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Sample records for cat visual cortex

  1. Cortical response field dynamics in cat visual cortex.

    Science.gov (United States)

    Sharon, Dahlia; Jancke, Dirk; Chavane, Frédéric; Na'aman, Shmuel; Grinvald, Amiram

    2007-12-01

    Little is known about the "inverse" of the receptive field--the region of cortical space whose spatiotemporal pattern of electrical activity is influenced by a given sensory stimulus. We refer to this activated area as the cortical response field, the properties of which remain unexplored. Here, the dynamics of cortical response fields evoked in visual cortex by small, local drifting-oriented gratings were explored using voltage-sensitive dyes. We found that the cortical response field was often characterized by a plateau of activity, beyond the rim of which activity diminished quickly. Plateau rim location was largely independent of stimulus orientation. However, approximately 20 ms following plateau onset, 1-3 peaks emerged on it and were amplified for 25 ms. Spiking was limited to the peak zones, whose location strongly depended on stimulus orientation. Thus, alongside selective amplification of a spatially restricted suprathreshold response, wider activation to just below threshold encompasses all orientation domains within a well-defined retinotopic vicinity of the current stimulus, priming the cortex for processing of subsequent stimuli. PMID:17395608

  2. Effect of Contrast on Visual Spatial Summation in Different Cell Categories in Cat Primary Visual Cortex.

    Directory of Open Access Journals (Sweden)

    Ke Chen

    Full Text Available Multiple cell classes have been found in the primary visual cortex, but the relationship between cell types and spatial summation has seldom been studied. Parvalbumin-expressing inhibitory interneurons can be distinguished from pyramidal neurons based on their briefer action potential durations. In this study, we classified V1 cells into fast-spiking units (FSUs and regular-spiking units (RSUs and then examined spatial summation at high and low contrast. Our results revealed that the excitatory classical receptive field and the suppressive non-classical receptive field expanded at low contrast for both FSUs and RSUs, but the expansion was more marked for the RSUs than for the FSUs. For most V1 neurons, surround suppression varied as the contrast changed from high to low. However, FSUs exhibited no significant difference in the strength of suppression between high and low contrast, although the overall suppression decreased significantly at low contrast for the RSUs. Our results suggest that the modulation of spatial summation by stimulus contrast differs across populations of neurons in the cat primary visual cortex.

  3. Neurochemical correlates of. gamma. -aminobutyrate (GABA) inhibition in cat visual cortex

    Energy Technology Data Exchange (ETDEWEB)

    Balcar, V.J.; Dreher, B. (Univ. of Sydney (Australia))

    1990-01-01

    High affinity binding of ({sup 3}H){gamma}-aminobutyric acid (GABA) to neuronal membranes from different parts of cat visual cortex was tested for sensitivity to GABA{sub A} agonists isoguvacine and THIP, GABA{sub A} antagonist SR95531 and GABA{sub B} agonist baclofen. Some of the GABA{sub A}-binding sites were found to have a very low affinity for THIP, suggesting the presence and, possibly, uneven distribution of non-synaptic GABA{sub A} receptors in cat visual cortex. There were no differences in K{sub m} and V{sub max} values of high affinity uptake of GABA and in the potency of K{sup +}-stimulated release of GABA, between primary and association cortices. Consequently, the present results indicate that despite the anatomical and physiological differences between the primary and association feline visual cortices the neurochemical characteristics of GABAergic inhibition are very similar in the two regions.

  4. Neurochemical correlates of γ-aminobutyrate (GABA) inhibition in cat visual cortex

    International Nuclear Information System (INIS)

    High affinity binding of [3H]γ-aminobutyric acid (GABA) to neuronal membranes from different parts of cat visual cortex was tested for sensitivity to GABAA agonists isoguvacine and THIP, GABAA antagonist SR95531 and GABAB agonist baclofen. Some of the GABAA-binding sites were found to have a very low affinity for THIP, suggesting the presence and, possibly, uneven distribution of non-synaptic GABAA receptors in cat visual cortex. There were no differences in Km and Vmax values of high affinity uptake of GABA and in the potency of K+-stimulated release of GABA, between primary and association cortices. Consequently, the present results indicate that despite the anatomical and physiological differences between the primary and association feline visual cortices the neurochemical characteristics of GABAergic inhibition are very similar in the two regions

  5. Directional tunings independent of orientation in the primary visual cortex of the cat

    Institute of Scientific and Technical Information of China (English)

    CHEN; Yao(

    2001-01-01

    [1]Movshon. J. A., Adelson, E. H., Gizzi, M. S. et al., The analysis of moving visual patterns, in Pattern Recognition Mechanisms (eds. Chagas, C., Gattass, R., Gross, C. G.), Vatican City: Ponticifica Academia Scientiarum, 1985, 117-151.[2]Gizzi. M. S., Katz, E., Schumer, R. A. et al., Selectivity for orientation and direction of motion of single neurons in cat striate and extrastriate visual cortex, J. Neurophysiol., 1990, 63: 1529-1543.[3]Nakayama, K., Silverman, G. H., The aperture problem. Ⅱ. Spatial integration of velocity information along contours, Vision Res., 1988, 28: 747-753.[4]Rubin. N., Hochstein, S., Solomon, S., Restricted ability to recover three-dimensional global motion from one-dimensional motion signals: Psychophysical observations, Vision Res., 1995, 35: 463-476.[5]Wang. Y., Wang, L., Li, B. et al., How is direction selectivity organized in the extrastriate visual area PMLS of the cat?Neuroreport, 1995, 63: 1969-1974.[6]Li, B., Wang, L, Wang, Y. et al,, Orientational and directional selectivities of visual neurons in the superior colliculus of the cat. Science in China, Ser. C, 1996, 39 (2): 123-132.[7]Hubel, D. H., Wiesel, T N., Receptive fields, binocular interaction and functional architecture in the cat's visual cortex, J.Physiol. (London), 1962, 168: 106-154.[8]Casanova, C., Savard, T., Nordmann, J. P. et al., Comparison of the responses to moving texture patterns of simple and complex cells in the cat's area 17, J. Neurophysiol., 1995, 74: 1271-1286.[9]Yang, J. K., Qi, X. L., Modem Biological Statistics (in Chinese), Hefei: Anhui Educational Publication, 1985, 160-215.[10]Shipp, S., Grant, S., Organization of reciprocal connections between area 17 and the lateral suprasylvian area of cat visual cortex, Visual Neurosci., 1991, 6: 339-355.[11]Albright, T. D., Stoner, G. R., Visual motion perception, Proc. Natl. Acad. Sci. USA, 1995, 92: 2433-2440.[12]Hammond, R, MacKay, D. M

  6. Directional tunings independent of orientation in the primary visual cortex of the cat

    Institute of Scientific and Technical Information of China (English)

    陈垚; 李兵; 李宝旺; 刁云程

    2001-01-01

    A family of moving ‘random-line' patterns was developed and used to study the directional tuning of 91 single units in cat primary visual cortex (V1). The results suggest that, in addition to the well-known orientation-dependent mechanism, there is also some kind of orientation-independent mechanism underlying the direction selectivity. The directional tuning of the neurons varies in accordance with the increase of orientation or non-orientation element in the stimulus.

