26

    The human brain has the extraordinary capability to transform cluttered sensory input into distinct object representations. For example, it is able to rapidly and seemingly without effort detect object categories in complex natural scenes. Surprisingly, category tuning is not sufficient to achieve conscious recognition of objects. What neural process beyond category extraction might elevate neural representations to the level where objects are consciously perceived? Here we show that visible and invisible faces produce similar category-selective responses in the ventral visual cortex. The pattern of neural activity evoked by visible faces could be used to decode the presence of invisible faces and vice versa. However, only visible faces caused extensive response enhancements and changes in neural oscillatory synchronization, as well as increased functional connectivity between higher and lower visual areas. We conclude that conscious face perception is more tightly linked to neural processes of sustained information integration and binding than to processes accommodating face category tuning.

  20. Random Wiring, Ganglion Cell Mosaics, and the Functional Architecture of the Visual Cortex.

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    Manuel Schottdorf

    2015-11-01

    Full Text Available The architecture of iso-orientation domains in the primary visual cortex (V1 of placental carnivores and primates apparently follows species invariant quantitative laws. Dynamical optimization models assuming that neurons coordinate their stimulus preferences throughout cortical circuits linking millions of cells specifically predict these invariants. This might indicate that V1's intrinsic connectome and its functional architecture adhere to a single optimization principle with high precision and robustness. To validate this hypothesis, it is critical to closely examine the quantitative predictions of alternative candidate theories. Random feedforward wiring within the retino-cortical pathway represents a conceptually appealing alternative to dynamical circuit optimization because random dimension-expanding projections are believed to generically exhibit computationally favorable properties for stimulus representations. Here, we ask whether the quantitative invariants of V1 architecture can be explained as a generic emergent property of random wiring. We generalize and examine the stochastic wiring model proposed by Ringach and coworkers, in which iso-orientation domains in the visual cortex arise through random feedforward connections between semi-regular mosaics of retinal ganglion cells (RGCs and visual cortical neurons. We derive closed-form expressions for cortical receptive fields and domain layouts predicted by the model for perfectly hexagonal RGC mosaics. Including spatial disorder in the RGC positions considerably changes the domain layout properties as a function of disorder parameters such as position scatter and its correlations across the retina. However, independent of parameter choice, we find that the model predictions substantially deviate from the layout laws of iso-orientation domains observed experimentally. Considering random wiring with the currently most realistic model of RGC mosaic layouts, a pairwise interacting point

  1. Chronic cellular imaging of mouse visual cortex during operant behavior and passive viewing

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    Mark L Andermann

    2010-03-01

    Full Text Available Nearby neurons in mammalian neocortex demonstrate a great diversity of cell types and connectivity patterns. The importance of this diversity for computation is not understood. While extracellular recording studies in visual cortex have provided a particularly rich description of behavioral modulation of neural activity, new methods are needed to dissect the contribution of specific circuit elements in guiding visual perception. Here, we describe a method for three-dimensional cellular imaging of neural activity in the awake mouse visual cortex during active discrimination and passive viewing of visual stimuli. Head-fixed mice demonstrated robust discrimination for many hundred trials per day after initial task acquisition. To record from multiple neurons during operant behavior with single-trial resolution and minimal artifacts, we built a sensitive microscope for two-photon calcium imaging, capable of rapid tracking of neurons in three dimensions. We demonstrate stable recordings of cellular calcium activity during discrimination behavior across hours, days, and weeks, using both synthetic and genetically-encoded calcium indicators. When combined with molecular and genetic technologies in mice (e.g., cell-type specific transgenic labeling, this approach allows the identification of neuronal classes in vivo. Physiological measurements from distinct classes of neighboring neurons will enrich our understanding of the coordinated roles of diverse elements of cortical microcircuits in guiding sensory perception and perceptual learning. Further, our method provides a high-throughput, chronic in vivo assay of behavioral influences on cellular activity that is applicable to a wide range of mouse models of neurologic disease.

  2. Glycine receptors support excitatory neurotransmitter release in developing mouse visual cortex

    Science.gov (United States)

    Kunz, Portia A; Burette, Alain C; Weinberg, Richard J; Philpot, Benjamin D

    2012-01-01

    Glycine receptors (GlyRs) are found in most areas of the brain, and their dysfunction can cause severe neurological disorders. While traditionally thought of as inhibitory receptors, presynaptic-acting GlyRs (preGlyRs) can also facilitate glutamate release under certain circumstances, although the underlying molecular mechanisms are unknown. In the current study, we sought to better understand the role of GlyRs in the facilitation of excitatory neurotransmitter release in mouse visual cortex. Using whole-cell recordings, we found that preGlyRs facilitate glutamate release in developing, but not adult, visual cortex. The glycinergic enhancement of neurotransmitter release in early development depends on the high intracellular to extracellular Cl− gradient maintained by the Na+–K+–2Cl− cotransporter and requires Ca2+ entry through voltage-gated Ca2+ channels. The glycine transporter 1, localized to glial cells, regulates extracellular glycine concentration and the activation of these preGlyRs. Our findings demonstrate a developmentally regulated mechanism for controlling excitatory neurotransmitter release in the neocortex. PMID:22988142

  3. Griffiths phase and long-range correlations in a biologically motivated visual cortex model

    Science.gov (United States)

    Girardi-Schappo, M.; Bortolotto, G. S.; Gonsalves, J. J.; Pinto, L. T.; Tragtenberg, M. H. R.

    2016-07-01

    Activity in the brain propagates as waves of firing neurons, namely avalanches. These waves’ size and duration distributions have been experimentally shown to display a stable power-law profile, long-range correlations and 1/f b power spectrum in vivo and in vitro. We study an avalanching biologically motivated model of mammals visual cortex and find an extended critical-like region - a Griffiths phase - characterized by divergent susceptibility and zero order parameter. This phase lies close to the expected experimental value of the excitatory postsynaptic potential in the cortex suggesting that critical be-havior may be found in the visual system. Avalanches are not perfectly power-law distributed, but it is possible to collapse the distributions and define a cutoff avalanche size that diverges as the network size is increased inside the critical region. The avalanches present long-range correlations and 1/f b power spectrum, matching experiments. The phase transition is analytically determined by a mean-field approximation.

  4. The role of the COMT val158met polymorphism in mediating aversive learning in visual cortex.

    Science.gov (United States)

    Gruss, L Forest; Langaee, Taimour; Keil, Andreas

    2016-01-15

    The catechol-O-methyltransferase (COMT) val158met single nucleotide polymorphism (SNP) alters metabolic activity of the COMT enzyme regulating catecholamines, with the Val (valine) allele resulting in 40% greater enzymatic activity than the Met (methionine) allele. Previous research has identified systematic inter-individual differences in cognitive and behavioral phenotypes related to this polymorphism, often attributed to the fact that extracellular dopamine in the prefrontal cortex is strongly affected by the COMT enzyme. The neurophysiological mechanisms mediating these inter-individual differences in specific brain systems and task contexts remain to be established however. In the current study, we examined the extent to which physio-mechanistic differences by COMT genotype affect somato-visceral and visual cortical responses to learned threat cues. Classical aversive differential conditioning was implemented using rapidly phase-reversing grating stimuli, previously shown to engage retinotopic visual cortex. Differential response patterns in sensory and autonomic systems were elicited by pairing one grating (CS+, conditioned stimulus), but not the other (CS-), with a noxious stimulus. Dense-array electroencephalography and somato-visceral measures of defensive reactivity were recorded in addition to self-report data. Individuals of the Val/Val genotype, compared to Met allele carriers, reliably showed greater initial enhancement in their visuocortical response to the CS+, accompanied by stronger defensive engagement, indexed by heart rate acceleration and startle potentiation. The finding that COMT polymorphism status affects threat cue reactivity at the visuocortical level is consistent with the notion that sensory processing of threat is facilitated by strong re-entrant bias signals from anterior areas, including the prefrontal cortex. Copyright © 2015 Elsevier Inc. All rights reserved.

  5. Retinotopic mapping of categorical and coordinate spatial relation processing in early visual cortex.

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    Ineke J M van der Ham

    Full Text Available Spatial relations are commonly divided in two global classes. Categorical relations concern abstract relations which define areas of spatial equivalence, whereas coordinate relations are metric and concern exact distances. Categorical and coordinate relation processing are thought to rely on at least partially separate neurocognitive mechanisms, as reflected by differential lateralization patterns, in particular in the parietal cortex. In this study we address this textbook principle from a new angle. We studied retinotopic activation in early visual cortex, as a reflection of attentional distribution, in a spatial working memory task with either a categorical or a coordinate instruction. Participants were asked to memorize a dot position, with regard to a central cross, and to indicate whether a subsequent dot position matched the first dot position, either categorically (opposite quadrant of the cross or coordinately (same distance to the centre of the cross. BOLD responses across the retinotopic maps of V1, V2, and V3 indicate that the spatial distribution of cortical activity was different for categorical and coordinate instructions throughout the retention interval; a more local focus was found during categorical processing, whereas focus was more global for coordinate processing. This effect was strongest for V3, approached significance in V2 and was absent in V1. Furthermore, during stimulus presentation the two instructions led to different levels of activation in V3 during stimulus encoding; a stronger increase in activity was found for categorical processing. Together this is the first demonstration that instructions for specific types of spatial relations may yield distinct attentional patterns which are already reflected in activity early in the visual cortex.

  6. The right frontopolar cortex is involved in visual-spatial prospective memory.

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    Alberto Costa

    Full Text Available The involvement of frontopolar cortex in mediating prospective memory processes has been evidenced by various studies, mainly by means of neuroimaging techniques. Recently, one transcranial magnetic stimulation study documented that transient inhibition of left Brodmann Area (BA 10 impaired verbal prospective memory. This result raises the issue of whether the BA 10 involvement in prospective memory functioning may be modulated by the physical characteristics of the stimuli used. The present study aimed to investigate the role of the frontopolar cortex in visual-spatial PM by means of the application of inhibitory theta-burst stimulation. Twelve volunteers were evaluated after inhibitory theta-burst stimulation over left BA 10, right BA10 and CZ (control condition. In the prospective memory procedure, sequences of four spatial positions (black squares each were presented. During the inter-sequence delay, subjects had to reproduce the sequence in the observed order (ongoing task forward or the reverse order (backward. At the occurrence of a target position, subjects had to press a key on the keyboard (prospective memory score. Recall and recognition of the target positions were also tested. We found that prospective memory accuracy was lower after theta-burst stimulation over right BA10 than CZ (p<0.01, whereas it was comparable in left BA10 and CZ conditions. No significant difference was found among the three conditions on recall and recognition of target positions and on ongoing task performance. Our findings provide a novel strong evidence for a specific involvement of right frontopolar cortex in visual-spatial prospective memory. In the context of previous data providing evidence for left BA 10 involvement in verbal prospective memory, our results also suggest material-specific lateralization of prospective memory processes in BA 10.

  7. The impact of early visual cortex transcranial magnetic stimulation on visual working memory precision and guess rate.

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    Rosanne L Rademaker

    Full Text Available Neuroimaging studies have demonstrated that activity patterns in early visual areas predict stimulus properties actively maintained in visual working memory. Yet, the mechanisms by which such information is represented remain largely unknown. In this study, observers remembered the orientations of 4 briefly presented gratings, one in each quadrant of the visual field. A 10Hz Transcranial Magnetic Stimulation (TMS triplet was applied directly at stimulus offset, or midway through a 2-second delay, targeting early visual cortex corresponding retinotopically to a sample item in the lower hemifield. Memory for one of the four gratings was probed at random, and participants reported this orientation via method of adjustment. Recall errors were smaller when the visual field location targeted by TMS overlapped with that of the cued memory item, compared to errors for stimuli probed diagonally to TMS. This implied topographic storage of orientation information, and a memory-enhancing effect at the targeted location. Furthermore, early pulses impaired performance at all four locations, compared to late pulses. Next, response errors were fit empirically using a mixture model to characterize memory precision and guess rates. Memory was more precise for items proximal to the pulse location, irrespective of pulse timing. Guesses were more probable with early TMS pulses, regardless of stimulus location. Thus, while TMS administered at the offset of the stimulus array might disrupt early-phase consolidation in a non-topographic manner, TMS also boosts the precise representation of an item at its targeted retinotopic location, possibly by increasing attentional resources or by injecting a beneficial amount of noise.

  8. The impact of early visual cortex transcranial magnetic stimulation on visual working memory precision and guess rate.

    Science.gov (United States)

    Rademaker, Rosanne L; van de Ven, Vincent G; Tong, Frank; Sack, Alexander T

    2017-01-01

    Neuroimaging studies have demonstrated that activity patterns in early visual areas predict stimulus properties actively maintained in visual working memory. Yet, the mechanisms by which such information is represented remain largely unknown. In this study, observers remembered the orientations of 4 briefly presented gratings, one in each quadrant of the visual field. A 10Hz Transcranial Magnetic Stimulation (TMS) triplet was applied directly at stimulus offset, or midway through a 2-second delay, targeting early visual cortex corresponding retinotopically to a sample item in the lower hemifield. Memory for one of the four gratings was probed at random, and participants reported this orientation via method of adjustment. Recall errors were smaller when the visual field location targeted by TMS overlapped with that of the cued memory item, compared to errors for stimuli probed diagonally to TMS. This implied topographic storage of orientation information, and a memory-enhancing effect at the targeted location. Furthermore, early pulses impaired performance at all four locations, compared to late pulses. Next, response errors were fit empirically using a mixture model to characterize memory precision and guess rates. Memory was more precise for items proximal to the pulse location, irrespective of pulse timing. Guesses were more probable with early TMS pulses, regardless of stimulus location. Thus, while TMS administered at the offset of the stimulus array might disrupt early-phase consolidation in a non-topographic manner, TMS also boosts the precise representation of an item at its targeted retinotopic location, possibly by increasing attentional resources or by injecting a beneficial amount of noise.

  9. Serotonergic Hallucinogen-Induced Visual Perceptual Alterations.

    Science.gov (United States)

    Kometer, Michael; Vollenweider, Franz X

    2016-11-30

    Serotonergic hallucinogens, such as lysergic acid diethylamide (LSD), psilocybin, and N,N-dimethyltryptamine (DMT), are famous for their capacity to temporally and profoundly alter an individual's visual experiences. These visual alterations show consistent attributes despite large inter- and intra-individual variances. Many reports document a common perception of colors as more saturated, with increased brightness and contrast in the environment ("Visual Intensifications"). Environmental objects might be altered in size ("Visual illusions") or take on a modified and special meaning for the subject ("Altered self-reference"). Subjects may perceive light flashes or geometrical figures containing recurrent patterns ("Elementary imagery and hallucinations") influenced by auditory stimuli ("Audiovisual synesthesia"), or they may envision images of people, animals, or landscapes ("Complex imagery and hallucinations") without any physical stimuli supporting their percepts. This wide assortment of visual phenomena suggests that one single neuropsychopharmacological mechanism is unlikely to explain such vast phenomenological diversity. Starting with mechanisms that act at the cellular level, the key role of 5-HT2A receptor activation and the subsequent increased cortical excitation will be considered. Next, it will be shown that area specific anatomical and dynamical features link increased excitation to the specific visual contents of hallucinations. The decrease of alpha oscillations by hallucinogens will then be introduced as a systemic mechanism for amplifying internal-driven excitation that overwhelms stimulus-induced excitations. Finally, the hallucinogen-induced parallel decrease of the N170 visual evoked potential and increased medial P1 potential will be discussed as key mechanisms for inducing a dysbalance between global integration and early visual gain that may explain several hallucinogen-induced visual experiences, including visual hallucinations, illusions

  10. Implied motion because of instability in Hokusai Manga activates the human motion-sensitive extrastriate visual cortex: an fMRI study of the impact of visual art.

    Science.gov (United States)

    Osaka, Naoyuki; Matsuyoshi, Daisuke; Ikeda, Takashi; Osaka, Mariko

    2010-03-10

    The recent development of cognitive neuroscience has invited inference about the neurosensory events underlying the experience of visual arts involving implied motion. We report functional magnetic resonance imaging study demonstrating activation of the human extrastriate motion-sensitive cortex by static images showing implied motion because of instability. We used static line-drawing cartoons of humans by Hokusai Katsushika (called 'Hokusai Manga'), an outstanding Japanese cartoonist as well as famous Ukiyoe artist. We found 'Hokusai Manga' with implied motion by depicting human bodies that are engaged in challenging tonic posture significantly activated the motion-sensitive visual cortex including MT+ in the human extrastriate cortex, while an illustration that does not imply motion, for either humans or objects, did not activate these areas under the same tasks. We conclude that motion-sensitive extrastriate cortex would be a critical region for perception of implied motion in instability.

  11. Functional magnetic resonance imaging of the visual cortex performed in children under sedation to assist in presurgical planning.

    Science.gov (United States)

    Li, Weier; Wait, Scott D; Ogg, Robert J; Scoggins, Matt A; Zou, Ping; Wheless, James; Boop, Frederick A

    2013-05-01

    Advances in brain imaging have allowed for more sophisticated mapping of crucial neural structures. Functional MRI (fMRI) measures local changes in blood oxygenation associated with changes in neural activity and is useful in mapping cortical activation. Applications of this imaging modality have generally been restricted to cooperative patients; however, fMRI has proven successful in localizing the motor cortex for neurosurgical planning in uncooperative children under sedation. The authors demonstrate that the use of fMRI to localize the visual cortex in sedated children can be safely and effectively performed, allowing for more accurate presurgical planning to spare visual structures. Between 2007 and 2009, 11 children (age range 1-11 years) underwent fMRI for neurosurgical planning while under sedation. Blood oxygen level-dependent fMRI was performed to detect visual cortex activation during stimulation through closed eyelids. Visual stimulation was presented in block design with periods of flashing light alternated with darkness. Functional MRI was successful in identifying visual cortex in each of the 11 children tested. There were no complications with propofol sedation or the fMRI. All children suffered from epilepsy, 5 had brain tumors, and 1 had tuberous sclerosis. After fMRI was performed, 6 patients underwent surgery. Frameless stereotactic guidance was synchronized with fMRI data to design an approach to spare visual structures during resection. There were no cases where a false negative led to unexpected visual field deficits or other side effects of surgery. In 2 cases, the fMRI results demonstrated that the tracts were already disrupted: in one case from a prior tumor operation and in another from dysplasia. Functional MRI for evaluation of visual pathways can be safely and reproducibly performed in young or uncooperative children under light sedation. Identification of primary visual cortex aids in presurgical planning to avoid vision loss in

  12. Activity in human visual and parietal cortex reveals object-based attention in working memory.

    Science.gov (United States)

    Peters, Benjamin; Kaiser, Jochen; Rahm, Benjamin; Bledowski, Christoph

    2015-02-25

    Visual attention enables observers to select behaviorally relevant information based on spatial locations, features, or objects. Attentional selection is not limited to physically present visual information, but can also operate on internal representations maintained in working memory (WM) in service of higher-order cognition. However, only little is known about whether attention to WM contents follows the same principles as attention to sensory stimuli. To address this question, we investigated in humans whether the typically observed effects of object-based attention in perception are also evident for object-based attentional selection of internal object representations in WM. In full accordance with effects in visual perception, the key behavioral and neuronal characteristics of object-based attention were observed in WM. Specifically, we found that reaction times were shorter when shifting attention to memory positions located on the currently attended object compared with equidistant positions on a different object. Furthermore, functional magnetic resonance imaging and multivariate pattern analysis of visuotopic activity in visual (areas V1-V4) and parietal cortex revealed that directing attention to one position of an object held in WM also enhanced brain activation for other positions on the same object, suggesting that attentional selection in WM activates the entire object. This study demonstrated that all characteristic features of object-based attention are present in WM and thus follows the same principles as in perception. Copyright © 2015 the authors 0270-6474/15/353360-10$15.00/0.

  13. Neurons in Primate Visual Cortex Alternate between Responses to Multiple Stimuli in Their Receptive Field

    Science.gov (United States)

    Li, Kang; Kozyrev, Vladislav; Kyllingsbæk, Søren; Treue, Stefan; Ditlevsen, Susanne; Bundesen, Claus

    2016-01-01

    A fundamental question concerning representation of the visual world in our brain is how a cortical cell responds when presented with more than a single stimulus. We find supportive evidence that most cells presented with a pair of stimuli respond predominantly to one stimulus at a time, rather than a weighted average response. Traditionally, the firing rate is assumed to be a weighted average of the firing rates to the individual stimuli (response-averaging model) (Bundesen et al., 2005). Here, we also evaluate a probability-mixing model (Bundesen et al., 2005), where neurons temporally multiplex the responses to the individual stimuli. This provides a mechanism by which the representational identity of multiple stimuli in complex visual scenes can be maintained despite the large receptive fields in higher extrastriate visual cortex in primates. We compare the two models through analysis of data from single cells in the middle temporal visual area (MT) of rhesus monkeys when presented with two separate stimuli inside their receptive field with attention directed to one of the two stimuli or outside the receptive field. The spike trains were modeled by stochastic point processes, including memory effects of past spikes and attentional effects, and statistical model selection between the two models was performed by information theoretic measures as well as the predictive accuracy of the models. As an auxiliary measure, we also tested for uni- or multimodality in interspike interval distributions, and performed a correlation analysis of simultaneously recorded pairs of neurons, to evaluate population behavior. PMID:28082892

  14. Reduced Haemodynamic Response in the Ageing Visual Cortex Measured by Absolute fNIRS.

    Directory of Open Access Journals (Sweden)

    Laura McKernan Ward

    Full Text Available The effect of healthy ageing on visual cortical activation is still to be fully explored. This study aimed to elucidate whether the haemodynamic response (HDR of the visual cortex altered as a result of ageing. Visually normal (healthy participants were presented with a simple visual stimulus (reversing checkerboard. Full optometric screening was implemented to identify two age groups: younger adults (n = 12, mean age 21 and older adults (n = 13, mean age 71. Frequency-domain Multi-distance (FD-MD functional Near-Infrared Spectroscopy (fNIRS was used to measure absolute changes in oxygenated [HbO] and deoxygenated [HbR] haemoglobin concentrations in the occipital cortices. Utilising a slow event-related design, subjects viewed a full field reversing checkerboard with contrast and check size manipulations (15 and 30 minutes of arc, 50% and 100% contrast. Both groups showed the characteristic response of increased [HbO] and decreased [HbR] during stimulus presentation. However, older adults produced a more varied HDR and often had comparable levels of [HbO] and [HbR] during both stimulus presentation and baseline resting state. Younger adults had significantly greater concentrations of both [HbO] and [HbR] in every investigation regardless of the type of stimulus displayed (p<0.05. The average variance associated with this age-related effect for [HbO] was 88% and [HbR] 91%. Passive viewing of a visual stimulus, without any cognitive input, showed a marked age-related decline in the cortical HDR. Moreover, regardless of stimulus parameters such as check size, the HDR was characterised by age. In concurrence with present neuroimaging literature, we conclude that the visual HDR decreases as healthy ageing proceeds.

  15. Spatial specificity of working memory representations in the early visual cortex.

    Science.gov (United States)

    Pratte, Michael S; Tong, Frank

    2014-03-19

    Recent fMRI decoding studies have demonstrated that early retinotopic visual areas exhibit similar patterns of activity during the perception of a stimulus and during the maintenance of that stimulus in working memory. These findings provide support for the sensory recruitment hypothesis that the mechanisms underlying perception serve as a foundation for visual working memory. However, a recent study by Ester, Serences, and Awh (2009) found that the orientation of a peripheral grating maintained in working memory could be classified from both the contralateral and ipsilateral regions of the primary visual cortex (V1), implying that, unlike perception, feature-specific information was maintained in a nonretinotopic manner. Here, we evaluated the hypothesis that early visual areas can maintain information in a spatially specific manner and will do so if the task encourages the binding of feature information to a specific location. To encourage reliance on spatially specific memory, our experiment required observers to retain the orientations of two laterally presented gratings. Multivariate pattern analysis revealed that the orientation of each remembered grating was classified more accurately based on activity patterns in the contralateral than in the ipsilateral regions of V1 and V2. In contrast, higher extrastriate areas exhibited similar levels of performance across the two hemispheres. A time-resolved analysis further indicated that the retinotopic specificity of the working memory representation in V1 and V2 was maintained throughout the retention interval. Our results suggest that early visual areas provide a cortical basis for actively maintaining information about the features and locations of stimuli in visual working memory.

  16. On Spike-Timing-Dependent-Plasticity, Memristive Devices, and building a Self-Learning Visual Cortex

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    Bernabe eLinares-Barranco

    2011-03-01

    Full Text Available In this paper we present a very exciting overlap between emergent nano technologyand neuroscience. We are linking one type of memristor nano technology devices to the biological synaptic updaterule known as Spike-Time-Dependent-Plasticity found in real biological synapses.Understanding this link allows neuromorphic engineers to develop circuit architecturesthat use this type of memristors to artificially emulate parts of the visual cortex. We focus on the type of memristors referred to as voltage driven memristors andfocus our discussions on a behavioral macro model for such devices.The implementationsresult in fully asynchronous architectures with neurons sending their action potentials notonly forwards but also backwards. One criticalaspect is to use neurons that generate spikes of specific shapes. By changing the shapes of the neuron action potential spikes we can tune and manipulatethe STDP learning rules for both excitatory and inhibitory synapses. We show howneurons and memristors can be interconnected to achieve large scale spiking learning systems,that follow a type of multiplicative STDP learning rule. We briefly extend the architecturesto use three-terminal transistors with similar memristive behavior.We illustrate how a V1 visual cortex layer can assembled and how it iscapable of learning to extract orientations from visual data coming from a real artificialCMOS spiking retina observing real life scenes. Finally, we discuss limitationsof currently available memristors.The results presented are based on behavioral simulations and do not take intoaccount non-idealities of devices and interconnects. The aim of this paper is to present, ina tutorial manner, aninitial framework for the possible development of fully asynchronous STDP learning neuromorphic architecturesexploiting two or three terminal memristive type devices. All files used for the simulations are made available through the journal web site.

  17. Classic and Golli Myelin Basic Protein have distinct developmental trajectories in human visual cortex

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    Caitlin R Siu

    2015-04-01

    Full Text Available Traditionally myelin is viewed as insulation around axons however more recent studies have shown it plays an important role in plasticity, axonal metabolism and neuroimmune signalling. Myelin is a complex multi-protein structure composed of hundreds of proteins, with Myelin Basic Protein (MBP being the most studied. MBP has two families: Classic-MBP that is necessary for activity driven compaction of myelin around axons, and Golli-MBP that is found in neurons, oligodendrocytes, and T cells, and has been called a 'molecular link' between the nervous and immune systems. In visual cortex myelin proteins interact with immune processes to affect experience-dependent plasticity. We studied myelin in human visual cortex using Western blotting to quantify Classic- and Golli-MBP expression in post-mortem tissue samples ranging in age from 20 days to 80 years. We found that Classic- and Golli-MBP have different patterns of change across the lifespan: Classic-MBP gradually increases to 42 years and then declines into aging; Golli-MBP has changes that are coincident with milestones in visual system sensitive period, before gradually increasing into aging. There are 3 stages in the balance between Classic- and Golli-MBP expression, with Golli-MBP dominating early, then shifting to Classic-MBP, and back to Golli-MBP in aging. Also Golli-MBP has a wave of high inter-individual variability during childhood. These results about cortical MBP expression are timely because they compliment recent advances in MRI techniques that produce high resolution maps of cortical myelin in normal and diseased brain. In addition the unique pattern of Golli-MBP expression across the lifespan suggests that it supports high levels of neuroimmune interaction in cortical development and in aging.

  18. Stimulus-entrained oscillatory activity propagates as waves from area 18 to 17 in cat visual cortex.

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    Lian Zheng

    Full Text Available Previous studies in cat visual cortex reported that area 18 can actively drive neurons in area 17 through cortico-cortical projections. However, the dynamics of such cortico-cortical interaction remains unclear. Here we used multielectrode arrays to examine the spatiotemporal pattern of neuronal activity in cat visual cortex across the 17/18 border. We found that full-field contrast reversal gratings evoked oscillatory wave activity propagating from area 18 to 17. The wave direction was independent of the grating orientation, and could not be accounted for by the spatial distribution of receptive field latencies, suggesting that the waves are largely mediated by intrinsic connections in the cortex. Different from the evoked waves, spontaneous waves propagated along both directions across the 17/18 border. Together, our results suggest that visual stimulation may enhance the flow of information from area 18 to 17.

  19. Paired-pulse behavior of visually evoked potentials recorded in human visual cortex using patterned paired-pulse stimulation.

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    Höffken, Oliver; Grehl, Torsten; Dinse, Hubert R; Tegenthoff, Martin; Bach, Michael

    2008-07-01

    Paired-pulse stimulation techniques are used as common tools to investigate cortical excitability and cortical plastic changes. Similar to investigations in the somatosensory and motor system here we applied a new paired-pulse paradigm to study the paired-pulse behavior of visually evoked potentials (VEPs) in 25 healthy subjects. VEPs were recorded and the responses to the first and the second P100 peak were analyzed at different SOAs [stimulus onset asynchrony (SOA) = interstimulus interval (ISI) + pulse duration (13 ms)]. Two measures describe the paired pulse interaction: the "amplitude ratio", the ratio of the second to the first amplitude, and the "latency shift", the difference of the inter-peak interval between the P100 peaks and the respective SOA. To separate alterations in the amplitude of the second VEP response due to changes in paired-pulse inhibition from those originating from superposition of the two waveforms, particularly at short SOAs, we created a waveform template from recordings made at SOAs of 1 s, where interaction can be assumed to be negligible. Superposed traces of VEP recordings were then created by adding two templates at delays corresponding to the SOAs used. The original recordings were then digitally subtracted from the traces obtained by superposition. Analysis of the subtracted traces revealed evidence that at short SOAs the second VEP response is substantially suppressed, a finding comparable to the paired-pulse inhibition described for motor and somatosensory cortex following paired-pulse stimulation. However, paired-pulse inhibition seen in V1 varied considerably from subject to subject, both in respect to amplitude, and to time of maximal inhibition. We found paired-pulse inhibition ranging from 12 to 76% (mean 34%) at SOAs between 80 (shortest discriminable SOA) and 320 ms (mean 128 ms). At intermediate SOAs between 80 and 720 ms (mean 215 ms) the amplitude ratios were between 94 and 145% (mean 116%) indicative of slight

  20. Synchronous Chaos and Broad Band Gamma Rhythm in a Minimal Multi-Layer Model of Primary Visual Cortex

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    Battaglia, Demian; Hansel, David

    2011-01-01

    Visually induced neuronal activity in V1 displays a marked gamma-band component which is modulated by stimulus properties. It has been argued that synchronized oscillations contribute to these gamma-band activity. However, analysis of Local Field Potentials (LFPs) across different experiments reveals considerable diversity in the degree of oscillatory behavior of this induced activity. Contrast-dependent power enhancements can indeed occur over a broad band in the gamma frequency range and spectral peaks may not arise at all. Furthermore, even when oscillations are observed, they undergo temporal decorrelation over very few cycles. This is not easily accounted for in previous network modeling of gamma oscillations. We argue here that interactions between cortical layers can be responsible for this fast decorrelation. We study a model of a V1 hypercolumn, embedding a simplified description of the multi-layered structure of the cortex. When the stimulus contrast is low, the induced activity is only weakly synchronous and the network resonates transiently without developing collective oscillations. When the contrast is high, on the other hand, the induced activity undergoes synchronous oscillations with an irregular spatiotemporal structure expressing a synchronous chaotic state. As a consequence the population activity undergoes fast temporal decorrelation, with concomitant rapid damping of the oscillations in LFPs autocorrelograms and peak broadening in LFPs power spectra. We show that the strength of the inter-layer coupling crucially affects this spatiotemporal structure. We predict that layer VI inactivation should induce global changes in the spectral properties of induced LFPs, reflecting their slower temporal decorrelation in the absence of inter-layer feedback. Finally, we argue that the mechanism underlying the emergence of synchronous chaos in our model is in fact very general. It stems from the fact that gamma oscillations induced by local delayed

  1. Synchronous chaos and broad band gamma rhythm in a minimal multi-layer model of primary visual cortex.

    Directory of Open Access Journals (Sweden)

    Demian Battaglia

    2011-10-01

    Full Text Available Visually induced neuronal activity in V1 displays a marked gamma-band component which is modulated by stimulus properties. It has been argued that synchronized oscillations contribute to these gamma-band activity. However, analysis of Local Field Potentials (LFPs across different experiments reveals considerable diversity in the degree of oscillatory behavior of this induced activity. Contrast-dependent power enhancements can indeed occur over a broad band in the gamma frequency range and spectral peaks may not arise at all. Furthermore, even when oscillations are observed, they undergo temporal decorrelation over very few cycles. This is not easily accounted for in previous network modeling of gamma oscillations. We argue here that interactions between cortical layers can be responsible for this fast decorrelation. We study a model of a V1 hypercolumn, embedding a simplified description of the multi-layered structure of the cortex. When the stimulus contrast is low, the induced activity is only weakly synchronous and the network resonates transiently without developing collective oscillations. When the contrast is high, on the other hand, the induced activity undergoes synchronous oscillations with an irregular spatiotemporal structure expressing a synchronous chaotic state. As a consequence the population activity undergoes fast temporal decorrelation, with concomitant rapid damping of the oscillations in LFPs autocorrelograms and peak broadening in LFPs power spectra. We show that the strength of the inter-layer coupling crucially affects this spatiotemporal structure. We predict that layer VI inactivation should induce global changes in the spectral properties of induced LFPs, reflecting their slower temporal decorrelation in the absence of inter-layer feedback. Finally, we argue that the mechanism underlying the emergence of synchronous chaos in our model is in fact very general. It stems from the fact that gamma oscillations induced by

  2. Asymmetrical interhemispheric connections develop in cat visual cortex after early unilateral convergent strabismus: Anatomy, physiology and mechanisms

    Directory of Open Access Journals (Sweden)

    Emmanuel eBui Quoc

    2012-01-01

    Full Text Available In the mammalian primary visual cortex, the corpus callosum contributes to the unification of the visual hemifields that project to the two hemispheres. Its development depends on visual experience. When the latter is abnormal, callosal connections must undergo dramatic anatomical and physiological changes. However, such data are sparse and incomplete. Thus, little is known about the consequences of abnormal postnatal visual experience on the development of callosal connections and their role in unifying representation of the two hemifields. Here, the effects of early unilateral convergent strabismus (a model of abnormal visual experience were fully characterized with respect to the development of the callosal connections in cat visual cortex, an experimental model for humans. Electrophysiological responses and 3D reconstruction of single callosal axons show that abnormally asymmetrical callosal connections develop after unilateral convergent strabismus, resulting from an extension of axonal branches of specific orders in the hemisphere ipsilateral to the deviated eye and a decreased number of nodes and terminals in the other (ipsilateral to the non deviated eye. Furthermore this asymmetrical organization prevents the establishment of a unifying representation of the two visual hemifields. As a general rule, we suggest that crossed and uncrossed retino-geniculo-cortical pathways contribute in succession to the development of the callosal maps in visual cortex.

  3. Adult deafness induces somatosensory conversion of ferret auditory cortex

    OpenAIRE

    Allman, Brian L.; Keniston, Leslie P.; Meredith, M. Alex

    2009-01-01

    In response to early or developmental lesions, responsiveness of sensory cortex can be converted from the deprived modality to that of the remaining sensory systems. However, little is known about capacity of the adult cortex for cross-modal reorganization. The present study examined the auditory cortices of animals deafened as adults, and observed an extensive somatosensory conversion within as little as 16 days after deafening. These results demonstrate that cortical cross-modal reorganizat...

  4. miR-132, an experience-dependent microRNA, is essential for visual cortex plasticity.

    Science.gov (United States)

    Mellios, Nikolaos; Sugihara, Hiroki; Castro, Jorge; Banerjee, Abhishek; Le, Chuong; Kumar, Arooshi; Crawford, Benjamin; Strathmann, Julia; Tropea, Daniela; Levine, Stuart S; Edbauer, Dieter; Sur, Mriganka

    2011-09-04

    Using quantitative analyses, we identified microRNAs (miRNAs) that were abundantly expressed in visual cortex and that responded to dark rearing and/or monocular deprivation. The most substantially altered miRNA, miR-132, was rapidly upregulated after eye opening and was delayed by dark rearing. In vivo inhibition of miR-132 in mice prevented ocular dominance plasticity in identified neurons following monocular deprivation and affected the maturation of dendritic spines, demonstrating its critical role in the plasticity of visual cortex circuits. © 2011 Nature America, Inc. All rights reserved.

  5. Evolutionary constraints on visual cortex architecture from the dynamics of hallucinations.

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    Butler, Thomas Charles; Benayoun, Marc; Wallace, Edward; van Drongelen, Wim; Goldenfeld, Nigel; Cowan, Jack

    2012-01-10

    In the cat or primate primary visual cortex (V1), normal vision corresponds to a state where neural excitation patterns are driven by external visual stimuli. A spectacular failure mode of V1 occurs when such patterns are overwhelmed by spontaneously generated spatially self-organized patterns of neural excitation. These are experienced as geometric visual hallucinations. The problem of identifying the mechanisms by which V1 avoids this failure is made acute by recent advances in the statistical mechanics of pattern formation, which suggest that the hallucinatory state should be very robust. Here, we report how incorporating physiologically realistic long-range connections between inhibitory neurons changes the behavior of a model of V1. We find that the sparsity of long-range inhibition in V1 plays a previously unrecognized but key functional role in preserving the normal vision state. Surprisingly, it also contributes to the observed regularity of geometric visual hallucinations. Our results provide an explanation for the observed sparsity of long-range inhibition in V1--this generic architectural feature is an evolutionary adaptation that tunes V1 to the normal vision state. In addition, it has been shown that exactly the same long-range connections play a key role in the development of orientation preference maps. Thus V1's most striking long-range features--patchy excitatory connections and sparse inhibitory connections--are strongly constrained by two requirements: the need for the visual state to be robust and the developmental requirements of the orientational preference map.

  6. Visual space and object space in the cerebral cortex of retinal disease patients.

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    Elfi Goesaert

    Full Text Available The lower areas of the hierarchically organized visual cortex are strongly retinotopically organized, with strong responses to specific retinotopic stimuli, and no response to other stimuli outside these preferred regions. Higher areas in the ventral occipitotemporal cortex show a weak eccentricity bias, and are mainly sensitive for object category (e.g., faces versus buildings. This study investigated how the mapping of eccentricity and category sensitivity using functional magnetic resonance imaging is affected by a retinal lesion in two very different low vision patients: a patient with a large central scotoma, affecting central input to the retina (juvenile macular degeneration, and a patient where input to the peripheral retina is lost (retinitis pigmentosa. From the retinal degeneration, we can predict specific losses of retinotopic activation. These predictions were confirmed when comparing stimulus activations with a no-stimulus fixation baseline. At the same time, however, seemingly contradictory patterns of activation, unexpected given the retinal degeneration, were observed when different stimulus conditions were directly compared. These unexpected activations were due to position-specific deactivations, indicating the importance of investigating absolute activation (relative to a no-stimulus baseline rather than relative activation (comparing different stimulus conditions. Data from two controls, with simulated scotomas that matched the lesions in the two patients also showed that retinotopic mapping results could be explained by a combination of activations at the stimulated locations and deactivations at unstimulated locations. Category sensitivity was preserved in the two patients. In sum, when we take into account the full pattern of activations and deactivations elicited in retinotopic cortex and throughout the ventral object vision pathway in low vision patients, the pattern of (deactivation is consistent with the retinal loss.

  7. Deconstructing visual scenes in cortex: gradients of object and spatial layout information.

    Science.gov (United States)

    Harel, Assaf; Kravitz, Dwight J; Baker, Chris I

    2013-04-01

    Real-world visual scenes are complex cluttered, and heterogeneous stimuli engaging scene- and object-selective cortical regions including parahippocampal place area (PPA), retrosplenial complex (RSC), and lateral occipital complex (LOC). To understand the unique contribution of each region to distributed scene representations, we generated predictions based on a neuroanatomical framework adapted from monkey and tested them using minimal scenes in which we independently manipulated both spatial layout (open, closed, and gradient) and object content (furniture, e.g., bed, dresser). Commensurate with its strong connectivity with posterior parietal cortex, RSC evidenced strong spatial layout information but no object information, and its response was not even modulated by object presence. In contrast, LOC, which lies within the ventral visual pathway, contained strong object information but no background information. Finally, PPA, which is connected with both the dorsal and the ventral visual pathway, showed information about both objects and spatial backgrounds and was sensitive to the presence or absence of either. These results suggest that 1) LOC, PPA, and RSC have distinct representations, emphasizing different aspects of scenes, 2) the specific representations in each region are predictable from their patterns of connectivity, and 3) PPA combines both spatial layout and object information as predicted by connectivity.

  8. Limits on perceptual encoding can be predicted from known receptive field properties of human visual cortex.

    Science.gov (United States)

    Cohen, Michael A; Rhee, Juliana Y; Alvarez, George A

    2016-01-01

    Human cognition has a limited capacity that is often attributed to the brain having finite cognitive resources, but the nature of these resources is usually not specified. Here, we show evidence that perceptual interference between items can be predicted by known receptive field properties of the visual cortex, suggesting that competition within representational maps is an important source of the capacity limitations of visual processing. Across the visual hierarchy, receptive fields get larger and represent more complex, high-level features. Thus, when presented simultaneously, high-level items (e.g., faces) will often land within the same receptive fields, while low-level items (e.g., color patches) will often not. Using a perceptual task, we found long-range interference between high-level items, but only short-range interference for low-level items, with both types of interference being weaker across hemifields. Finally, we show that long-range interference between items appears to occur primarily during perceptual encoding and not during working memory maintenance. These results are naturally explained by the distribution of receptive fields and establish a link between perceptual capacity limits and the underlying neural architecture. (c) 2015 APA, all rights reserved).

  9. Audiovisual Modulation in Mouse Primary Visual Cortex Depends on Cross-Modal Stimulus Configuration and Congruency.

    Science.gov (United States)

    Meijer, Guido T; Montijn, Jorrit S; Pennartz, Cyriel M A; Lansink, Carien S

    2017-09-06

    The sensory neocortex is a highly connected associative network that integrates information from multiple senses, even at the level of the primary sensory areas. Although a growing body of empirical evidence supports this view, the neural mechanisms of cross-modal integration in primary sensory areas, such as the primary visual cortex (V1), are still largely unknown. Using two-photon calcium imaging in awake mice, we show that the encoding of audiovisual stimuli in V1 neuronal populations is highly dependent on the features of the stimulus constituents. When the visual and auditory stimulus features were modulated at the same rate (i.e., temporally congruent), neurons responded with either an enhancement or suppression compared with unisensory visual stimuli, and their prevalence was balanced. Temporally incongruent tones or white-noise bursts included in audiovisual stimulus pairs resulted in predominant response suppression across the neuronal population. Visual contrast did not influence multisensory processing when the audiovisual stimulus pairs were congruent; however, when white-noise bursts were used, neurons generally showed response suppression when the visual stimulus contrast was high whereas this effect was absent when the visual contrast was low. Furthermore, a small fraction of V1 neurons, predominantly those located near the lateral border of V1, responded to sound alone. These results show that V1 is involved in the encoding of cross-modal interactions in a more versatile way than previously thought.SIGNIFICANCE STATEMENT The neural substrate of cross-modal integration is not limited to specialized cortical association areas but extends to primary sensory areas. Using two-photon imaging of large groups of neurons, we show that multisensory modulation of V1 populations is strongly determined by the individual and shared features of cross-modal stimulus constituents, such as contrast, frequency, congruency, and temporal structure. Congruent

  10. Spatial spread of local field potential is band-pass in the primary visual cortex.

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    Dubey, Agrita; Ray, Supratim

    2016-10-01

    Local field potential (LFP) is a valuable tool in understanding brain function and in brain machine-interfacing applications. However, there is no consensus on the spatial extent of the cortex that contributes to the LFP (its "spatial spread"), with different studies reporting values between a few hundred micrometers and several millimeters. Furthermore, the dependency of the spatial spread on frequency, which could reflect properties of the network architecture and extracellular medium, is not well studied, with theory and models predicting either "all-pass" (frequency-independent) or "low-pass" behavior. Surprisingly, we found the LFP spread to be "band-pass" in the primate primary visual cortex, with the greatest spread in the high-gamma range (60-150 Hz). This was accompanied by an increase in phase coherency across neighboring sites in the same frequency range, consistent with the findings of a recent model that reconciles previous studies by suggesting that spatial spread depends on neuronal correlations. Copyright © 2016 the American Physiological Society.

  11. The right frontopolar cortex is involved in visual-spatial prospective memory.

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    Costa, Alberto; Oliveri, Massimiliano; Barban, Francesco; Bonnì, Sonia; Koch, Giacomo; Caltagirone, Carlo; Carlesimo, Giovanni A

    2013-01-01

    The involvement of frontopolar cortex in mediating prospective memory processes has been evidenced by various studies, mainly by means of neuroimaging techniques. Recently, one transcranial magnetic stimulation study documented that transient inhibition of left Brodmann Area (BA) 10 impaired verbal prospective memory. This result raises the issue of whether the BA 10 involvement in prospective memory functioning may be modulated by the physical characteristics of the stimuli used. The present study aimed to investigate the role of the frontopolar cortex in visual-spatial PM by means of the application of inhibitory theta-burst stimulation. Twelve volunteers were evaluated after inhibitory theta-burst stimulation over left BA 10, right BA10 and CZ (control condition). In the prospective memory procedure, sequences of four spatial positions (black squares) each were presented. During the inter-sequence delay, subjects had to reproduce the sequence in the observed order (ongoing task forward) or the reverse order (backward). At the occurrence of a target position, subjects had to press a key on the keyboard (prospective memory score). Recall and recognition of the target positions were also tested. We found that prospective memory accuracy was lower after theta-burst stimulation over right BA10 than CZ (pvisual-spatial prospective memory. In the context of previous data providing evidence for left BA 10 involvement in verbal prospective memory, our results also suggest material-specific lateralization of prospective memory processes in BA 10.

  12. Plasticity in the Human Visual Cortex: An Ophthalmology-Based Perspective

    Science.gov (United States)

    Rosa, Andreia Martins; Silva, Maria Fátima; Murta, Joaquim

    2013-01-01

    Neuroplasticity refers to the ability of the brain to reorganize the function and structure of its connections in response to changes in the environment. Adult human visual cortex shows several manifestations of plasticity, such as perceptual learning and adaptation, working under the top-down influence of attention. Plasticity results from the interplay of several mechanisms, including the GABAergic system, epigenetic factors, mitochondrial activity, and structural remodeling of synaptic connectivity. There is also a downside of plasticity, that is, maladaptive plasticity, in which there are behavioral losses resulting from plasticity changes in the human brain. Understanding plasticity mechanisms could have major implications in the diagnosis and treatment of ocular diseases, such as retinal disorders, cataract and refractive surgery, amblyopia, and in the evaluation of surgical materials and techniques. Furthermore, eliciting plasticity could open new perspectives in the development of strategies that trigger plasticity for better medical and surgical outcomes. PMID:24205505

  13. High baseline activity in inferior temporal cortex improves neural and behavioral discriminability during visual categorization

    Directory of Open Access Journals (Sweden)

    Nazli eEmadi

    2014-11-01

    Full Text Available Spontaneous firing is a ubiquitous property of neural activity in the brain. Recent literature suggests that this baseline activity plays a key role in perception. However, it is not known how the baseline activity contributes to neural coding and behavior. Here, by recording from the single neurons in the inferior temporal cortex of monkeys performing a visual categorization task, we thoroughly explored the relationship between baseline activity, the evoked response, and behavior. Specifically we found that a low-frequency (< 8 Hz oscillation in the spike train, prior and phase-locked to the stimulus onset, was correlated with increased gamma power and neuronal baseline activity. This enhancement of the baseline activity was then followed by an increase in the neural selectivity and the response reliability and eventually a higher behavioral performance.

  14. P1-27: Localizing Regions Activated by Surface Gloss in Macaque Visual Cortex by fMRI

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    Gouki Okazawa

    2012-10-01

    Full Text Available Surface properties of objects such as gloss provide important information about the states or materials of objects in our visual experiences. Previous studies have shown that there are cortical regions responding to shapes, colors, faces etc. in the macaque visual cortex. However, we still lack the information about where the surface properties are processed in the macaque visual cortex. In this study, we examined whether there are regions activated by surface gloss, an important surface property, in the macaque visual cortex by using functional magnetic resonance imaging (fMRI. We trained two monkeys to fixate on a small spot on the screen in MRI scanner, while the images of glossy and matte objects were presented. As a control condition for low-level image features, such as spatial frequency or luminance contrast, we generated scrambled images by locally randomizing the luminance phases of images using wavelet filters. By contrasting the responses to glossy images to those to matte and scrambled images, we found the activation in wide regions along the ventral visual pathway including V1, V2, V3, V4, and the posterior part of the inferior temporal (IT cortex. In one monkey, we also found the activations in the central part of IT cortex. In another control experiment, we manipulated the image contrasts and found that the responses in these regions cannot be explained simply by the image contrasts. These results suggest that surface gloss is processed along the ventral pathway and, in the IT cortex there are distinct regions processing surface gloss.

  15. A reaction-diffusion model to capture disparity selectivity in primary visual cortex.

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    Mohammed Sultan Mohiuddin Siddiqui

    Full Text Available Decades of experimental studies are available on disparity selective cells in visual cortex of macaque and cat. Recently, local disparity map for iso-orientation sites for near-vertical edge preference is reported in area 18 of cat visual cortex. No experiment is yet reported on complete disparity map in V1. Disparity map for layer IV in V1 can provide insight into how disparity selective complex cell receptive field is organized from simple cell subunits. Though substantial amounts of experimental data on disparity selective cells is available, no model on receptive field development of such cells or disparity map development exists in literature. We model disparity selectivity in layer IV of cat V1 using a reaction-diffusion two-eye paradigm. In this model, the wiring between LGN and cortical layer IV is determined by resource an LGN cell has for supporting connections to cortical cells and competition for target space in layer IV. While competing for target space, the same type of LGN cells, irrespective of whether it belongs to left-eye-specific or right-eye-specific LGN layer, cooperate with each other while trying to push off the other type. Our model captures realistic 2D disparity selective simple cell receptive fields, their response properties and disparity map along with orientation and ocular dominance maps. There is lack of correlation between ocular dominance and disparity selectivity at the cell population level. At the map level, disparity selectivity topography is not random but weakly clustered for similar preferred disparities. This is similar to the experimental result reported for macaque. The details of weakly clustered disparity selectivity map in V1 indicate two types of complex cell receptive field organization.

  16. Modafinil improves methamphetamine-induced object recognition deficits and restores prefrontal cortex ERK signaling in mice.

    Science.gov (United States)

    González, Betina; Raineri, Mariana; Cadet, Jean Lud; García-Rill, Edgar; Urbano, Francisco J; Bisagno, Veronica

    2014-12-01

    Chronic use of methamphetamine (METH) leads to long-lasting cognitive dysfunction in humans and in animal models. Modafinil is a wake-promoting compound approved for the treatment of sleeping disorders. It is also prescribed off label to treat METH dependence. In the present study, we investigated whether modafinil could improve cognitive deficits induced by sub-chronic METH treatment in mice by measuring visual retention in a Novel Object Recognition (NOR) task. After sub-chronic METH treatment (1 mg/kg, once a day for 7 days), mice performed the NOR task, which consisted of habituation to the object recognition arena (5 min a day, 3 consecutive days), training session (2 equal objects, 10 min, day 4), and a retention session (1 novel object, 5 min, day 5). One hour before the training session, mice were given a single dose of modafinil (30 or 90 mg/kg). METH-treated mice showed impairments in visual memory retention, evidenced by equal preference of familiar and novel objects during the retention session. The lower dose of modafinil (30 mg/kg) had no effect on visual retention scores in METH-treated mice, while the higher dose (90 mg/kg) rescued visual memory retention to control values. We also measured extracellular signal-regulated kinase (ERK) phosphorylation in medial prefrontal cortex (mPFC), hippocampus, and nucleus accumbens (NAc) of METH- and vehicle-treated mice that received modafinil 1 h before exposure to novel objects in the training session, compared to mice placed in the arena without objects. Elevated ERK phosphorylation was found in the mPFC of vehicle-treated mice, but not in METH-treated mice, exposed to objects. The lower dose of modafinil had no effect on ERK phosphorylation in METH-treated mice, while 90 mg/kg modafinil treatment restored the ERK phosphorylation induced by novelty in METH-treated mice to values comparable to controls. We found neither a novelty nor treatment effect on ERK phosphorylation in hippocampus or NAc of vehicle

  17. Canine and human visual cortex intact and responsive despite early retinal blindness from RPE65 mutation.

    Directory of Open Access Journals (Sweden)

    Geoffrey K Aguirre

    2007-06-01

    Full Text Available RPE65 is an essential molecule in the retinoid-visual cycle, and RPE65 gene mutations cause the congenital human blindness known as Leber congenital amaurosis (LCA. Somatic gene therapy delivered to the retina of blind dogs with an RPE65 mutation dramatically restores retinal physiology and has sparked international interest in human treatment trials for this incurable disease. An unanswered question is how the visual cortex responds after prolonged sensory deprivation from retinal dysfunction. We therefore studied the cortex of RPE65-mutant dogs before and after retinal gene therapy. Then, we inquired whether there is visual pathway integrity and responsivity in adult humans with LCA due to RPE65 mutations (RPE65-LCA.RPE65-mutant dogs were studied with fMRI. Prior to therapy, retinal and subcortical responses to light were markedly diminished, and there were minimal cortical responses within the primary visual areas of the lateral gyrus (activation amplitude mean +/- standard deviation [SD] = 0.07% +/- 0.06% and volume = 1.3 +/- 0.6 cm(3. Following therapy, retinal and subcortical response restoration was accompanied by increased amplitude (0.18% +/- 0.06% and volume (8.2 +/- 0.8 cm(3 of activation within the lateral gyrus (p < 0.005 for both. Cortical recovery occurred rapidly (within a month of treatment and was persistent (as long as 2.5 y after treatment. Recovery was present even when treatment was provided as late as 1-4 y of age. Human RPE65-LCA patients (ages 18-23 y were studied with structural magnetic resonance imaging. Optic nerve diameter (3.2 +/- 0.5 mm was within the normal range (3.2 +/- 0.3 mm, and occipital cortical white matter density as judged by voxel-based morphometry was slightly but significantly altered (1.3 SD below control average, p = 0.005. Functional magnetic resonance imaging in human RPE65-LCA patients revealed cortical responses with a markedly diminished activation volume (8.8 +/- 1.2 cm(3 compared to controls

  18. Adult deafness induces somatosensory conversion of ferret auditory cortex.

    Science.gov (United States)

    Allman, Brian L; Keniston, Leslie P; Meredith, M Alex

    2009-04-07

    In response to early or developmental lesions, responsiveness of sensory cortex can be converted from the deprived modality to that of the remaining sensory systems. However, little is known about capacity of the adult cortex for cross-modal reorganization. The present study examined the auditory cortices of animals deafened as adults, and observed an extensive somatosensory conversion within as little as 16 days after deafening. These results demonstrate that cortical cross-modal reorganization can occur after the period of sensory system maturation.

  19. Layer-specific entrainment of gamma-band neural activity by the alpha rhythm in monkey visual cortex

    NARCIS (Netherlands)

    Spaak, E.; Bonnefond, M.; Maier, A.; Leopold, D.A.; Jensen, O.

    2012-01-01

    Although the mammalian neocortex has a clear laminar organization, layer-specific neuronal computations remain to be uncovered. Several studies suggest that gamma band activity in primary visual cortex (V1) is produced in granular and superficial layers and is associated with the processing of

  20. Suppression of metabolic activity caused by infantile strabismus and strabismic amblyopia in striate visual cortex of macaque monkeys.

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    Wong, Agnes M F; Burkhalter, Andreas; Tychsen, Lawrence

    2005-02-01

    Suppression is a major sensorial abnormality in humans and monkeys with infantile strabismus. We previously reported evidence of metabolic suppression in the visual cortex of strabismic macaques, using the mitochondrial enzyme cytochrome oxidase as an anatomic label. The purpose of this study was to further elucidate alterations in cortical metabolic activity, with or without amblyopia. Six macaque monkeys were used in the experiments (four strabismic and two control). Three of the strabismic monkeys had naturally occurring, infantile strabismus (two esotropic, one exotropic). The fourth strabismic monkey had infantile microesotropia induced by alternating monocular occlusion in the first months of life. Ocular motor behaviors and visual acuity were tested after infancy in each animal, and development of stereopsis was recorded during infancy in one strabismic and one control monkey. Ocular dominance columns (ODCs) of the striate visual cortex (area V1) were labeled using cytochrome oxidase (CO) histochemistry alone, or CO in conjunction with an anterograde tracer ([H 3 ]proline or WGA-HRP) injected into one eye. Each of the strabismic monkeys showed inequalities of metabolic activity in ODCs of opposite ocularity, visible as rows of lighter CO staining, corresponding to ODCs of lower metabolic activity, alternating with rows of darker CO staining, corresponding to ODCs of higher metabolic activity. In monkeys who had infantile strabismus and unilateral amblyopia, lower metabolic activity was found in (suppressed) ODCs driven by the nondominant eye in each hemisphere. In monkeys who had infantile esotropia and alternating fixation (no amblyopia), metabolic activity was lower in ODCs driven by the ipsilateral eye in each hemisphere. The suppression included a monocular core zone at the center of ODCs and binocular border zones at the boundaries of ODCs. This suppression was not evident in the monocular lamina of the LGN, indicating an intracortical rather than

  1. Sustained happiness? Lack of repetition suppression in right-ventral visual cortex for happy faces.

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    Suzuki, Atsunobu; Goh, Joshua O S; Hebrank, Andrew; Sutton, Bradley P; Jenkins, Lucas; Flicker, Blair A; Park, Denise C

    2011-09-01

    Emotional stimuli have been shown to preferentially engage initial attention but their sustained effects on neural processing remain largely unknown. The present study evaluated whether emotional faces engage sustained neural processing by examining the attenuation of neural repetition suppression to repeated emotional faces. Repetition suppression of neural function refers to the general reduction of neural activity when processing a repeated stimulus. Preferential processing of emotional face stimuli, however, should elicit sustained neural processing such that repetition suppression to repeated emotional faces is attenuated relative to faces with no emotional content. We measured the reduction of functional magnetic resonance imaging signals associated with immediate repetition of neutral, angry and happy faces. Whereas neutral faces elicited the greatest suppression in ventral visual cortex, followed by angry faces, repetition suppression was the most attenuated for happy faces. Indeed, happy faces showed almost no repetition suppression in part of the right-inferior occipital and fusiform gyri, which play an important role in face-identity processing. Our findings suggest that happy faces are associated with sustained visual encoding of face identity and thereby assist in the formation of more elaborate representations of the faces, congruent with findings in the behavioral literature.

  2. BACE1 Is Necessary for Experience-Dependent Homeostatic Synaptic Plasticity in Visual Cortex

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    Emily Petrus

    2014-01-01

    Full Text Available Alzheimer’s disease (AD is the most common form of age-related dementia, which is thought to result from overproduction and/or reduced clearance of amyloid-beta (Aβ peptides. Studies over the past few decades suggest that Aβ is produced in an activity-dependent manner and has physiological relevance to normal brain functions. Similarly, physiological functions for β- and γ-secretases, the two key enzymes that produce Aβ by sequentially processing the amyloid precursor protein (APP, have been discovered over recent years. In particular, activity-dependent production of Aβ has been suggested to play a role in homeostatic regulation of excitatory synaptic function. There is accumulating evidence that activity-dependent immediate early gene Arc is an activity “sensor,” which acts upstream of Aβ production and triggers AMPA receptor endocytosis to homeostatically downregulate the strength of excitatory synaptic transmission. We previously reported that Arc is critical for sensory experience-dependent homeostatic reduction of excitatory synaptic transmission in the superficial layers of visual cortex. Here we demonstrate that mice lacking the major neuronal β-secretase, BACE1, exhibit a similar phenotype: stronger basal excitatory synaptic transmission and failure to adapt to changes in visual experience. Our results indicate that BACE1 plays an essential role in sensory experience-dependent homeostatic synaptic plasticity in the neocortex.

  3. Pupil size directly modulates the feedforward response in human primary visual cortex independently of attention.

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    Bombeke, Klaas; Duthoo, Wout; Mueller, Sven C; Hopf, Jens-Max; Boehler, C Nico

    2016-02-15

    Controversy revolves around the question of whether psychological factors like attention and emotion can influence the initial feedforward response in primary visual cortex (V1). Although traditionally, the electrophysiological correlate of this response in humans (the C1 component) has been found to be unaltered by psychological influences, a number of recent studies have described attentional and emotional modulations. Yet, research into psychological effects on the feedforward V1 response has neglected possible direct contributions of concomitant pupil-size modulations, which are known to also occur under various conditions of attentional load and emotional state. Here we tested the hypothesis that such pupil-size differences themselves directly affect the feedforward V1 response. We report data from two complementary experiments, in which we used procedures that modulate pupil size without differences in attentional load or emotion while simultaneously recording pupil-size and EEG data. Our results confirm that pupil size indeed directly influences the feedforward V1 response, showing an inverse relationship between pupil size and early V1 activity. While it is unclear in how far this effect represents a functionally-relevant adaptation, it identifies pupil-size differences as an important modulating factor of the feedforward response of V1 and could hence represent a confounding variable in research investigating the neural influence of psychological factors on early visual processing. Copyright © 2015 Elsevier Inc. All rights reserved.

  4. Synaptic Mechanisms of Activity-Dependent Remodeling in Visual Cortex during Monocular Deprivation

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    Cynthia D. Rittenhouse

    2009-01-01

    Full Text Available It has long been appreciated that in the visual cortex, particularly within a postnatal critical period for experience-dependent plasticity, the closure of one eye results in a shift in the responsiveness of cortical cells toward the experienced eye. While the functional aspects of this ocular dominance shift have been studied for many decades, their cortical substrates and synaptic mechanisms remain elusive. Nonetheless, it is becoming increasingly clear that ocular dominance plasticity is a complex phenomenon that appears to have an early and a late component. Early during monocular deprivation, deprived eye cortical synapses depress, while later during the deprivation open eye synapses potentiate. Here we review current literature on the cortical mechanisms of activity-dependent plasticity in the visual system during the critical period. These studies shed light on the role of activity in shaping neuronal structure and function in general and can lead to insights regarding how learning is acquired and maintained at the neuronal level during normal and pathological brain development.

  5. Millisecond Coupling of Local Field Potentials to Synaptic Currents in the Awake Visual Cortex.

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    Haider, Bilal; Schulz, David P A; Häusser, Michael; Carandini, Matteo

    2016-04-06

    The cortical local field potential (LFP) is a common measure of population activity, but its relationship to synaptic activity in individual neurons is not fully established. This relationship has been typically studied during anesthesia and is obscured by shared slow fluctuations. Here, we used patch-clamp recordings in visual cortex of anesthetized and awake mice to measure intracellular activity; we then applied a simple method to reveal its coupling to the simultaneously recorded LFP. LFP predicted membrane potential as accurately as synaptic currents, indicating a major role for synaptic currents in the relationship between cortical LFP and intracellular activity. During anesthesia, cortical LFP predicted excitation far better than inhibition; during wakefulness, it predicted them equally well, and visual stimulation further enhanced predictions of inhibition. These findings reveal a central role for synaptic currents, and especially inhibition, in the relationship between the subthreshold activity of individual neurons and the cortical LFP during wakefulness. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  6. Binocular flash suppression in the primary visual cortex of anesthetized and awake macaques.

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    Hamed Bahmani

    Full Text Available Primary visual cortex (V1 was implicated as an important candidate for the site of perceptual suppression in numerous psychophysical and imaging studies. However, neurophysiological results in awake monkeys provided evidence for competition mainly between neurons in areas beyond V1. In particular, only a moderate percentage of neurons in V1 were found to modulate in parallel with perception with magnitude substantially smaller than the physical preference of these neurons. It is yet unclear whether these small modulations are rooted from local circuits in V1 or influenced by higher cognitive states. To address this question we recorded multi-unit spiking activity and local field potentials in area V1 of awake and anesthetized macaque monkeys during the paradigm of binocular flash suppression. We found that a small but significant modulation was present in both the anesthetized and awake states during the flash suppression presentation. Furthermore, the relative amplitudes of the perceptual modulations were not significantly different in the two states. We suggest that these early effects of perceptual suppression might occur locally in V1, in prior processing stages or within early visual cortical areas in the absence of top-down feedback from higher cognitive stages that are suppressed under anesthesia.

  7. Timing of early activity in the visual cortex as revealed by simultaneous MEG and ERG recordings.

    Science.gov (United States)

    Inui, Koji; Sannan, Hiromi; Miki, Kensaku; Kaneoke, Yoshiki; Kakigi, Ryusuke

    2006-03-01

    To clarify the latency of the earliest cortical activity in visual processing, electroretinograms (ERGs) and visual evoked magnetic fields (VEFs) following flash stimulation were recorded simultaneously in six human subjects. Flash stimuli were applied to the right eye and ERGs were recorded from a skin electrode placed on the lower lid. ERGs showed two major deflections in all subjects: an eyelid-negativity around 20 ms and a positivity around 60 ms corresponding to an a- and b-waves, respectively. The mean onset and peak latency of the earliest component of VEFs (37 M) was 30.2 and 36.9 ms, respectively. There was a linear correlation between the peak latency of the a-wave and the onset latency of the 37 M (r=0.90, P=0.011). When a single equivalent current dipole analysis was applied to the 37 M, four out of six subjects showed highly reliable results. The generator of the 37 M was estimated to be located in the striate cortex in all four subjects. Since post-receptoral activities in the retina are expected to start around the peak of the a-wave (20 ms), the early cortical activity, which appears 10 ms later than the a-wave peak, is considered to be the earliest cortical activity following flash stimulation.

  8. Role of early visual cortex in trans-saccadic memory of object features.

    Science.gov (United States)

    Malik, Pankhuri; Dessing, Joost C; Crawford, J Douglas

    2015-08-01

    Early visual cortex (EVC) participates in visual feature memory and the updating of remembered locations across saccades, but its role in the trans-saccadic integration of object features is unknown. We hypothesized that if EVC is involved in updating object features relative to gaze, feature memory should be disrupted when saccades remap an object representation into a simultaneously perturbed EVC site. To test this, we applied transcranial magnetic stimulation (TMS) over functional magnetic resonance imaging-localized EVC clusters corresponding to the bottom left/right visual quadrants (VQs). During experiments, these VQs were probed psychophysically by briefly presenting a central object (Gabor patch) while subjects fixated gaze to the right or left (and above). After a short memory interval, participants were required to detect the relative change in orientation of a re-presented test object at the same spatial location. Participants either sustained fixation during the memory interval (fixation task) or made a horizontal saccade that either maintained or reversed the VQ of the object (saccade task). Three TMS pulses (coinciding with the pre-, peri-, and postsaccade intervals) were applied to the left or right EVC. This had no effect when (a) fixation was maintained, (b) saccades kept the object in the same VQ, or (c) the EVC quadrant corresponding to the first object was stimulated. However, as predicted, TMS reduced performance when saccades (especially larger saccades) crossed the remembered object location and brought it into the VQ corresponding to the TMS site. This suppression effect was statistically significant for leftward saccades and followed a weaker trend for rightward saccades. These causal results are consistent with the idea that EVC is involved in the gaze-centered updating of object features for trans-saccadic memory and perception.