  7. Absolute Depth Sensitivity in Cat Primary Visual Cortex under Natural Viewing Conditions.

    Science.gov (United States)

    Pigarev, Ivan N; Levichkina, Ekaterina V

    2016-01-01

    Mechanisms of 3D perception, investigated in many laboratories, have defined depth either relative to the fixation plane or to other objects in the visual scene. It is obvious that for efficient perception of the 3D world, additional mechanisms of depth constancy could operate in the visual system to provide information about absolute distance. Neurons with properties reflecting some features of depth constancy have been described in the parietal and extrastriate occipital cortical areas. It has also been shown that, for some neurons in the visual area V1, responses to stimuli of constant angular size differ at close and remote distances. The present study was designed to investigate whether, in natural free gaze viewing conditions, neurons tuned to absolute depths can be found in the primary visual cortex (area V1). Single-unit extracellular activity was recorded from the visual cortex of waking cats sitting on a trolley in front of a large screen. The trolley was slowly approaching the visual scene, which consisted of stationary sinusoidal gratings of optimal orientation rear-projected over the whole surface of the screen. Each neuron was tested with two gratings, with spatial frequency of one grating being twice as high as that of the other. Assuming that a cell is tuned to a spatial frequency, its maximum response to the grating with a spatial frequency twice as high should be shifted to a distance half way closer to the screen in order to attain the same size of retinal projection. For hypothetical neurons selective to absolute depth, location of the maximum response should remain at the same distance irrespective of the type of stimulus. It was found that about 20% of neurons in our experimental paradigm demonstrated sensitivity to particular distances independently of the spatial frequencies of the gratings. We interpret these findings as an indication of the use of absolute depth information in the primary visual cortex.

  8. [Effects of ketamine and urethane on stimulation-induced c-fos expression in neurons of cat visual cortex].

    Science.gov (United States)

    Wang, Ke; Zhu, Hui; Chen, Cui-Yun; Li, Peng; Jin, Cai-Hong; Wang, Zi-Lu; Jiang, San; Hua, Tian-Miao

    2013-12-01

    The effects of ketamine and urethane on neuronal activities remain in debate. As a member of immediate early genes family, the expression of c-fos is stimulation dependent and could be treated as an index to evaluate the strength of neural activities. In this study, SABC immunohistochemical techniques were applied to compare the c-fos expression in neurons of the primary visual cortex (V1) of cats and therefore, to evaluate the effects of acute anesthesia with ketamine HCl and uethane on inhibiting neural activities. Our results showed that compared with control cats, there were no significant differences with the average densities of Nissl-stained V1 neurons in each cortical layers of either urethane or ketamine anesthetized cats. In urethane anesthetized cats, neither the average densities nor the immunoreactive intensities of c-fos positive V1 neurons showed significant difference with that of control ones. However, both the average densities and immunoreactive intensities of c-fos positive V1 neurons in ketamine anesthetized cats decreased significantly compared with that of control and urethane anesthetized cats. These results suggested that ketamine has strong inhibitory effects on the activities of visual cortical neurons, whereas urethane did not. PMID:24415690

  9. 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.

  10. A Postnatal Critical Period for Orientation Plasticity in the Cat Visual Cortex

    OpenAIRE

    Shigeru Tanaka; Toshiki Tani; Jérôme Ribot; Kazunori O'Hashi; Kazuyuki Imamura

    2009-01-01

    Orientation selectivity of primary visual cortical neurons is an important requisite for shape perception. Although numerous studies have been previously devoted to a question of how orientation selectivity is established and elaborated in early life, how the susceptibility of orientation plasticity to visual experience changes in time remains unclear. In the present study, we showed a postnatal sensitive period profile for the modifiability of orientation selectivity in the visual cortex of ...

  11. The Emergence of Contrast-Invariant Orientation Tuning in Simple Cells of Cat Visual Cortex

    OpenAIRE

    Finn, Ian M.; Priebe, Nicholas J.; Ferster, David

    2007-01-01

    Simple cells in primary visual cortex exhibit contrast-invariant orientation tuning, in seeming contradiction to feed-forward models relying on lateral geniculate nucleus (LGN) input alone. Contrast invariance has therefore been thought to depend on the presence of intracortical lateral inhibition. In vivo intracellular recordings instead suggest that contrast invariance can be explained by three properties of the excitatory pathway. 1) Depolarizations evoked by orthogonal stimuli are determi...

  12. Interplay of orientation selectivity and the power of low- and high-gamma bands in the cat primary visual cortex.

    Science.gov (United States)

    Bharmauria, Vishal; Bachatene, Lyes; Ouelhazi, Afef; Cattan, Sarah; Chanauria, Nayan; Etindele-Sosso, Faustin Armel; Rouat, Jean; Molotchnikoff, Stéphane

    2016-05-01

    Gamma oscillations are ubiquitous in brain and are believed to be inevitable for information processing in brain. Here, we report that distinct bands (low, 30-40Hz and high gamma, 60-80Hz) of stimulus-triggered gamma oscillations are systematically linked to the orientation selectivity index (OSI) of neurons in the cat primary visual cortex. The gamma-power is high for the highly selective neurons in the low-gamma band, whereas it is high for the broadly selective neurons in the high-gamma band. We suggest that the low-gamma band is principally implicated in feed-forward excitatory flow, whereas the high-gamma band governs the flow of this excitation. PMID:27033667

  13. Synchrony between orientation-selective neurons is modulated during adaptation-induced plasticity in cat visual cortex

    Directory of Open Access Journals (Sweden)

    Shumikhina Svetlana

    2008-07-01

    Full Text Available Abstract Background Visual neurons respond essentially to luminance variations occurring within their receptive fields. In primary visual cortex, each neuron is a filter for stimulus features such as orientation, motion direction and velocity, with the appropriate combination of features eliciting maximal firing rate. Temporal correlation of spike trains was proposed as a potential code for linking the neuronal responses evoked by various features of a same object. In the present study, synchrony strength was measured between cells following an adaptation protocol (prolonged exposure to a non-preferred stimulus which induce plasticity of neurons' orientation preference. Results Multi-unit activity from area 17 of anesthetized adult cats was recorded. Single cells were sorted out and (1 orientation tuning curves were measured before and following 12 min adaptation and 60 min after adaptation (2 pairwise synchrony was measured by an index that was normalized in relation to the cells' firing rate. We first observed that the prolonged presentation of a non-preferred stimulus produces attractive (58% and repulsive (42% shifts of cell's tuning curves. It follows that the adaptation-induced plasticity leads to changes in preferred orientation difference, i.e. increase or decrease in tuning properties between neurons. We report here that, after adaptation, the neuron pairs that shared closer tuning properties display a significant increase of synchronization. Recovery from adaptation was accompanied by a return to the initial synchrony level. Conclusion We conclude that synchrony reflects the similarity in neurons' response properties, and varies accordingly when these properties change.

  14. Noise-improved signal detection in cat primary visual cortex via a well-balanced stochastic resonance-like procedure.

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    Funke, Klaus; Kerscher, Nicolas J; Wörgötter, Florentin

    2007-09-01

    Adding noise to a weak signal can paradoxically improve signal detection, a process called 'stochastic resonance' (SR). In the visual system, noise might be introduced by the image jitter resulting from high-frequency eye movements, like eye microtremor and microsaccades. To test whether this kind of noise might be beneficial or detrimental for cortical signal detection, we performed single-unit recordings from area 17 of anaesthetized cats while jittering the visual stimulus in a frequency and amplitude range resembling the possible range of eye movements. We used weak, sub- and peri-threshold visual stimuli, on top of which we superimposed noise with variable jitter amplitude. In accordance with the typical SR effect, we found that small noise levels actually increased the signal-to-noise ratio (SNR) of previously weak cortical visual responses, while originally strong responses were little affected or even reduced. Above a certain noise level, the SNR dropped a little, but not as a result of increased background activity - as would be proposed by SR theory - but because of a lowered response to signal and noise. Therefore, it seems that the ascending visual pathway optimally utilizes signal detection improvement by a SR-like process, while at the same time preventing spurious noise-induced activity and keeping the SNR sufficiently high.

  15. Spatial dynamics of receptive fields in cat primary visual cortex related to the temporal structure of thalamocortical feedforward activity. Experiments and models.