  9. Scene content is predominantly conveyed by high spatial frequencies in scene-selective visual cortex.

    Science.gov (United States)

    Berman, Daniel; Golomb, Julie D; Walther, Dirk B

    2017-01-01

    In complex real-world scenes, image content is conveyed by a large collection of intertwined visual features. The visual system disentangles these features in order to extract information about image content. Here, we investigate the role of one integral component: the content of spatial frequencies in an image. Specifically, we measure the amount of image content carried by low versus high spatial frequencies for the representation of real-world scenes in scene-selective regions of human visual cortex. To this end, we attempted to decode scene categories from the brain activity patterns of participants viewing scene images that contained the full spatial frequency spectrum, only low spatial frequencies, or only high spatial frequencies, all carefully controlled for contrast and luminance. Contrary to the findings from numerous behavioral studies and computational models that have highlighted how low spatial frequencies preferentially encode image content, decoding of scene categories from the scene-selective brain regions, including the parahippocampal place area (PPA), was significantly more accurate for high than low spatial frequency images. In fact, decoding accuracy was just as high for high spatial frequency images as for images containing the full spatial frequency spectrum in scene-selective areas PPA, RSC, OPA and object selective area LOC. We also found an interesting dissociation between the posterior and anterior subdivisions of PPA: categories were decodable from both high and low spatial frequency scenes in posterior PPA but only from high spatial frequency scenes in anterior PPA; and spatial frequency was explicitly decodable from posterior but not anterior PPA. Our results are consistent with recent findings that line drawings, which consist almost entirely of high spatial frequencies, elicit a neural representation of scene categories that is equivalent to that of full-spectrum color photographs. Collectively, these findings demonstrate the

  10. Scene content is predominantly conveyed by high spatial frequencies in scene-selective visual cortex.

    Directory of Open Access Journals (Sweden)

    Daniel Berman

    Full Text Available In complex real-world scenes, image content is conveyed by a large collection of intertwined visual features. The visual system disentangles these features in order to extract information about image content. Here, we investigate the role of one integral component: the content of spatial frequencies in an image. Specifically, we measure the amount of image content carried by low versus high spatial frequencies for the representation of real-world scenes in scene-selective regions of human visual cortex. To this end, we attempted to decode scene categories from the brain activity patterns of participants viewing scene images that contained the full spatial frequency spectrum, only low spatial frequencies, or only high spatial frequencies, all carefully controlled for contrast and luminance. Contrary to the findings from numerous behavioral studies and computational models that have highlighted how low spatial frequencies preferentially encode image content, decoding of scene categories from the scene-selective brain regions, including the parahippocampal place area (PPA, was significantly more accurate for high than low spatial frequency images. In fact, decoding accuracy was just as high for high spatial frequency images as for images containing the full spatial frequency spectrum in scene-selective areas PPA, RSC, OPA and object selective area LOC. We also found an interesting dissociation between the posterior and anterior subdivisions of PPA: categories were decodable from both high and low spatial frequency scenes in posterior PPA but only from high spatial frequency scenes in anterior PPA; and spatial frequency was explicitly decodable from posterior but not anterior PPA. Our results are consistent with recent findings that line drawings, which consist almost entirely of high spatial frequencies, elicit a neural representation of scene categories that is equivalent to that of full-spectrum color photographs. Collectively, these findings

  11. Three counting methods agree on cell and neuron number in chimpanzee primary visual cortex

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    Daniel James Miller

    2014-05-01

    Full Text Available Determining the cellular composition of specific brain regions is crucial to our understanding of the function of neurobiological systems. It is therefore useful to identify the extent to which different methods agree when estimating the same properties of brain circuitry. In this study, we estimated the number of neuronal and non-neuronal cells in the primary visual cortex (area 17 or V1 of both hemispheres from a single chimpanzee. Specifically, we processed samples distributed across V1 of the right hemisphere after cortex was flattened into a sheet using two variations of the isotropic fractionator cell and neuron counting method. We processed the left hemisphere as serial brain slices for stereological investigation. The goal of this study was to evaluate the agreement between these methods in the most direct manner possible by comparing estimates of cell density across one brain region of interest in a single individual. In our hands, these methods produced similar estimates of the total cellular population (approximately 1 billion as well as the number of neurons (approximately 675 million in chimpanzee V1, providing evidence that both techniques estimate the same parameters of interest. In addition, our results indicate the strengths of each distinct tissue preparation procedure, highlighting the importance of attention to anatomical detail. In summary, we found that the isotropic fractionator and the stereological optical fractionator produced concordant estimates of the cellular composition of V1, and that this result supports the conclusion that chimpanzees conform to the primate pattern of exceptionally high packing density in V1. Ultimately, our data suggest that investigators can optimize their experimental approach by using any of these counting methods to obtain reliable cell and neuron counts.

  12. Uncorrelated Neural Firing in Mouse Visual Cortex during Spontaneous Retinal Waves

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    Matthew T. Colonnese

    2017-09-01

    Full Text Available Synchronous firing among the elements of forming circuits is critical for stabilization of synapses. Understanding the nature of these local network interactions during development can inform models of circuit formation. Within cortex, spontaneous activity changes throughout development. Unlike the adult, early spontaneous activity occurs in discontinuous population bursts separated by long silent periods, suggesting a high degree of local synchrony. However, whether the micro-patterning of activity within early bursts is unique to this early age and specifically tuned for early development is poorly understood, particularly within the column. To study this we used single-shank multi-electrode array recordings of spontaneous activity in the visual cortex of non-anesthetized neonatal mice to quantify single-unit firing rates, and applied multiple measures of network interaction and synchrony throughout the period of map formation and immediately after eye-opening. We find that despite co-modulation of firing rates on a slow time scale (hundreds of ms, the number of coactive neurons, as well as pair-wise neural spike-rate correlations, are both lower before eye-opening. In fact, on post-natal days (P6–9 correlated activity was lower than expected by chance, suggesting active decorrelation of activity during early bursts. Neurons in lateral geniculate nucleus developed in an opposite manner, becoming less correlated after eye-opening. Population coupling, a measure of integration in the local network, revealed a population of neurons with particularly strong local coupling present at P6–11, but also an adult-like diversity of coupling at all ages, suggesting that a neuron’s identity as locally or distally coupled is determined early. The occurrence probabilities of unique neuronal “words” were largely similar at all ages suggesting that retinal waves drive adult-like patterns of co-activation. These findings suggest that the bursts of

  13. Inactivation of the Prelimbic Cortex Impairs the Context-Induced Reinstatement of Ethanol Seeking.

    Science.gov (United States)

    Palombo, Paola; Leao, Rodrigo M; Bianchi, Paula C; de Oliveira, Paulo E C; Planeta, Cleopatra da Silva; Cruz, Fábio C

    2017-01-01

    Evidence indicates that drug relapse in humans is often provoked by exposure to the self-administered drug-associated context. An animal model called "ABA renewal procedure" has been used to study the context-induced relapse to drug seeking. Here, we reported a new and feasible training procedure for the ABA renewal method to explore the role of the prelimbic cortex in context-induced relapse to ethanol seeking. By using a saccharin fading technique, we trained rats to self-administer ethanol (10%). The drug delivery was paired with a discrete tone-light cue. Lever pressing was subsequently extinguished in a non-drug-associated context in the presence of the discrete cue. Rats were subsequently tested for reinstatement in contexts A or B, under extinction conditions. Ethanol-associated context induced the reinstatement of ethanol seeking and increased the expression of Fos in the prelimbic cortex. The rate of neural activation in the prelimbic cortex was 3.4% in the extinction context B and 7.7% in the drug-associated context A, as evidenced by double-labeling of Fos and the neuron-specific protein NeuN. The reversible inactivation of the neural activity in the prelimbic cortex with gamma-Aminobutyric acid (GABA) receptor agonists (muscimol + baclofen) attenuated the context-induced reinstatement of ethanol self-administration. These results demonstrated that the neuronal activation of the prelimbic cortex is involved in the context-induced reinstatement of ethanol seeking.

  14. Electrical neuroimaging reveals content-specific effects of threat in primary visual cortex and fronto-parietal attentional networks.

    Science.gov (United States)

    Rossi, Valentina; Pourtois, Gilles

    2014-09-01

    Whereas effects of anticipatory anxiety on attention are usually assumed to remain largely undifferentiated, discrepant findings in the literature suggest that, depending on its content and causes, different modulatory effects on attention control and early sensory processing may arise. Using electrical neuroimaging and psychophysiology in a cross-over design, we tested the hypothesis that different types of anticipatory anxiety (bodily vs. psychological), transiently induced in healthy participants, had dissociable effects on brain systems regulating attention control. Attention control corresponded to the ability to maintain efficient goal-directed processing (indexed by the P300 ERP component and by activations in the attentional networks), as well as the ability to filter out irrelevant stimuli in early sensory cortex (C1 component, indexing attentional gating in V1). Results showed that while psychosocial threat, very much like perceptual load, primarily led to a stronger gating in V1, bodily threat resulted in impaired goal-directed processing within the fronto-parietal attentional network, as well as decreased filtering in V1. These results suggest that anticipatory anxiety is multifaceted, exerting different effects on attention control and early visual processing depending on its sub-type. Copyright © 2014 Elsevier Inc. All rights reserved.

  15. Experimentally-induced dissociation impairs visual memory.

    Science.gov (United States)

    Brewin, Chris R; Mersaditabari, Niloufar

    2013-12-01

    Dissociation is a phenomenon common in a number of psychological disorders and has been frequently suggested to impair memory for traumatic events. In this study we explored the effects of dissociation on visual memory. A dissociative state was induced experimentally using a mirror-gazing task and its short-term effects on memory performance were investigated. Sixty healthy individuals took part in the experiment. Induced dissociation impaired visual memory performance relative to a control condition; however, the degree of dissociation was not associated with lower memory scores in the experimental group. The results have theoretical and practical implications for individuals who experience frequent dissociative states such as patients with posttraumatic stress disorder (PTSD). Copyright © 2013 Elsevier Inc. All rights reserved.

  16. Development of Glutamatergic Proteins in Human Visual Cortex across the Lifespan.

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    Siu, Caitlin R; Beshara, Simon P; Jones, David G; Murphy, Kathryn M

    2017-06-21

    Traditionally, human primary visual cortex (V1) has been thought to mature within the first few years of life, based on anatomical studies of synapse formation, and establishment of intracortical and intercortical connections. Human vision, however, develops well beyond the first few years. Previously, we found prolonged development of some GABAergic proteins in human V1 (Pinto et al., 2010). Yet as >80% of synapses in V1 are excitatory, it remains unanswered whether the majority of synapses regulating experience-dependent plasticity and receptive field properties develop late, like their inhibitory counterparts. To address this question, we used Western blotting of postmortem tissue from human V1 (12 female, 18 male) covering a range of ages. Then we quantified a set of postsynaptic glutamatergic proteins (PSD-95, GluA2, GluN1, GluN2A, GluN2B), calculated indices for functional pairs that are developmentally regulated (GluA2:GluN1; GluN2A:GluN2B), and determined interindividual variability. We found early loss of GluN1, prolonged development of PSD-95 and GluA2 into late childhood, protracted development of GluN2A until ∼40 years, and dramatic loss of GluN2A in aging. The GluA2:GluN1 index switched at ∼1 year, but the GluN2A:GluN2B index continued to shift until ∼40 year before changing back to GluN2B in aging. We also identified young childhood as a stage of heightened interindividual variability. The changes show that human V1 develops gradually through a series of five orchestrated stages, making it likely that V1 participates in visual development and plasticity across the lifespan. SIGNIFICANCE STATEMENT Anatomical structure of human V1 appears to mature early, but vision changes across the lifespan. This discrepancy has fostered two hypotheses: either other aspects of V1 continue changing, or later changes in visual perception depend on extrastriate areas. Previously, we showed that some GABAergic synaptic proteins change across the lifespan, but most

  17. Sleep deprivation impairs object-selective attention: a view from the ventral visual cortex.

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    Julian Lim

    Full Text Available BACKGROUND: Most prior studies on selective attention in the setting of total sleep deprivation (SD have focused on behavior or activation within fronto-parietal cognitive control areas. Here, we evaluated the effects of SD on the top-down biasing of activation of ventral visual cortex and on functional connectivity between cognitive control and other brain regions. METHODOLOGY/PRINCIPAL FINDINGS: Twenty-three healthy young adult volunteers underwent fMRI after a normal night of sleep (RW and after sleep deprivation in a counterbalanced manner while performing a selective attention task. During this task, pictures of houses or faces were randomly interleaved among scrambled images. Across different blocks, volunteers responded to house but not face pictures, face but not house pictures, or passively viewed pictures without responding. The appearance of task-relevant pictures was unpredictable in this paradigm. SD resulted in less accurate detection of target pictures without affecting the mean false alarm rate or response time. In addition to a reduction of fronto-parietal activation, attending to houses strongly modulated parahippocampal place area (PPA activation during RW, but this attention-driven biasing of PPA activation was abolished following SD. Additionally, SD resulted in a significant decrement in functional connectivity between the PPA and two cognitive control areas, the left intraparietal sulcus and the left inferior frontal lobe. CONCLUSIONS/SIGNIFICANCE: SD impairs selective attention as evidenced by reduced selectivity in PPA activation. Further, reduction in fronto-parietal and ventral visual task-related activation suggests that it also affects sustained attention. Reductions in functional connectivity may be an important additional imaging parameter to consider in characterizing the effects of sleep deprivation on cognition.

  18. Spike train encoding by regular-spiking cells of the visual cortex.

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    Carandini, M; Mechler, F; Leonard, C S; Movshon, J A

    1996-11-01

    1. To study the encoding of input currents into output spike trains by regular-spiking cells, we recorded intracellularly from slices of the guinea pig visual cortex while injecting step, sinusoidal, and broadband noise currents. 2. When measured with sinusoidal currents, the frequency tuning of the spike responses was markedly band-pass. The preferred frequency was between 8 and 30 Hz, and grew with stimulus amplitude and mean intensity. 3. Stimulation with broadband noise currents dramatically enhanced the gain of the spike responses at low and high frequencies, yielding an essentially flat frequency tuning between 0.1 and 130 Hz. 4. The averaged spike responses to sinusoidal currents exhibited two nonlinearities: rectification and spike synchronization. By contrast, no nonlinearity was evident in the averaged responses to broadband noise stimuli. 5. These properties of the spike responses were not present in the membrane potential responses. The latter were roughly linear, and their frequency tuning was low-pass and well fit by a single-compartment passive model of the cell membrane composed of a resistance and a capacitance in parallel (RC circuit). 6. To account for the spike responses, we used a "sandwich model" consisting of a low-pass linear filter (the RC circuit), a rectification nonlinearity, and a high-pass linear filter. The model is described by six parameters and predicts analog firing rates rather than discrete spikes. It provided satisfactory fits to the firing rate responses to steps, sinusoids, and broadband noise currents. 7. The properties of spike encoding are consistent with temporal nonlinearities of the visual responses in V1, such as the dependence of response frequency tuning and latency on stimulus contrast and bandwidth. We speculate that one of the roles of the high-frequency membrane potential fluctuations observed in vivo could be to amplify and linearize the responses to lower, stimulus-related frequencies.

  19. Sleep Deprivation Impairs Object-Selective Attention: A View from the Ventral Visual Cortex

    Science.gov (United States)

    Lim, Julian; Tan, Jiat Chow; Parimal, Sarayu; Dinges, David F.; Chee, Michael W. L.

    2010-01-01

    Background Most prior studies on selective attention in the setting of total sleep deprivation (SD) have focused on behavior or activation within fronto-parietal cognitive control areas. Here, we evaluated the effects of SD on the top-down biasing of activation of ventral visual cortex and on functional connectivity between cognitive control and other brain regions. Methodology/Principal Findings Twenty-three healthy young adult volunteers underwent fMRI after a normal night of sleep (RW) and after sleep deprivation in a counterbalanced manner while performing a selective attention task. During this task, pictures of houses or faces were randomly interleaved among scrambled images. Across different blocks, volunteers responded to house but not face pictures, face but not house pictures, or passively viewed pictures without responding. The appearance of task-relevant pictures was unpredictable in this paradigm. SD resulted in less accurate detection of target pictures without affecting the mean false alarm rate or response time. In addition to a reduction of fronto-parietal activation, attending to houses strongly modulated parahippocampal place area (PPA) activation during RW, but this attention-driven biasing of PPA activation was abolished following SD. Additionally, SD resulted in a significant decrement in functional connectivity between the PPA and two cognitive control areas, the left intraparietal sulcus and the left inferior frontal lobe. Conclusions/Significance SD impairs selective attention as evidenced by reduced selectivity in PPA activation. Further, reduction in fronto-parietal and ventral visual task-related activation suggests that it also affects sustained attention. Reductions in functional connectivity may be an important additional imaging parameter to consider in characterizing the effects of sleep deprivation on cognition. PMID:20140099

  20. Activity-dependent regulation of MHC class I expression in the developing primary visual cortex of the common marmoset monkey

    Directory of Open Access Journals (Sweden)

    Schlumbohm Christina

    2011-01-01

    Full Text Available Abstract Background Several recent studies have highlighted the important role of immunity-related molecules in synaptic plasticity processes in the developing and adult mammalian brains. It has been suggested that neuronal MHCI (major histocompatibility complex class I genes play a role in the refinement and pruning of synapses in the developing visual system. As a fast evolutionary rate may generate distinct properties of molecules in different mammalian species, we studied the expression of MHCI molecules in a nonhuman primate, the common marmoset monkey (Callithrix jacchus. Methods and results Analysis of expression levels of MHCI molecules in the developing visual cortex of the common marmoset monkeys revealed a distinct spatio-temporal pattern. High levels of expression were detected very early in postnatal development, at a stage when synaptogenesis takes place and ocular dominance columns are formed. To determine whether the expression of MHCI molecules is regulated by retinal activity, animals were subjected to monocular enucleation. Levels of MHCI heavy chain subunit transcripts in the visual cortex were found to be elevated in response to monocular enucleation. Furthermore, MHCI heavy chain immunoreactivity revealed a banded pattern in layer IV of the visual cortex in enucleated animals, which was not observed in control animals. This pattern of immunoreactivity indicated that higher expression levels were associated with retinal activity coming from the intact eye. Conclusions These data demonstrate that, in the nonhuman primate brain, expression of MHCI molecules is regulated by neuronal activity. Moreover, this study extends previous findings by suggesting a role for neuronal MHCI molecules during synaptogenesis in the visual cortex.

  1. D-Serine and Glycine Differentially Control Neurotransmission during Visual Cortex Critical Period.

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    Claire N J Meunier

    Full Text Available N-methyl-D-aspartate receptors (NMDARs play a central role in synaptic plasticity. Their activation requires the binding of both glutamate and d-serine or glycine as co-agonist. The prevalence of either co-agonist on NMDA-receptor function differs between brain regions and remains undetermined in the visual cortex (VC at the critical period of postnatal development. Here, we therefore investigated the regulatory role that d-serine and/or glycine may exert on NMDARs function and on synaptic plasticity in the rat VC layer 5 pyramidal neurons of young rats. Using selective enzymatic depletion of d-serine or glycine, we demonstrate that d-serine and not glycine is the endogenous co-agonist of synaptic NMDARs required for the induction and expression of Long Term Potentiation (LTP at both excitatory and inhibitory synapses. Glycine on the other hand is not involved in synaptic efficacy per se but regulates excitatory and inhibitory neurotransmission by activating strychnine-sensitive glycine receptors, then producing a shunting inhibition that controls neuronal gain and results in a depression of synaptic inputs at the somatic level after dendritic integration. In conclusion, we describe for the first time that in the VC both D-serine and glycine differentially regulate somatic depolarization through the activation of distinct synaptic and extrasynaptic receptors.

  2. Receptive field properties of neurons in the primary visual cortex under photopic and scotopic lighting conditions.

    Science.gov (United States)

    Duffy, Kevin R; Hubel, David H

    2007-09-01

    Knowledge of the physiology of the primate visual cortex (area V-1) comes mostly from studies done in photopic conditions, in which retinal cones are active and rods play little or no part. Conflicting results have come from research into the effects of dark adaptation on receptive field organization of cells in the retina and the lateral geniculate nucleus. These studies claim either that the effect of the surround disappears with dark adaptation or that it does not. The current study has as its objective a comparison of responses of V-1 cells in awake-alert macaque monkeys under conditions of light and dark adaptation. We reasoned that basic receptive field properties of V-1 cells such as orientation selectivity, direction selectivity, and end-stopping should be preserved in scotopic conditions if the receptive field organization of antecedent cells is maintained in dim light. Our results indicate that dark adaptation does not alter basic V-1 receptive field characteristics such as selectivity for orientation, direction, and bar length.

  3. High-density diffuse optical tomography of term infant visual cortex in the nursery

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    Liao, Steve M.; Ferradal, Silvina L.; White, Brian R.; Gregg, Nicholas; Inder, Terrie E.; Culver, Joseph P.

    2012-08-01

    Advancements in antenatal and neonatal medicine over the last few decades have led to significant improvement in the survival rates of sick newborn infants. However, this improvement in survival has not been matched by a reduction in neurodevelopmental morbidities with increasing recognition of the diverse cognitive and behavioral challenges that preterm infants face in childhood. Conventional neuroimaging modalities, such as cranial ultrasound and magnetic resonance imaging, provide an important definition of neuroanatomy with recognition of brain injury. However, they fail to define the functional integrity of the immature brain, particularly during this critical developmental period. Diffuse optical tomography methods have established success in imaging adult brain function; however, few studies exist to demonstrate their feasibility in the neonatal population. We demonstrate the feasibility of using recently developed high-density diffuse optical tomography (HD-DOT) to map functional activation of the visual cortex in healthy term-born infants. The functional images show high contrast-to-noise ratio obtained in seven neonates. These results illustrate the potential for HD-DOT and provide a foundation for investigations of brain function in more vulnerable newborns, such as preterm infants.

  4. Determinants of Global Color-Based Selection in Human Visual Cortex.

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    Bartsch, Mandy V; Boehler, Carsten N; Stoppel, Christian M; Merkel, Christian; Heinze, Hans-Jochen; Schoenfeld, Mircea A; Hopf, Jens-Max

    2015-09-01

    Feature attention operates in a spatially global way, with attended feature values being prioritized for selection outside the focus of attention. Accounts of global feature attention have emphasized feature competition as a determining factor. Here, we use magnetoencephalographic recordings in humans to test whether competition is critical for global feature selection to arise. Subjects performed a color/shape discrimination task in one visual field (VF), while irrelevant color probes were presented in the other unattended VF. Global effects of color attention were assessed by analyzing the response to the probe as a function of whether or not the probe's color was a target-defining color. We find that global color selection involves a sequence of modulations in extrastriate cortex, with an initial phase in higher tier areas (lateral occipital complex) followed by a later phase in lower tier retinotopic areas (V3/V4). Importantly, these modulations appeared with and without color competition in the focus of attention. Moreover, early parts of the modulation emerged for a task-relevant color not even present in the focus of attention. All modulations, however, were eliminated during simple onset-detection of the colored target. These results indicate that global color-based attention depends on target discrimination independent of feature competition in the focus of attention. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  5. Pyramidal cells make specific connections onto smooth (GABAergic neurons in mouse visual cortex.

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    Rita Bopp

    2014-08-01

    Full Text Available One of the hallmarks of neocortical circuits is the predominance of recurrent excitation between pyramidal neurons, which is balanced by recurrent inhibition from smooth GABAergic neurons. It has been previously described that in layer 2/3 of primary visual cortex (V1 of cat and monkey, pyramidal cells filled with horseradish peroxidase connect approximately in proportion to the spiny (excitatory, 95% and 81%, respectively and smooth (GABAergic, 5% and 19%, respectively dendrites found in the neuropil. By contrast, a recent ultrastructural study of V1 in a single mouse found that smooth neurons formed 51% of the targets of the superficial layer pyramidal cells. This suggests that either the neuropil of this particular mouse V1 had a dramatically different composition to that of V1 in cat and monkey, or that smooth neurons were specifically targeted by the pyramidal cells in that mouse. We tested these hypotheses by examining similar cells filled with biocytin in a sample of five mice. We found that the average composition of the neuropil in V1 of these mice was similar to that described for cat and monkey V1, but that the superficial layer pyramidal cells do form proportionately more synapses with smooth dendrites than the equivalent neurons in cat or monkey. These distributions may underlie the distinct differences in functional architecture of V1 between rodent and higher mammals.

  6. Cerebellum to motor cortex paired associative stimulation induces bidirectional STDP-like plasticity in human motor cortex

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    Ming-Kuei eLu

    2012-09-01

    Full Text Available The cerebellum is crucially important for motor control and motor adaptation. Recent non-invasive brain stimulation studies have indicated the possibility to alter the excitability of the cerebellum and its projections to the contralateral motor cortex, with behavioral consequences on motor control and motor adaptation. Here we sought to induce bidirectional spike-timing dependent plasticity (STDP-like modifications of motor cortex (M1 excitability by application of paired associative stimulation (PAS in healthy subjects. Conditioning stimulation over the right lateral cerebellum (CB preceded focal TMS of the left M1 hand area at an interstimulus interval of 2 ms (CB→M1 PAS2ms, 6 ms (CB→M1 PAS6ms or 10 ms (CB→M1 PAS10ms or randomly alternating intervals of 2 and 10 ms (CB→M1 PASControl. Effects of PAS on M1 excitability were assessed by the motor evoked potential (MEP amplitude, short-interval intracortical inhibition (SICI, intracortical facilitation (ICF and cerebellar-motor cortex inhibition (CBI in the first dorsal interosseous muscle of the right hand. CB→M1 PAS2ms resulted in MEP potentiation, CB→M1 PAS6ms and CB→M1 PAS10ms in MEP depression, and CB→M1 PASControl in no change. The MEP changes lasted for 30-60 min after PAS. SICI and CBI decreased non-specifically after all PAS protocols, while ICF remained unaltered. The physiological mechanisms underlying these MEP changes are carefully discussed. Findings support the notion of bidirectional STDP-like plasticity in M1 mediated by associative stimulation of the cerebello-dentato-thalamo-cortical pathway and M1. Future studies may investigate the behavioral significance of this plasticity.

  7. Investigation of human visual cortex responses to flickering light using functional near infrared spectroscopy and constrained ICA

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    Nguyen Duc Thang

    2014-11-01

    Full Text Available The human visual sensitivity to the flickering light has been under investigation for decades. The finding of research in this area can contribute to the understanding of human visual system mechanism and visual disorders, and establishing diagnosis and treatment of diseases. The aim of this study is to investigate the effects of the flickering light to the visual cortex by monitoring the hemodynamic responses of the brain with the functional near infrared spectroscopy (fNIRS method. Since the acquired fNIRS signals are affected by physiological factors and measurement artifacts, constrained independent component analysis (cICA was applied to extract the actual fNIRS responses from the obtained data. The experimental results revealed significant changes (p < 0.0001 of the hemodynamic responses of the visual cortex from the baseline when the flickering stimulation was activated. With the uses of cICA, the contrast to noise ratio (CNR, reflecting the contrast of hemodynamic concentration between rest and task, became larger. This indicated the improvement of the fNIRS signals when the noise was eliminated. In subsequent studies, statistical analysis was used to infer the correlation between the fNIRS signals and the visual stimulus. We found that there was a slight decrease of the oxygenated hemoglobin concentration (about 5.69% over four frequencies when the modulation increased. However, the variations of oxy and deoxy-hemoglobin were not statistically significant.

  8. Single Prazosin Infusion in Prelimbic Cortex Fosters Extinction of Amphetamine-Induced Conditioned Place Preference.

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    Latagliata, Emanuele C; Lo Iacono, Luisa; Chiacchierini, Giulia; Sancandi, Marco; Rava, Alessandro; Oliva, Valeria; Puglisi-Allegra, Stefano

    2017-01-01

    Exposure to drug-associated cues to induce extinction is a useful strategy to contrast cue-induced drug seeking. Norepinephrine (NE) transmission in medial prefrontal cortex has a role in the acquisition and extinction of conditioned place preference induced by amphetamine. We have reported recently that NE in prelimbic cortex delays extinction of amphetamine-induced conditioned place preference (CPP). A potential involvement of α1-adrenergic receptors in the extinction of appetitive conditioned response has been also suggested, although their role in prelimbic cortex has not been yet fully investigated. Here, we investigated the effects of the α1-adrenergic receptor antagonist prazosin infusion in the prelimbic cortex of C57BL/6J mice on expression and extinction of amphetamine-induced CPP. Acute prelimbic prazosin did not affect expression of amphetamine-induced CPP on the day of infusion, while in subsequent days it produced a clear-cut advance of extinction of preference for the compartment previously paired with amphetamine (Conditioned stimulus, CS). Moreover, prazosin-treated mice that had extinguished CS preference showed increased mRNA expression of brain-derived neurotrophic factor (BDNF) and post-synaptic density 95 (PSD-95) in the nucleus accumbens shell or core, respectively, thus suggesting that prelimbic α1-adrenergic receptor blockade triggers neural adaptations in subcortical areas that could contribute to the extinction of cue-induced drug-seeking behavior. These results show that the pharmacological blockade of α1-adrenergic receptors in prelimbic cortex by a single infusion is able to induce extinction of amphetamine-induced CPP long before control (vehicle) animals, an effect depending on contingent exposure to retrieval, since if infused far from or after reactivation it did not affect preference. Moreover, they suggest strongly that the behavioral effects depend on post-treatment neuroplasticity changes in corticolimbic network, triggered

  9. A period of structural plasticity at the axon initial segment in developing visual cortex

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    Annika eGutzmann

    2014-03-01

    Full Text Available Cortical networks are shaped by sensory experience and are most susceptible to modifications during critical periods characterized by enhanced plasticity at the structural and functional level. A system particularly well-studied in this context is the mammalian visual system. Plasticity has been documented for the somatodendritic compartment of neurons in detail. A neuronal microdomain not yet studied in this context is the axon initial segment (AIS located at the proximal axon segment. It is a specific electrogenic axonal domain and the site of action potential generation. Recent studies showed that structure and function of the AIS can be dynamically regulated. Here we hypothesize that the AIS shows a dynamic regulation during maturation of the visual cortex. We therefore analyzed AIS length development from embryonic day (E 12.5 to adulthood in mice. A tri-phasic time course of AIS length remodeling during development was observed. AIS first appeared at E14.5 and increased in length throughout the postnatal period to a peak between postnatal day (P 10 to P15 (eyes open P13-14. Then, AIS length was reduced significantly around the beginning of the critical period for ocular dominance plasticity (CP, P21. Shortest AIS were observed at the peak of the CP (P28, followed by a moderate elongation towards the end of the CP (P35. To test if the dynamic maturation of the AIS is influenced by eye opening (onset of activity, animals were deprived of visual input before and during the CP. Deprivation for 1 week prior to eye opening did not affect AIS length development. However, deprivation from P0-P28 and P14-P28 resulted in AIS length distribution similar to the peak at P15. In other words, deprivation from birth prevents the transient shortening of the AIS and maintains an immature AIS length. These results are the first to suggest a dynamic maturation of the AIS in cortical neurons and point to novel mechanisms in the development of neuronal

  10. Fourier Descriptors Based on the Structure of the Human Primary Visual Cortex with Applications to Object Recognition

    OpenAIRE

    Bohi, Amine; Prandi, Dario; Guis, Vincente; Bouchara, Frédéric; Gauthier, Jean-Paul

    2016-01-01

    International audience; In this paper we propose a supervised object recognition method using new global features and inspired by the model of the human primary visual cortex V1 as the semidiscrete roto-translation group $SE(2,N)=\\mathbb Z_N\\rtimes \\mathbb{R}^2$. The proposed technique is based on generalized Fourier descriptors on the latter group, which are invariant to natural geometric transformations (rotations, translations). These descriptors are then used to feed an SVM classifier. We...

  11. Optic nerve, superior colliculus, visual thalamus, and primary visual cortex of the northern elephant seal (Mirounga angustirostris) and California sea lion (Zalophus californianus).

    Science.gov (United States)

    Turner, Emily C; Sawyer, Eva K; Kaas, Jon H

    2017-06-15

    The northern elephant seal (Mirounga angustirostris) and California sea lion (Zalophus californianus) are members of a diverse clade of carnivorous mammals known as pinnipeds. Pinnipeds are notable for their large, ape-sized brains, yet little is known about their central nervous system. Both the northern elephant seal and California sea lion spend most of their lives at sea, but each also spends time on land to breed and give birth. These unique coastal niches may be reflected in specific evolutionary adaptations to their sensory systems. Here, we report on components of the visual pathway in these two species. We found evidence for two classes of myelinated fibers within the pinniped optic nerve, those with thick myelin sheaths (elephant seal: 9%, sea lion: 7%) and thin myelin sheaths (elephant seal: 91%, sea lion: 93%). In order to investigate the architecture of the lateral geniculate nucleus, superior colliculus, and primary visual cortex, we processed brain sections from seal and sea lion pups for Nissl substance, cytochrome oxidase, and vesicular glutamate transporters. As in other carnivores, the dorsal lateral geniculate nucleus consisted of three main layers, A, A1, and C, while each superior colliculus similarly consisted of seven distinct layers. The sea lion visual cortex is located at the posterior side of cortex between the upper and lower banks of the postlateral sulcus, while the elephant seal visual cortex extends far more anteriorly along the dorsal surface and medial wall. These results are relevant to comparative studies related to the evolution of large brains. © 2017 Wiley Periodicals, Inc.

  12. Neuronal expression of c-Fos after epicortical and intracortical electric stimulation of the primary visual cortex.

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    Neyazi, Belal; Schwabe, Kerstin; Alam, Mesbah; Krauss, Joachim K; Nakamura, Makoto

    2016-11-01

    Electrical stimulation of the primary visual cortex (V1) is an experimental approach for visual prostheses. We here compared the response to intracortical and epicortical stimulation of the primary visual cortex by using c-Fos immunoreactivity as a marker for neuronal activation. The primary visual cortex of male Sprague Dawley rats was unilaterally stimulated for four hours using bipolar electrodes placed either intracortically in layer IV (n=26) or epicortically (n=20). Four different current intensities with a constant pulse width of 200μs and a constant frequency of 10Hz were used, for intracortical stimulation with an intensity of 0μA (sham-stimulation), 10μA, 20μA and 40μA, and for epicortical stimulation 0μA, 400μA, 600μA and 800μA. Subsequently all animals underwent c-Fos immunostaining and c-Fos expression was assessed in layer I-VI of the primary visual cortex within 200μm and 400μm distance to the stimulation site. C-Fos expression was higher after intracortical stimulation compared to epicortical stimulation, even though ten times lower current intensities were applied. Furthermore intracortical stimulation resulted in more focal neuronal activation than epicortical stimulation. C-Fos expression was highest after intracortical stimulation with 20μA compared to all other intensities. Epicortical stimulation showed a linear increase of c-Fos expression with the highest expression at 800μA. Sham stimulation showed similar expression of c-Fos in both hemispheres. The contralateral hemisphere was not affected by intracortical or epicortical stimulation of either intensities. In summary, intracortical stimulation resulted in more focal neuronal activation with less current than epicortical stimulation. This model may be used as a simple but reliable model to evaluate electrodes for microstimulation of the primary visual cortex before testing in more complex settings. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Visual object agnosia is associated with a breakdown of object-selective responses in the lateral occipital cortex.

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    Ptak, Radek; Lazeyras, François; Di Pietro, Marie; Schnider, Armin; Simon, Stéphane R

    2014-07-01

    Patients with visual object agnosia fail to recognize the identity of visually presented objects despite preserved semantic knowledge. Object agnosia may result from damage to visual cortex lying close to or overlapping with the lateral occipital complex (LOC), a brain region that exhibits selectivity to the shape of visually presented objects. Despite this anatomical overlap the relationship between shape processing in the LOC and shape representations in object agnosia is unknown. We studied a patient with object agnosia following isolated damage to the left occipito-temporal cortex overlapping with the LOC. The patient showed intact processing of object structure, yet often made identification errors that were mainly based on the global visual similarity between objects. Using functional Magnetic Resonance Imaging (fMRI) we found that the damaged as well as the contralateral, structurally intact right LOC failed to show any object-selective fMRI activity, though the latter retained selectivity for faces. Thus, unilateral damage to the left LOC led to a bilateral breakdown of neural responses to a specific stimulus class (objects and artefacts) while preserving the response to a different stimulus class (faces). These findings indicate that representations of structure necessary for the identification of objects crucially rely on bilateral, distributed coding of shape features. Copyright © 2014 Elsevier Ltd. All rights reserved.

  14. High-alpha band synchronization across frontal, parietal and visual cortex mediates behavioral and neuronal effects of visuospatial attention.

    Science.gov (United States)

    Lobier, Muriel; Palva, J Matias; Palva, Satu

    2018-01-15

    Visuospatial attention prioritizes processing of attended visual stimuli. It is characterized by lateralized alpha-band (8-14 Hz) amplitude suppression in visual cortex and increased neuronal activity in a network of frontal and parietal areas. It has remained unknown what mechanisms coordinate neuronal processing among frontoparietal network and visual cortices and implement the attention-related modulations of alpha-band amplitudes and behavior. We investigated whether large-scale network synchronization could be such a mechanism. We recorded human cortical activity with magnetoencephalography (MEG) during a visuospatial attention task. We then identified the frequencies and anatomical networks of inter-areal phase synchronization from source localized MEG data. We found that visuospatial attention is associated with robust and sustained long-range synchronization of cortical oscillations exclusively in the high-alpha (10-14 Hz) frequency band. This synchronization connected frontal, parietal and visual regions and was observed concurrently with amplitude suppression of low-alpha (6-9 Hz) band oscillations in visual cortex. Furthermore, stronger high-alpha phase synchronization was associated with decreased reaction times to attended stimuli and larger suppression of alpha-band amplitudes. These results thus show that high-alpha band phase synchronization is functionally significant and could coordinate the neuronal communication underlying the implementation of visuospatial attention. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. Feed-forward, feedback and lateral interactions in membrane potentials and spike trains from the visual cortex in vivo.

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    Eriksson, David; Roland, Per

    2006-01-01

    Neurons in the visual cortex receive input from the lateral geniculate nucleus (feed-forward), higher order visual areas (feedback) and local neurons in the surroundings (lateral interactions). Here we first briefly review the approximate timing and proportion of these three types of influences on the membrane potentials in visual areas 17, 18 and 19. Then we present original results from an independent component analysis of multiunit spike trains in the same visual areas to resolve the contribution from these three sources. We stimulated the visual cortex of the ferret with a small transient contrast square stimulus and recorded the multiunit activity in areas 17, 18 and 19 with single or multiple electrodes. The spike trains had three reproducible components having their maxima at 40, 55 and 105ms after the start of the presentation of the stimulus. The time course of the third component was significantly correlated with the population membrane potential in the supragranular layers of areas 17, 18 and 19. The first spike train component was interpreted as a feed-forward response, the second spike train component as driving the laterally spreading depolarization and the third spike train component as the firing caused by the lateral spreading- and the feedback depolarization.

  16. Practice makes perfect: the neural substrates of tactile discrimination by Mah-Jong experts include the primary visual cortex

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    Honda Manabu

    2006-12-01

    Full Text Available Abstract Background It has yet to be determined whether visual-tactile cross-modal plasticity due to visual deprivation, particularly in the primary visual cortex (V1, is solely due to visual deprivation or if it is a result of long-term tactile training. Here we conducted an fMRI study with normally-sighted participants who had undergone long-term training on the tactile shape discrimination of the two dimensional (2D shapes on Mah-Jong tiles (Mah-Jong experts. Eight Mah-Jong experts and twelve healthy volunteers who were naïve to Mah-Jong performed a tactile shape matching task using Mah-Jong tiles with no visual input. Furthermore, seven out of eight experts performed a tactile shape matching task with unfamiliar 2D Braille characters. Results When participants performed tactile discrimination of Mah-Jong tiles, the left lateral occipital cortex (LO and V1 were activated in the well-trained subjects. In the naïve subjects, the LO was activated but V1 was not activated. Both the LO and V1 of the well-trained subjects were activated during Braille tactile discrimination tasks. Conclusion The activation of V1 in subjects trained in tactile discrimination may represent altered cross-modal responses as a result of long-term training.

  17. Multi-timescale measurements of brain responses in visual cortex during functional stimulation using time-resolved spectroscopy

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    Lebid, Solomiya; O'Neill, Raymond; Markham, Charles; Ward, Tomás; Coyle, Shirley

    2005-06-01

    Studies of neurovascular coupling (hemodynamic changes and neuronal activation) in the visual cortex using a time-domain single photon counting system have been undertaken. The system operates in near infrared (NIR) range of spectrum and allows functional brain monitoring to be done non-invasively. The detection system employs a photomultiplier and multi-channel scaler to detect and record emerging photons with sub-microsecond resolution (the effective collection time per curve point is ~ 200 ns). Localisation of the visual evoked potentials in the brain was done using knowledge obtained from electroencephalographic (EEG) studies and previous frequency-domain optical NIR spectroscopic systems. The well-known approach of visual stimulation of the human brain, which consists of an alternating black and white checkerboard pattern used previously for the EEG study of neural responses, is applied here. The checkerboard pattern is synchronized with the multi-channel scaler system and allows the analysis of time variation in back-scattered light, at different stimulation frequencies. Slow hemodynamic changes in the human brain due to Hb-HbO2 changes in the blood flow were observed, which is evidence of the system's capability to monitor these changes. Monocular visual tests were undertaken and compared with those done with an EEG system. In some subjects a fast optical response on a time scale commensurate with the neural activity associated with the visual cortex was detected. Future work will concentrate on improved experimental protocols and apparatus to confirm the existence of this important physiological signal.

  18. The effect of synaptic plasticity on orientation selectivity in a balanced model of primary visual cortex

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    Gonzalo Cogno, Soledad; Mato, Germán

    2015-01-01

    Orientation selectivity is ubiquitous in the primary visual cortex (V1) of mammals. In cats and monkeys, V1 displays spatially ordered maps of orientation preference. Instead, in mice, squirrels, and rats, orientation selective neurons in V1 are not spatially organized, giving rise to a seemingly random pattern usually referred to as a salt-and-pepper layout. The fact that such different organizations can sharpen orientation tuning leads to question the structural role of the intracortical connections; specifically the influence of plasticity and the generation of functional connectivity. In this work, we analyze the effect of plasticity processes on orientation selectivity for both scenarios. We study a computational model of layer 2/3 and a reduced one-dimensional model of orientation selective neurons, both in the balanced state. We analyze two plasticity mechanisms. The first one involves spike-timing dependent plasticity (STDP), while the second one considers the reconnection of the interactions according to the preferred orientations of the neurons. We find that under certain conditions STDP can indeed improve selectivity but it works in a somehow unexpected way, that is, effectively decreasing the modulated part of the intracortical connectivity as compared to the non-modulated part of it. For the reconnection mechanism we find that increasing functional connectivity leads, in fact, to a decrease in orientation selectivity if the network is in a stable balanced state. Both counterintuitive results are a consequence of the dynamics of the balanced state. We also find that selectivity can increase due to a reconnection process if the resulting connections give rise to an unstable balanced state. We compare these findings with recent experimental results. PMID:26347615

  19. Anatomy of hierarchy: feedforward and feedback pathways in macaque visual cortex.

    Science.gov (United States)

    Markov, Nikola T; Vezoli, Julien; Chameau, Pascal; Falchier, Arnaud; Quilodran, René; Huissoud, Cyril; Lamy, Camille; Misery, Pierre; Giroud, Pascale; Ullman, Shimon; Barone, Pascal; Dehay, Colette; Knoblauch, Kenneth; Kennedy, Henry

    2014-01-01

    The laminar location of the cell bodies and terminals of interareal connections determines the hierarchical structural organization of the cortex and has been intensively studied. However, we still have only a rudimentary understanding of the connectional principles of feedforward (FF) and feedback (FB) pathways. Quantitative analysis of retrograde tracers was used to extend the notion that the laminar distribution of neurons interconnecting visual areas provides an index of hierarchical distance (percentage of supragranular labeled neurons [SLN]). We show that: 1) SLN values constrain models of cortical hierarchy, revealing previously unsuspected areal relations; 2) SLN reflects the operation of a combinatorial distance rule acting differentially on sets of connections between areas; 3) Supragranular layers contain highly segregated bottom-up and top-down streams, both of which exhibit point-to-point connectivity. This contrasts with the infragranular layers, which contain diffuse bottom-up and top-down streams; 4) Cell filling of the parent neurons of FF and FB pathways provides further evidence of compartmentalization; 5) FF pathways have higher weights, cross fewer hierarchical levels, and are less numerous than FB pathways. Taken together, the present results suggest that cortical hierarchies are built from supra- and infragranular counterstreams. This compartmentalized dual counterstream organization allows point-to-point connectivity in both bottom-up and top-down directions. Copyright © 2013 Wiley Periodicals, Inc. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

  20. Construction of direction selectivity through local energy computations in primary visual cortex.

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    Lochmann, Timm; Blanche, Timothy J; Butts, Daniel A

    2013-01-01

    Despite detailed knowledge about the anatomy and physiology of neurons in primary visual cortex (V1), the large numbers of inputs onto a given V1 neuron make it difficult to relate them to the neuron's functional properties. For example, models of direction selectivity (DS), such as the Energy Model, can successfully describe the computation of phase-invariant DS at a conceptual level, while leaving it unclear how such computations are implemented by cortical circuits. Here, we use statistical modeling to derive a description of DS computation for both simple and complex cells, based on physiologically plausible operations on their inputs. We present a new method that infers the selectivity of a neuron's inputs using extracellular recordings in macaque in the context of random bar stimuli and natural movies in cat. Our results suggest that DS is initially constructed in V1 simple cells through summation and thresholding of non-DS inputs with appropriate spatiotemporal relationships. However, this de novo construction of DS is rare, and a majority of DS simple cells, and all complex cells, appear to receive both excitatory and suppressive inputs that are already DS. For complex cells, these numerous DS inputs typically span a fraction of their overall receptive fields and have similar spatiotemporal tuning but different phase and spatial positions, suggesting an elaboration to the Energy Model that incorporates spatially localized computation. Furthermore, we demonstrate how these computations might be constructed from biologically realizable components, and describe a statistical model consistent with the feed-forward framework suggested by Hubel and Wiesel.

  1. Construction of direction selectivity through local energy computations in primary visual cortex.

    Directory of Open Access Journals (Sweden)

    Timm Lochmann

    Full Text Available Despite detailed knowledge about the anatomy and physiology of neurons in primary visual cortex (V1, the large numbers of inputs onto a given V1 neuron make it difficult to relate them to the neuron's functional properties. For example, models of direction selectivity (DS, such as the Energy Model, can successfully describe the computation of phase-invariant DS at a conceptual level, while leaving it unclear how such computations are implemented by cortical circuits. Here, we use statistical modeling to derive a description of DS computation for both simple and complex cells, based on physiologically plausible operations on their inputs. We present a new method that infers the selectivity of a neuron's inputs using extracellular recordings in macaque in the context of random bar stimuli and natural movies in cat. Our results suggest that DS is initially constructed in V1 simple cells through summation and thresholding of non-DS inputs with appropriate spatiotemporal relationships. However, this de novo construction of DS is rare, and a majority of DS simple cells, and all complex cells, appear to receive both excitatory and suppressive inputs that are already DS. For complex cells, these numerous DS inputs typically span a fraction of their overall receptive fields and have similar spatiotemporal tuning but different phase and spatial positions, suggesting an elaboration to the Energy Model that incorporates spatially localized computation. Furthermore, we demonstrate how these computations might be constructed from biologically realizable components, and describe a statistical model consistent with the feed-forward framework suggested by Hubel and Wiesel.

  2. ERK pathway activation bidirectionally affects visual recognition memory and synaptic plasticity in the perirhinal cortex

    Directory of Open Access Journals (Sweden)

    Davide eSilingardi

    2011-12-01

    Full Text Available ERK 1,2 pathway mediates experience-dependent gene transcription in neurons and several studies have identified its pivotal role in experience-dependent synaptic plasticity and in forms of long term memory involving hippocampus, amygdala or striatum. The perirhinal cortex (PRHC plays an essential role in familiarity-based object recognition memory. It is still unknown whether ERK activation in PRHC is necessary for recognition memory consolidation. Most important, it is unknown whether by modulating the gain of the ERK pathway it is possible to bidirectionally affect visual recognition memory and PRHC synaptic plasticity.We have first pharmacologically blocked ERK activation in the PRHC of adult mice and found that this was sufficient to impair long term recognition memory in a familiarity-based task, the Object Recognition Task (ORT. We have then tested performance in the ORT in Ras-GRF1 knock-out (KO mice, which exhibit a reduced activation of ERK by neuronal activity, and in ERK1 KO mice, which have an increased activation of ERK2 and exhibit enhanced striatal plasticity and striatal mediated memory. We found that Ras-GRF1 KO mice have normal short-term memory but display a long term memory deficit; memory reconsolidation is also impaired. On the contrary, ERK1 KO mice exhibit a better performance than WT mice at 72 hour retention interval, suggesting a longer lasting recognition memory. In parallel with behavioural data, LTD was strongly reduced and LTP was significantly smaller in PRHC slices from Ras-GRF1 KO than in WT mice while enhanced LTP and LTD were found in PRHC slices from ERK1 KO mice.

  3. Different origins of gamma rhythm and high-gamma activity in macaque visual cortex.

    Directory of Open Access Journals (Sweden)

    Supratim Ray

    2011-04-01

    Full Text Available During cognitive tasks electrical activity in the brain shows changes in power in specific frequency ranges, such as the alpha (8-12 Hz or gamma (30-80 Hz bands, as well as in a broad range above ∼80 Hz, called the high-gamma band. The role or significance of this broadband high-gamma activity is unclear. One hypothesis states that high-gamma oscillations serve just like gamma oscillations, operating at a higher frequency and consequently at a faster timescale. Another hypothesis states that high-gamma power is related to spiking activity. Because gamma power and spiking activity tend to co-vary during most stimulus manipulations (such as contrast modulations or cognitive tasks (such as attentional modulation, it is difficult to dissociate these two hypotheses. We studied the relationship between high-gamma power, gamma rhythm, and spiking activity in the primary visual cortex (V1 of awake monkeys while varying the stimulus size, which increased the gamma power but decreased the firing rate, permitting a dissociation. We found that gamma power became anti-correlated with the high-gamma power, suggesting that the two phenomena are distinct and have different origins. On the other hand, high-gamma power remained tightly correlated with spiking activity under a wide range of stimulus manipulations. We studied this relationship using a signal processing technique called Matching Pursuit and found that action potentials are associated with sharp transients in the LFP with broadband power, which is visible at frequencies as low as ∼50 Hz. These results distinguish broadband high-gamma activity from gamma rhythms as an easily obtained and reliable electrophysiological index of neuronal firing near the microelectrode. Further, they highlight the importance of making a careful dissociation between gamma rhythms and spike-related transients that could be incorrectly decomposed as rhythms using traditional signal processing methods.

  4. Presynaptic development at L4 to l2/3 excitatory synapses follows different time courses in visual and somatosensory cortex.

    Science.gov (United States)

    Cheetham, Claire E J; Fox, Kevin

    2010-09-22

    Visual and somatosensory cortices exhibit profound experience-dependent plasticity during development and adulthood and are common model systems for probing the synaptic and molecular mechanisms of plasticity. However, comparisons between the two areas may be confounded by a lack of accurate information on their relative rates of development. In this study, we used whole-cell recording in acute brain slices to study synaptic development in mouse barrel and visual cortex. We found that short-term plasticity (STP) switched from strong depression at postnatal day (P)12 to weaker depression and facilitation in mature cortex. However, presynaptic maturation was delayed by ∼2 weeks at layer (L)4 to L2/3 excitatory synapses in visual cortex relative to barrel cortex. This developmental delay was pathway-specific; maturation of L2/3 to L2/3 synapses occurred over similar timescales in barrel and visual cortex. The developmental increase in the paired-pulse ratio to values greater than unity was mirrored by a developmental decrease in presynaptic release probability. Therefore, L4 to L2/3 excitatory synapses had lower release probabilities and showed greater short-term facilitation in barrel cortex than in visual cortex at P28. Postsynaptic mechanisms could not account for the delayed maturation of STP in visual cortex. These findings indicate that synaptic development is delayed in the L4 to L2/3 pathway in visual cortex, and emphasize the need to take into account the changes in synaptic properties that occur during development when comparing plasticity mechanisms in different cortical areas.

  5. Asymmetric activation in the prefrontal cortex by sound-induced affect.

    Science.gov (United States)

    Kim, Wuon-Shik; Yoon, Young-Ro; Kim, Kyo-Heon; Jho, Moon-Jae; Lee, Sang-Tae

    2003-12-01

    This study is based on previous information regarding asymmetric activation in the prefrontal cortex by film-induced affects, as well as the inverse proportionality of prefrontal cortex activity to power in the alpha band of EEG. To search for a specific EEG band where the asymmetric activation in the prefrontal cortex by sound-induced affects is mainly reflected, we measured 32 college students' EEGs; 11 bands ranged from 6.5 to 35.0 Hz, at Fp1 and Fp2 sites. The power in the alpha band (8.0 to 13.0 Hz) at Fp2, especially in the alpha-2 band (9.0 to 11.0 Hz) increased while the students listened to music, during which participants reported positive affect. In contrast, the power at Fp1 increased while the students listened to noise, during which participants reported negative affect. These results imply that sound-induced positive affect increases relative left-sided activation in the prefrontal cortex, whereas induced negative affect elicits the opposite pattern of asymmetric activation.

  6. Emerging feed-forward inhibition allows the robust formation of direction selectivity in the developing ferret visual cortex.

    Science.gov (United States)

    Van Hooser, Stephen D; Escobar, Gina M; Maffei, Arianna; Miller, Paul

    2014-06-01

    The computation of direction selectivity requires that a cell respond to joint spatial and temporal characteristics of the stimulus that cannot be separated into independent components. Direction selectivity in ferret visual cortex is not present at the time of eye opening but instead develops in the days and weeks following eye opening in a process that requires visual experience with moving stimuli. Classic Hebbian or spike timing-dependent modification of excitatory feed-forward synaptic inputs is unable to produce direction-selective cells from unselective or weakly directionally biased initial conditions because inputs eventually grow so strong that they can independently drive cortical neurons, violating the joint spatial-temporal activation requirement. Furthermore, without some form of synaptic competition, cells cannot develop direction selectivity in response to training with bidirectional stimulation, as cells in ferret visual cortex do. We show that imposing a maximum lateral geniculate nucleus (LGN)-to-cortex synaptic weight allows neurons to develop direction-selective responses that maintain the requirement for joint spatial and temporal activation. We demonstrate that a novel form of inhibitory plasticity, postsynaptic activity-dependent long-term potentiation of inhibition (POSD-LTPi), which operates in the developing cortex at the time of eye opening, can provide synaptic competition and enables robust development of direction-selective receptive fields with unidirectional or bidirectional stimulation. We propose a general model of the development of spatiotemporal receptive fields that consists of two phases: an experience-independent establishment of initial biases, followed by an experience-dependent amplification or modification of these biases via correlation-based plasticity of excitatory inputs that compete against gradually increasing feed-forward inhibition. Copyright © 2014 the American Physiological Society.

  7. Functional source separation applied to induced visual gamma activity.

    Science.gov (United States)

    Barbati, Giulia; Porcaro, Camillo; Hadjipapas, Avgis; Adjamian, Peyman; Pizzella, Vittorio; Romani, Gian Luca; Seri, Stefano; Tecchio, Franca; Barnes, Gareth R

    2008-02-01

    Objective of this work was to explore the performance of a recently introduced source extraction method, FSS (Functional Source Separation), in recovering induced oscillatory change responses from extra-cephalic magnetoencephalographic (MEG) signals. Unlike algorithms used to solve the inverse problem, FSS does not make any assumption about the underlying biophysical source model; instead, it makes use of task-related features (functional constraints) to estimate source/s of interest. FSS was compared with blind source separation (BSS) approaches such as Principal and Independent Component Analysis, PCA and ICA, which are not subject to any explicit forward solution or functional constraint, but require source uncorrelatedness (PCA), or independence (ICA). A visual MEG experiment with signals recorded from six subjects viewing a set of static horizontal black/white square-wave grating patterns at different spatial frequencies was analyzed. The beamforming technique Synthetic Aperture Magnetometry (SAM) was applied to localize task-related sources; obtained spatial filters were used to automatically select BSS and FSS components in the spatial area of interest. Source spectral properties were investigated by using Morlet-wavelet time-frequency representations and significant task-induced changes were evaluated by means of a resampling technique; the resulting spectral behaviours in the gamma frequency band of interest (20-70 Hz), as well as the spatial frequency-dependent gamma reactivity, were quantified and compared among methods. Among the tested approaches, only FSS was able to estimate the expected sustained gamma activity enhancement in primary visual cortex, throughout the whole duration of the stimulus presentation for all subjects, and to obtain sources comparable to invasively recorded data.

  8. Diffusion tensor imaging detects early cerebral cortex abnormalities in neuronal architecture induced by bilateral neonatal enucleation: An experimental model in the ferret

    Directory of Open Access Journals (Sweden)

    Andrew S Bock

    2010-10-01

    Full Text Available Diffusion tensor imaging (DTI is a technique that non-invasively provides quantitative measures of water translational diffusion, including fractional anisotropy (FA, that are sensitive to the shape and orientation of cellular elements, such as axons, dendrites and cell somas. For several neurodevelopmental disorders, histopathological investigations have identified abnormalities in the architecture of pyramidal neurons at early stages of cerebral cortex development. To assess the potential capability of DTI to detect neuromorphological abnormalities within the developing cerebral cortex, we compare changes in cortical FA with changes in neuronal architecture and connectivity induced by bilateral enucleation at postnatal day 7 (BEP7 in ferrets. We show here that the visual callosal pattern in BEP7 ferrets is more irregular and occupies a significantly greater cortical area compared to controls at adulthood. To determine whether development of the cerebral cortex is altered in BEP7 ferrets in a manner detectable by DTI, cortical FA was compared in control and BEP7 animals on postnatal day 31. Visual cortex, but not rostrally-adjacent non-visual cortex, exhibits higher FA than control animals, consistent with BEP7 animals possessing axonal and dendritic arbors of reduced complexity than age-matched controls. Subsequent to DTI, Golgi staining and analysis methods were used to identify regions, restricted to visual areas, in which the orientation distribution of neuronal processes is significantly more concentrated than in control ferrets. Together, these findings suggest that DTI can be of utility for detecting abnormalities associated with neurodevelopmental disorders at early stages of cerebral cortical development, and that the neonatally-enucleated ferret is a useful animal model system for systematically assessing the potential of this new diagnostic strategy.

  9. BDNF Expression in Perirhinal Cortex is Associated with Exercise-Induced Improvement in Object Recognition Memory

    OpenAIRE

    Hopkins, Michael E.; Bucci, David J.

    2010-01-01

    Physical exercise induces widespread neurobiological adaptations and improves learning and memory. Most research in this field has focused on hippocampus-based spatial tasks and changes in brain-derived neurotrophic factor (BDNF) as a putative substrate underlying exercise-induced cognitive improvements. Chronic exercise can also be anxiolytic and causes adaptive changes in stress reactivity. The present study employed a perirhinal cortex-dependent object recognition task as well as the eleva...

  10. Object class recognition based on compressive sensing with sparse features inspired by hierarchical model in visual cortex

    Science.gov (United States)

    Lu, Pei; Xu, Zhiyong; Yu, Huapeng; Chang, Yongxin; Fu, Chengyu; Shao, Jianxin

    2012-11-01

    According to models of object recognition in cortex, the brain uses a hierarchical approach in which simple, low-level features having high position and scale specificity are pooled and combined into more complex, higher-level features having greater location invariance. At higher levels, spatial structure becomes implicitly encoded into the features themselves, which may overlap, while explicit spatial information is coded more coarsely. In this paper, the importance of sparsity and localized patch features in a hierarchical model inspired by visual cortex is investigated. As in the model of Serre, Wolf, and Poggio, we first apply Gabor filters at all positions and scales; feature complexity and position/scale invariance are then built up by alternating template matching and max pooling operations. In order to improve generalization performance, the sparsity is proposed and data dimension is reduced by means of compressive sensing theory and sparse representation algorithm. Similarly, within computational neuroscience, adding the sparsity on the number of feature inputs and feature selection is critical for learning biologically model from the statistics of natural images. Then, a redundancy dictionary of patch-based features that could distinguish object class from other categories is designed and then object recognition is implemented by the process of iterative optimization. The method is test on the UIUC car database. The success of this approach suggests a proof for the object class recognition in visual cortex.

  11. Molecular Mechanisms at the Basis of Plasticity in the Developing Visual Cortex: Epigenetic Processes and Gene Programs

    Directory of Open Access Journals (Sweden)

    José Fernando Maya-Vetencourt

    2013-01-01

    Full Text Available Neuronal circuitries in the mammalian visual system change as a function of experience. Sensory experience modifies neuronal networks connectivity via the activation of different physiological processes such as excitatory/inhibitory synaptic transmission, neurotrophins, and signaling of extracellular matrix molecules. Long-lasting phenomena of plasticity occur when intracellular signal transduction pathways promote epigenetic alterations of chromatin structure that regulate the induction of transcription factors that in turn drive the expression of downstream targets, the products of which then work via the activation of structural and functional mechanisms that modify synaptic connectivity. Here, we review recent findings in the field of visual cortical plasticity while focusing on how physiological mechanisms associated with experience promote structural changes that determine functional modifications of neural circuitries in V1. We revise the role of microRNAs as molecular transducers of environmental stimuli and the role of immediate early genes that control gene expression programs underlying plasticity in the developing visual cortex.

  12. Painful tonic heat stimulation induces GABA accumulation in the prefrontal cortex in man

    DEFF Research Database (Denmark)

    Kupers, Ron; Danielsen, Else R; Kehlet, Henrik

    2009-01-01

    Relatively little is known on pain-induced neurotransmitter release in the human cerebral cortex. We used proton magnetic resonance spectroscopy (1H-MRS) during tonic painful heat stimulation to test the hypothesis of increases in both glutamate and GABA, two neurotransmitters with a key role...... in pain processing. Using a 3T MR scanner, we acquired spectra from the rostral anterior cingulate cortex (rACC) in 13 healthy right-handed subjects at rest and during painful heat stimulation. The painful stimulus consisted of a suprathreshold painful tonic heat pulse, which was delivered to the right...... that GABA is released in the human cerebral cortex during painful stimulation. The results are in line with animal findings on the role of GABA in pain processing and with studies in humans showing analgesic efficacy of GABA-related drugs in clinical pain conditions....

  13. Light-Emitting Diode (LED) therapy improves occipital cortex damage by decreasing apoptosis and increasing BDNF-expressing cells in methanol-induced toxicity in rats.

    Science.gov (United States)

    Ghanbari, Amir; Ghareghani, Majid; Zibara, Kazem; Delaviz, Hamdallah; Ebadi, Elham; Jahantab, Mohammad Hossein

    2017-05-01

    Methanol-induced retinal toxicity, frequently associated with elevated free radicals and cell edema, is characterized by progressive retinal ganglion cell (RGC) death and vision loss. Previous studies investigated the effect of photomodulation on RGCs, but not the visual cortex. In this study, the effect of 670nm Light-Emitting Diode (LED) therapy on RGCs and visual cortex recovery was investigated in a seven-day methanol-induced retinal toxicity protocol in rats. Methanol administration showed a reduction in the number of RGCs, loss of neurons (neuronal nuclear antigen, NeuN+), activation of glial fibrillary acidic protein (GFAP+) expressing cells, suppression of brain-derived neurotrophic factor (BDNF+) positive cells, increase in apoptosis (caspase 3+) and enhancement of nitric oxide (NO) release in serum and brain. On the other hand, LED therapy significantly reduced RGC death, in comparison to the methanol group. In addition, the number of BDNF positive cells was significantly higher in the visual cortex of LED-treated group, in comparison to methanol-intoxicated and control groups. Moreover, LED therapy caused a significant decrease in cell death (caspase 3+ cells) and a significant reduction in the NO levels, both in serum and brain tissue, in comparison to methanol-intoxicated rats. Overall, LED therapy demonstrated a number of beneficial effects in decreasing oxidative stress and in functional recovery of RGCs and visual cortex. Our data suggest that LED therapy could be a potential condidate as a non-invasive approach for treatment of retinal damage, which needs further clinicl studies. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  14. Dendritic morphology of pyramidal neurones of the visual cortex of the rat. IV: Electrical geometry.

    Science.gov (United States)

    Larkman, A U; Major, G; Stratford, K J; Jack, J J

    1992-09-08

    Features of the dendritic morphology of pyramidal neurones of the visual cortex of the rat that are relevant to the development of models of their passive electrical geometry were investigated. The sample of 39 neurones that was used came from layers 2/3 and 5. They had been recorded from and injected intracellularly with horseradish peroxidase (HRP) in vitro as part of a previous study (Larkman and Mason, J. Neurosci 10:1407, 1990). These cells had been reconstructed and measured previously by light microscopy. The relationship between the diameters of parent and daughter dendrites during branching was examined. It was found that most dendrites did not closely obey the "3/2 branch power relationship" required for representation of the dendrites as single equivalent cylinders. Estimates of total neuronal membrane area ranged from 27,100 +/- 7,900 microns2 for layer 2/3 cells to 52,200 +/- 11,800 microns2 for thick layer 5 cells. Dendritic spines contributed approximately half the total membrane area. Both neuronal input resistance and the ratio of membrane time constant to input resistance were correlated with neuronal membrane area as measured anatomically. The relative electrical lengths of the different dendrites of individual neurones were investigated, by using simple transformations to take account of the differences in diameter and spine density between dendritic segments. A novel "morphotonic" transformation is described that represents the purely morphological component of electrotonic length. Morphotonic lengths can be converted into electrotonic lengths by division by a "morphoelectric factor" ([Rm/Ri]1/2). This procedure has the advantage of separating the steps involving anatomical and electrical parameters. These transformations indicated that the dendrites of the apical terminal arbor were much longer electrically than the basal or apical oblique dendrites. In relative electrical terms, most apical oblique trees arose extremely close to the soma, and

  15. Structural synaptic remodeling in the perirhinal cortex of adult and old rats following object-recognition visual training.

    Science.gov (United States)

    Platano, D; Bertoni-Freddari, C; Fattoretti, P; Giorgetti, B; Grossi, Y; Balietti, M; Casoli, T; Di Stefano, G; Aicardi, G

    2006-01-01

    The ultrastructural features of layer II synapses in the perirhinal cortex of adult (4- to 6-month-old) and old (25- to 27-month-old) rats exposed to a six-session object recognition visual training were investigated by morphometric methods. The comparative analysis showed a higher synaptic numeric density, a lower synaptic average area, and a lower percentage of megasynapses (S > 0.5 microm2) in old trained rats versus controls, and a higher percentage of small (S < 0.15 microm2) junctions in adult trained rats versus controls. The more marked synaptic remodeling underlying memory consolidation in the perirhinal cortex of old rats might reflect a pre-existing lower dynamic status.

  16. Environmental Enrichment Rescues Binocular Matching of Orientation Preference in the Mouse Visual Cortex.

    Science.gov (United States)

    Levine, Jared N; Chen, Hui; Gu, Yu; Cang, Jianhua

    2017-06-14

    Neural circuits are shaped by experience during critical periods of development. Sensory deprivation during these periods permanently compromises an organism's ability to perceive the outside world. In the mouse visual system, normal visual experience during a critical period in early life drives the matching of individual cortical neurons' orientation preferences through the two eyes, likely a key step in the development of binocular vision. Here, in mice of both sexes, we show that the binocular matching process is completely blocked by monocular deprivation spanning the entire critical period. We then show that 3 weeks of environmental enrichment (EE), a paradigm of enhanced sensory, motor, and cognitive stimulation, is sufficient to rescue binocular matching to the level seen in unmanipulated mice. In contrast, 6 weeks of conventional housing only resulted in a partial rescue. Finally, we use two-photon calcium imaging to track the matching process chronically in individual cells during EE-induced rescue. We find that for cells that are clearly dominated by one of the two eyes, the input representing the weaker eye changes its orientation preference to align with that of the dominant eye. These results thus reveal ocular dominance as a key driver of the binocular matching process, and suggest a model whereby the dominant input instructs the development of the weaker input. Such a mechanism may operate in the development of other systems that need to integrate inputs from multiple sources to generate normal neuronal functions.SIGNIFICANCE STATEMENT Critical periods are developmental windows of opportunity that ensure the proper wiring of neural circuits, as well as windows of vulnerability when abnormal experience could cause lasting damage to the developing brain. In the visual system, critical period plasticity drives the establishment of binocularly matched orientation preferences in cortical neurons. Here, we show that binocular matching is completely

  17. Non-invasive brain stimulation of motor cortex induces embodiment when integrated with virtual reality feedback.

    Science.gov (United States)

    Bassolino, M; Franza, M; Bello Ruiz, J; Pinardi, M; Schmidlin, T; Stephan, M A; Solca, M; Serino, A; Blanke, O

    2018-02-20

    Previous evidence highlighted the multisensory-motor origin of embodiment - i.e., the experience of having a body and of being in control of it- and the possibility of experimentally manipulating it. For instance, an illusory feeling of embodiment towards a fake hand can be triggered by providing synchronous visuo-tactile stimulation to the hand of participants and to a fake hand or by asking participants to move their hand and observe a fake hand moving accordingly (rubber hand illusion, RHI). Here we tested whether it is possible to manipulate embodiment not through stimulation of the participant's hand, but by directly tapping into the brain's hand representation via non-invasive brain stimulation. To this aim, we combined transcranial magnetic stimulation (TMS) to activate the hand corticospinal representation with virtual reality (VR) to provide matching (as contrasted to non-matching) visual feedback, mimicking involuntary hand movements evoked by TMS. We show that the illusory embodiment occurred when TMS pulses were temporally matched with VR feedback, but not when TMS was administered outside primary motor cortex, (M1, over the vertex) or when stimulating M1 at a lower intensity (that did not activate peripheral muscles). Behavioral (questionnaires) and neurophysiological (motor-evoked-potentials, TMS-evoked-movements) measures further indicated that embodiment was not explained by stimulation per se, but depended on the temporal coherence between TMS-induced activation of hand corticospinal representation and the virtual bodily feedback. This reveals that non-invasive brain stimulation may replace the application of external tactile hand cues and motor components related to volition, planning, and anticipation. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  18. Effects of Vision Restoration Training on Early Visual Cortex in Patients With Cerebral Blindness Investigated With Functional Magnetic Resonance Imaging

    NARCIS (Netherlands)

    Raemaekers, M.; Bergsma, D.P.; van Wezel, Richard Jack Anton; van der Wildt, G.J.; van den Berg, A.V.

    Cerebral blindness is a loss of vision as a result of postchiasmatic damage to the visual pathways. Parts of the lost visual field can be restored through training. However, the neuronal mechanisms through which training effects occur are still unclear. We therefore assessed training-induced changes

  19. Competition for attentional resources between low spatial frequency content of emotional images and a foreground task in early visual cortex.