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    Suder, Katrin; Funke, Klaus; Zhao, Yongqiang; Kerscher, Nicolas; Wennekers, Thomas; Wörgötter, Florentin

    2002-06-01

    We investigated how changes in the temporal firing rate of thalamocortical activity affect the spatiotemporal structure of receptive field (RF) subunits in cat primary visual cortex. Spike activity of 67 neurons (48 simple, 19 complex cells) was extracellulary recorded from area 17/18 of anesthetized and paralyzed cats. A total of 107 subfields (on/off) were mapped by applying a reverse correlation technique to the activity elicited by bright and dark rectangles flashed for 300 ms in a 20x10 grid. We found that the width of the (suprathreshold) discharge fields shrank on average by 22% during this 300-ms-long stimulus presentation time. Fifty-eight subfields (54%) shrank by more than 20% of peak width and only ten (less than 10%) showed a slight increase over time. The main size reduction took place 40-60 ms after response onset, which corresponded to the transition from transient peak firing to tonic visual activity in thalamocortical relay cells (TC). The experimentally obtained RFs were then fitted with the aid of a neural field model of the primary visual pathway. Assuming a Gaussian-shaped spatial sensitivity profile across the RF subfield width, the model allowed us to estimate the subthreshold RF (depolarization field, D-field) from the minimal discharge field (MDF). The model allowed us to test to what degree the temporal dynamics of thalamocortical activity contributes to the spatiotemporal changes of cortical RFs. To this end, we performed the fitting procedure either with a pure feedforward model or with a field model that also included intracortical feedback. Spatial and temporal parameters obtained from fits of the experimental RFs matched closely to those achieved by simulating a pure feedforward system with the field model but were not compatible with additional intracortical feedback. Thus, our results show that dot stimulation, which optimally excites thalamocortical cells, leads to a shrinkage with respect to the size of the RF subfield at the

  16. Population Receptive Field Dynamics in Human Visual Cortex

    NARCIS (Netherlands)

    Haak, Koen V.; Cornelissen, Frans W.; Morland, Antony B.

    2012-01-01

    Seminal work in the early nineties revealed that the visual receptive field of neurons in cat primary visual cortex can change in location and size when artificial scotomas are applied. Recent work now suggests that these single neuron receptive field dynamics also pertain to the neuronal population

  17. Orientation-tuned surround suppression in mouse visual cortex

    NARCIS (Netherlands)

    Self, Matthew W; Lorteije, Jeannette A M; Vangeneugden, Joris; van Beest, Enny H; Grigore, Mihaela E; Levelt, Christiaan N; Heimel, J.A.; Roelfsema, Pieter R

    2014-01-01

    The firing rates of neurons in primary visual cortex (V1) are suppressed by large stimuli, an effect known as surround suppression. In cats and monkeys, the strength of suppression is sensitive to orientation; responses to regions containing uniform orientations are more suppressed than those contai

  18. Age-related changes of structures in cerebellar cortex of cat

    Indian Academy of Sciences (India)

    Changzheng Zhang; Tianmiao Hua; Zaiman Zhu; Xun Luo

    2006-03-01

    We studied the structures of the cerebellar cortex of young adult and old cats for age-related changes, which were statistically analysed. Nissl staining was used to visualize the cortical neurons. The immunohistochemical method was used to display glial fibrillary acidic protein (GFAP)-immunoreactive (IR) astrocytes and neurofilament-immunoreactive (NF-IR) neurons. Under the microscope, the thickness of the cerebellar cortex was measured; and the density of neurons in all the layers as well as that of GFAP-IR cells in the granular layer was analysed. Compared with young adult cats, the thickness of the molecular layer and total cerebellar cortex was significantly decreased in old cats, and that of the granular layer increased. The density of neurons in each layer was significantly lower in old cats than in young adult ones. Astrocytes in old cats were significantly denser than in young adult ones, and accompanied by evident hypertrophy of the cell bodies and enhanced immunoreaction of GFAP substance. Purkinje cells (PCs) in old cats showed much fewer NF-IR dendrites than those in young adults. The above findings indicate a loss of neurons and decrease in the number of dendrites of the PCs in the aged cerebellar cortex, which might underlie the functional decline of afferent efficacy and information integration in the senescent cerebellum. An age-dependent enhancement of activity of the astrocytes may exert a protective effect on neurons in the aged cerebellum.

  19. Influence of the midbrain reticular formation irradiation with luminescent incoherent light on evoked potential of cerebral cortex in cats

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    Malinovskaya, Svetlana L.; Abakarov, Asadulla; Monich, Victor A.

    1996-11-01

    In acute experiments on cats it is shown, that direct, of- low-intensity incoherent light exposure on midbrain reticular formation, cases brain cortex projection areas functional state changes, which find expression in shifting amplitude of both positive and negative components of cortex evoked potentials on visual stimuli.

  20. Expression of NogoA in 21a area of visual cortex in visual developing normal cat and strabismic amblyopia cat%NogoA在视觉发育期正常猫和斜视性弱视猫视皮层21a区的表达

    Institute of Scientific and Technical Information of China (English)

    郭珍; 刘冰; 林锦镛; 赵堪兴

    2012-01-01

    Background The study of the molecular mechanism of visual plasticity is helpful for the explaining and prevention of strabismus and amblyopia.The effect and significance of NogoA in the strabismus and amblyopia formation are attracting more attention. Objective The present study was to investigate the expression of NogoA in 21a area of visual cortex in strabismic-induced amblyopia cats and explore the possible molecular mechanism of strabismic-induced amblyopia. Methods Sixteen 4-week old clean cats were randomizedly divided into normal group and strabismic-induced amblyopia group and eight for each group.The strabismic-induced amblyopia models were created by cutting off the external rectus in 8 cats.Pattern visual evoked potentials ( P-VEP ) were recorded 1 week after operation and compared with normal cats,and depression of amplitude and prolongation of implied time of P100 wave were as the successful criterion of model.The 200 ml paraformaldehyde was infused via heart to fax the brain under the deep anesthesia and then the cats were sacrificed and the brain cortex sections were prepared.The morphology of 21a zone of cat visual cortex was examined by haematoxylin and eosin staining,and the expressions of NogoA in 21a area of visual cortex were detected by immunohistochemistry with a monoclonal antiNogoA antibody.The use of the animals complied with the Regulations for the Administration of Affair Concerning Experimental Animals by State Science and Technology Commission. Results The implied time and amplitude ratio of VEP P100 wave were (98.10±7.07)ms and (0.83±0.14) in normal group,and those in strabismic-induced amblyopia group were (108.50±6.95 )ms and (0.35 ±0.09 ),showing significant differences between two groups (t=4.450,P=0.005 ; t =5.970,P =0.005 ).The numbers of neurons were similar in 21a area of visual cortex between the two groups,but the volume of the neurons was lessen in strabismic-induced amblyopia group.The positive cell densities for Nogo

  1. Visual discrimination learning under switching procedure in visually deprived cats.

    Science.gov (United States)

    Zernicki, B

    1999-04-01

    Previous studies have shown that fine visual discrimination learning is severely impaired in cats binocularly deprived in the early period of life (BD cats) and also somewhat in control cats reared with open eyes in the limited laboratory environment (C cats) compared with cats reared in a normal rural environment (N cats). It was concluded that visual deprivation impairs perceptual learning. In the present study discriminative stimuli were dissimilar and so the task was perceptually easy, but using a switching procedure made it associatively difficult. In regular trials a gate with a grating pattern was positive and a blank gate negative, whereas in switching trials the meaning of the gates was reversed. The switching stimulus was intermittent light in some stages of training and intermittent tone in others. Learning was severely impaired in BD cats and somewhat in C cats and the deficit was similar under visual and auditory switching. Thus, early visual deprivation impairs associative learning. The impairment probably includes associations between switching stimulus and instrumental responses and configural associations between switching stimulus and discriminative stimuli. PMID:10212071

  2. Orientation-tuned surround suppression in mouse visual cortex

    OpenAIRE

    Self, Matthew W.; Lorteije, Jeannette A. M.; Vangeneugden, Joris; van Beest, Enny H; Grigore, Mihaela E; Levelt, Christiaan N.; Heimel, J.A.; Roelfsema, Pieter R.

    2014-01-01

    The firing rates of neurons in primary visual cortex (V1) are suppressed by large stimuli, an effect known as surround suppression. In cats and monkeys, the strength of suppression is sensitive to orientation; responses to regions containing uniform orientations are more suppressed than those containing orientation contrast. This effect is thought to be important for scene segmentation, but the underlying neural mechanisms are poorly understood. We asked whether it is possible to study these ...