    Science.gov (United States)

    Müller, Matthias M; Gundlach, Christopher

    2017-03-01

    Low spatial frequency (LSF) image content has been proposed to play a superior functional role in emotional content extraction via the magnocellular pathway biasing attentional resources toward emotional content in visual cortex. We investigated whether emotionally unpleasant complex images that were presented either unfiltered or with LSF content only in the background while subjects performed a foreground task will withdraw more attentional resources from the task compared to unemotional, neutral images (distraction paradigm). We measured steady-state visual evoked potentials (SSVEPs) driven by flickering stimuli of a foreground task. Unfiltered unpleasant images resulted in a significant reduction of SSVEP amplitude compared to neutral images. No statistically significant differences were found with LSF background images. In a behavioral control experiment, we found no significant differences for complexity ratings between unfiltered and LSF pictures. Content identification was possible for unfiltered and LSF picture (correct responses > 74%). An additional EEG study examined typical emotion-related components for complex images presented either as unfiltered, LSF, or high spatial frequency (HSF, as an additional control) filtered, unpleasant, and neutral images. We found a significant main effect of emotional valence in the early posterior negativity. Late positive potential differences were only found for unfiltered and HSF images. Results suggest that, while LSF content is sufficient to allow for content and emotional cue extraction when images were presented alone, LSF content is not salient enough to serve as emotional distractor that withdraws attentional resources from a foreground task in early visual cortex. © 2016 Society for Psychophysiological Research.

  20. Hierarchical development of the primate visual cortex, as revealed by neurofilament immunoreactivity: early maturation of the middle temporal area (MT).

    Science.gov (United States)

    Bourne, James A; Rosa, Marcello G P

    2006-03-01

    It has been suggested that the development of the cerebral cortex reflects its hierarchical organization, with the primary sensory areas being the first to reach structural and functional maturity, and higher-order association areas being the last. In the present study, we labelled the cortex of New World marmoset monkeys of late fetal and early postnatal ages with an antibody to non-phosphorylated neurofilament, a marker of structural maturation of a subset of pyramidal cells. Supporting the concept of hierarchical maturation, we found that at birth labelled cells were found in the primary visual, auditory and somatosensory areas, but not in most other cortical fields. The exception was visual area MT, which revealed an infragranular pattern of labelling comparable to the one observed in the primary areas, as well as some supragranular staining. In MT, an adult-like pattern of labelled cells, including both supragranular and infragranular layer neurons, emerged within the first postnatal month. In comparison, the development of other extrastriate areas was delayed, with the first signs of neurofilament staining not present until the third week. The present results support the concept of MT as another primary visual area, an idea previously advanced on the basis of functional and anatomical evidence.

  1. Heavy charged-particle induced lesions in rabbit cerebral cortex

    Energy Technology Data Exchange (ETDEWEB)

    Woodruff, K.H.; Lyman, J.T.; Fabrikant, J.I.

    1988-02-01

    Fourteen male rabbits received single doses of 20, 40, and 80 Gy of neon irradiation with an extended Bragg peak. They were sacrificed at 1 day, 1 week, and 6 months post-irradiation. The tissue changes which showed a significant time-dose relationship were leakage of carbon particles from blood vessels, focal arachnoiditis, hemorrhage, cystic necrosis, and a total histopathologic score using a point system of grading. The focal nature of the lesions was clearly demonstrated with 2 mm thick macrotome sections. The transition zone between damaged brain and microscopically normal appearing brain was less than 1 mm and the tissue damage induced was morphologically similar to that of other radiation modalities. These findings may have important therapeutic implications for patients. The sharply demarcated boundaries of heavy charged-particle induced lesions suggest these beams will be useful for obliterating tissue in areas where it is critical that a transition from undamaged to severely damaged tissue must occur over a short distance, such as in the central nervous system.

  2. A family of activity-dependent neuronal cell-surface chondroitin sulfate proteoglycans in cat visual cortex.

    Science.gov (United States)

    Lander, C; Kind, P; Maleski, M; Hockfield, S

    1997-03-15

    Monoclonal antibody Cat-301 recognizes a chondroitin sulfate proteoglycan (CSPG) expressed on the extracellular surface of cell bodies and proximal dendrites of specific subsets of neurons in many areas of the mammalian CNS, including the cat visual cortex. The Cat-301 CSPG is first detected at the close of the critical period in development, a period during which the pattern of neuronal activity determines the mature synaptic circuitry and neuronal phenotype. In the cat visual cortex, dark-rearing from birth prolongs the duration of the critical period and attenuates the expression of the Cat-301 antigen, implicating the Cat-301 CSPG in the cellular mechanisms that terminate the period of synaptic plasticity. Because the Cat-301 antigen is expressed on only a limited subset of neurons, we have further examined the molecular heterogeneity among neuronal cell-surface CSPGs and have asked (1) whether other neuronal subsets carry distinct CSPGs and (2) whether the activity-dependent expression of the Cat-301 CSPG is a property generalizable to related cell-surface CSPGs. Here, we report two new monoclonal antibodies, Cat-315 and Cat-316, which together with Cat-301 define a family of at least seven related yet distinct CSPGs. These three antibodies define nonidentical subsets of neurons in the cat visual cortex. The expression of normal levels of these CSPGs is reduced by dark-rearing. Together, these data show that the family of cell-surface CSPGs is molecularly diverse, that different sets of neurons express distinct complements of cell-surface antigens, and that the regulation of CSPG expression by activity may be a general feature of neuronal cell-surface CSPGs.

  3. Aberrant parietal cortex developmental trajectories in girls with Turner syndrome and related visual-spatial cognitive development: a preliminary study.

    Science.gov (United States)

    Green, Tamar; Chromik, Lindsay C; Mazaika, Paul K; Fierro, Kyle; Raman, Mira M; Lazzeroni, Laura C; Hong, David S; Reiss, Allan L

    2014-09-01

    Turner syndrome (TS) arises from partial or complete absence of the X-chromosome in females. Girls with TS show deficits in visual-spatial skills as well as reduced brain volume and surface area in the parietal cortex which supports these cognitive functions. Thus, measuring the developmental trajectory of the parietal cortex and the associated visual-spatial cognition in TS may provide novel insights into critical brain-behavior associations. In this longitudinal study, we acquired structural MRI data and assessed visual-spatial skills in 16 (age: 8.23 ± 2.5) girls with TS and 13 age-matched controls over two time-points. Gray and white matter volume, surface area and cortical thickness were calculated from surfaced based segmentation of bilateral parietal cortices, and the NEPSY Arrows subtest was used to assess visual-spatial ability. Volumetric and cognitive scalars were modeled to obtain estimates of age-related change. The results show aberrant growth of white matter volume (P = 0.011, corrected) and surface area (P = 0.036, corrected) of the left superior parietal regions during childhood in girls with TS. Other parietal sub-regions were significantly smaller in girls with TS at both time-points but did not show different growth trajectories relative to controls. Furthermore, we found that visual-spatial skills showed a widening deficit for girls with TS relative to controls (P = 0.003). Young girls with TS demonstrate an aberrant trajectory of parietal cortical and cognitive development during childhood. Elucidating aberrant neurodevelopmental trajectories in this population is critical for determining specific stages of brain maturation that are particularly dependent on TS-related genetic and hormonal factors. © 2014 Wiley Periodicals, Inc.

  4. Covert oculo-manual coupling induced by visually guided saccades.

    Directory of Open Access Journals (Sweden)

    Luca eFalciati

    2013-10-01

    Full Text Available Hand pointing to objects under visual guidance is one of the most common motor behaviors in everyday life. In natural conditions, gaze and arm movements are commonly aimed at the same target and the accuracy of both systems is considerably enhanced if eye and hand move together. Evidence supports the viewpoint that gaze and limb control systems are not independent but at least partially share a common neural controller. The aim of the present study was to verify whether a saccade execution induces excitability changes in the upper-limb corticospinal system (CSS, even in the absence of a manual response. This effect would provide evidence for the existence of a common drive for ocular and arm motor systems during fast aiming movements. Single-pulse TMS was applied to the left motor cortex of 19 subjects during a task involving visually guided saccades, and motor evoked potentials (MEPs induced in hand and wrist muscles of the contralateral relaxed arm were recorded. Subjects had to make visually guided saccades to one of 6 positions along the horizontal meridian (±5°, ±10° or ±15°. During each trial, TMS was randomly delivered at one of 3 different time delays: shortly after the end of the saccade or 300 ms or 540 ms after saccade onset. Fast eye movements towards a peripheral target were accompanied by changes in upper-limb CSS excitability. MEP amplitude was highest immediately after the end of the saccade and gradually decreased at longer TMS delays. In addition to the change in overall CSS excitability, MEPs were specifically modulated in different muscles, depending on the target position and the TMS delay. By applying a simple model of a manual pointing movement, we demonstrated that the observed changes in CSS excitability are compatible with the facilitation of an arm motor program for a movement aimed at the same target of the gaze. These results provide evidence in favor of the existence of a common drive for both eye and arm

  5. Magnetic stimulation of the dorsolateral prefrontal cortex dissociates fragile visual short-term memory from visual working memory

    NARCIS (Netherlands)

    Sligte, I.G.; Wokke, M.E.; Tesselaar, J.P.; Scholte, H.S.; Lamme, V.A.F.

    2011-01-01

    To guide our behavior in successful ways, we often need to rely on information that is no longer in view, but maintained in visual short-term memory (VSTM). While VSTM is usually broken down into iconic memory (brief and high-capacity store) and visual working memory (sustained, yet limited-capacity

  6. Transformation from a Retinal to a Cyclopean Representation in Human Visual Cortex

    NARCIS (Netherlands)

    Barendregt, Martijn; Harvey, Ben M.; Rokers, Bas; Dumoulin, Serge O.

    2015-01-01

    We experience our visual world as seen from a single viewpoint, even though our two eyes receive slightly different images. One role of the visual system is to combine the two retinal images into a single representation of the visual field, sometimes called the cyclopean image [1]. Conventional

  7. Two critical periods in early visual cortex during figure-ground segregation

    NARCIS (Netherlands)

    Wokke, M.E.; Sligte, I.G.; Scholte, H.S.; Lamme, V.A.F.

    2012-01-01

    .The ability to distinguish a figure from its background is crucial for visual perception. To date, it remains unresolved where and how in the visual system different stages of figure-ground segregation emerge. Neural correlates of figure border detection have consistently been found in early visual

  8. [Wavelet packet extraction and entropy analysis of telemetry EEG from the prelimbic cortex of medial prefrontal cortex in morphine-induced CPP rats].

    Science.gov (United States)

    Bai, Yu; Bai, Jia-Ming; Li, Jing; Li, Min; Yu, Ran; Pan, Qun-Wan

    2014-12-25

    The purpose of the present study is to analyze the relationship between the telemetry electroencephalogram (EEG) changes of the prelimbic (PL) cortex and the drug-seeking behavior of morphine-induced conditioned place preference (CPP) rats by using the wavelet packet extraction and entropy measurement. The recording electrode was stereotactically implanted into the PL cortex of rats. The animals were then divided randomly into operation-only control and morphine-induced CPP groups, respectively. A CPP video system in combination with an EEG wireless telemetry device was used for recording EEG of PL cortex when the rats shuttled between black-white or white-black chambers. The telemetry recorded EEGs were analyzed by wavelet packet extraction, Welch power spectrum estimate, normalized amplitude and Shannon entropy algorithm. The results showed that, compared with operation-only control group, the left PL cortex's EEG of morphine-induced CPP group during black-white chamber shuttling exhibited the following changes: (1) the amplitude of average EEG for each frequency bands extracted by wavelet packet was reduced; (2) the Welch power intensity was increased significantly in 10-50 Hz EEG band (P EEG (P EEG changes in morphine-induced CPP group rat may be related to animals' drug-seeking motivation and behavior launching.

  9. Anatomy of hierarchy: feedforward and feedback pathways in macaque visual cortex

    NARCIS (Netherlands)

    Markov, N.T.; Vezoli, J.; Chameau, P.; Falchier, A.; Quilodran, R.; Huissoud, C.; Lamy, C.; Misery, P.; Giroud, P.; Ullman, S.; Barone, P.; Dehay, C.; Knoblauch, K.; Kennedy, H.

    2014-01-01

    The laminar location of the cell bodies and terminals of interareal connections determines the hierarchical structural organization of the cortex and has been intensively studied. However, we still have only a rudimentary understanding of the connectional principles of feedforward (FF) and feedback

  10. Novel Architectures for Image Processing Based on Computer Simulation and Psychophysical Studies of Human Visual Cortex.

    Science.gov (United States)

    1986-01-02

    1f E PROCESSING BASED ON COMPUTER SIMULATION AND PSYCHOPHYSICAL STUD Professor Eric L. Schwartz 13a. TYPE OF REPORT I136, TIME COVE RED 114. OAT ...monkey," Z. Neur2ys., vol. 40, pp. 1392-1405, 1977. . Pollen , D., J. R. Lee, and J. H. Taylor, "How does the striate cortex begin the reconstruction

  11. The prefrontal cortex shows context-specific changes in effective connectivity to motor or visual cortex during the selection of action or colour

    DEFF Research Database (Denmark)

    Rowe, James B.; Stephan, Klaas E.; Friston, Karl

    2005-01-01

    The role of the prefrontal cortex remains controversial. Neuroimaging studies support modality-specific and process-specific functions related to working memory and attention. Its role may also be defined by changes in its influence over other brain regions including sensory and motor cortex. We...... used functional magnetic imaging (fMRI) to study the free selection of actions and colours. Control conditions used externally specified actions and colours. The prefrontal cortex was activated during free selection, regardless of modality, in contrast to modality-specific activations outside...... prefrontal cortex. Structural equation modelling (SEM) of fMRI data was used to test the hypothesis that although the same regions of prefrontal cortex may be active in tasks within different domains, there is task-dependent effective connectivity between prefrontal cortex and non-prefrontal cortex. The SEM...

  12. Selectivity in Postencoding Connectivity with High-Level Visual Cortex Is Associated with Reward-Motivated Memory.

    Science.gov (United States)

    Murty, Vishnu P; Tompary, Alexa; Adcock, R Alison; Davachi, Lila

    2017-01-18

    Reward motivation has been demonstrated to enhance declarative memory by facilitating systems-level consolidation. Although high-reward information is often intermixed with lower reward information during an experience, memory for high value information is prioritized. How is this selectivity achieved? One possibility is that postencoding consolidation processes bias memory strengthening to those representations associated with higher reward. To test this hypothesis, we investigated the influence of differential reward motivation on the selectivity of postencoding markers of systems-level memory consolidation. Human participants encoded intermixed, trial-unique memoranda that were associated with either high or low-value during fMRI acquisition. Encoding was interleaved with periods of rest, allowing us to investigate experience-dependent changes in connectivity as they related to later memory. Behaviorally, we found that reward motivation enhanced 24 h associative memory. Analysis of patterns of postencoding connectivity showed that, even though learning trials were intermixed, there was significantly greater connectivity with regions of high-level, category-selective visual cortex associated with high-reward trials. Specifically, increased connectivity of category-selective visual cortex with both the VTA and the anterior hippocampus predicted associative memory for high- but not low-reward memories. Critically, these results were independent of encoding-related connectivity and univariate activity measures. Thus, these findings support a model by which the selective stabilization of memories for salient events is supported by postencoding interactions with sensory cortex associated with reward. Reward motivation is thought to promote memory by supporting memory consolidation. Yet, little is known as to how brain selects relevant information for subsequent consolidation based on reward. We show that experience-dependent changes in connectivity of both the

  13. Visual cortex in dementia with Lewy bodies: magnetic resonance imaging study

    Science.gov (United States)

    Taylor, John-Paul; Firbank, Michael J.; He, Jiabao; Barnett, Nicola; Pearce, Sarah; Livingstone, Anthea; Vuong, Quoc; McKeith, Ian G.; O’Brien, John T.

    2012-01-01

    Background Visual hallucinations and visuoperceptual deficits are common in dementia with Lewy bodies, suggesting that cortical visual function may be abnormal. Aims To investigate: (1) cortical visual function using functional magnetic resonance imaging (fMRI); and (2) the nature and severity of perfusion deficits in visual areas using arterial spin labelling (ASL)-MRI. Method In total, 17 participants with dementia with Lewy bodies (DLB group) and 19 similarly aged controls were presented with simple visual stimuli (checkerboard, moving dots, and objects) during fMRI and subsequently underwent ASL-MRI (DLB group n = 15, control group n = 19). Results Functional activations were evident in visual areas in both the DLB and control groups in response to checkerboard and objects stimuli but reduced visual area V5/MT (middle temporal) activation occurred in the DLB group in response to motion stimuli. Posterior cortical perfusion deficits occurred in the DLB group, particularly in higher visual areas. Conclusions Higher visual areas, particularly occipito-parietal, appear abnormal in dementia with Lewy bodies, while there is a preservation of function in lower visual areas (V1 and V2/3). PMID:22500014

  14. Proteolytic Regulation of Synaptic Plasticity in the Mouse Primary Visual Cortex: Analysis of Matrix Metalloproteinase 9 Deficient Mice.

    Directory of Open Access Journals (Sweden)

    Emily A Kelly

    2015-09-01

    Full Text Available The extracellular matrix (ECM is known to play important roles in regulating neuronal recovery from injury. The ECM can also impact physiological synaptic plasticity, although this process is less well understood. To understand the impact of the ECM on synaptic function and remodeling in vivo, we examined ECM composition and proteolysis in a well-established model of experience-dependent plasticity in the visual cortex. We describe a rapid change in ECM protein composition during ocular dominance plasticity in adolescent mice, and a loss of ECM remodeling in mice that lack the extracellular protease, matrix metalloproteinase-9 (MMP9. Loss of MMP9 also attenuated functional ocular dominance plasticity following monocular deprivation and reduced excitatory synapse density and spine density in sensory cortex. While we observed no change in the morphology of existing dendritic spines, spine dynamics were altered, and MMP9 knock-out (KO mice showed increased turnover of dendritic spines over a period of 2 days. We also analyzed the effects of MMP9 loss on microglia, as these cells are involved in extracellular remodeling and have been recently shown to be important for synaptic plasticity. MMP9 KO mice exhibited very limited changes in microglial morphology. Ultrastructural analysis, however, showed that the extracellular space surrounding microglia was increased, with concomitant increases in microglial inclusions, suggesting possible changes in microglial function in the absence of MMP9. Taken together, our results show that MMP9 contributes to ECM degradation, synaptic dynamics and sensory-evoked plasticity in the mouse visual cortex.

  15. Seeing without the Occipito-Parietal Cortex: Simultagnosia as a Shrinkage of the Attentional Visual Field

    OpenAIRE

    Michel, Fran?ois; Henaff, Marie-Anne

    2004-01-01

    Following bi-parietal lesions patient AT showed a severe inability to relocate her attention within a visual field which perimetry proved to be near-normal. An experimental approach with tasks testing visuo-spatial attention demonstrated a shrinkage of A.T.’s attentional visual field. With her visual attention narrowed to a kind of functional tunnel vision, the patient exhibited simultanagnosia (Wolpert, 1924), a symptom previously described in 1909 by Balint under the label of Psychic paraly...

  16. PDT-induced epigenetic changes in the mouse cerebral cortex: a protein microarray study.

    Science.gov (United States)

    Demyanenko, S V; Uzdensky, A B; Sharifulina, S A; Lapteva, T O; Polyakova, L P

    2014-01-01

    Photodynamic therapy (PDT) is used for cancer treatment including brain tumors. But the role of epigenetic processes in photodynamic injury of normal brain tissue is unknown. 5-Aminolevulinic acid (ALA), a precursor of protoporphyrin IX (PpIX), was used to photosensitize mouse cerebral cortex. PpIX accumulation in cortical tissue was measured spectrofluorometrically. Hematoxylin/eosin, gallocyanin-chromalum and immunohistochemical staining were used to study morphological changes in PDT-treated cerebral cortex. Proteomic antibody microarrays were used to evaluate expression of 112 proteins involved in epigenetic regulation. ALA administration induced 2.5-fold increase in the PpIX accumulation in the mouse brain cortex compared to untreated mice. Histological study demonstrated PDT-induced injury of some neurons and cortical vessels. ALA-PDT induced dimethylation of histone H3, upregulation of histone deacetylases HDAC-1 and HDAC-11, and DNA methylation-dependent protein Kaiso that suppressed transcriptional activity. Upregulation of HDAC-1 and H3K9me2 was confirmed immunohistochemically. Down-regulation of transcription factor FOXC2, PABP, and hBrm/hsnf2a negatively regulated transcription. Overexpression of phosphorylated histone H2AX indicated activation of DNA repair, but down-regulation of MTA1/MTA1L1 and PML - impairment of DNA repair. Overexpression of arginine methyltransferase PRMT5 correlated with up-regulation of transcription factor E2F4 and importin α5/7. ALA-PDT injures and kills some but not all neurons and caused limited microvascular alterations in the mouse cerebral cortex. It alters expression of some proteins involved in epigenetic regulation of transcription, histone modification, DNA repair, nuclear protein import, and proliferation. These data indicate epigenetic markers of photo-oxidative injury of normal brain tissue. © 2013.

  17. Neuropeptide S overcomes short term memory deficit induced by sleep restriction by increasing prefrontal cortex activity.

    Science.gov (United States)

    Thomasson, Julien; Canini, Frédéric; Poly-Thomasson, Betty; Trousselard, Marion; Granon, Sylvie; Chauveau, Frédéric

    2017-09-20

    Sleep restriction (SR) impairs short term memory (STM) that might be related to different processes. Neuropeptide S (NPS), an endogenous neuropeptide that improves short term memory, activates arousal and decreases anxiety is likely to counteract the SR-induced impairment of STM. The objective of the present study was to find common cerebral pathways in sleep restriction and NPS action in order to ultimately antagonize SR effect on memory. The STM was assessed using a spontaneous spatial alternation task in a T-maze. C57-Bl/6J male mice were distributed in 4 groups according to treatment (0.1nmol of NPS or vehicle intracerebroventricular injection) and to 20h-SR. Immediately after behavioural testing, regional c-fos immunohistochemistry was performed and used as a neural activation marker for spatial short term memory (prefrontal cortex, dorsal hippocampus) and emotional reactivity (basolateral amygdala and ventral hippocampus). Anxiety-like behaviour was assessed using elevated-plus maze task. Results showed that SR impaired short term memory performance and decreased neuronal activation in cingular cortex.NPS injection overcame SR-induced STM deficits and increased neuronal activation in infralimbic cortex. SR spared anxiety-like behavior in the elevated-plus maze. Neural activation in basolateral nucleus of amygdala and ventral hippocampus were not changed after SR.In conclusion, the present study shows that NPS overcomes SR-induced STM deficits by increasing prefrontal cortex activation independently of anxiety-like behaviour. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

  18. Ventral medial prefrontal cortex neuronal ensembles mediate context-induced relapse to heroin.

    Science.gov (United States)

    Bossert, Jennifer M; Stern, Anna L; Theberge, Florence R M; Cifani, Carlo; Koya, Eisuke; Hope, Bruce T; Shaham, Yavin

    2011-04-01

    In a rat model of context-induced relapse to heroin, we identified sparsely distributed ventral medial prefrontal cortex (mPFC) neurons that were activated by the heroin-associated context. Selective pharmacogenetic inactivation of these neurons inhibited context-induced drug relapse. A small subset of ventral mPFC neurons formed neuronal ensembles that encode the learned associations between heroin reward and heroin-associated contexts; re-activation of these neuronal ensembles by drug-associated contexts during abstinence provoked drug relapse.

  19. Manganese-enhanced MRI of layer-specific activity in the visual cortex from awake and free-moving rats.

    Science.gov (United States)

    Bissig, David; Berkowitz, Bruce A

    2009-02-01

    Cortical responses to visual stimulation have been studied extensively in the rodent, but often require post-stimulation ex vivo examination of the tissue. Here, we test the hypothesis that visual stimulus-dependent cortical activity from awake and free-moving rats can be encoded following systemically administered MnCl(2), and activity subsequently readout using manganese-enhanced MRI (MEMRI), a technique that can be performed without sacrificing the animal. Unanesthetized Sprague-Dawley rats, with or without systemic injection of MnCl(2), were maintained for 8 h in either a visually stimulating environment or darkness. To identify vision-dependent changes in cortical activity, animals were anesthetized and cortices were examined by 3D RARE MEMRI. Mean signal intensities in sub-cortical regions (e.g., superior colliculus and the lateral geniculate), and cortical regions (primary and accessory visual cortices) were compared. Cortex linearization was performed to aid in layer-specific signal intensity comparisons. Manganese administration alone globally increased signal intensity in the brain (Pdark adapted rats. Such differences went undetected without layer-specific analysis. We demonstrate, for the first time, the feasibility of layer-specific stimulus-dependant non-invasive MEMRI readout after encoding activity in awake and free moving rats. Future MEMRI studies are envisioned that measure the effects on cortical activity of sensory stimulation, as well as normal development, disease, plasticity, and therapy in longitudinal studies.

  20. Self-regulation of inter-hemispheric visual cortex balance through real-time fMRI neurofeedback training.

    Science.gov (United States)

    Robineau, F; Rieger, S W; Mermoud, C; Pichon, S; Koush, Y; Van De Ville, D; Vuilleumier, P; Scharnowski, F

    2014-10-15

    Recent advances in neurofeedback based on real-time functional magnetic resonance imaging (fMRI) allow for learning to control spatially localized brain activity in the range of millimeters across the entire brain. Real-time fMRI neurofeedback studies have demonstrated the feasibility of self-regulating activation in specific areas that are involved in a variety of functions, such as perception, motor control, language, and emotional processing. In most of these previous studies, participants trained to control activity within one region of interest (ROI). In the present study, we extended the neurofeedback approach by now training healthy participants to control the interhemispheric balance between their left and right visual cortices. This was accomplished by providing feedback based on the difference in activity between a target visual ROI and the corresponding homologue region in the opposite hemisphere. Eight out of 14 participants learned to control the differential feedback signal over the course of 3 neurofeedback training sessions spread over 3 days, i.e., they produced consistent increases in the visual target ROI relative to the opposite visual cortex. Those who learned to control the differential feedback signal were subsequently also able to exert that control in the absence of neurofeedback. Such learning to voluntarily control the balance between cortical areas of the two hemispheres might offer promising rehabilitation approaches for neurological or psychiatric conditions associated with pathological asymmetries in brain activity patterns, such as hemispatial neglect, dyslexia, or mood disorders. Copyright © 2014 Elsevier Inc. All rights reserved.

  1. The predicting brain: anticipation of moving objects in human visual cortex

    NARCIS (Netherlands)

    Schellekens, W.

    2015-01-01

    The human brain is nearly constantly subjected to visual motion signals originating from a large variety of external sources. It is the job of the central nervous system to determine correspondence among visual motion input across spatially distant locations within certain time frames. In order to

  2. Two eyes, one vision: binocular motion perception in human visual cortex

    NARCIS (Netherlands)

    Barendregt, M.

    2016-01-01

    An important aspect of human vision is the fact that it is binocular, i.e. that we have two eyes. As a result, the brain nearly always receives two slightly different images of the same visual scene. Yet, we only perceive a single image and thus our brain has to actively combine the binocular visual

  3. Functional and structural remodeling of glutamate synapses in prefrontal and frontal cortex induced by behavioral stress

    Directory of Open Access Journals (Sweden)

    Laura eMusazzi

    2015-04-01

    Full Text Available Increasing evidence has shown that the pathophysiology of neuropsychiatric disorders, including mood disorders, is associated with abnormal function and regulation of the glutamatergic system. Consistently, preclinical studies on stress-based animal models of pathology showed that glucocorticoids and stress exert crucial effects on neuronal excitability and function, especially in cortical and limbic areas. In prefrontal and frontal cortex, acute stress was shown to induce enhancement of glutamate release/transmission dependent on activation of corticosterone receptors. Although the mechanisms whereby stress affects glutamate transmission have not yet been fully understood, it was shown that synaptic, non-genomic action of corticosterone is required to increase the readily releasable pool of glutamate vesicles but is not sufficient to enhance transmission in prefrontal and frontal cortex. Slower, partly genomic mechanisms are probably necessary for the enhancement of glutamate transmission induced by stress.Combined evidence has suggested that the changes in glutamate release and transmission are responsible for the dendritic remodeling and morphological changes induced by stress and it has been argued that sustained alterations of glutamate transmission may play a key role in the long-term structural/functional changes associated with mood disorders in patients. Intriguingly, modifications of the glutamatergic system induced by stress in the prefrontal cortex seem to be biphasic. Indeed, while the fast response to stress suggests an enhancement in the number of excitatory synapses, synaptic transmission and working memory, long-term adaptive changes -including those consequent to chronic stress- induce opposite effects. Better knowledge of the cellular effectors involved in this biphasic effect of stress may be useful to understand the pathophysiology of stress-related disorders, and open new paths for the development of therapeutic approaches.

  4. Reduced visual cortex gray matter volume and thickness in young adults who witnessed domestic violence during childhood.

    Directory of Open Access Journals (Sweden)

    Akemi Tomoda

    Full Text Available Exposure to interparental violence is associated with negative outcomes, such as depression, post-traumatic stress disorder and reduced cognitive abilities. However, little is known about the potential effects of witnessing domestic violence during childhood on gray matter volume (GMV or cortical thickness. High-resolution 3.0 T volumetric scans (Siemens Trio Scanner were obtained on 52 subjects (18-25 years including 22 (6 males/16 females with a history of visually witnessing episodes of domestic violence, and 30 (8 males/22 females unexposed control subjects, with neither a current nor past DSM-IV Axis I or II disorder. Potential confounding effects of age, gender, level of parental verbal aggression, parental education, financial stress, full scale IQ, and total GMV, or average thickness were modeled using voxel based morphometry and FreeSurfer. Witnessing domestic violence subjects had a 6.1% GMV reduction in the right lingual gyrus (BA18 (P = 0.029, False Discovery Rate corrected peak level. Thickness in this region was also reduced, as was thickness in V2 bilaterally and left occipital pole. Theses regions were maximally sensitive to exposure to witnessing domestic violence between 11-13 years of age. Regional reductions in GMV and thickness were observed in both susceptible and resilient witnessing domestic violence subjects. Results in subjects witnessing domestic violence were similar to previously reported results in subjects with childhood sexual abuse, as the primary region affected was visual cortex. Brain regions that process and convey the adverse sensory input of the abuse may be specifically modified by this experience, particularly in subjects exposed to a single type of maltreatment. Exposure to multiple types of maltreatment is more commonly associated with morphological alterations in corticolimbic regions. These findings fit with preclinical studies showing that visual cortex is a highly plastic structure.

  5. Effective Connectivity from Early Visual Cortex to Posterior Occipitotemporal Face Areas Supports Face Selectivity and Predicts Developmental Prosopagnosia.

    Science.gov (United States)

    Lohse, Michael; Garrido, Lucia; Driver, Jon; Dolan, Raymond J; Duchaine, Bradley C; Furl, Nicholas

    2016-03-30

    Face processing is mediated by interactions between functional areas in the occipital and temporal lobe, and the fusiform face area (FFA) and anterior temporal lobe play key roles in the recognition of facial identity. Individuals with developmental prosopagnosia (DP), a lifelong face recognition impairment, have been shown to have structural and functional neuronal alterations in these areas. The present study investigated how face selectivity is generated in participants with normal face processing, and how functional abnormalities associated with DP, arise as a function of network connectivity. Using functional magnetic resonance imaging and dynamic causal modeling, we examined effective connectivity in normal participants by assessing network models that include early visual cortex (EVC) and face-selective areas and then investigated the integrity of this connectivity in participants with DP. Results showed that a feedforward architecture from EVC to the occipital face area, EVC to FFA, and EVC to posterior superior temporal sulcus (pSTS) best explained how face selectivity arises in both controls and participants with DP. In this architecture, the DP group showed reduced connection strengths on feedforward connections carrying face information from EVC to FFA and EVC to pSTS. These altered network dynamics in DP contribute to the diminished face selectivity in the posterior occipitotemporal areas affected in DP. These findings suggest a novel view on the relevance of feedforward projection from EVC to posterior occipitotemporal face areas in generating cortical face selectivity and differences in face recognition ability. Areas of the human brain showing enhanced activation to faces compared to other objects or places have been extensively studied. However, the factors leading to this face selectively have remained mostly unknown. We show that effective connectivity from early visual cortex to posterior occipitotemporal face areas gives rise to face

  6. Epigallocatechin-3-gallate attenuates acrylamide-induced apoptosis and astrogliosis in rat cerebral cortex.

    Science.gov (United States)

    He, Yin; Tan, Dehong; Bai, Bing; Wu, Zhaoxia; Ji, Shujuan

    2017-05-01

    The potent neurotoxic agent acrylamide (ACR) is formed during Maillard reaction in food processing. Epigallocatechin-3-gallate (EGCG), a major bioactive component of green tea, is an antioxidant, but its effects on ACR-induced neurotoxicity are unclear. Here, we investigated the neuroprotective effects of EGCG against ACR-induced apoptosis and astrogliosis in the cerebral cortex. Rats were pretreated with EGCG for 4 d and then co-administered ACR for 14 d. Immunohistochemical analysis of glial fibrillary acidic protein and 8-hydroxy-2'-deoxyguanosine indicated that EGCG attenuated astrogliosis and DNA damage in ACR-treated rats. Analysis of DNA fragmentation and protein expression of Bax, Bcl-2, caspase 3, and cytochrome c revealed that EGCG inhibited ACR-induced apoptosis. Furthermore, EGCG inhibited oxidative stress by enhancing the activity of antioxidant enzymes and glutathione levels and reducing the formation of reactive oxygen species and lipid peroxidation. Taken together, our data demonstrate that EGCG inhibits ACR-induced apoptosis and astrogliosis in the cerebral cortex.

  7. Visual face-movement sensitive cortex is relevant for auditory-only speech recognition.

    Science.gov (United States)

    Riedel, Philipp; Ragert, Patrick; Schelinski, Stefanie; Kiebel, Stefan J; von Kriegstein, Katharina

    2015-07-01

    It is commonly assumed that the recruitment of visual areas during audition is not relevant for performing auditory tasks ('auditory-only view'). According to an alternative view, however, the recruitment of visual cortices is thought to optimize auditory-only task performance ('auditory-visual view'). This alternative view is based on functional magnetic resonance imaging (fMRI) studies. These studies have shown, for example, that even if there is only auditory input available, face-movement sensitive areas within the posterior superior temporal sulcus (pSTS) are involved in understanding what is said (auditory-only speech recognition). This is particularly the case when speakers are known audio-visually, that is, after brief voice-face learning. Here we tested whether the left pSTS involvement is causally related to performance in auditory-only speech recognition when speakers are known by face. To test this hypothesis, we applied cathodal transcranial direct current stimulation (tDCS) to the pSTS during (i) visual-only speech recognition of a speaker known only visually to participants and (ii) auditory-only speech recognition of speakers they learned by voice and face. We defined the cathode as active electrode to down-regulate cortical excitability by hyperpolarization of neurons. tDCS to the pSTS interfered with visual-only speech recognition performance compared to a control group without pSTS stimulation (tDCS to BA6/44 or sham). Critically, compared to controls, pSTS stimulation additionally decreased auditory-only speech recognition performance selectively for voice-face learned speakers. These results are important in two ways. First, they provide direct evidence that the pSTS is causally involved in visual-only speech recognition; this confirms a long-standing prediction of current face-processing models. Secondly, they show that visual face-sensitive pSTS is causally involved in optimizing auditory-only speech recognition. These results are in line

  8. The temporal dynamics of object processing in visual cortex during the transition from distributed to focused spatial attention.

    Science.gov (United States)

    Wu, Chien-Te; Libertus, Melissa E; Meyerhoff, Karen L; Woldorff, Marty G

    2011-12-01

    Several major cognitive neuroscience models have posited that focal spatial attention is required to integrate different features of an object to form a coherent perception of it within a complex visual scene. Although many behavioral studies have supported this view, some have suggested that complex perceptual discrimination can be performed even with substantially reduced focal spatial attention, calling into question the complexity of object representation that can be achieved without focused spatial attention. In the present study, we took a cognitive neuroscience approach to this problem by recording cognition-related brain activity both to help resolve the questions about the role of focal spatial attention in object categorization processes and to investigate the underlying neural mechanisms, focusing particularly on the temporal cascade of these attentional and perceptual processes in visual cortex. More specifically, we recorded electrical brain activity in humans engaged in a specially designed cued visual search paradigm to probe the object-related visual processing before and during the transition from distributed to focal spatial attention. The onset times of the color popout cueing information, indicating where within an object array the subject was to shift attention, was parametrically varied relative to the presentation of the array (i.e., either occurring simultaneously or being delayed by 50 or 100 msec). The electrophysiological results demonstrate that some levels of object-specific representation can be formed in parallel for multiple items across the visual field under spatially distributed attention, before focal spatial attention is allocated to any of them. The object discrimination process appears to be subsequently amplified as soon as focal spatial attention is directed to a specific location and object. This set of novel neurophysiological findings thus provides important new insights on fundamental issues that have been long

  9. The temporal dynamics of implicit processing of non-letter, letter, and word-forms in the human visual cortex

    Directory of Open Access Journals (Sweden)

    Lawrence Gregory Appelbaum

    2009-11-01

    Full Text Available The decoding of visually presented line segments into letters, and letters into words, is critical to fluent reading abilities. Here we investigate the temporal dynamics of visual orthographic processes, focusing specifically on right hemisphere contributions and interactions between the hemispheres involved in the implicit processing of visually presented words, consonants, false fonts, and symbolic strings. High-density EEG was recorded while participants detected infrequent, simple, perceptual targets (dot strings embedded amongst a of character strings. Beginning at 130ms, orthographic and non-orthographic stimuli were distinguished by a sequence of ERP effects over occipital recording sites. These early latency occipital effects were dominated by enhanced right-sided negative-polarity activation for non-orthographic stimuli that peaked at around 180ms. This right-sided effect was followed by bilateral positive occipital activity for false-fonts, but not symbol strings. Moreover the size of components of this later positive occipital wave was inversely correlated with the right-sided ROcc180 wave, suggesting that subjects who had larger early right-sided activation for non-orthographic stimuli had less need for more extended bilateral (e.g. interhemispheric processing of those stimuli shortly later. Additional early (130-150ms negative-polarity activity over left occipital cortex and longer-latency centrally distributed responses (>300ms were present, likely reflecting implicit activation of the previously reported ‘visual-word-form’ area and N400-related responses, respectively. Collectively, these results provide a close look at some relatively unexplored portions of the temporal flow of information processing in the brain related to the implicit processing of potentially linguistic information and provide valuable information about the interactions between hemispheres supporting visual orthographic processing.

  10. Plasticity in bilateral superior temporal cortex: Effects of deafness and cochlear implantation on auditory and visual speech processing.

    Science.gov (United States)

    Anderson, Carly A; Lazard, Diane S; Hartley, Douglas E H

    2017-01-01

    While many individuals can benefit substantially from cochlear implantation, the ability to perceive and understand auditory speech with a cochlear implant (CI) remains highly variable amongst adult recipients. Importantly, auditory performance with a CI cannot be reliably predicted based solely on routinely obtained information regarding clinical characteristics of the CI candidate. This review argues that central factors, notably cortical function and plasticity, should also be considered as important contributors to the observed individual variability in CI outcome. Superior temporal cortex (STC), including auditory association areas, plays a crucial role in the processing of auditory and visual speech information. The current review considers evidence of cortical plasticity within bilateral STC, and how these effects may explain variability in CI outcome. Furthermore, evidence of audio-visual interactions in temporal and occipital cortices is examined, and relation to CI outcome is discussed. To date, longitudinal examination of changes in cortical function and plasticity over the period of rehabilitation with a CI has been restricted by methodological challenges. The application of functional near-infrared spectroscopy (fNIRS) in studying cortical function in CI users is becoming increasingly recognised as a potential solution to these problems. Here we suggest that fNIRS offers a powerful neuroimaging tool to elucidate the relationship between audio-visual interactions, cortical plasticity during deafness and following cochlear implantation, and individual variability in auditory performance with a CI. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

  11. [Monitoring depth of anesthesia and effect analysis in primary visual cortex of rats based on complexity of local field potential].

    Science.gov (United States)

    Li, Xiaoyuan; Shi, Li; Wan, Hong; Hu, Yuxia

    2014-04-01

    In the present study carried out in our laboratory, we recorded local field potential (LFP) signals in primary visual cortex (V1 area) of rats during the anesthesia process in the electrophysiological experiments of invasive microelectrode array implant, and obtained time evolutions of complexity measure Lempel-ziv complexity (LZC) by nonlinear dynamic analysis method. Combined with judgment criterion of tail flick latency to thermal stimulus and heart rate, the visual stimulation experiments are carried out to verify the reliability of anesthetized states by complexity analysis. The experimental results demonstrated that the time varying complexity measures LZC of LFP signals of different channels were similar to each other in the anesthesia process. In the same anesthesia state, the difference of complexity measure LZC between neuronal responses before and after visual stimulation was not significant. However, the complexity LZC in different anesthesia depths had statistical significances. Furthermore, complexity threshold value represented the depth of anesthesia was determined using optimization method. The reliability and accuracy of monitoring the depth of anesthesia using complexity measure LZC of LFP were all high. It provided an effective method of realtime monitoring depth of anesthesia for craniotomy patients in clinical operation.

  12. Competitive interactions of attentional resources in early visual cortex during sustained visuospatial attention within or between visual hemifields: evidence for the different-hemifield advantage.

    Science.gov (United States)

    Walter, Sabrina; Quigley, Cliodhna; Mueller, Matthias M

    2014-05-01

    Performing a task across the left and right visual hemifields results in better performance than in a within-hemifield version of the task, termed the different-hemifield advantage. Although recent studies used transient stimuli that were presented with long ISIs, here we used a continuous objective electrophysiological (EEG) measure of competitive interactions for attentional processing resources in early visual cortex, the steady-state visual evoked potential (SSVEP). We frequency-tagged locations in each visual quadrant and at central fixation by flickering light-emitting diodes (LEDs) at different frequencies to elicit distinguishable SSVEPs. Stimuli were presented for several seconds, and participants were cued to attend to two LEDs either in one (Within) or distributed across left and right visual hemifields (Across). In addition, we introduced two reference measures: one for suppressive interactions between the peripheral LEDs by using a task at fixation where attention was withdrawn from the periphery and another estimating the upper bound of SSVEP amplitude by cueing participants to attend to only one of the peripheral LEDs. We found significantly greater SSVEP amplitude modulations in Across compared with Within hemifield conditions. No differences were found between SSVEP amplitudes elicited by the peripheral LEDs when participants attended to the centrally located LEDs compared with when peripheral LEDs had to be ignored in Across and Within trials. Attending to only one LED elicited the same SSVEP amplitude as Across conditions. Although behavioral data displayed a more complex pattern, SSVEP amplitudes were well in line with the predictions of the different-hemifield advantage account during sustained visuospatial attention.

  13. Layer-specific chromatin accessibility landscapes reveal regulatory networks in adult mouse visual cortex

    Science.gov (United States)

    Gray, Lucas T; Yao, Zizhen; Nguyen, Thuc Nghi; Kim, Tae Kyung; Zeng, Hongkui; Tasic, Bosiljka

    2017-01-01

    Mammalian cortex is a laminar structure, with each layer composed of a characteristic set of cell types with different morphological, electrophysiological, and connectional properties. Here, we define chromatin accessibility landscapes of major, layer-specific excitatory classes of neurons, and compare them to each other and to inhibitory cortical neurons using the Assay for Transposase-Accessible Chromatin with high-throughput sequencing (ATAC-seq). We identify a large number of layer-specific accessible sites, and significant association with genes that are expressed in specific cortical layers. Integration of these data with layer-specific transcriptomic profiles and transcription factor binding motifs enabled us to construct a regulatory network revealing potential key layer-specific regulators, including Cux1/2, Foxp2, Nfia, Pou3f2, and Rorb. This dataset is a valuable resource for identifying candidate layer-specific cis-regulatory elements in adult mouse cortex. DOI: http://dx.doi.org/10.7554/eLife.21883.001 PMID:28112643

  14. Functional magnetic resonance imaging of delay and trace eyeblink conditioning in the primary visual cortex of the rabbit.

    Science.gov (United States)

    Miller, Michael J; Weiss, Craig; Song, Xiaomu; Iordanescu, Gheorghe; Disterhoft, John F; Wyrwicz, Alice M

    2008-05-07

    The primary sensory cortices have been shown in recent years to undergo experience- and learning-related plasticity under a variety of experimental circumstances. In this study, we used functional magnetic resonance imaging (fMRI) in parallel with both delay and trace eyeblink conditioning to image the learning-related functional activation within the primary visual cortex (V1) of awake, behaving rabbits. We expected that the differing level of forebrain dependence between these two conditioning paradigms should produce a differential blood oxygenation level-dependent (BOLD) functional response in V1. Our results showed a significant expansion of activated volume within V1, particularly early in learning, after training with the more cognitively demanding trace paradigm. In contrast, the simpler delay paradigm produced an increase in the magnitude of the BOLD response in activated voxels, but no significant change in activated volume. No accompanying learning-related changes were observed in the primary somatosensory cortex, which mediates the unconditioned stimulus. These results suggest that the recruitment of additional neurons within V1 is necessary to support the more demanding memory imposed by the trace interval. To our knowledge, this work is the first functional imaging study to compare directly trace and delay eyeblink conditioning in an animal model.

  15. Switching between internally and externally focused attention in obsessive-compulsive disorder: Abnormal visual cortex activation and connectivity.

    Science.gov (United States)

    Stern, Emily R; Muratore, Alexandra F; Taylor, Stephan F; Abelson, James L; Hof, Patrick R; Goodman, Wayne K

    2017-07-30

    Obsessive-compulsive disorder (OCD) is characterized by excessive absorption with internally-generated distressing thoughts and urges, with difficulty incorporating external information running counter to their fears and concerns. In the present study, we experimentally probed this core feature of OCD through the use of a novel attention switching task that investigates transitions between internally focused (IF) and externally focused (EF) attentional states. Eighteen OCD patients and 18 controls imagined positive and negative personal event scenarios (IF state) or performed a color-word Stroop task (EF state). The IF/EF states were followed by a target detection (TD) task requiring responses to external stimuli. Compared to controls, OCD patients made significantly more errors and showed reduced activation of superior and inferior occipital cortex, thalamus, and putamen during TD following negative IF, with the inferior occipital hypoactivation being significantly greater for TD following negative IF compared to TD following the other conditions. Patients showed stronger functional connectivity between the inferior occipital region and dorsomedial prefrontal cortex. These findings point to an OCD-related impairment in the visual processing of external stimuli specifically when they follow a period of negative internal focus, and suggest that future treatments may wish to target the transition between attentional states. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  16. The cortical eye proprioceptive signal modulates neural activity in higher-order visual cortex as predicted by the variation in visual sensitivity

    DEFF Research Database (Denmark)

    Balslev, Daniela; Siebner, Hartwig R; Paulson, Olaf B

    2012-01-01

    in the eye proprioceptive representation in human left somatosensory cortex (S1(EYE)), so that after 1Hz repetitive transcranial magnetic stimulation (rTMS) over S1(EYE), targets presented nearer the center of the orbit are detected more accurately. Here we used whole-brain functional magnetic resonance...... imaging to map areas where S1(EYE)-rTMS affects the neural response evoked by retinally identical stimuli depending on the direction of rotation of the right eye. After S1(EYE)-rTMS, a single area in the left cuneus outside Brodmann Areas 17/18 showed an increased neuronal response to a right hemifield...... target when the right eye was rotated leftwards as compared with when it was rotated rightwards. This effect was larger after S1(EYE)-rTMS than after rTMS of a control area in the motor cortex. The neural response to retinally identical stimuli in this area could be predicted from the changes in visual...

  17. [The size of cells providing interhemispheric and intrahemispheric connections in the visual cortex of binocular vision-impaired cats].

    Science.gov (United States)

    Alekseenko, S V; Toporova, S N; Shkorbatova, P Iu

    2011-03-01

    The size (somatic area) of 658 cells located in layers 2/3 of cortical areas 17, 18 of both hemispheres in intact monocularly deprived and bilateral strabismic cats was measured. These cells were retrogradely labelled after injections of horseradish peroxidase into ocular dominance columns in areas 17, 18. In all groups of cats, the mean somatic area of callosal cells was significantly larger than the mean somatic area of intrahemispheric cells. It was found that the mean somatic area of callosal cells was increased by 26.6% in monocularly deprived cats and by 20.2% in strabismic cats in relation to the mean somatic area of callosal cells in intact cats. In addition, the mean somatic area of intrahemispheric cells in monocularly deprived cats was indistinguishable from the mean somatic area of intrahemispheric cells in strabismic cats and in intact cats. It is concluded that early binocular vision impairments produce enlargement of callosal cells' size in the visual cortex.

  18. BDNF expression in perirhinal cortex is associated with exercise-induced improvement in object recognition memory.

    Science.gov (United States)

    Hopkins, Michael E; Bucci, David J

    2010-09-01

    Physical exercise induces widespread neurobiological adaptations and improves learning and memory. Most research in this field has focused on hippocampus-based spatial tasks and changes in brain-derived neurotrophic factor (BDNF) as a putative substrate underlying exercise-induced cognitive improvements. Chronic exercise can also be anxiolytic and causes adaptive changes in stress-reactivity. The present study employed a perirhinal cortex-dependent object recognition task as well as the elevated plus maze to directly test for interactions between the cognitive and anxiolytic effects of exercise in male Long Evans rats. Hippocampal and perirhinal cortex tissue was collected to determine whether the relationship between BDNF and cognitive performance extends to this non-spatial and non-hippocampal-dependent task. We also examined whether the cognitive improvements persisted once the exercise regimen was terminated. Our data indicate that 4weeks of voluntary exercise every-other-day improved object recognition memory. Importantly, BDNF expression in the perirhinal cortex of exercising rats was strongly correlated with object recognition memory. Exercise also decreased anxiety-like behavior, however there was no evidence to support a relationship between anxiety-like behavior and performance on the novel object recognition task. There was a trend for a negative relationship between anxiety-like behavior and hippocampal BDNF. Neither the cognitive improvements nor the relationship between cognitive function and perirhinal BDNF levels persisted after 2weeks of inactivity. These are the first data demonstrating that region-specific changes in BDNF protein levels are correlated with exercise-induced improvements in non-spatial memory, mediated by structures outside the hippocampus and are consistent with the theory that, with regard to object recognition, the anxiolytic and cognitive effects of exercise may be mediated through separable mechanisms. Copyright 2010 Elsevier

  19. The effect of learning on the function of monkey extrastriate visual cortex.

    Directory of Open Access Journals (Sweden)

    Gregor Rainer

    2004-02-01

    Full Text Available One of the most remarkable capabilities of the adult brain is its ability to learn and continuously adapt to an ever-changing environment. While many studies have documented how learning improves the perception and identification of visual stimuli, relatively little is known about how it modifies the underlying neural mechanisms. We trained monkeys to identify natural images that were degraded by interpolation with visual noise. We found that learning led to an improvement in monkeys' ability to identify these indeterminate visual stimuli. We link this behavioral improvement to a learning-dependent increase in the amount of information communicated by V4 neurons. This increase was mediated by a specific enhancement in neural activity. Our results reveal a mechanism by which learning increases the amount of information that V4 neurons are able to extract from the visual environment. This suggests that V4 plays a key role in resolving indeterminate visual inputs by coordinated interaction between bottom-up and top-down processing streams.

  20. The Effect of Learning on the Function of Monkey Extrastriate Visual Cortex

    Science.gov (United States)

    Lee, Han; Logothetis, Nikos K

    2004-01-01

    One of the most remarkable capabilities of the adult brain is its ability to learn and continuously adapt to an ever-changing environment. While many studies have documented how learning improves the perception and identification of visual stimuli, relatively little is known about how it modifies the underlying neural mechanisms. We trained monkeys to identify natural images that were degraded by interpolation with visual noise. We found that learning led to an improvement in monkeys' ability to identify these indeterminate visual stimuli. We link this behavioral improvement to a learning-dependent increase in the amount of information communicated by V4 neurons. This increase was mediated by a specific enhancement in neural activity. Our results reveal a mechanism by which learning increases the amount of information that V4 neurons are able to extract from the visual environment. This suggests that V4 plays a key role in resolving indeterminate visual inputs by coordinated interaction between bottom-up and top-down processing streams. PMID:14966538

  1. Requirement of keratan sulfate proteoglycan phosphacan with a specific sulfation pattern for critical period plasticity in the visual cortex.

    Science.gov (United States)

    Takeda-Uchimura, Yoshiko; Uchimura, Kenji; Sugimura, Taketoshi; Yanagawa, Yuchio; Kawasaki, Toshisuke; Komatsu, Yukio; Kadomatsu, Kenji

    2015-12-01

    Proteoglycans play important roles in regulating the development and functions of the brain. They consist of a core protein and glycosaminoglycans, which are long sugar chains of repeating disaccharide units with sulfation. A recent study demonstrated that the sulfation pattern of chondroitin sulfate on proteoglycans contributes to regulation of the critical period of experience-dependent plasticity in the mouse visual cortex. In the present study, we investigated the role of keratan sulfate (KS), another glycosaminoglycan, in critical period plasticity in the mouse visual cortex. Immunohistochemical analyses demonstrated the presence of KS containing disaccharide units of N-acetylglucosamine (GlcNAc)-6-sulfate and nonsulfated galactose during the critical period, although KS containing disaccharide units of GlcNAc-6-sulfate and galactose-6-sulfate was already known to disappear before that period. The KS chains were distributed diffusely in the extracellular space and densely around the soma of a large population of excitatory and inhibitory neurons. Electron microscopic analysis revealed that the KS was localized within the perisynaptic spaces and dendrites but not in presynaptic sites. KS was mainly located on phosphacan. In mice deficient in GlcNAc-6-O-sulfotransferase 1, which is one of the enzymes necessary for the synthesis of KS chains, the expression of KS was one half that in wild-type mice. In the knockout mice, monocular deprivation during the critical period resulted in a depression of deprived-eye responses but failed to produce potentiation of nondeprived-eye responses. In addition, T-type Ca(2+) channel-dependent long-term potentiation (LTP), which occurs only during the critical period, was not observed. These results suggest that regulation by KS-phosphacan with a specific sulfation pattern is necessary for the generation of LTP and hence the potentiation of nondeprived-eye responses after monocular deprivation. Copyright © 2015 Elsevier Inc. All

  2. Interlayer Repulsion of Retinal Ganglion Cell Mosaics Regulates Spatial Organization of Functional Maps in the Visual Cortex.

    Science.gov (United States)

    Jang, Jaeson; Paik, Se-Bum

    2017-12-13

    In higher mammals, orientation tuning of neurons is organized into a quasi-periodic pattern in the primary visual cortex. Our previous model studies suggested that the topography of cortical orientation maps may originate from moiré interference of ON and OFF retinal ganglion cell (RGC) mosaics, but did not account for how the consistent spatial period of maps could be achieved. Here we address this issue with two crucial findings on the development of RGC mosaics: first, homotypic local repulsion between RGCs can develop a long-range hexagonal periodicity. Second, heterotypic interaction restrains the alignment of ON and OFF mosaics, and generates a periodic interference pattern map with consistent spatial frequency. To validate our model, we quantitatively analyzed the RGC mosaics in cat data, and confirmed that the observed retinal mosaics showed evidence of heterotypic interactions, contrary to the previous view that ON and OFF mosaics are developed independently.SIGNIFICANCE STATEMENT Orientation map is one of the most studied functional maps in the brain, but it has remained unanswered how the consistent spatial periodicity of maps could be developed. In the current study, we address this issue with our developmental model for the retinal origin of orientation map. We showed that local repulsive interactions between retinal ganglion cells (RGCs) can develop a hexagonal periodicity in the RGC mosaics and restrict the alignment between ON and OFF mosaics, so that they generate a periodic pattern with consistent spatial frequency for both the RGC mosaics and the cortical orientation maps. Our results demonstrate that the organization of functional maps in visual cortex, including its structural consistency, may be constrained by a retinal blueprint. Copyright © 2017 the authors 0270-6474/17/3712141-12$15.00/0.

  3. Dopamine release in human striatum induced by repetitive transcranial magnetic stimulation over dorsolateral prefrontal cortex

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Sang Soo; Yoon, Eun Jin; Kim, Yu Kyeong; Lee, Won Woo; Kim, Sang Eun [Seoul National University College of Medicine, Seoul (Korea, Republic of)

    2005-07-01

    Animal study suggests that prefrontal cortex plays an important Animal studies suggest that prefrontal cortex plays an important role in the modulation of dopamine (DA) release in subcortical areas. However, little is known about the relationship between DA release and prefrontal activation in human. We investigated whether repetitive transcranial magnetic stimulation (rTMS) over left dorsolateral prefrontal cortex (DLPFC) influences DA release in human striatum with SPECT measurements of striatal binding of [123I)iodobenzamide (IBZM), a DA D2 receptor radioligand that is sensitive to endogenous DA. Five healthy male volunteers (age, 25{+-}2 yr) were studied with brain [123I]IBZM SPECT under three conditions (resting, Sham stimulation, and active rTMS over left DLPFC), while receiving a bolus plus constant infusion of [123I]IBZM DLPFC was defined as a 6 cm anterior and 1cm lateral from the primary motor cortex. rTMS session consisted of three blocks, in each block, 15 trains of 2 see duration were delivered with 10 Hz stimulation frequency, 100% motor threshold, and between-train intervals of 10 sec. Striatal V3', calculated as (striatal - occipital) / occipital activity ratio, was measured under equilibrium condition, at baseline and after sham and active rTMS. Sham stimulation did not affect striatal V3'. rTMS over DLPFC induced reduction of V3' in the ipsilateral and contralateral striatum by 9.7% {+-} 1.3% and 10.6% {+-} 3.2%, respectively, compared with sham procedures (P < 0.01 and P < 0.01, respectively), indicating striatal DA release elicited by rTMS over DLPFC. V3' reduction in the ipsilateral caudate nucleus was greater than that in the contralateral caudate nucleus (9.9% {+-} 4.5% vs. 6.6% {+-} 3.1%, P < 0.05). These data demonstrate DA release in human striatum induced by rTMS over DLPFC, supporting that cortico-striatal fibers originating in prefrontal cortex are involved in local DA release.

  4. Cathodal tDCS over the left prefrontal cortex diminishes choice-induced preference change.

    Science.gov (United States)

    Mengarelli, Flavia; Spoglianti, Silvia; Avenanti, Alessio; di Pellegrino, Giuseppe

    2015-05-01

    In everyday life, people often find themselves facing difficult decisions between options that are equally attractive. Cognitive dissonance theory states that after making a difficult choice between 2 equally preferred options, individuals no longer find the alternatives similarly desirable. Rather, they often change their existing preferences to align more closely with the choice they have just made. Despite the relevance of cognitive dissonance in modulating behavior, little is known about the brain processes crucially involved in choice-induced preference change. In the present study, we applied cathodal transcranial Direct Current Stimulation (tDCS) with the aim of downregulating the activity of the left or the right dorsolateral prefrontal cortex (DLPFC) during a revised version of Brehm's (in 1956. Post-decision changes in the desirability of alternatives. J Abnorm Soc Psychol. 52:384-389) free-choice paradigm. We found that cathodal tDCS over the left, but not over the right, DLPFC caused a reduction of the typical behavior-induced preference change relative to sham stimulation. Our findings highlight the role of prefrontal cortex in cognitive dissonance and provide evidence that left DLPFC plays a necessary role in the implementation of choice-induced preference change. © The Author 2013. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  5. Seeing without the Occipito-Parietal Cortex: Simultagnosia as a Shrinkage of the Attentional Visual Field

    Directory of Open Access Journals (Sweden)

    François Michel

    2004-01-01

    Full Text Available Following bi-parietal lesions patient AT showed a severe inability to relocate her attention within a visual field which perimetry proved to be near-normal. An experimental approach with tasks testing visuo-spatial attention demonstrated a shrinkage of A.T.’s attentional visual field. With her visual attention narrowed to a kind of functional tunnel vision, the patient exhibited simultanagnosia (Wolpert, 1924, a symptom previously described in 1909 by Balint under the label of Psychic paralysis of “Gaze”. In striking contrast AT showed an efficient and effortless perception of complex natural scenes, which, according to recent work in normal subjects, necessitate few if any attentional resources.

  6. Seeing without the Occipito-Parietal Cortex: Simultagnosia as a Shrinkage of the Attentional Visual Field

    Science.gov (United States)

    Michel, François; Henaff, Marie-Anne

    2004-01-01

    Following bi-parietal lesions patient AT showed a severe inability to relocate her attention within a visual field which perimetry proved to be near-normal. An experimental approach with tasks testing visuo-spatial attention demonstrated a shrinkage of A.T.’s attentional visual field. With her visual attention narrowed to a kind of functional tunnel vision, the patient exhibited simultanagnosia (Wolpert, 1924), a symptom previously described in 1909 by Balint under the label of Psychic paralysis of “Gaze”. In striking contrast AT showed an efficient and effortless perception of complex natural scenes, which, according to recent work in normal subjects, necessitate few if any attentional resources. PMID:15201489

  7. Seeing without the occipito-parietal cortex: Simultagnosia as a shrinkage of the attentional visual field.

    Science.gov (United States)

    Michel, François; Henaff, Marie-Anne

    2004-01-01

    Following bi-parietal lesions patient AT showed a severe inability to relocate her attention within a visual field which perimetry proved to be near-normal. An experimental approach with tasks testing visuo-spatial attention demonstrated a shrinkage of A.T.'s attentional visual field. With her visual attention narrowed to a kind of functional tunnel vision, the patient exhibited simultanagnosia (Wolpert, 1924), a symptom previously described in 1909 by Balint under the label of Psychic paralysis of "Gaze". In striking contrast AT showed an efficient and effortless perception of complex natural scenes, which, according to recent work in normal subjects, necessitate few if any attentional resources. Copyright 2004 IOS Press

  8. Effects of Fluoxetine and Visual Experience on Glutamatergic and GABAergic Synaptic Proteins in Adult Rat Visual Cortex123

    Science.gov (United States)

    Beshara, Simon; Beston, Brett R.; Pinto, Joshua G. A.

    2015-01-01

    Abstract Fluoxetine has emerged as a novel treatment for persistent amblyopia because in adult animals it reinstates critical period-like ocular dominance plasticity and promotes recovery of visual acuity. Translation of these results from animal models to the clinic, however, has been challenging because of the lack of understanding of how this selective serotonin reuptake inhibitor affects glutamatergic and GABAergic synaptic mechanisms that are essential for experience-dependent plasticity. An appealing hypothesis is that fluoxetine recreates a critical period (CP)-like state by shifting synaptic mechanisms to be more juvenile. To test this we studied the effect of fluoxetine treatment in adult rats, alone or in combination with visual deprivation [monocular deprivation (MD)], on a set of highly conserved presynaptic and postsynaptic proteins (synapsin, synaptophysin, VGLUT1, VGAT, PSD-95, gephyrin, GluN1, GluA2, GluN2B, GluN2A, GABAAα1, GABAAα3). We did not find evidence that fluoxetine shifted the protein amounts or balances to a CP-like state. Instead, it drove the balances in favor of the more mature subunits (GluN2A, GABAAα1). In addition, when fluoxetine was paired with MD it created a neuroprotective-like environment by normalizing the glutamatergic gain found in adult MDs. Together, our results suggest that fluoxetine treatment creates a novel synaptic environment dominated by GluN2A- and GABAAα1-dependent plasticity. PMID:26730408

  9. Activation of the mouse primary visual cortex by medial prefrontal subregion stimulation is not mediated by cholinergic basalo-cortical projections

    Directory of Open Access Journals (Sweden)

    Hoang Nam eNguyen

    2015-02-01

    Full Text Available The medial prefrontal cortex (mPFC exerts top-down control of primary visual cortex (V1 activity. As there is no direct neuronal projection from mPFC to V1, this functional connection may use an indirect route, i.e., via basalo-cortical cholinergic projections. The cholinergic projections to V1 originate from neurons in the horizontal limb of the diagonal band of Broca (HDB, which receive neuronal projections from the ventral part of the mPFC, composed of prelimbic (PrL and infralimbic cortices (IL. Therefore, the objective of this study was to determine whether electrical stimulation of mice mPFC subregions activate 1 V1 neurons and 2 HDB cholinergic neurons, suggesting that the HDB serves as a relay point in the mPFC-V1 interaction. Neuronal activation was quantified using c-Fos immunocytochemistry or thallium autometallography for each V1 layer using automated particle analysis tools and optical density measurement. Stimulation of IL and PrL induced significantly higher c-Fos expression or thallium labelling in layers II/III and V of V1 in the stimulated hemisphere only. A HDB cholinergic neuron-specific lesion by saporin administration reduced IL-induced c-Fos expression in layers II/III of V1 but not in layer V. However, there was no c-Fos expression or thallium labelling in the HDB neurons, suggesting that this area was not activated by IL stimulation. Stimulation of another mPFC subarea, the anterior cingulate cortex (AC, which is involved in attention and receives input from V1, activated neither V1 nor HDB. The present results indicate that IL and PrL, but not AC, stimulation activates V1 with the minor involvement of the HDB cholinergic projections. These results suggest a functional link between the ventral mPFC and V1, but this function is only marginally supported by HDB cholinergic neurons and may involve other brain regions.

  10. Changes in cue-induced, prefrontal cortex activity with video-game play.

    Science.gov (United States)

    Han, Doug Hyun; Kim, Yang Soo; Lee, Yong Sik; Min, Kyung Joon; Renshaw, Perry F

    2010-12-01

    Brain responses, particularly within the orbitofrontal and cingulate cortices, to Internet video-game cues in college students are similar to those observed in patients with substance dependence in response to the substance-related cues. In this study, we report changes in brain activity between baseline and following 6 weeks of Internet video-game play. We hypothesized that subjects with high levels of self-reported craving for Internet video-game play would be associated with increased activity in the prefrontal cortex, particularly the orbitofrontal and anterior cingulate cortex. Twenty-one healthy university students were recruited. At baseline and after a 6-week period of Internet video-game play, brain activity during presentation of video-game cues was assessed using 3T blood oxygen level dependent functional magnetic resonance imaging. Craving for Internet video-game play was assessed by self-report on a 7-point visual analogue scale following cue presentation. During a standardized 6-week video-game play period, brain activity in the anterior cingulate and orbitofrontal cortex of the excessive Internet game-playing group (EIGP) increased in response to Internet video-game cues. In contrast, activity observed in the general player group (GP) was not changed or decreased. In addition, the change of craving for Internet video games was positively correlated with the change in activity of the anterior cingulate in all subjects. These changes in frontal-lobe activity with extended video-game play may be similar to those observed during the early stages of addiction.

  11. Animate and Inanimate Objects in Human Visual Cortex: Evidence for Task-Independent Category Effects

    Science.gov (United States)

    Wiggett, Alison J.; Pritchard, Iwan C.; Downing, Paul E.

    2009-01-01

    Evidence from neuropsychology suggests that the distinction between animate and inanimate kinds is fundamental to human cognition. Previous neuroimaging studies have reported that viewing animate objects activates ventrolateral visual brain regions, whereas inanimate objects activate ventromedial regions. However, these studies have typically…

  12. Visual cortex activity predicts subjective experience after reading books with colored letters

    NARCIS (Netherlands)

    Colizoli, O.; Murre, J.M.J.; Scholte, H.S.; van Es, D.M.; Knapen, T.; Rouw, R.

    2016-01-01

    One of the most astonishing properties of synesthesia is that the evoked concurrent experiences are perceptual. Is it possible to acquire similar effects after learning cross-modal associations that resemble synesthetic mappings? In this study, we examine whether brain activation in early visual

  13. The representation of erroneously perceived stimuli in the primary visual cortex

    NARCIS (Netherlands)

    Roelfsema, P. R.; Spekreijse, H.

    2001-01-01

    In order to attain a correct interpretation of an ambiguous visual stimulus, the brain may have to elaborate on the sensory evidence. Are the neurons that carry the sensory evidence also involved in generating an interpretation? To address this question, we studied the activity of neurons in the

  14. Body-selective areas in the visual cortex are less active in children than in adults

    NARCIS (Netherlands)

    Ross, Paddy D.; de Gelder, Beatrice; Crabbe, Frances; Grosbras, Marie-Helene

    2014-01-01

    Our ability to read other people's non-verbal signals gets refined throughout childhood and adolescence. How this is paralleled by brain development has been investigated mainly with regards to face perception, showing a protracted functional development of the face-selective visual cortical areas.

  15. Attraction of position preference by spatial attention throughout human visual cortex.

    Science.gov (United States)

    Klein, Barrie P; Harvey, Ben M; Dumoulin, Serge O

    2014-10-01

    Voluntary spatial attention concentrates neural resources at the attended location. Here, we examined the effects of spatial attention on spatial position selectivity in humans. We measured population receptive fields (pRFs) using high-field functional MRI (fMRI) (7T) while subjects performed an attention-demanding task at different locations. We show that spatial attention attracts pRF preferred positions across the entire visual field, not just at the attended location. This global change in pRF preferred positions systematically increases up the visual hierarchy. We model these pRF preferred position changes as an interaction between two components: an attention field and a pRF without the influence of attention. This computational model suggests that increasing effects of attention up the hierarchy result primarily from differences in pRF size and that the attention field is similar across the visual hierarchy. A similar attention field suggests that spatial attention transforms different neural response selectivities throughout the visual hierarchy in a similar manner. Copyright © 2014 Elsevier Inc. All rights reserved.