  3. 硬脑膜上微电极植入并记录家猫视皮层电活动%Recording visual cortex electrical activity through flexible microelectrode array implanted on duramater endocranium of cats

    Institute of Scientific and Technical Information of China (English)

    刘娜; 石卫卫; 陈丽峰; 侯文生; 阴正勤

    2011-01-01

    目的 建立初级视皮层区硬脑膜上柔性微电极阵列记录视皮层电活动的方法,比较黑白棋盘格图形和黑白闪烁刺激在诱发视觉诱发电位(visual evoked potential,VEP)方面的差异.方法 成年健康家猫5只,静脉持续麻醉,肌松、呼吸机人工通气,采用自行设计的柔性微电极阵列,微创植入并固定于视皮层定位区的硬脑膜上.比较无视觉刺激和有视觉刺激的视皮层电活动,验证是否能记录到VEP;给予闪光和图形视觉刺激,记录和比较视觉诱发电位的峰值和潜伏期.结果 通过微创手术将微电极阵列植入并固定在视皮层定位区的硬脑膜外;在硬脑膜外微电极阵列可记录到有效VEP;黑白棋盘格图形刺激与黑白闪烁刺激相比,前者诱发的VEP谷峰值显著高于后者(P<0.01),而诱发的VEP波谷潜伏期较后者长(P<0.05),且波峰潜伏期则显著长于后者(P<0.01).结论 在视皮层定位区硬脑膜外首创的微创植入并固定柔性微电极阵列的方法 适用性、重复性好,黑白棋盘格图形刺激优于黑白闪烁刺激,经硬脑膜外利用微电极阵列记录诱发电位是可行的.%Objective To establish a new experiment method for recording visual cortex electrical activity through flexible microelectrode array being implanted on the duramater endocranium above visual cortex, and compare the difference between the visual evoked potential (VEP) evoked by black and white flare and that evoked by black and white checker. Methods A total of 5 health adult cats of both sexes were anesthetized, and artificially ventilated by breathing machine. Then flexible microelectrode array designed by our group was implanted on the epidural area outside of visual cortex location region. The results of visual cortex electrical activity evoked by without any visual stimulus or with visual stimulus was compared in order to record VEP. Then flash (black and white flare, F) and graphic (black and white

  4. Network and external perturbation induce burst synchronisation in cat cerebral cortex

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    Lameu, Ewandson L.; Borges, Fernando S.; Borges, Rafael R.; Batista, Antonio M.; Baptista, Murilo S.; Viana, Ricardo L.

    2016-05-01

    The brain of mammals are divided into different cortical areas that are anatomically connected forming larger networks which perform cognitive tasks. The cat cerebral cortex is composed of 65 areas organised into the visual, auditory, somatosensory-motor and frontolimbic cognitive regions. We have built a network of networks, in which networks are connected among themselves according to the connections observed in the cat cortical areas aiming to study how inputs drive the synchronous behaviour in this cat brain-like network. We show that without external perturbations it is possible to observe high level of bursting synchronisation between neurons within almost all areas, except for the auditory area. Bursting synchronisation appears between neurons in the auditory region when an external perturbation is applied in another cognitive area. This is a clear evidence that burst synchronisation and collective behaviour in the brain might be a process mediated by other brain areas under stimulation.

  5. Numbers of specific types of neuron in layer IVab of cat striate cortex.

    OpenAIRE

    Solnick, B; Davis, T L; Sterling, P

    1984-01-01

    Layer IVab of the visual cortex (area 17) of the cat contains about 51,400 neurons per mm3, including about 400-1200 per mm3 of each of three categories of neuron believed from previous work to represent discrete types. Each type forms about 0.5-1.5% of all the IVab neurons, which suggests that the total number of types in this layer might be much greater than previously supposed, perhaps as many as 50 or more. From their densities and estimates of their dendritic fields, we calculate that ea...

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

    Science.gov (United States)

    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. PMID:25100854

  7. Conceptual size representation in ventral visual cortex.

    Science.gov (United States)

    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. PMID:26731198

  8. Characterization of the blood-oxygen level-dependent (BOLD) response in cat auditory cortex using high-field fMRI.

    Science.gov (United States)

    Brown, Trecia A; Joanisse, Marc F; Gati, Joseph S; Hughes, Sarah M; Nixon, Pam L; Menon, Ravi S; Lomber, Stephen G

    2013-01-01

    Much of what is known about the cortical organization for audition in humans draws from studies of auditory cortex in the cat. However, these data build largely on electrophysiological recordings that are both highly invasive and provide less evidence concerning macroscopic patterns of brain activation. Optical imaging, using intrinsic signals or dyes, allows visualization of surface-based activity but is also quite invasive. Functional magnetic resonance imaging (fMRI) overcomes these limitations by providing a large-scale perspective of distributed activity across the brain in a non-invasive manner. The present study used fMRI to characterize stimulus-evoked activity in auditory cortex of an anesthetized (ketamine/isoflurane) cat, focusing specifically on the blood-oxygen-level-dependent (BOLD) signal time course. Functional images were acquired for adult cats in a 7 T MRI scanner. To determine the BOLD signal time course, we presented 1s broadband noise bursts between widely spaced scan acquisitions at randomized delays (1-12 s in 1s increments) prior to each scan. Baseline trials in which no stimulus was presented were also acquired. Our results indicate that the BOLD response peaks at about 3.5s in primary auditory cortex (AI) and at about 4.5 s in non-primary areas (AII, PAF) of cat auditory cortex. The observed peak latency is within the range reported for humans and non-human primates (3-4 s). The time course of hemodynamic activity in cat auditory cortex also occurs on a comparatively shorter scale than in cat visual cortex. The results of this study will provide a foundation for future auditory fMRI studies in the cat to incorporate these hemodynamic response properties into appropriate analyses of cat auditory cortex. PMID:23000258

  9. Orientational and directional selectivities of visual neurons in the superior colliculus of the cat

    Institute of Scientific and Technical Information of China (English)

    李兵; 王磊; 王毅; 刁云程

    1996-01-01

    Based on quantitative analyses of the response characteristics of visual neurons in the superior colliculus to moving optical bar stimuli, it is demonstrated for the first time that the visual neurons in superior colliculus of the cat have, to some extent, orientational selectivity. The significance of this selectivity is discussed in reference to its morphological substrate and physiological functions. In addition, both the directional and orientational selectivities in the superior colliculus are relatively weak when compared with those in the primary visual cortex, and the majority of the neurons prefer upward or downward motion in the visual field.

  10. Binocular form deprivation influences the visual cortex

    Institute of Scientific and Technical Information of China (English)

    Mingming Liu; Chuanhuang Weng; Hanping Xie; Wei Qin

    2012-01-01

    1a-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors are considered to play a crucial role in synaptic plasticity in the developing visual cortex. In this study, we established a rat model of binocular form deprivation by suturing the rat binocular eyelids before eye-opening at postnatal day 14. During development, the decay time of excitatory postsynaptic currents mediated by 1a-amino-3- hydroxy-5-methyl-4-isoxazolepropionic acid receptors of normal rats became longer after eyeopening; however, the decay time did not change significantly in binocular form deprivation rats. The peak value in the normal group became gradually larger with age, but there was no significant change in the binocular form deprivation group. These findings indicate that binocular form deprivation influences the properties of excitatory postsynaptic currents mediated by β-amino-3- hydroxy-5-methyl-4-isoxazolepropionic acid receptors in the rat visual cortex around the end of the critical period, indicating that form stimulation is associated with the experience-dependent modification of neuronal synapses in the visual cortex.