  16. Visually Induced Dizziness in Children and Validation of the Pediatric Visually Induced Dizziness Questionnaire

    Directory of Open Access Journals (Sweden)

    Marousa Pavlou

    2017-12-01

    Full Text Available AimsTo develop and validate the Pediatric Visually Induced Dizziness Questionnaire (PVID and quantify the presence and severity of visually induced dizziness (ViD, i.e., symptoms induced by visual motion stimuli including crowds and scrolling computer screens in children.Methods169 healthy (female n = 89; recruited from mainstream schools, London, UK and 114 children with a primary migraine, concussion, or vestibular disorder diagnosis (female n = 62, aged 6–17 years, were included. Children with primary migraine were recruited from mainstream schools while children with concussion or vestibular disorder were recruited from tertiary balance centers in London, UK, and Pittsburgh, PA, USA. Children completed the PVID, which assesses the frequency of dizziness and unsteadiness experienced in specific environmental situations, and Strength and Difficulties Questionnaire (SDQ, a brief behavioral screening instrument.ResultsThe PVID showed high internal consistency (11 items; α = 0.90. A significant between-group difference was noted with higher (i.e., worse PVID scores for patients vs. healthy participants (U = 2,436.5, z = −10.719, p < 0.001; a significant difference was noted between individual patient groups [χ2(2 = 11.014, p = 0.004] but post hoc analysis showed no significant pairwise comparisons. The optimal cut-off score for discriminating between individuals with and without abnormal ViD levels was 0.45 out of 3 (sensitivity 83%, specificity 75%. Self-rated emotional (U = 2,730.0, z = −6.169 and hyperactivity (U = 3,445.0, z = −4.506 SDQ subscale as well as informant (U = 188.5, z = −3.916 and self-rated (U = 3,178.5, z = −5.083 total scores were significantly worse for patients compared to healthy participants (p < 0.001.ConclusionViD is common in children with a primary concussion, migraine, or vestibular diagnosis. The PVID is a valid measure for

  17. Differences in Visual-Spatial Input May Underlie Different Compression Properties of Firing Fields for Grid Cell Modules in Medial Entorhinal Cortex

    Science.gov (United States)

    2015-11-19

    RESEARCH ARTICLE Differences in Visual -Spatial Input May Underlie Different Compression Properties of Firing Fields for Grid Cell Modules in Medial...gmail.com Abstract Firing fields of grid cells in medial entorhinal cortex show compression or expansion after manipulations of the location of...present a model for differences in the response of modules to barrier location that arise from different mechanisms for the influence of visual

  18. COMPUTER-BASED PRIMARY VISUAL CORTEX TRAINING FOR TREATMENT OF LOW MYOPIA AND EARLY PRESBYOPIA

    Science.gov (United States)

    Durrie, Daniel; McMinn, Peter Shaw

    2007-01-01

    Purpose The NeuroVision technology is a noninvasive, patient-specific, perceptual learning program based on visual stimulation and facilitation of neural connections at the cortical level, involving a computerized visual training regimen using Gabor patches, to improve contrast sensitivity and visual acuity. The efficacy of NeuroVision in enhancing uncorrected visual acuity (UCVA) and unaided contrast sensitivity function (CSF) in patients with low myopia or early presbyopia was evaluated. Methods Seventeen patients with low myopia (up to −1.75 D) and 21 patients with early presbyopia (up to +2.50 D add) were recruited in 2 clinical sites. Eleven myopic and 18 presbyopic patients underwent the NeuroVision program (treatment group), and 9 patients performed visual examinations only, serving as a control group. Results The low myopia treatment group achieved a mean improvement of 2.2 logMAR lines in unaided VA, from 0.42 to 0.20 logMAR. Unaided CSF improved at all spatial frequencies (1.5, 3, 6, 12, 18 cpd). The early presbyopia treatment group achieved a mean improvement of 2.2 logMAR lines in near UCVA, from 0.47 to 0.25 logMAR. Near unaided CSF also improved at all spatial frequencies. The control patients in both arms of the study have not shown any significant change in vision. Additionally, the mean refractive error in all groups remained unchanged after treatment. Conclusions Results to date suggest that the NeuroVision technology is effective in improving UCVA and unaided CSF in low myopia and early presbyopia. PMID:18427602

  19. Stress induced a shift from dorsal hippocampus to prefrontal cortex-dependent memory retrieval: role of regional corticosterone.

    OpenAIRE

    Gaelle eDominguez; Pierre eFaucher; Nadia eHenkous; Ali eKrazem; Christophe ePierard; Daniel eBeracochea

    2014-01-01

    Most of the deleterious effects of stress on memory retrieval are due to a dysfunction of the hippocampo-prefrontal cortex interplay. The role of the stress-induced regional corticosterone increase in such dysfunction remains however unclear, since there is no published study as yet dedicated to measuring corticosterone concentrations simultaneously in both the prefrontal cortex (mPFC) and the hippocampus (dHPC) in relation with memory impairments. To that aim, we first showed in Experiment 1...

  20. Alterations in visual cortical activation and connectivity with prefrontal cortex during working memory updating in major depressive disorder.

    Science.gov (United States)

    Le, Thang M; Borghi, John A; Kujawa, Autumn J; Klein, Daniel N; Leung, Hoi-Chung

    2017-01-01

    alterations in activity patterns of the visual association areas, their connectivity with the prefrontal cortex, and their relationship with core clinical characteristics. These results highlight the role of information updating deficits in the cognitive control and symptomatology of depression.

  1. Alterations in visual cortical activation and connectivity with prefrontal cortex during working memory updating in major depressive disorder

    Directory of Open Access Journals (Sweden)

    Thang M. Le

    2017-01-01

    revealed by alterations in activity patterns of the visual association areas, their connectivity with the prefrontal cortex, and their relationship with core clinical characteristics. These results highlight the role of information updating deficits in the cognitive control and symptomatology of depression.

  2. Visual cortex reactivity in sedated children examined with perfusion MRI (FAIR)

    DEFF Research Database (Denmark)

    Born, A.P.; Rostrup, Egill; Miranda Gimenez-Ricco, Maria Jo

    2002-01-01

    Sleeping and sedated children can respond to visual stimulation with a decrease in blood oxygenation level dependent (BOLD) functional MRI signal response. The contribution of metabolic and hemodynamic parameters to this inverse signal response is incompletely understood. It has been hypothesized...... that it is caused by a relatively greater increase of oxygen consumption compared to rCBF (regional cerebral blood flow) increase. We studied the rCBF changes during visual stimulation in four sedated children, aged 4-71 months, and four alert adults, with an arterial water spin labeling technique (FAIR) and BOLD f....... Future studies will have to address if this response pattern is a consequence of age or sleep/sedation...

  3. Treadmill exercise induces age and protocol-dependent epigenetic changes in prefrontal cortex of Wistar rats.

    Science.gov (United States)

    Cechinel, Laura Reck; Basso, Carla Giovana; Bertoldi, Karine; Schallenberger, Bruna; de Meireles, Louisiana Carolina Ferreira; Siqueira, Ionara Rodrigues

    2016-10-15

    Some studies have linked age-related beneficial effects of exercise and epigenetic mechanisms. Although, the impact of treadmill exercise on histone acetylation, histone and DNA methylation marks in aged cortices yet remains poorly understood. Considering the role of frontal cortex on brain functions, we investigated the potential of different exercise protocols, single session and daily exercise, to modulate epigenetic marks, namely global H4 acetylation, histone methyltransferase activity (HMT H3K27) and levels of DNA methytransferase (DNMT1 and DNMT3b) in prefrontal cortices from 3 and 21-months aged Wistar rats. The animals were submitted to two treadmill exercise protocols, single session (20min) or daily moderate (20min/day during 14days). The daily exercise protocol induced an increased in histone H4 acetylation levels in prefrontal cortices of 21-months-old rats, without any effects in young adult group. DNMT3b levels were increased in aged cortices of animals submitted to single session of exercise. These results indicate that prefrontal cortex is susceptible to epigenetic changes in a protocol dependent-manner and that H4 acetylation levels and DNMT3b content changes might be linked at least in part to exercise-induced effects on brain functions. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Novel implantable imaging system for enabling simultaneous multiplanar and multipoint analysis for fluorescence potentiometry in the visual cortex.

    Science.gov (United States)

    Kobayashi, Takuma; Motoyama, Mayumi; Masuda, Hiroyuki; Ohta, Yasumi; Haruta, Makito; Noda, Toshihiko; Sasagawa, Kiyotaka; Tokuda, Takashi; Tamura, Hideki; Ishikawa, Yasuyuki; Shiosaka, Sadao; Ohta, Jun

    2012-01-01

    Techniques for fast, noninvasive measurement of neuronal excitability within a broad area will be of major importance for analyzing and understanding neuronal networks and animal behavior in neuroscience field. In this research, a novel implantable imaging system for fluorescence potentiometry was developed using a complementary metal-oxide semiconductor (CMOS) technology, and its application to the analysis of cultured brain slices and the brain of a living mouse is described. A CMOS image sensor, small enough to be implanted into the brain, with light-emitting diodes and an absorbing filter was developed to enable real-time fluorescence imaging. The sensor, in conjunction with a voltage-sensitive dye, was certainly able to visualize the potential statuses of neurons and obtain physiological responses in both right and left visual cortex simultaneously by using multiple sensors for the first time. This accomplished multiplanar and multipoint measurement provides multidimensional information from different aspects. The light microsensors do not disturb the animal behavior. This implies that the imaging system can combine functional fluorescence imaging in the brain with behavioral experiments in a freely moving animal. Copyright © 2012 Elsevier B.V. All rights reserved.

  5. Effect of CGRP and sumatriptan on the BOLD response in visual cortex

    DEFF Research Database (Denmark)

    Asghar, Mohammed Sohail; Hansen, Adam E; Larsson, Henrik B W

    2012-01-01

    % of the participants reported headache after CGRP. We found no changes in brain activity after CGRP (P = 0.12) or after placebo (P = 0.41). Sumatriptan did not affect brain activity after CGRP (P = 0.71) or after placebo (P = 0.98). Systemic CGRP or sumatriptan has no direct effects on the BOLD activity in visual...

  6. Reactivation of visual cortex during memory retrieval: content specificity and emotional modulation.

    Science.gov (United States)

    Hofstetter, Christoph; Achaibou, Amal; Vuilleumier, Patrik

    2012-04-15

    Studies on memory retrieval suggest a reactivation of cortical regions engaged during encoding, such that visual or auditory areas reactivate for visual or auditory memories. The content specificity and any emotion dependency of such reactivations are still unclear. Because distinct visual areas are specialized in processing distinct stimulus categories, we tested for face and word specific reactivations during a memory task using functional magnetic resonance imaging (fMRI). Furthermore, because visual processing and memory are both modulated by emotion, we compared reactivation for stimuli encoded in a neutral or emotionally significant context. In the learning phase, participants studied pairs of stimuli that consisted of either a scene and a face, or a scene and a word. Scenes were either neutral or negative, but did not contain faces or words. In the test phase scenes were presented alone (one in turn), and participants indicated whether it was previously paired with a face, a word, or was new. Results from the test phase showed activation in a functionally defined face-responsive region in the right fusiform gyrus, as well as in a word-responsive region in the left inferior temporal gyrus, for scenes previously paired with faces and words, respectively. Reactivation tended to be larger in both the face- and word-responsive regions when the associated scene was negative as compared to neutral. However, relative to neutral context, the recall of faces and words paired with a negative context produced smaller activations in brain regions associated with social and semantic processing, respectively, as well as poorer memory performance overall. Taken together, these results support the idea of cortical memory reactivations, even at a content-specific level, and further suggest that emotional context may produce opposite effects on reactivations in early sensory areas and more elaborate processing in higher-level cortical areas. Copyright © 2012 Elsevier Inc

  7. Orientation and motion-specific visual cortex responses in infants born preterm.

    Science.gov (United States)

    Birtles, Deirdre B; Braddick, Oliver J; Wattam-Bell, John; Wilkinson, Andrew R; Atkinson, Janette

    2007-12-03

    Orientation-specific cortical responses develop earlier in infancy than motion-specific responses. The maturation of orientation-reversal and direction-reversal visual evoked potentials was evaluated in 17 healthy, low risk, preterm infants (born delayed maturation of motion processing. Reasons for the vulnerability of motion processing are discussed; the results may reflect anomalies of white matter development in preterm infants that are undetected by ultrasonography.

  8. Involvement of posterior cingulate cortex in ketamine-induced psychosis relevant behaviors in rats.

    Science.gov (United States)

    Ma, Jingyi; Leung, L Stan

    2018-02-15

    The involvement of posterior cingulate cortex (PCC) on ketamine-induced psychosis relevant behaviors was investigated in rats. Bilateral infusion of muscimol, a GABA A receptor agonist, into the PCC significantly antagonized ketamine-induced deficit in prepulse inhibition of a startle reflex (PPI), deficit in gating of hippocampal auditory evoked potentials, and behavioral hyperlocomotion in a dose dependent manner. Local infusion of ketamine directly into the PCC also induced a PPI deficit. Systemic injection of ketamine (3mg/kg,s.c.) induced an increase in power of electrographic activity in the gamma band (30-100Hz) in both the PCC and the hippocampus; peak theta (4-10Hz) power was not significantly altered, but peak theta frequency was increased by ketamine. In order to exclude volume conduction from the hippocampus to PCC, inactivation of the hippocampus was made by local infusion of muscimol into the hippocampus prior to ketamine administration. Muscimol in the hippocampus effectively blocked ketamine-induced increase of gamma power in the hippocampus but not in the PCC, suggesting independent generation of gamma waves in PCC and hippocampus. It is suggested that the PCC is part of the brain network mediating ketamine-induced psychosis related behaviors. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Turning visual shapes into sounds: early stages of reading acquisition revealed in the ventral occipitotemporal cortex.

    Science.gov (United States)

    Perrone-Bertolotti, M; Vidal, J R; de Palma, L; Hamamé, C M; Ossandon, T; Kahane, P; Minotti, L; Bertrand, O; Lachaux, J-P

    2014-04-15

    The exact role of the left ventral occipitotemporal cortex (VOTC) during the initial stages of reading acquisition is a hotly debated issue, especially regarding the comparative effect of learning on early stimulus-dependent vs. later task-dependent processes. We show that this controversy can be solved with high-temporal resolution intracerebral EEG recordings of the VOTC. We measured High-Frequency Activity (50-150 Hz) as a proxy of population-level spiking activity while participants learned Japanese Katakana symbols, and found that learning primarily affects top-down/task-dependent neural processing, after a few minutes only. In contrast, adaptation of early bottom-up/stimulus-dependent processing takes several days to adapt and provides the basis for fluent reading. Such evidence that two consecutive stages of neural processing, stimulus- and task-dependent are differentially affected by learning, can reconcile seemingly opposite hypotheses on the role of the VOTC during reading acquisition. Copyright © 2013 Elsevier Inc. All rights reserved.

  10. Theta-burst transcranial magnetic stimulation to the prefrontal or parietal cortex does not impair metacognitive visual awareness.

    Directory of Open Access Journals (Sweden)

    Daniel Bor

    Full Text Available Neuroimaging studies commonly associate dorsolateral prefrontal cortex (DLPFC and posterior parietal cortex with conscious perception. However, such studies only investigate correlation, rather than causation. In addition, many studies conflate objective performance with subjective awareness. In an influential recent paper, Rounis and colleagues addressed these issues by showing that continuous theta burst transcranial magnetic stimulation (cTBS applied to the DLPFC impaired metacognitive (subjective awareness for a perceptual task, while objective performance was kept constant. We attempted to replicate this finding, with minor modifications, including an active cTBS control site. Using a between-subjects design for both DLPFC and posterior parietal cortices, we found no evidence of a cTBS-induced metacognitive impairment. In a second experiment, we devised a highly rigorous within-subjects cTBS design for DLPFC, but again failed to find any evidence of metacognitive impairment. One crucial difference between our results and the Rounis study is our strict exclusion of data deemed unsuitable for a signal detection theory analysis. Indeed, when we included this unstable data, a significant, though invalid, metacognitive impairment was found. These results cast doubt on previous findings relating metacognitive awareness to DLPFC, and inform the current debate concerning whether or not prefrontal regions are preferentially implicated in conscious perception.

  11. Noise-induced cell death in the mouse medial geniculate body and primary auditory cortex.

    Science.gov (United States)

    Basta, Dietmar; Tzschentke, Barbara; Ernst, Arne

    Noise-induced effects within the inner ear have been well investigated for several years. However, this peripheral damage cannot fully explain the audiological symptoms in noise-induced hearing loss (NIHL), e.g. tinnitus, recruitment, reduced speech intelligibility, hyperacusis. There are few reports on central noise effects. Noise can induce an apoptosis of neuronal tissue within the lower auditory pathway. Higher auditory structures (e.g. medial geniculate body, auditory cortex) are characterized by metabolic changes after noise exposure. However, little is known about the microstructural changes of the higher auditory pathway after noise exposure. The present paper was therefore aimed at investigating the cell density in the medial geniculate body (MGB) and the primary auditory cortex (AI) after noise exposure. Normal hearing mice were exposed to noise (10 kHz center frequency at 115 dB SPL for 3 h) at the age of 21 days under anesthesia (Ketamin/Rompun, 10:1). After 1 week, auditory brainstem response recordings (ABR) were performed in noise exposed and normal hearing animals. After fixation, the brain was microdissected and stained (Kluever-Barrera). The cell density in the MGB subdivisions and the AI were determined by counting the cells within a grid. Noise-exposed animals showed a significant ABR threshold shift over the whole frequency range. Cell density was significantly reduced in all subdivisions of the MGB and in layers IV-VI of AI. The present findings demonstrate a significant noise-induced change of the neuronal cytoarchitecture in central key areas of auditory processing. These changes could contribute to the complex psychoacoustic symptoms after NIHL.

  12. Cannabis cue-induced brain activation correlates with drug craving in limbic and visual salience regions: Preliminary results

    Science.gov (United States)

    Charboneau, Evonne J.; Dietrich, Mary S.; Park, Sohee; Cao, Aize; Watkins, Tristan J; Blackford, Jennifer U; Benningfield, Margaret M.; Martin, Peter R.; Buchowski, Maciej S.; Cowan, Ronald L.

    2013-01-01

    Craving is a major motivator underlying drug use and relapse but the neural correlates of cannabis craving are not well understood. This study sought to determine whether visual cannabis cues increase cannabis craving and whether cue-induced craving is associated with regional brain activation in cannabis-dependent individuals. Cannabis craving was assessed in 16 cannabis-dependent adult volunteers while they viewed cannabis cues during a functional MRI (fMRI) scan. The Marijuana Craving Questionnaire was administered immediately before and after each of three cannabis cue-exposure fMRI runs. FMRI blood-oxygenation-level-dependent (BOLD) signal intensity was determined in regions activated by cannabis cues to examine the relationship of regional brain activation to cannabis craving. Craving scores increased significantly following exposure to visual cannabis cues. Visual cues activated multiple brain regions, including inferior orbital frontal cortex, posterior cingulate gyrus, parahippocampal gyrus, hippocampus, amygdala, superior temporal pole, and occipital cortex. Craving scores at baseline and at the end of all three runs were significantly correlated with brain activation during the first fMRI run only, in the limbic system (including amygdala and hippocampus) and paralimbic system (superior temporal pole), and visual regions (occipital cortex). Cannabis cues increased craving in cannabis-dependent individuals and this increase was associated with activation in the limbic, paralimbic, and visual systems during the first fMRI run, but not subsequent fMRI runs. These results suggest that these regions may mediate visually cued aspects of drug craving. This study provides preliminary evidence for the neural basis of cue-induced cannabis craving and suggests possible neural targets for interventions targeted at treating cannabis dependence. PMID:24035535

  13. Shedding light on emotional perception: Interaction of brightness and semantic content in extrastriate visual cortex.

    Science.gov (United States)

    Schettino, Antonio; Keil, Andreas; Porcu, Emanuele; Müller, Matthias M

    2016-06-01

    The rapid extraction of affective cues from the visual environment is crucial for flexible behavior. Previous studies have reported emotion-dependent amplitude modulations of two event-related potential (ERP) components - the N1 and EPN - reflecting sensory gain control mechanisms in extrastriate visual areas. However, it is unclear whether both components are selective electrophysiological markers of attentional orienting toward emotional material or are also influenced by physical features of the visual stimuli. To address this question, electrical brain activity was recorded from seventeen male participants while viewing original and bright versions of neutral and erotic pictures. Bright neutral scenes were rated as more pleasant compared to their original counterpart, whereas erotic scenes were judged more positively when presented in their original version. Classical and mass univariate ERP analysis showed larger N1 amplitude for original relative to bright erotic pictures, with no differences for original and bright neutral scenes. Conversely, the EPN was only modulated by picture content and not by brightness, substantiating the idea that this component is a unique electrophysiological marker of attention allocation toward emotional material. Complementary topographic analysis revealed the early selective expression of a centro-parietal positivity following the presentation of original erotic scenes only, reflecting the recruitment of neural networks associated with sustained attention and facilitated memory encoding for motivationally relevant material. Overall, these results indicate that neural networks subtending the extraction of emotional information are differentially recruited depending on low-level perceptual features, which ultimately influence affective evaluations. Copyright © 2016 Elsevier Inc. All rights reserved.

  14. Analysis of EEG Phase Property with Pulse and Noise Stimuli in Visual Cortex (V1)

    Science.gov (United States)

    Ogawa, Yutaro; Takeno, Shohei; Kotani, Kiyoshi; Jimbo, Yasuhiko

    Event Related Potential (ERP) of brain EEG (Electroencephalogram) activity plays an important role in EEG phase synchronization and/or hemodynamic responses measured by fMRI (functional Magnetic Resonance Imaging). However, the specific mechanism of ERP generation is still unclear. In this study, pulse and noise type visual stimuli are administered to subjects. Then the phase response of the EEG in α-waves is analyzed. As a result, the magnitudes of the phase response are varied by the stimulus administered phase and no power increase is observed. These results indicate that the ERP in α-waves is generated by the phase resetting of brain activity.

  15. TMS-EEG reveals hemispheric asymmetries in top-down influences of posterior intraparietal cortex on behavior and visual event-related potentials.

    Science.gov (United States)

    Koivisto, Mika; Grassini, Simone; Hurme, Mikko; Salminen-Vaparanta, Niina; Railo, Henry; Vorobyev, Victor; Tallus, Jussi; Paavilainen, Teemu; Revonsuo, Antti

    2017-11-11

    Clinical data and behavioral studies using transcranial magnetic stimulation (TMS) suggest right-hemisphere dominance for top-down modulation of visual processing in humans. We used concurrent TMS-EEG to directly test for hemispheric differences in causal influences of the right and left intraparietal cortex on visual event-related potentials (ERPs). We stimulated the left and right posterior part of intraparietal sulcus (IPS1) while the participants were viewing and rating the visibility of bilaterally presented Gabor patches. Subjective visibility ratings showed that TMS of right IPS shifted the visibility toward the right hemifield, while TMS of left IPS did not have any behavioral effect. TMS of right IPS, but not left one, reduced the amplitude of posterior N1 potential, 180-220 ms after stimulus-onset. The attenuation of N1 occurred bilaterally over the posterior areas of both hemispheres. Consistent with previous TMS-fMRI studies, this finding suggests that the right IPS has top-down control on the neural processing in visual cortex. As N1 most probably reflects reactivation of early visual areas, the current findings support the view that the posterior parietal cortex in the right hemisphere amplifies recurrent interactions in ventral visual areas during the time-window that is critical for conscious perception. Copyright © 2017. Published by Elsevier Ltd.

  16. Auditory Cortex Tracks Both Auditory and Visual Stimulus Dynamics Using Low-Frequency Neuronal Phase Modulation

    Science.gov (United States)

    Luo, Huan; Liu, Zuxiang; Poeppel, David

    2010-01-01

    Integrating information across sensory domains to construct a unified representation of multi-sensory signals is a fundamental characteristic of perception in ecological contexts. One provocative hypothesis deriving from neurophysiology suggests that there exists early and direct cross-modal phase modulation. We provide evidence, based on magnetoencephalography (MEG) recordings from participants viewing audiovisual movies, that low-frequency neuronal information lies at the basis of the synergistic coordination of information across auditory and visual streams. In particular, the phase of the 2–7 Hz delta and theta band responses carries robust (in single trials) and usable information (for parsing the temporal structure) about stimulus dynamics in both sensory modalities concurrently. These experiments are the first to show in humans that a particular cortical mechanism, delta-theta phase modulation across early sensory areas, plays an important “active” role in continuously tracking naturalistic audio-visual streams, carrying dynamic multi-sensory information, and reflecting cross-sensory interaction in real time. PMID:20711473

  17. Visual cortex reactivity in sedated children examined with perfusion MRI (FAIR)

    DEFF Research Database (Denmark)

    Born, A P; Rostrup, E; Miranda, M J

    2002-01-01

    Sleeping and sedated children can respond to visual stimulation with a decrease in blood oxygenation level dependent (BOLD) functional MRI signal response. The contribution of metabolic and hemodynamic parameters to this inverse signal response is incompletely understood. It has been hypothesized...... that it is caused by a relatively greater increase of oxygen consumption compared to rCBF (regional cerebral blood flow) increase. We studied the rCBF changes during visual stimulation in four sedated children, aged 4-71 months, and four alert adults, with an arterial water spin labeling technique (FAIR) and BOLD f......MRI in a 1.5T MR scanner. In the children, FAIR signal decreased by a mean of 0.96% (range 0.77-1.05) of the baseline periods of the non-selective images, while BOLD signal decreased by 2.03% (range 1.99-2.93). In the adults, FAIR and BOLD signal increased by 0.88% (range 0.8-0.99) and 2.63% (range 1...

  18. A comparison of fMRI adaptation and multivariate pattern classification analysis in visual cortex.

    Science.gov (United States)

    Sapountzis, Panagiotis; Schluppeck, Denis; Bowtell, Richard; Peirce, Jonathan W

    2010-01-15

    Functional magnetic resonance imaging (fMRI) has become a ubiquitous tool in cognitive neuroscience. The technique allows noninvasive measurements of cortical responses in the human brain, but only on the millimeter scale. Because a typical voxel contains many thousands of neurons with varied properties, establishing the selectivity of their responses directly is impossible. In recent years, two methods using fMRI aimed at studying the selectivity of neuronal populations on a 'subvoxel' scale have been heavily used. The first technique, fMRI adaptation, relies on the observation that the blood oxygen level-dependent (BOLD) response in a given voxel is reduced after prolonged presentation of a stimulus, and that this reduction is selective to the characteristics of the repeated stimuli (adapters). The second technique, multivariate pattern analysis (MVPA), makes use of multivariate statistics to recover small biases in individual voxels in their responses to different stimuli. It is thought that these biases arise due to the uneven distribution of neurons (with different properties) sampled by the many voxels in the imaged volume. These two techniques have not been compared explicitly, however, and little is known about their relative sensitivities. Here, we compared fMRI results from orientation-specific visual adaptation and orientation-classification by MVPA, using optimized experimental designs for each, and found that the multivariate pattern classification approach was more sensitive to small differences in stimulus orientation than the adaptation paradigm. Estimates of orientation selectivity obtained with the two methods were, however, very highly correlated across visual areas.

  19. Impaired Activation of Visual Attention Network for Motion Salience Is Accompanied by Reduced Functional Connectivity between Frontal Eye Fields and Visual Cortex in Strabismic Amblyopia

    Directory of Open Access Journals (Sweden)

    Sheila G. Crewther

    2017-04-01

    Full Text Available Strabismic amblyopia is now acknowledged to be more than a simple loss of acuity and to involve alterations in visually driven attention, though whether this applies to both stimulus-driven and goal-directed attention has not been explored. Hence we investigated monocular threshold performance during a motion salience-driven attention task involving detection of a coherent dot motion target in one of four quadrants in adult controls and those with strabismic amblyopia. Psychophysical motion thresholds were impaired for the strabismic amblyopic eye, requiring longer inspection time and consequently slower target speed for detection compared to the fellow eye or control eyes. We compared fMRI activation and functional connectivity between four ROIs of the occipital-parieto-frontal visual attention network [primary visual cortex (V1, motion sensitive area V5, intraparietal sulcus (IPS and frontal eye fields (FEF], during a suprathreshold version of the motion-driven attention task, and also a simple goal-directed task, requiring voluntary saccades to targets randomly appearing along a horizontal line. Activation was compared when viewed monocularly by controls and the amblyopic and its fellow eye in strabismics. BOLD activation was weaker in IPS, FEF and V5 for both tasks when viewing through the amblyopic eye compared to viewing through the fellow eye or control participants' non-dominant eye. No difference in V1 activation was seen between the amblyopic and fellow eye, nor between the two eyes of control participants during the motion salience task, though V1 activation was significantly less through the amblyopic eye than through the fellow eye and control group non-dominant eye viewing during the voluntary saccade task. Functional correlations of ROIs within the attention network were impaired through the amblyopic eye during the motion salience task, whereas this was not the case during the voluntary saccade task. Specifically, FEF showed

  20. Visual cortex modulates the magnitude but not the selectivity of looming-evoked responses in the superior colliculus of awake mice.

    Science.gov (United States)

    Zhao, Xinyu; Liu, Mingna; Cang, Jianhua

    2014-10-01

    Neural circuits in the brain often receive inputs from multiple sources, such as the bottom-up input from early processing stages and the top-down input from higher-order areas. Here we study the function of top-down input in the mouse superior colliculus (SC), which receives convergent inputs from the retina and visual cortex. Neurons in the superficial SC display robust responses and speed tuning to looming stimuli that mimic approaching objects. The looming-evoked responses are reduced by almost half when the visual cortex is optogenetically silenced in awake, but not in anesthetized, mice. Silencing the cortex does not change the looming speed tuning of SC neurons, or the response time course, except at the lowest tested speed. Furthermore, the regulation of SC responses by the corticotectal input is organized retinotopically. This effect we revealed may thus provide a potential substrate for the cortex, an evolutionarily new structure, to modulate SC-mediated visual behaviors. Copyright © 2014 Elsevier Inc. All rights reserved.

  1. Modulation of synaptic transmission by adenosine in layer 2/3 of the rat visual cortex in vitro

    Science.gov (United States)

    Bannon, Nicholas; Zhang, Pei; Ilin, Vladimir; Chistiakova, Marina; Volgushev, Maxim

    2014-01-01

    Adenosine is a wide-spread endogenous neuromodulator. In the central nervous system it activates A1 and A2A receptors (A1Rs and A2ARs) which have differential distributions, different affinities to adenosine, are coupled to different G-proteins, and have opposite effects on synaptic transmission. Although effects of adenosine are studied in detail in several brain areas, such as hippocampus and striatum, the heterogeneity of the effects of A1R and A 2A R activation and their differential distribution preclude generalization over brain areas and cell types. Here we study adenosine's effects on excitatory synaptic transmission to layer 2/3 pyramidal neurons in slices of the rat visual cortex. We measured effects of bath application of adenosine receptor ligands on evoked EPSPs, miniature EPSPs (mEPSPs), and membrane properties. Adenosine reduced the amplitude of evoked EPSPs and EPSCs, and reduced frequency of mEPSPs in a concentration dependent and reversible manner. Concurrent with EPSP/C amplitude reduction was an increase in the paired-pulse ratio. These effects were blocked by application of the selective A1R antagonist DPCPX, suggesting that activation of presynaptic A1Rs suppresses excitatory transmission by reducing release probability. Adenosine (20 μM) hyperpolarized the cell membrane from 65.3±1.5 to -67.7±1.8 mV, and reduced input resistance from 396.5±44.4 to 314.0±36.3 MOhm (~20%). These effects were also abolished by DPCPX, suggesting postsynaptic A1Rs. Application of the selective A2AR antagonist SCH-58261 on the background of high adenosine concentrations revealed an additional decrease in EPSP amplitude. Moreover, application of the A2AR agonist CGS-21680 led to an A1R-dependent increase in mEPSP frequency. Dependence of the A2AR effects on the A1R availability suggests interaction between these receptors, whereby A2ARs exert their facilitatory effect on synaptic transmission by inhibiting the A1R mediated suppression. Our results demonstrate

  2. Corticothalamic projections from the primary visual cortex in rats: a single fiber study using biocytin as an anterograde tracer.

    Science.gov (United States)

    Bourassa, J; Deschênes, M

    1995-05-01

    This study investigates the pattern of axonal projections of single corticothalamic neurons from the rat primary visual cortex. Microiontophoretic injections of biocytin were made in cortical laminae V and VI to label small pools of corticothalamic cells and their intrathalamic axonal projections. After a survival period of 48 h, the animals were perfused and the tissue was processed for biocytin histochemistry. On the basis of the intrathalamic distribution of axonal fields and the types of terminations found in the thalamus, three types of corticothalamic projections were identified. (1) Cells of the upper part of lamina VI projected to the dorsal lateral geniculate nucleus where they arborized in rostrocaudally oriented bands or "rods" parallel to the lines of projection of retinal afferents. (2) Cells of the lower part of lamina VI projected to the lateral part of the lateral posterior nucleus and they also sent collaterals to the dorsal lateral geniculate nucleus where they participated in the formation of rods. (3) The corticothalamic projection of lamina V cells originated from collaterals of corticofugal cells whose main axons reached the tectum and/or the pontine nuclei. These collaterals never terminated within the dorsal lateral geniculate nucleus; they arborized in the lateral posterior, lateral dorsal and ventral lateral geniculate nuclei. All corticothalamic cells from lamina VI displayed the same type of axonal network made of long branches decorated by terminal boutons emitted "en passant" at the tip of fine stalks. Corticothalamic fibers arising from lamina V, however, generated varicose endings in restricted regions of their target nuclei. All corticothalamic axons derived from lamina VI cells, but not those derived from lamina V cells, gave off collaterals as they traversed the thalamic reticular complex. These results demonstrate that corticothalamic fibers arising from the rat primary visual cortex display a lamina-dependent projection pattern

  3. Gravity influences the visual representation of object tilt in parietal cortex.

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    Rosenberg, Ari; Angelaki, Dora E

    2014-10-22

    Sensory systems encode the environment in egocentric (e.g., eye, head, or body) reference frames, creating inherently unstable representations that shift and rotate as we move. However, it is widely speculated that the brain transforms these signals into an allocentric, gravity-centered representation of the world that is stable and independent of the observer's spatial pose. Where and how this representation may be achieved is currently unknown. Here we demonstrate that a subpopulation of neurons in the macaque caudal intraparietal area (CIP) visually encodes object tilt in nonegocentric coordinates defined relative to the gravitational vector. Neuronal responses to the tilt of a visually presented planar surface were measured with the monkey in different spatial orientations (upright and rolled left/right ear down) and then compared. This revealed a continuum of representations in which planar tilt was encoded in a gravity-centered reference frame in approximately one-tenth of the comparisons, intermediate reference frames ranging between gravity-centered and egocentric in approximately two-tenths of the comparisons, and in an egocentric reference frame in less than half of the comparisons. Altogether, almost half of the comparisons revealed a shift in the preferred tilt and/or a gain change consistent with encoding object orientation in nonegocentric coordinates. Through neural network modeling, we further show that a purely gravity-centered representation of object tilt can be achieved directly from the population activity of CIP-like units. These results suggest that area CIP may play a key role in creating a stable, allocentric representation of the environment defined relative to an "earth-vertical" direction. Copyright © 2014 the authors 0270-6474/14/3414170-11$15.00/0.