  11. Evidence for visual cortical area homologs in cat and macaque monkey.

    Science.gov (United States)

    Payne, B R

    1993-01-01

    The maps of visuotopically discrete visual cerebral cortical areas in the cat and the macaque monkey are compared and gaps in knowledge are identified that limit such comparisons. Cat areas 17, 18, and 19 can be equated with macaque areas V1, V2, and V3, respectively, based on criteria of relative position in the cortical mantle, internal organization of visual field representations, and trans- and subcortical connections. Using these same criteria, a visual area on the medial bank of the lateral suprasylvian sulcus (area PMLS) in the cat can be equated with macaque area V5. The equivalences are supported by data on neuronal receptive field properties and the contributions the areas make to visual behavior. Although the data are scanty for most other visual areas, there are enough data tentatively to equate collectively cat areas 20a and 20b with macaque areas TF and TH and to liken cat areas 21a and 21b with macaque area V4. What is not clear is if there is a region in cat that is equivalent to area TE in the macaque monkey. If there is, it likely lies on the banks of the posterior suprasylvian sulcus between areas 20 and 21 and the polysensory cortex of the posterior ectosylvian gyrus. Knowledge gained from prior research on macaque areas V4 and TE can be used to formulate specific additional investigations of cat area 21 and the uncharted posterior suprasylvian sulcus. In addition, prior investigations carried out on cat area 20 can be used to devise specific explorations of macaque areas TF and TH.

  12. Differential Modification of Cortical and Thalamic Projections to Cat Primary Auditory Cortex Following Early- and Late-Onset Deafness.

    Science.gov (United States)

    Chabot, Nicole; Butler, Blake E; Lomber, Stephen G

    2015-10-15

    Following sensory deprivation, primary somatosensory and visual cortices undergo crossmodal plasticity, which subserves the remaining modalities. However, controversy remains regarding the neuroplastic potential of primary auditory cortex (A1). To examine this, we identified cortical and thalamic projections to A1 in hearing cats and those with early- and late-onset deafness. Following early deafness, inputs from second auditory cortex (A2) are amplified, whereas the number originating in the dorsal zone (DZ) decreases. In addition, inputs from the dorsal medial geniculate nucleus (dMGN) increase, whereas those from the ventral division (vMGN) are reduced. In late-deaf cats, projections from the anterior auditory field (AAF) are amplified, whereas those from the DZ decrease. Additionally, in a subset of early- and late-deaf cats, area 17 and the lateral posterior nucleus (LP) of the visual thalamus project concurrently to A1. These results demonstrate that patterns of projections to A1 are modified following deafness, with statistically significant changes occurring within the auditory thalamus and some cortical areas. Moreover, we provide anatomical evidence for small-scale crossmodal changes in projections to A1 that differ between early- and late-onset deaf animals, suggesting that potential crossmodal activation of primary auditory cortex differs depending on the age of deafness onset.

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

    Directory of Open Access Journals (Sweden)

    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.

  14. 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

    . Stimulus–response curves were constructed by recording the intensity of the reported phosphenes evoked in the contralateral visual field at range of TMS intensities. Phosphene measurements revealed that MD produced a rapid and robust decrease in cortical excitability relative to a control condition without......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...... MD. The cortical excitability returned to preinterventional baseline levels within 3 h after the end of MD. The results show that in contrast to the excitability increase in response to BD, MD acutely triggers a reversible decrease in visual cortical excitability. This shows that the pattern...

  15. Effects of healthy aging on human primary visual cortex

    OpenAIRE

    2012-01-01

    Aging often results in reduced visual acuity from changes in both the eye and neural circuits [1-4]. In normally aging subjects, primary visual cortex has been shown to have reduced responses to visual stimulation [5]. It is not known, however, to what extent aging affects visual field representations and population receptive sizes in human primary visual cortex. Here we use functional MRI (fMRI) and population receptive field (pRF) modeling [6] to measure angular and eccentric retinotopic re...

  16. Functional magnetic resonance imaging evaluation of visual cortex activation in patients with anterior visual pathway lesions

    Institute of Scientific and Technical Information of China (English)

    Xiufeng Song; Guohua Wang; Tong Zhang; Lei Feng; Peng An; Yueli Zhu

    2012-01-01

    The aim of this study was to examine the secondary visual cortex functional disorder in patients with glaucoma and large pituitary adenoma by functional magnetic resonance imaging, and to determine the correlation between visual field defect and primary visual cortex activation. Results showed that single eye stimulation resulted in bilateral visual cortex activation in patients with glaucoma or large pituitary adenoma. Compared with the normal control group, the extent and intensity of visual cortex activation was decreased after left and right eye stimulation, and functional magnetic resonance imaging revealed a correlation between visual field defects and visual cortex activation in patients with glaucoma and large pituitary adenoma. These functional magnetic resonance imaging data suggest that anterior optic pathway lesions can cause secondary functional disorder of the visual cortex, and that visual defects are correlated with visual cortex activation.

  17. Phase sensitivity of complex cells in primary visual cortex.

    Science.gov (United States)

    Hietanen, M A; Cloherty, S L; van Kleef, J P; Wang, C; Dreher, B; Ibbotson, M R

    2013-05-01

    Neurons in the primary visual cortex are often classified as either simple or complex based on the linearity (or otherwise) of their response to spatial luminance contrast. In practice, classification is typically based on Fourier analysis of a cell's response to an optimal drifting sine-wave grating. Simple cells are generally considered to be linear and produce responses modulated at the fundamental frequency of the stimulus grating. In contrast, complex cells exhibit significant nonlinearities that reduce the response at the fundamental frequency. Cells can therefore be easily and objectively classified based on the relative modulation of their responses - the ratio of the phase-sensitive response at the fundamental frequency of the stimulus (F₁) to the phase-invariant sustained response (F₀). Cells are classified as simple if F₁/F₀>1 and complex if F₁/F₀<1. This classification is broadly consistent with criteria based on the spatial organisation of cells' receptive fields and is accordingly presumed to reflect disparate functional roles of simple and complex cells in coding visual information. However, Fourier analysis of spiking responses is sensitive to the number of spikes available - F₁/F₀ increases as the number of spikes is reduced, even for phase-invariant complex cells. Moreover, many complex cells encountered in the laboratory exhibit some phase sensitivity, evident as modulation of their responses at the fundamental frequency. There currently exists no objective quantitative means of assessing the significance or otherwise of these modulations. Here we derive a statistical basis for objectively assessing whether the modulation of neuronal responses is reliable, thereby adding a level of statistical certainty to measures of phase sensitivity. We apply our statistical analysis to neuronal responses to moving sine-wave gratings recorded from 367 cells in cat primary visual cortex. We find that approximately 60% of complex cells exhibit

  18. An approach to visual cortex operation: optical neuron model

    OpenAIRE

    Martín Pereda, José Antonio; González Marcos, Ana

    1994-01-01

    Several works have been published in the last years concerning the modelling and implementation of the visual cortex operation. Most of them present simple neurons with just two different responses, namely inhibitory and excitatory. Some of the different types of visual cortex cells are simulated in these configurations.

  19. Reorganization of neuronal circuits in growing visual cortex

    Science.gov (United States)

    Keil, Wolfgang; Loewel, Siegrid; Wolf, Fred; Kaschube, Matthias

    2009-03-01

    The dynamics of reorganization of large cortical circuits is rooted in plasticity of individual synapses, but rules governing the collective behavior of large networks of neurons are only poorly understood. The postnatal brain growth partly evoked by extensive formation of new synaptic connections may expose cortical areas to a 'natural perturbation' sufficiently strong to observe signatures of large scale reorganization. Quantifying large sets of imaging data from juvenile cat visual cortex, we observe a novel mode of reorganization of domains that prefer inputs from one eye or the other. Our theoretical analysis shows that this mode can be explained quantitatively by the so called Zigzag instability, a dynamical reorganization, well-known in the field of pattern formation in physics, by which 2D isotropic Turing patterns respond to an increase in their typical spatial scale with a zigzag-like bending of domains. We point out that this instability has in fact been predicted, albeit implicitly, by most models of visual cortical development that have been proposed so far. We conclude that cortical networks can undergo large scale reorganizations during normal postnatal development.