  4. Informative features of local field potential signals in primary visual cortex during natural image stimulation.

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    Seyedhosseini, Mojtaba; Shushruth, S; Davis, Tyler; Ichida, Jennifer M; House, Paul A; Greger, Bradley; Angelucci, Alessandra; Tasdizen, Tolga

    2015-03-01

    The local field potential (LFP) is of growing importance in neurophysiology as a metric of network activity and as a readout signal for use in brain-machine interfaces. However, there are uncertainties regarding the kind and visual field extent of information carried by LFP signals, as well as the specific features of the LFP signal conveying such information, especially under naturalistic conditions. To address these questions, we recorded LFP responses to natural images in V1 of awake and anesthetized macaques using Utah multielectrode arrays. First, we have shown that it is possible to identify presented natural images from the LFP responses they evoke using trained Gabor wavelet (GW) models. Because GW models were devised to explain the spiking responses of V1 cells, this finding suggests that local spiking activity and LFPs (thought to reflect primarily local synaptic activity) carry similar visual information. Second, models trained on scalar metrics, such as the evoked LFP response range, provide robust image identification, supporting the informative nature of even simple LFP features. Third, image identification is robust only for the first 300 ms following image presentation, and image information is not restricted to any of the spectral bands. This suggests that the short-latency broadband LFP response carries most information during natural scene viewing. Finally, best image identification was achieved by GW models incorporating information at the scale of ∼ 0.5° in size and trained using four different orientations. This suggests that during natural image viewing, LFPs carry stimulus-specific information at spatial scales corresponding to few orientation columns in macaque V1. Copyright © 2015 the American Physiological Society.

  5. A synchrony-dependent influence of sounds on activity in visual cortex measured using functional near-infrared spectroscopy (fNIRS).

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    Wiggins, Ian M; Hartley, Douglas E H

    2015-01-01

    Evidence from human neuroimaging and animal electrophysiological studies suggests that signals from different sensory modalities interact early in cortical processing, including in primary sensory cortices. The present study aimed to test whether functional near-infrared spectroscopy (fNIRS), an emerging, non-invasive neuroimaging technique, is capable of measuring such multisensory interactions. Specifically, we tested for a modulatory influence of sounds on activity in visual cortex, while varying the temporal synchrony between trains of transient auditory and visual events. Related fMRI studies have consistently reported enhanced activation in response to synchronous compared to asynchronous audiovisual stimulation. Unexpectedly, we found that synchronous sounds significantly reduced the fNIRS response from visual cortex, compared both to asynchronous sounds and to a visual-only baseline. It is possible that this suppressive effect of synchronous sounds reflects the use of an efficacious visual stimulus, chosen for consistency with previous fNIRS studies. Discrepant results may also be explained by differences between studies in how attention was deployed to the auditory and visual modalities. The presence and relative timing of sounds did not significantly affect performance in a simultaneously conducted behavioral task, although the data were suggestive of a positive relationship between the strength of the fNIRS response from visual cortex and the accuracy of visual target detection. Overall, the present findings indicate that fNIRS is capable of measuring multisensory cortical interactions. In multisensory research, fNIRS can offer complementary information to the more established neuroimaging modalities, and may prove advantageous for testing in naturalistic environments and with infant and clinical populations.

  6. A synchrony-dependent influence of sounds on activity in visual cortex measured using functional near-infrared spectroscopy (fNIRS.

    Directory of Open Access Journals (Sweden)

    Ian M Wiggins

    Full Text Available Evidence from human neuroimaging and animal electrophysiological studies suggests that signals from different sensory modalities interact early in cortical processing, including in primary sensory cortices. The present study aimed to test whether functional near-infrared spectroscopy (fNIRS, an emerging, non-invasive neuroimaging technique, is capable of measuring such multisensory interactions. Specifically, we tested for a modulatory influence of sounds on activity in visual cortex, while varying the temporal synchrony between trains of transient auditory and visual events. Related fMRI studies have consistently reported enhanced activation in response to synchronous compared to asynchronous audiovisual stimulation. Unexpectedly, we found that synchronous sounds significantly reduced the fNIRS response from visual cortex, compared both to asynchronous sounds and to a visual-only baseline. It is possible that this suppressive effect of synchronous sounds reflects the use of an efficacious visual stimulus, chosen for consistency with previous fNIRS studies. Discrepant results may also be explained by differences between studies in how attention was deployed to the auditory and visual modalities. The presence and relative timing of sounds did not significantly affect performance in a simultaneously conducted behavioral task, although the data were suggestive of a positive relationship between the strength of the fNIRS response from visual cortex and the accuracy of visual target detection. Overall, the present findings indicate that fNIRS is capable of measuring multisensory cortical interactions. In multisensory research, fNIRS can offer complementary information to the more established neuroimaging modalities, and may prove advantageous for testing in naturalistic environments and with infant and clinical populations.

  7. [Telemetry EEG of parietal association cortex in heroin-induced CPP rats].

    Science.gov (United States)

    Pan, Qun-Wan; Zhu, Zai-Man; Li, Jing; Li, Min; Zhou, Hong-Min

    2014-01-01

    To determine the relationship between EEG changes of parietal association cortex (PtA) and drug-seeking behaviors of heroin-induced conditioned place preference (CPP) rats. Stereotaxic electrode was buried in the PtA of rats, which were then divided randomly into heroin-induced CPP group and operation-only control group. A CPP video system in combination with EEG wireless telemetry was used for recording PtA EEG and the behaviors of the rats-staying in black or white chamber of the video box; shuttling between black-white chambers or between white-black chambers. No significant difference in percentage of the telemetry EEG waves was found between the two groups of rats when they stayed in the black or white chambers. The heroin-induced CPP rats had increased percentage of delta waves (P rats shuttled between white-black chambers. EEG changes on PtA of heroin-induced CPP rats differ between staying and shuttling states. Such changes may not be associated with drug-seeking behaviors.

  8. Object Representations in Human Visual Cortex Formed Through Temporal Integration of Dynamic Partial Shape Views.

    Science.gov (United States)

    Orlov, Tanya; Zohary, Ehud

    2018-01-17

    We typically recognize visual objects using the spatial layout of their parts, which are present simultaneously on the retina. Therefore, shape extraction is based on integration of the relevant retinal information over space. The lateral occipital complex (LOC) can represent shape faithfully in such conditions. However, integration over time is sometimes required to determine object shape. To study shape extraction through temporal integration of successive partial shape views, we presented human participants (both men and women) with artificial shapes that moved behind a narrow vertical or horizontal slit. Only a tiny fraction of the shape was visible at any instant at the same retinal location. However, observers perceived a coherent whole shape instead of a jumbled pattern. Using fMRI and multivoxel pattern analysis, we searched for brain regions that encode temporally integrated shape identity. We further required that the representation of shape should be invariant to changes in the slit orientation. We show that slit-invariant shape information is most accurate in the LOC. Importantly, the slit-invariant shape representations matched the conventional whole-shape representations assessed during full-image runs. Moreover, when the same slit-dependent shape slivers were shuffled, thereby preventing their spatiotemporal integration, slit-invariant shape information was reduced dramatically. The slit-invariant representation of the various shapes also mirrored the structure of shape perceptual space as assessed by perceptual similarity judgment tests. Therefore, the LOC is likely to mediate temporal integration of slit-dependent shape views, generating a slit-invariant whole-shape percept. These findings provide strong evidence for a global encoding of shape in the LOC regardless of integration processes required to generate the shape percept. SIGNIFICANCE STATEMENT Visual objects are recognized through spatial integration of features available simultaneously on

  9. Stress-induced cognitive dysfunction: hormone-neurotransmitter interactions in the prefrontal cortex

    Directory of Open Access Journals (Sweden)

    Rebecca M Shansky

    2013-04-01

    Full Text Available The mechanisms and neural circuits that drive emotion and cognition are inextricably linked. Activation of the hypothalamic-pituitary-adrenal (HPA axis as a result of stress or other causes of arousal initiates a flood of hormone and neurotransmitter release throughout the brain, affecting the way we think, decide, and behave. This review will focus on factors that influence the function of the prefrontal cortex (PFC, a brain region that governs higher-level cognitive processes and executive function. The PFC becomes markedly impaired by stress, producing measurable deficits in working memory. These deficits arise from the interaction of multiple neuromodulators, including glucocorticoids, catecholamines, and gonadal hormones; here we will discuss the non- human primate and rodent literature that has furthered our understanding of the circuitry, receptors, and signaling cascades responsible for stress-induced prefrontal dysfunction.

  10. SHR overexpression induces the formation of supernumerary cell layers with cortex cell identity in rice.

    Science.gov (United States)

    Henry, S; Dievart, A; Divol, F; Pauluzzi, G; Meynard, D; Swarup, R; Wu, S; Gallagher, K L; Périn, C

    2017-05-01

    The number of root cortex cell layers varies among plants, and many species have several cortical cell layers. We recently demonstrated that the two rice orthologs of the Arabidopsis SHR gene, OsSHR1 and OsSHR2, could complement the A. thaliana shr mutant. Moreover, OsSHR1 and OsSHR2 expression in A. thaliana roots induced the formation of extra root cortical cell layers. In this article, we demonstrate that the overexpression of AtSHR and OsSHR2 in rice roots leads to plants with wide and short roots that contain a high number of extra cortical cell layers. We hypothesize that SHR genes share a conserved function in the control of cortical cell layer division and the number of ground tissue cell layers in land plants. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. Impaired Functional Connectivity in the Prefrontal Cortex: A Mechanism for Chronic Stress-Induced Neuropsychiatric Disorders

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    Ignacio Negrón-Oyarzo

    2016-01-01

    Full Text Available Chronic stress-related psychiatric diseases, such as major depression, posttraumatic stress disorder, and schizophrenia, are characterized by a maladaptive organization of behavioral responses that strongly affect the well-being of patients. Current evidence suggests that a functional impairment of the prefrontal cortex (PFC is implicated in the pathophysiology of these diseases. Therefore, chronic stress may impair PFC functions required for the adaptive orchestration of behavioral responses. In the present review, we integrate evidence obtained from cognitive neuroscience with neurophysiological research with animal models, to put forward a hypothesis that addresses stress-induced behavioral dysfunctions observed in stress-related neuropsychiatric disorders. We propose that chronic stress impairs mechanisms involved in neuronal functional connectivity in the PFC that are required for the formation of adaptive representations for the execution of adaptive behavioral responses. These considerations could be particularly relevant for understanding the pathophysiology of chronic stress-related neuropsychiatric disorders.

  12. Transcranial direct current stimulation of the motor cortex in waking resting state induces motor imagery.

    Science.gov (United States)

    Speth, Jana; Speth, Clemens; Harley, Trevor A

    2015-11-01

    This study investigates if anodal and cathodal transcranial direct current stimulation (tDCS) of areas above the motor cortex (C3) influences spontaneous motor imagery experienced in the waking resting state. A randomized triple-blinded design was used, combining neurophysiological techniques with tools of quantitative mentation report analysis from cognitive linguistics. The results indicate that while spontaneous motor imagery rarely occurs under sham stimulation, general and athletic motor imagery (classified as athletic disciplines), is induced by anodal tDCS. This insight may have implications beyond basic consciousness research. Motor imagery and corresponding motor cortical activation have been shown to benefit later motor performance. Electrophysiological manipulations of motor imagery could in the long run be used for rehabilitative tDCS protocols benefitting temporarily immobile clinical patients who cannot perform specific motor imagery tasks - such as dementia patients, infants with developmental and motor disorders, and coma patients. Copyright © 2015 Elsevier Inc. All rights reserved.

  13. Figure and Ground in the Visual Cortex: V2 Combines Stereoscopic Cues with Gestalt Rules

    Science.gov (United States)

    Qiu, Fangtu T.; von der Heydt, Rüdiger

    2006-01-01

    Figure-ground organization is a process by which the visual system identifies some image regions as foreground and others as background, inferring three-dimensional (3D) layout from 2D displays. A recent study reported that edge responses of neurons in area V2 are selective for side-of-figure, suggesting that figure-ground organization is encoded in the contour signals (border-ownership coding). Here we show that area V2 combines two strategies of computation, one that exploits binocular stereoscopic information for the definition of local depth order, and another that exploits the global configuration of contours (gestalt factors). These are combined in single neurons so that the ‘near’ side of the preferred 3D edge generally coincides with the preferred side-of-figure in 2D displays. Thus, area V2 represents the borders of 2D figures as edges of surfaces, as if the figures were objects in 3D space. Even in 3D displays gestalt factors influence the responses and can enhance or null the stereoscopic depth information. PMID:15996555

  14. A wire length minimization approach to ocular dominance patterns in mammalian visual cortex

    Science.gov (United States)

    Chklovskii, Dmitri B.; Koulakov, Alexei A.

    2000-09-01

    The primary visual area (V1) of the mammalian brain is a thin sheet of neurons. Because each neuron is dominated by either right or left eye one can treat V1 as a binary mixture of neurons. The spatial arrangement of neurons dominated by different eyes is known as the ocular dominance (OD) pattern. We propose a theory for OD patterns based on the premise that they are evolutionary adaptations to minimize the length of intra-cortical connections. Thus, the existing OD patterns are obtained by solving a wire length minimization problem. We divide all the neurons into two classes: right- and left-eye dominated. We find that if the number of connections of each neuron with the neurons of the same class differs from that with the other class, the segregation of neurons into monocular regions indeed reduces the wire length. The shape of the regions depends on the relative number of neurons in the two classes. If both classes are equally represented we find that the optimal OD pattern consists of alternating stripes. If one class is less numerous than the other, the optimal OD pattern consists of patches of the underrepresented (ipsilateral) eye dominated neurons surrounded by the neurons of the other class. We predict the transition from stripes to patches when the fraction of neurons dominated by the ipsilateral eye is about 40%. This prediction agrees with the data in macaque and Cebus monkeys. Our theory can be applied to other binary cortical systems.

  15. Body-Selective Areas in the Visual Cortex are less active in Children than in Adults

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    Paddy D Ross

    2014-11-01

    Full Text Available Our ability to read other people’s non-verbal signals gets refined throughout childhood and adolescence. How this is paralleled by brain development has been investigated mainly with regards to face perception, showing a protracted functional development of the face-selective visual cortical areas. In view of the importance of whole-body expressions in interpersonal communication it is important to understand the development of brain areas sensitive to these social signals.Here we used functional magnetic resonance imaging (fMRI to compare brain activity in a group of 24 children (age 6-11 and 26 adults while they passively watched short videos of body or object movements. We observed activity in similar regions in both groups; namely the extra-striate body area (EBA, fusiform body area (FBA, posterior superior temporal sulcus (pSTS, amygdala and premotor regions. Adults showed additional activity in the inferior frontal gyrus. Within the main body-selective regions (EBA, FBA and pSTS, the strength and spatial extent of fMRI signal change was larger in adults than in children. Multivariate Bayesian analysis showed that the spatial pattern of neural representation within those regions did not change over age.Our results indicate, for the first time, that body perception, like face perception, is still maturing through the second decade of life.

  16. Culture differences in neural processing of faces and houses in the ventral visual cortex.

    Science.gov (United States)

    Goh, Joshua O S; Leshikar, Eric D; Sutton, Bradley P; Tan, Jiat Chow; Sim, Sam K Y; Hebrank, Andrew C; Park, Denise C

    2010-06-01

    Behavioral and eye-tracking studies on cultural differences have found that while Westerners have a bias for analytic processing and attend more to face features, East Asians are more holistic and attend more to contextual scenes. In this neuroimaging study, we hypothesized that these culturally different visual processing styles would be associated with cultural differences in the selective activity of the fusiform regions for faces, and the parahippocampal and lingual regions for contextual stimuli. East Asians and Westerners passively viewed face and house stimuli during an functional magnetic resonance imaging experiment. As expected, we observed more selectivity for faces in Westerners in the left fusiform face area (FFA) reflecting a more analytic processing style. Additionally, Westerners showed bilateral activity to faces in the FFA whereas East Asians showed more right lateralization. In contrast, no cultural differences were detected in the parahippocampal place area (PPA), although there was a trend for East Asians to show greater house selectivity than Westerners in the lingual landmark area, consistent with more holistic processing in East Asians. These findings demonstrate group biases in Westerners and East Asians that operate on perceptual processing in the brain and are consistent with previous eye-tracking data that show cultural biases to faces.

  17. Slow biasing of processing resources in early visual cortex is preceded by emotional cue extraction in emotion-attention competition.

    Science.gov (United States)

    Schönwald, Liane I; Müller, Matthias M

    2014-04-01

    In our previous studies on competition for attentional processing resources in early visual cortex between a foreground task and distracting emotional background images we found that emotional background images withdraw attentional resources from the foreground task after about 400 ms. Costs in behavioral data and a significant reduction of the steady state visual evoked potential (SSVEP) amplitude that was elicited by the foreground task lasted for several hundred milliseconds. We speculated that the differential effect in SSVEP amplitudes is preceded by the extraction of the emotional cue. Event related potential (ERP) studies to emotional and neutral complex images identified an early posterior negativity (EPN) as a robust neural signature of emotional cue extraction. The late positive potential (LPP) was related to in-depth processing of the emotional image. We extracted ERPs that were evoked by the onset of background images concurrently with the SSVEP that was elicited by the foreground task. Emotional compared to neutral background pictures evoked a more negative EPN at about 190 ms and a more positive LPP at about 700 ms after image onset. SSVEP amplitudes became significantly smaller with emotional background images after about 400 ms lasting for several hundred ms. Interestingly, we found no significant correlations between the three components, indicating that they act independently. Source localizations resulted in nonoverlapping cortical generators. Results suggest a cascade of perceptual processes: Extraction of the emotional cue preceded biasing of attentional resources away from the foreground task towards the emotional image for an evaluation of the picture content. Copyright © 2013 Wiley Periodicals, Inc.

  18. Visual cortex responses to single- and simultaneous multiple-electrode stimulation of the retina: implications for retinal prostheses.

    Science.gov (United States)

    Shivdasani, Mohit N; Fallon, James B; Luu, Chi D; Cicione, Rosemary; Allen, Penny J; Morley, John W; Williams, Chris E

    2012-09-19

    The aim of this study was to compare simultaneous stimulation of multiple electrodes to single-electrode stimulation in a retinal prosthesis. A platinum electrode array was implanted into the suprachoroidal space in six normally sighted anesthetized cats. Multiunit activity from the primary visual cortex in response to retinal stimulation was recorded. Cortical thresholds, yield of responses, dynamic ranges, and the spread of retinal activation were measured for three modes of stimulation: single electrode, half-row (six-electrode horizontal line), and column (seven-electrode vertical line). Stimulation of the best half-rows and columns was found to elicit activity with higher yield and lower charge thresholds per electrode compared to the best single electrodes. Dynamic ranges between the three modes were similar. As expected, peak voltages measured for columns and half-rows were lower than those measured for single electrodes. Spread of retinal activation, determined by the increase in threshold with distance in the retina from the best site, was found to be similar between single- and multiple-electrode stimulation but dependent on orientation. The lower thresholds, higher yield, equivalent dynamic ranges, and equivalent spread of retinal activation observed from simultaneous stimulation of multiple electrodes may be due to current and/or neural summation within the retina. Such stimulation techniques could be useful for the presentation of lines and edges of objects using a suprachoroidal retinal stimulator with low voltage compliance. Furthermore, the results suggest that more complex visual processing strategies in addition to sequential stimulation of individual electrodes should be considered for retinal prostheses.

  19. Characterization of high-resolution Gradient Echo and Spin Echo EPI for fMRI in the human visual cortex at 7T.

    Science.gov (United States)

    Rua, Catarina; Costagli, Mauro; Symms, Mark R; Biagi, Laura; Donatelli, Graziella; Cosottini, Mirco; Del Guerra, Alberto; Tosetti, Michela

    2017-07-01

    The increased signal-to-noise ratio (SNR) offered by functional Magnetic Resonance Imaging (fMRI) at 7T allows the acquisition of functional data at sub-millimetric spatial resolutions. However, simply reducing partial volume effects is not sufficient to precisely localize task-induced activation due to the indirect mechanisms that relate brain function and the changes in the measured signal. In this work T2* and T2 weighted Echo Planar Imaging (EPI) schemes based on Gradient Recalled Echo (GRE) and Spin Echo (SE) were evaluated in terms of temporal SNR, percent signal change, contrast to noise ratio (CNR), activation volume, and sensitivity and specificity to gray matter. Datasets were acquired during visual stimulation at in-plane resolutions ranging between 1.5×1.5mm(2) and 0.75×0.75mm(2) targeting the early visual cortex. While similar activation foci were obtained in all acquisitions, at in-plane resolutions of 1.0×1.0mm(2) and larger voxel sizes the T2 weighted contrast of SE-EPI allowed the identification of the activation site with better spatial accuracy. However, at sub-millimetric resolutions the decrease in temporal SNR significantly hampered the sensitivity and the extent of the activation site. On the other hand, high resolution T2* weighted data collected with GRE-EPI provided higher CNR and sensitivity, benefiting from the decreased physiological and partial volume effects. However, spurious activations originating from regions of blood drainage were still present in GRE data, and simple thresholding techniques were found to be inadequate for the removal of such contributions. The combination of 2-class and 3-class automated segmentations, performed directly in EPI space, allowed the selection of active voxels in gray matter. This approach could enable GRE-EPI to accurately map functional activity with satisfactory CNR and specificity to the true site of activation. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. The enhanced information flow from visual cortex to frontal area facilitates SSVEP response: evidence from model-driven and data-driven causality analysis

    Science.gov (United States)

    Li, Fali; Tian, Yin; Zhang, Yangsong; Qiu, Kan; Tian, Chunyang; Jing, Wei; Liu, Tiejun; Xia, Yang; Guo, Daqing; Yao, Dezhong; Xu, Peng

    2015-10-01

    The neural mechanism of steady-state visual evoked potentials (SSVEP) is still not clearly understood. Especially, only certain frequency stimuli can evoke SSVEP. Our previous network study reveals that 8 Hz stimulus that can evoke strong SSVEP response shows the enhanced linkage strength between frontal and visual cortex. To further probe the directed information flow between the two cortex areas for various frequency stimuli, this paper develops a causality analysis based on the inversion of double columns model using particle swarm optimization (PSO) to characterize the directed information flow between visual and frontal cortices with the intracranial rat electroencephalograph (EEG). The estimated model parameters demonstrate that the 8 Hz stimulus shows the enhanced directional information flow from visual cortex to frontal lobe facilitates SSVEP response, which may account for the strong SSVEP response for 8 Hz stimulus. Furthermore, the similar finding is replicated by data-driven causality analysis. The inversion of neural mass model proposed in this study may be helpful to provide the new causality analysis to link the physiological model and the observed datasets in neuroscience and clinical researches.

  1. Localization of Nitric Oxide Synthase-containing Neurons in the Bat Visual Cortex and Co-localization with Calcium-binding Proteins.

    Science.gov (United States)

    Gu, Ya-Nan; Kim, Hang-Gu; Jeon, Chang-Jin

    2015-08-27

    Microchiroptera (microbats) is a suborder of bats thought to have degenerated vision. However, many recent studies have shown that they have visual ability. In this study, we labeled neuronal nitric oxide synthase (nNOS)-the synthesizing enzyme of the gaseous non-synaptic neurotransmitter nitric oxide-and co-localized it with calbindin D28K (CB), calretinin (CR), and parvalbumin (PV) in the visual cortex of the greater horseshoe bat (Rhinolophus ferrumequinum, a species of microbats). nNOS-immunoreactive (IR) neurons were found in all layers of the visual cortex. Intensely labeled neurons were most common in layer IV, and weakly labeled neurons were most common in layer VI. Majority of the nNOS-IR neurons were round- or oval-type neurons; no pyramidal-type neurons were found. None of these neurons co-localized with CB, CR, or PV. However, the synthesis of nitric oxide in the bat visual cortex by nNOS does not depend on CB, CR, or PV.

  2. Intrinsic-signal optical imaging reveals cryptic ocular dominance columns in primary visual cortex of new world owl monkeys

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    Peter M Kaskan

    2007-10-01

    Full Text Available A significant concept in neuroscience is that sensory areas of the neocortex have evolved the remarkable ability to represent a number of stimulus features within the confines of a global map of the sensory periphery. Modularity, the term often used to describe the inhomogeneous nature of the neocortex, is without a doubt an important organizational principle of early sensory areas, such as the primary visual cortex (V1. Ocular dominance columns, one type of module in V1, are found in many primate species as well as in carnivores. Yet, their variable presence in some New World monkey species and complete absence in other species has been enigmatic. Here, we demonstrate that optical imaging reveals the presence of ocular dominance columns in the superficial layers of V1 of owl monkeys (Aotus trivirgatus, even though the geniculate inputs related to each eye are highly overlapping in layer 4. The ocular dominance columns in owl monkeys revealed by optical imaging are circular in appearance. The distance between left eye centers and right eye centers is approximately 650 µm. We find no relationship between ocular dominance centers and other modular organizational features such as orientation pinwheels or the centers of the cytochrome oxidase blobs. These results are significant because they suggest that functional columns may exist in the absence of obvious differences in the distributions of activating inputs and ocular dominance columns may be more widely distributed across mammalian taxa than commonly suggested.

  3. Evidence for Individual Face Discrimination in Non-Face Selective Areas of the Visual Cortex in Acquired Prosopagnosia

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    Laurence Dricot

    2008-01-01

    Full Text Available Two areas in the human occipito-temporal cortex respond preferentially to faces: ‘the fusiform face area’ (‘FFA’ and the ‘occipital face area’ (‘OFA’. However, it is unclear whether these areas have an exclusive role in processing faces, or if sub-maximal responses in other visual areas such as the lateral occipital complex (LOC are also involved. To clarify this issue, we tested a brain-damaged patient (PS presenting a face-selective impairment with functional magnetic resonance imaging (fMRI. The right hemisphere lesion of the prosoagnosic patient encompasses the ‘OFA’ but preserves the ‘FFA’ and LOC [14,16]. Using fMRI-adaptation, we found a larger response to different faces than repeated faces in the ventral part of the LOC both for normals and the patient, next to her right hemisphere lesion. This observation indicates that following prosopagnosia, areas that do not respond preferentially to faces such as the ventral part of the LOC (vLOC may still be recruited to subtend residual perception of individual faces.

  4. Evidence for Individual Face Discrimination in Non-Face Selective Areas of the Visual Cortex in Acquired Prosopagnosia

    Science.gov (United States)

    Dricot, Laurence; Sorger, Bettina; Schiltz, Christine; Goebel, Rainer; Rossion, Bruno

    2008-01-01

    Two areas in the human occipito-temporal cortex respond preferentially to faces: ‘the fusiform face area’ (‘FFA’) and the ‘occipital face area’ (‘OFA’). However, it is unclear whether these areas have an exclusive role in processing faces, or if sub-maximal responses in other visual areas such as the lateral occipital complex (LOC) are also involved. To clarify this issue, we tested a brain-damaged patient (PS) presenting a face-selective impairment with functional magnetic resonance imaging (fMRI). The right hemisphere lesion of the prosoagnosic patient encompasses the ‘OFA’ but preserves the ‘FFA’ and LOC [14,16]. Using fMRI-adaptation, we found a larger response to different faces than repeated faces in the ventral part of the LOC both for normals and the patient, next to her right hemisphere lesion. This observation indicates that following prosopagnosia, areas that do not respond preferentially to faces such as the ventral part of the LOC (vLOC) may still be recruited to subtend residual perception of individual faces. PMID:18413922

  5. Transcranial Stimulation of the Dorsolateral Prefrontal Cortex Prevents Stress-Induced Working Memory Deficits.

    Science.gov (United States)

    Bogdanov, Mario; Schwabe, Lars

    2016-01-27

    Stress is known to impair working memory performance. This disruptive effect of stress on working memory has been linked to a decrease in the activity of the dorsolateral prefrontal cortex (dlPFC). In the present experiment, we tested whether transcranial direct current stimulation (tDCS) of the dlPFC can prevent stress-induced working memory impairments. We tested 120 healthy participants in a 2 d, sham-controlled, double-blind between-subjects design. Participants completed a test of their individual baseline working memory capacity on day 1. On day 2, participants were exposed to either a stressor or a control manipulation before they performed a visuospatial and a verbal working memory task. While participants completed the tasks, anodal, cathodal, or sham tDCS was applied over the right dlPFC. Stress impaired working memory performance in both tasks, albeit to a lesser extent in the verbal compared with the visuospatial working memory task. This stress-induced working memory impairment was prevented by anodal, but not sham or cathodal, stimulation of the dlPFC. Compared with sham or cathodal stimulation, anodal tDCS led to significantly better working memory performance in both tasks after stress. Our findings indicate a causal role of the dlPFC in working memory impairments after acute stress and point to anodal tDCS as a promising tool to reduce cognitive deficits related to working memory in stress-related mental disorders, such as depression, schizophrenia, or post-traumatic stress disorder. Working memory deficits are prominent in stress-related mental disorders, such as depression, schizophrenia, or post-traumatic stress disorder. Similar working memory impairments have been observed in healthy individuals exposed to acute stress. So far, attempts to prevent such stress-induced working memory deficits focused mainly on pharmacological interventions. Here, we tested the idea that transcranial direct current stimulation of the dorsolateral prefrontal

  6. Effect of serotonin on paired associative stimulation-induced plasticity in the human motor cortex.

    Science.gov (United States)

    Batsikadze, Giorgi; Paulus, Walter; Kuo, Min-Fang; Nitsche, Michael A

    2013-10-01

    Serotonin modulates diverse brain functions. Beyond its clinical antidepressant effects, it improves motor performance, learning and memory formation. These effects might at least be partially caused by the impact of serotonin on neuroplasticity, which is thought to be an important foundation of the respective functions. In principal accordance, selective serotonin reuptake inhibitors enhance long-term potentiation-like plasticity induced by transcranial direct current stimulation (tDCS) in humans. As other neuromodulators have discernable effects on different kinds of plasticity in humans, here we were interested to explore the impact of serotonin on paired associative stimulation (PAS)-induced plasticity, which induces a more focal kind of plasticity, as compared with tDCS, shares some features with spike timing-dependent plasticity, and is thought to be relative closely related to learning processes. In this single-blinded, placebo-controlled, randomized crossover study, we administered a single dose of 20 mg citalopram or placebo medication and applied facilitatory- and excitability-diminishing PAS to the left motor cortex of 14 healthy subjects. Cortico-spinal excitability was explored via single-pulse transcranial magnetic stimulation-elicited MEP amplitudes up to the next evening after plasticity induction. After citalopram administration, inhibitory PAS-induced after-effects were abolished and excitatory PAS-induced after-effects were enhanced trendwise, as compared with the respective placebo conditions. These results show that serotonin modulates PAS-induced neuroplasticity by shifting it into the direction of facilitation, which might help to explain mechanism of positive therapeutic effects of serotonin in learning and medical conditions characterized by enhanced inhibitory or reduced facilitatory plasticity, including depression and stroke.

  7. [Retinotopic organization of the human visual cortex: a 3T fMRI study].

    Science.gov (United States)

    Hoffart, L; Conrath, J; Matonti, F; Galland, F; Wotawa, N; Chavane, F; Castet, E; Ridings, B; Masson, G S

    2007-10-01

    INTRODUCTION. We used high-field (3T) functional magnetic resonance imaging (fMRI) to map the retinotopic organization of human cortical areas. Retinotopic maps were reconstructed using existing mapping techniques. Stimuli were made of a rotating wedge stimulus, which provided angular coordinate maps, and an expanding or contracting ring, which provided eccentricity coordinate maps. Stimuli consisted of a grey background alternating with a flickering checkerboard. A Brucker 3T scanner equipped with a head coil and a custom optical system was used to acquire sets of echoplanar images of 20 occipital coronal slices within a RT of 2.111 ms and an 8 mm3 voxel resolution. Surface models of each subject's occipital lobes were constructed using the Brainvisa software from a sagittal T1-weighted image with a 1 mm3 voxel resolution. The cortical models were then inflated to obtain unfolded surfaces. Statistical analyses of the functional data were made under SPM99, and the response amplitudes were finally assigned to the cortical reconstructed surfaces. We identified boundaries between different early visual areas (V1, V2, V3) using eccentricity and polar angle retinotopic maps and detection of reversals in the representation of the polar angle. Both complete maps and reversals corresponding to the V1/V2 borders were clearly visible with a single recording session. Also, we were able to compare data from subjects across various fMRI acquisitions and found that there was a strong correlation between maps acquired at different sessions for the same subject. We developed a quick (mapping method at 3T, which makes it possible to study the cortical remapping in patients with retinal scotomas.

  8. Heterogenous migraine aura symptoms correlate with visual cortex functional magnetic resonance imaging responses

    DEFF Research Database (Denmark)

    Arngrim, Nanna; Hougaard, Anders; Ahmadi, Khazar

    2017-01-01

    Objective: Migraine aura is sparsely studied due to the highly challenging task of capturing patients during aura. Cortical spreading depression (CSD) is likely the underlying phenomenon of aura. The possible correlation between the multifaceted phenomenology of aura symptoms and the effects of CSD...... on the brain has not been ascertained. Methods: Five migraine patients were studied during various forms of aura symptoms induced by hypoxia, sham hypoxia, or physical exercise with concurrent photostimulation. The blood oxygenation level–dependent (BOLD) functional magnetic resonance imaging (fMRI) signal...... corresponding bihemispherical changes in BOLD response. Interpretation: These findings suggest that different aura symptoms reflect different types of cerebral dysfunction, which correspond to specific changes in BOLD signal reactivity. Furthermore, we provide evidence of bilateral CSD recorded by fMRI during...

  9. A causal role for posterior medial frontal cortex in choice-induced preference change.

    Science.gov (United States)

    Izuma, Keise; Akula, Shyam; Murayama, Kou; Wu, Daw-An; Iacoboni, Marco; Adolphs, Ralph

    2015-02-25

    After a person chooses between two items, preference for the chosen item will increase and preference for the unchosen item will decrease because of the choice made. In other words, we tend to justify or rationalize our past behavior by changing our attitude. This phenomenon of choice-induced preference change has been traditionally explained by cognitive dissonance theory. Choosing something that is disliked or not choosing something that is liked are both cognitively inconsistent and, to reduce this inconsistency, people tend to change their subsequently stated preference in accordance with their past choices. Previously, human neuroimaging studies identified posterior medial frontal cortex (pMFC) as a key brain region involved in cognitive dissonance. However, it remains unknown whether the pMFC plays a causal role in inducing preference change after cognitive dissonance. Here, we demonstrate that 25 min, 1 Hz repetitive transcranial magnetic stimulation applied over the pMFC significantly reduces choice-induced preference change compared with sham stimulation or control stimulation over a different brain region, demonstrating a causal role for the pMFC. Copyright © 2015 the authors 0270-6474/15/353598-09$15.00/0.

  10. Prenatal phencyclidine treatment induces behavioral deficits through impairment of GABAergic interneurons in the prefrontal cortex