  20. Interocular transfer of adaptation in the primary visual cortex.

    Science.gov (United States)

    Howarth, Christopher M; Vorobyov, Vasily; Sengpiel, Frank

    2009-08-01

    Prolonged viewing of an unchanging pattern causes adaptation, which can be demonstrated by visual aftereffects such as the tilt and waterfall illusions. In normal observers, these typically exhibit interocular transfer (IOT), being observed when the adapting and test stimuli are shown to different eyes. Convergence of inputs from both eyes upon binocular neurons only occurs in the primary visual cortex (V1), and adaptation is substantially a cortical phenomenon. However, little is known about a physiological substrate of IOT in V1 and how it relates to the binocularity of neurons and local ocular dominance (OD) column architecture. We employed optical imaging to obtain OD maps in cat V1 and recorded from single neurons at targeted penetration sites to quantify their adaptation by drifting gratings when adapter and test stimulus were presented either to the same or to the opposite eyes. In contrast to earlier reports, clear IOT of adaptation was observed for binocular as well as monocular neurons; at population level, its strength amounted to 55%. Moreover, the position of the cells with respect to OD column borders had no significant effect on the strength of IOT. IOT does not appear to strongly depend on conventional binocularity of neurons.

  1. Retinal oscillations carry visual information to cortex

    Directory of Open Access Journals (Sweden)

    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.

  2. Specificity of auditory-guided visual perceptual learning suggests crossmodal plasticity in early visual cortex

    OpenAIRE

    Beer, Anton L.; Watanabe, Takeo

    2009-01-01

    Sounds modulate visual perception. Blind humans show altered brain activity in early visual cortex. However, it is still unclear whether crossmodal activity in visual cortex results from unspecific top-down feedback, a lack of visual input, or genuinely reflects crossmodal interactions at early sensory levels. We examined how sounds affect visual perceptual learning in sighted adults. Visual motion discrimination was tested prior to and following eight sessions in which observers were exposed...

  3. 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.

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

    OpenAIRE

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

    2014-01-01

    The ventromedial prefrontal cortex plays a crucial role in regulating emotion and social behavior, yet the precise mechanisms underlying this function remain unclear. Using eye-tracking in patients with brain lesions, Wolf et al. show that ventromedial prefrontal cortex is critical for directing visual attention during facial emotion recognition.

  5. Connectivity Changes Underlying Neurofeedback Training of Visual Cortex Activity

    OpenAIRE

    Frank Scharnowski; Maria Joao Rosa; Narly Golestani; Chloe Hutton; Oliver Josephs; Nikolaus Weiskopf; Geraint Rees

    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 activ...

  6. Visual Cortex Plasticity Following Peripheral Damage To The Visual System: fMRI Evidence.

    Science.gov (United States)

    Lemos, João; Pereira, Daniela; Castelo-Branco, Miguel

    2016-10-01

    Over the last two decades, functional magnetic resonance imaging (fMRI) has become a powerful research method to investigate cortical visual plasticity. Abnormal fMRI response patterns have been occasionally detected in the visually deprived cortex of patients with bilateral retinal diseases. Controversy remains whether these observations indicate structural reorganization of the visual cortex or unmasking of previously silent cortico-cortical connections. In optic nerve diseases, there is weak evidence showing that early visual cortex seems to lack reorganization, while higher-order visual areas undergo plastic changes which may contribute to optimise visual function. There is however accumulating imaging evidence demonstrating trans-synaptic degeneration of the visual cortex in patients with disease of the anterior visual pathways. This may preclude the use of restorative treatments in these patients. Here, we review and update the body of fMRI evidence on visual cortical plasticity. PMID:27542799

  7. Human primary visual cortex topography imaged via positron tomography

    International Nuclear Information System (INIS)

    The visuotopic structure of primary visual cortex was studied in a group of 7 human volunteers using positron emission transaxial tomography (PETT) and 18F-labeled 2-deoxy-2-fluoro-D-glucose ([18F]DG). A computer animation was constructed with a spatial structure which was matched to estimates of human cortical magnification factor and to striate cortex stimulus preferences. A lateralized cortical 'checker-board' pattern of [18F]DG was stimulated in primary visual cortex by having subjects view this computer animation following i.v. injection of [18F]DG. The spatial structure of the stimulus was designed to produce an easily recognizable 'signature' in a series of 9 serial PETT scans obtained from each of a group of 7 volunteers. The predicted lateralized topographic 'signature' was observed in 6 of 7 subjects. Applications of this method for further PETT studies of human visual cortex are discussed. (Auth.)

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

    Directory of Open Access Journals (Sweden)

    Lotfi B Merabet

    Full Text Available BACKGROUND: 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. METHODOLOGY/PRINCIPAL FINDINGS: 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. CONCLUSIONS/SIGNIFICANCE: 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

  9. 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

    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 pict

  10. Effects of Static Magnetic Fields on the Visual Cortex: reversible Visual Deficits and Reduction of Neuronal Activity.

    Science.gov (United States)

    Aguila, Jordi; Cudeiro, Javier; Rivadulla, Casto

    2016-02-01

    Noninvasive brain stimulation techniques have been successfully used to modulate brain activity, have become a highly useful tool in basic and clinical research and, recently, have attracted increased attention due to their putative use as a method for neuro-enhancement. In this scenario, transcranial static magnetic stimulation (SMS) of moderate strength might represent an affordable, simple, and complementary method to other procedures, such as Transcranial Magnetic Stimulation or direct current stimulation, but its mechanisms and effects are not thoroughly understood. In this study, we show that static magnetic fields applied to visual cortex of awake primates cause reversible deficits in a visual detection task. Complementary experiments in anesthetized cats show that the visual deficits are a consequence of a strong reduction in neural activity. These results demonstrate that SMS is able to effectively modulate neuronal activity and could be considered to be a tool to be used for different purposes ranging from experimental studies to clinical applications.

  11. Audiovisual Association Learning in the Absence of Primary Visual Cortex

    OpenAIRE

    Seirafi, Mehrdad; De Weerd, Peter; Pegna, Alan J.; de Gelder, Beatrice

    2016-01-01

    Learning audiovisual associations is mediated by the primary cortical areas; however, recent animal studies suggest that such learning can take place even in the absence of the primary visual cortex. Other studies have demonstrated the involvement of extra-geniculate pathways and especially the superior colliculus (SC) in audiovisual association learning. Here, we investigated such learning in a rare human patient with complete loss of the bilateral striate cortex. We carried out an implicit ...

  12. A disinhibitory microcircuit initiates critical period plasticity in visual cortex

    OpenAIRE

    Kuhlman, Sandra J.; Olivas, Nicholas D.; Tring, Elaine; Ikrar, Taruna; Xu, Xiangmin; Trachtenberg, Joshua T.

    2013-01-01

    Early sensory experience instructs the maturation of neural circuitry in cortex 1,2 . This has been extensively studied in the primary visual cortex where loss of vision to one eye permanently degrades cortical responsiveness to that eye 3,4 , a phenomenon known as ocular dominance plasticity (ODP). Cortical inhibition mediates this process 4-6 , but the precise role of specific classes of inhibitory neurons in ODP is controversial. Here we report that evoked firing rates of binocular excitat...

  13. High-Field Functional Imaging of Pitch Processing in Auditory Cortex of the Cat.

    Directory of Open Access Journals (Sweden)

    Blake E Butler

    Full Text Available The perception of pitch is a widely studied and hotly debated topic in human hearing. Many of these studies combine functional imaging techniques with stimuli designed to disambiguate the percept of pitch from frequency information present in the stimulus. While useful in identifying potential "pitch centres" in cortex, the existence of truly pitch-responsive neurons requires single neuron-level measures that can only be undertaken in animal models. While a number of animals have been shown to be sensitive to pitch, few studies have addressed the location of cortical generators of pitch percepts in non-human models. The current study uses high-field functional magnetic resonance imaging (fMRI of the feline brain in an attempt to identify regions of cortex that show increased activity in response to pitch-evoking stimuli. Cats were presented with iterated rippled noise (IRN stimuli, narrowband noise stimuli with the same spectral profile but no perceivable pitch, and a processed IRN stimulus in which phase components were randomized to preserve slowly changing modulations in the absence of pitch (IRNo. Pitch-related activity was not observed to occur in either primary auditory cortex (A1 or the anterior auditory field (AAF which comprise the core auditory cortex in cats. Rather, cortical areas surrounding the posterior ectosylvian sulcus responded preferentially to the IRN stimulus when compared to narrowband noise, with group analyses revealing bilateral activity centred in the posterior auditory field (PAF. This study demonstrates that fMRI is useful for identifying pitch-related processing in cat cortex, and identifies cortical areas that warrant further investigation. Moreover, we have taken the first steps in identifying a useful animal model for the study of pitch perception.

  14. Stimulus Dependence of Gamma Oscillations in Human Visual Cortex.

    Science.gov (United States)

    Hermes, D; Miller, K J; Wandell, B A; Winawer, J

    2015-09-01

    A striking feature of some field potential recordings in visual cortex is a rhythmic oscillation within the gamma band (30-80 Hz). These oscillations have been proposed to underlie computations in perception, attention, and information transmission. Recent studies of cortical field potentials, including human electrocorticography (ECoG), have emphasized another signal within the gamma band, a nonoscillatory, broadband signal, spanning 80-200 Hz. It remains unclear under what conditions gamma oscillations are elicited in visual cortex, whether they are necessary and ubiquitous in visual encoding, and what relationship they have to nonoscillatory, broadband field potentials. We demonstrate that ECoG responses in human visual cortex (V1/V2/V3) can include robust narrowband gamma oscillations, and that these oscillations are reliably elicited by some spatial contrast patterns (luminance gratings) but not by others (noise patterns and many natural images). The gamma oscillations can be conspicuous and robust, but because they are absent for many stimuli, which observers can see and recognize, the oscillations are not necessary for seeing. In contrast, all visual stimuli induced broadband spectral changes in ECoG responses. Asynchronous neural signals in visual cortex, reflected in the broadband ECoG response, can support transmission of information for perception and recognition in the absence of pronounced gamma oscillations. PMID:24855114

  15. Deep Hierarchies in the Primate Visual Cortex

    DEFF Research Database (Denmark)

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

    2013-01-01

    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...... 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...

  16. Areas of cat auditory cortex as defined by neurofilament proteins expressing SMI-32.

    Science.gov (United States)

    Mellott, Jeffrey G; Van der Gucht, Estel; Lee, Charles C; Carrasco, Andres; Winer, Jeffery A; Lomber, Stephen G

    2010-08-01

    The monoclonal antibody SMI-32 was used to characterize and distinguish individual areas of cat auditory cortex. SMI-32 labels non-phosphorylated epitopes on the high- and medium-molecular weight subunits of neurofilament proteins in cortical pyramidal cells and dendritic trees with the most robust immunoreactivity in layers III and V. Auditory areas with unique patterns of immunoreactivity included: primary auditory cortex (AI), second auditory cortex (AII), dorsal zone (DZ), posterior auditory field (PAF), ventral posterior auditory field (VPAF), ventral auditory field (VAF), temporal cortex (T), insular cortex (IN), anterior auditory field (AAF), and the auditory field of the anterior ectosylvian sulcus (fAES). Unique patterns of labeling intensity, soma shape, soma size, layers of immunoreactivity, laminar distribution of dendritic arbors, and labeled cell density were identified. Features that were consistent in all areas included: layers I and IV neurons are immunonegative; nearly all immunoreactive cells are pyramidal; and immunoreactive neurons are always present in layer V. To quantify the results, the numbers of labeled cells and dendrites, as well as cell diameter, were collected and used as tools for identifying and differentiating areas. Quantification of the labeling patterns also established profiles for ten auditory areas/layers and their degree of immunoreactivity. Areal borders delineated by SMI-32 were highly correlated with tonotopically-defined areal boundaries. Overall, SMI-32 immunoreactivity can delineate ten areas of cat auditory cortex and demarcate topographic borders. The ability to distinguish auditory areas with SMI-32 is valuable for the identification of auditory cerebral areas in electrophysiological, anatomical, and/or behavioral investigations.

  17. Crossmodal Association of Visual and Haptic Material Properties of Objects in the Monkey Ventral Visual Cortex.

    Science.gov (United States)

    Goda, Naokazu; Yokoi, Isao; Tachibana, Atsumichi; Minamimoto, Takafumi; Komatsu, Hidehiko

    2016-04-01

    Just by looking at an object, we can recognize its non-visual properties, such as hardness. The visual recognition of non-visual object properties is generally accurate [1], and influences actions toward the object [2]. Recent studies suggest that, in the primate brain, this may involve the ventral visual cortex, which represents objects in a way that reflects not only visual but also non-visual object properties, such as haptic roughness, hardness, and weight [3-7]. This new insight raises a fundamental question: how does the visual cortex come to represent non-visual properties--knowledge that cannot be acquired directly through vision? Here we addressed this unresolved question using fMRI in macaque monkeys. Specifically, we explored whether and how simple visuo-haptic experience--just seeing and touching objects made of various materials--can shape representational content in the visual cortex. We measured brain activity evoked by viewing images of objects before and after the monkeys acquired the visuo-haptic experience and decoded the representational space from the activity patterns [8]. We show that simple long-term visuo-haptic experience greatly impacts representation in the posterior inferior temporal cortex, the higher ventral visual cortex. After the experience, but not before, the activity pattern in this region well reflected the haptic material properties of the experienced objects. Our results suggest that neural representation of non-visual object properties in the visual cortex emerges through long-term crossmodal exposure to objects. This highlights the importance of unsupervised learning of crossmodal associations through everyday experience [9-12] for shaping representation in the visual cortex. PMID:26996504

  18. Antagonistic otolith-visual units in cat vestibular nuclei

    Science.gov (United States)

    Daunton, Nancy G.; Christensen, Carol A.

    1992-01-01

    The nature of neural coding of visual (Vis) and vestibular (Vst) information on translational motion in the region of the vestibular nuclei was investigated using extracellular single-unit recordings in alert adult cats. Responses were recorded and averaged over 60 cycles of stimulation in the vertical and horizontal planes, which included the Vst (movement of the animal in the dark), Vis (movement within lighted visual surround), and combined Vis and Vst (movement of the animal within the lighted stationary visual surround). Data are reported on responses to stimulations along the axis showing maximal sensitivity. A small number of units were identified that showed an antagonistic relationship between their Vis and Vst responses (since they were maximally excited by Vis and by Vst stimulations in the same direction). Results suggest that antagonistic units may belong to an infrequently encountered, but functionally distinct, class of neurons.

  19. Retinotopically defined primary visual cortex in Williams syndrome

    OpenAIRE

    Olsen, Rosanna K.; Kippenhan, J. Shane; Japee, Shruti; Kohn, Philip; Mervis, Carolyn B.; Saad, Ziad S.; Morris, Colleen A.; Meyer-Lindenberg, Andreas; Berman, Karen Faith

    2009-01-01

    Williams syndrome, caused by a hemizygous microdeletion on chromosome 7q11.23, is characterized by severe impairment in visuospatial construction. To examine potential contributions of early visual processing to this cognitive problem, we functionally mapped the size and neuroanatomical variability of primary visual cortex (V1) in high-functioning adults with Williams syndrome and age- and IQ-matched control participants from the general population by using fMRI-based retinotopic mapping and ...

  20. "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). ...

  1. 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. PMID:26679216

  2. Associative Hebbian Synaptic Plasticity in Primate Visual Cortex

    Science.gov (United States)

    Huang, Shiyong; Rozas, Carlos; Treviño, Mario; Contreras, Jessica; Yang, Sunggu; Song, Lihua; Yoshioka, Takashi; Lee, Hey-Kyoung

    2014-01-01

    In primates, the functional connectivity of adult primary visual cortex is susceptible to be modified by sensory training during perceptual learning. It is widely held that this type of neural plasticity might involve mechanisms like long-term potentiation (LTP) and long-term depression (LTD). NMDAR-dependent forms of LTP and LTD are particularly attractive because in rodents they can be induced in a Hebbian manner by near coincidental presynaptic and postsynaptic firing, in a paradigm termed spike timing-dependent plasticity (STDP). These fundamental properties of LTP and LTD, Hebbian induction and NMDAR dependence, have not been examined in primate cortex. Here we demonstrate these properties in the primary visual cortex of the rhesus macaque (Macaca mulatta), and also show that, like in rodents, STDP is gated by neuromodulators. These findings indicate that the cellular principles governing cortical plasticity are conserved across mammalian species, further validating the use of rodents as a model system. PMID:24872561

  3. Preferential Encoding of Visual Categories in Parietal Cortex Compared to Prefrontal Cortex

    OpenAIRE

    Swaminathan, Sruthi K.; Freedman, David J

    2012-01-01

    The ability to recognize the behavioral significance, or category membership, of sensory stimuli is critical for interpreting the meaning of events in our environment. Prior neurophysiological studies of visual categorization found categorical representations of stimuli in prefrontal cortex (PFC), an area closely associated with cognitive and executive functions. Recent studies have also identified neuronal category signals in parietal areas typically associated with visual-spatial processing...

  4. Perceptual Learning and Dynamic Changes in Primary Visual Cortex

    OpenAIRE

    Carmel, David; Carrasco, Marisa

    2008-01-01

    Perceptual learning is the improved performance that follows practice in a perceptual task. In this issue of Neuron, Yotsumoto et al. use fMRI to show that stimuli presented at the location used in training initially evoke greater activation in primary visual cortex than stimuli presented elsewhere, but this difference disappears once learning asymptotes.

  5. Population response characteristics of intrinsic signals in the cat somatosensory cortex following canine mechanical stimulation.

    Science.gov (United States)

    Tao, Jianxiang; Wang, Jian; Li, Zhong; Meng, Jianjun; Yu, Hongbo

    2016-08-01

    Intrinsic signal optical imaging has been widely used to measure functional maps in various sensory cortices due to better spatial resolution and sensitivity for detecting cortical neuroplasticity. However, application of this technique in dentistry has not been reported. In this study, intrinsic signal optical imaging was used to investigate mechanically driven responses in the cat somatosensory cortex, when punctate mechanical stimuli were applied to maxillary canines. The global signal and its spatial organization pattern were obtained. Global signal strength gradually increased with stimulus strength. There was no significant difference in response strength between contralateral and ipsilateral mechanical stimulation. A slightly greater response was recorded in the sigmoidal gyrus than in the coronal gyrus. The cat somatosensory cortex activated by sensory inputs from mechanical stimulation of canines lacks both topographical and functional organization. It is not organized into columns that represent sensory input from each tooth or direction of stimulation. These results demonstrate that intrinsic signal optical imaging is a valid tool for investigating neural responses and neuroplasticity in the somatosensory cortex that represents teeth. PMID:27163378

  6. Reverse sequencing syllables of spoken words activates primary visual cortex.

    Science.gov (United States)

    Ino, Tadashi; Asada, Tomohiko; Hirose, Syuichi; Ito, Jin; Fukuyama, Hidenao

    2003-10-27

    Using fMRI, we investigated the neural correlates for sequencing the individual syllables of spoken words in reverse order. The comparison of this task to a control task requiring subjects to repeat identical syllables given acoustically revealed the activation of the primary visual cortex. Because one syllable is generally expressed by one kana character (Japanese phonogram), most subjects used a strategy in which the kana character string corresponding to the word was imagined visually and then read mentally in reverse order to perform the task effectively. Such strategy was not used during a control condition. These results suggest that the primary visual cortex plays a role in the generation of an imagined string.

  7. Accurate stepping on a narrow path: mechanics, EMG, and motor cortex activity in the cat.

    Science.gov (United States)

    Farrell, Brad J; Bulgakova, Margarita A; Sirota, Mikhail G; Prilutsky, Boris I; Beloozerova, Irina N

    2015-11-01

    How do cats manage to walk so graciously on top of narrow fences or windowsills high above the ground while apparently exerting little effort? In this study we investigated cat full-body mechanics and the activity of limb muscles and motor cortex during walking along a narrow 5-cm path on the ground. We tested the hypotheses that during narrow walking 1) lateral stability would be lower because of the decreased base-of-support area and 2) the motor cortex activity would increase stride-related modulation because of imposed demands on lateral stability and paw placement accuracy. We measured medio-lateral and rostro-caudal dynamic stability derived from the extrapolated center of mass position with respect to the boundaries of the support area. We found that cats were statically stable in the frontal plane during both unconstrained and narrow-path walking. During narrow-path walking, cats walked slightly slower with more adducted limbs, produced smaller lateral forces by hindlimbs, and had elevated muscle activities. Of 174 neurons recorded in cortical layer V, 87% of forelimb-related neurons (from 114) and 90% of hindlimb-related neurons (from 60) had activities during narrow-path walking distinct from unconstrained walking: more often they had a higher mean discharge rate, lower depth of stride-related modulation, and/or longer period of activation during the stride. These activity changes appeared to contribute to control of accurate paw placement in the medio-lateral direction, the width of the stride, rather than to lateral stability control, as the stability demands on narrow-path and unconstrained walking were similar.

  8. Neural mechanisms of perceptual grouping in human visual cortex

    Institute of Scientific and Technical Information of China (English)

    MAO Lihua; HAN Shihui; GUO Chunyan; JIANG Yi

    2004-01-01

    The current work examined neural substrates of perceptual grouping in human visual cortex using event-related potential (ERP) recording. Stimulus arrays consisted of local elements that were either evenly spaced (uniform stimuli) or grouped into columns or rows by proximity or color similarity (grouping stimuli). High-density ERPs were recorded while subjects identified orientations of perceptual groups in stimulus arrays that were presented randomly in one of the four quadrants of the visual field. Both uniform and grouping stimulus arrays elicited an early ERP component (C1), which peaked at about 70 ms after stimulus onset and changed its polarity as a function of stimulated elevations. Dipole modeling based on realistic- head boundary-element models revealed generators of the C1 component in the calcarine cortex. The C1 was modulated by perceptual grouping of local elements based on proximity, and this grouping effect was stronger in the upper than in the lower visual field. The findings provide ERP evidence for the engagement of human primary visual cortex in the early stage of perceptual grouping.

  9. The neural representation of Arabic digits in visual cortex

    Directory of Open Access Journals (Sweden)

    Lien ePeters

    2015-09-01

    Full Text Available In this study, we investigated how Arabic digits are represented in the visual cortex, and how their representation changes throughout the ventral visual processing stream, compared to the representation of letters. We probed these questions with two fMRI experiments. In Experiment 1, we explored whether we could find brain regions that were more activated for digits than for number words in a subtraction task. One such region was detected in lateral occipital cortex. However, the activity in this region might have been confounded by string length – number words contain more characters than digits. We therefore conducted a second experiment in which string length was systematically controlled. Experiment 2 revealed that the findings of the first experiment were task dependent (as it was only observed in a task in which numerosity was relevant or stimulus dependent (as it was only observed when the number of characters of a stimulus was not controlled.We further explored the characteristics of the activation patterns for digit and letter strings across the ventral visual processing stream through multi-voxel pattern analyses. We found an alteration in representations throughout the ventral processing stream from clustering based on amount of visual information in primary visual cortex towards clustering based on symbolic stimulus category higher in the visual hierarchy. The present findings converge to the conclusion that in the ventral visual system, as far as can be detected with fMRI, the distinction between Arabic digits and letter strings is represented in terms of distributed patterns rather than separate regions.

  10. The neural representation of Arabic digits in visual cortex

    Science.gov (United States)

    Peters, Lien; De Smedt, Bert; Op de Beeck, Hans P.

    2015-01-01

    In this study, we investigated how Arabic digits are represented in the visual cortex, and how their representation changes throughout the ventral visual processing stream, compared to the representation of letters. We probed these questions with two functional magnetic resonance imaging (fMRI) experiments. In Experiment 1, we explored whether we could find brain regions that were more activated for digits than for number words in a subtraction task. One such region was detected in lateral occipital cortex. However, the activity in this region might have been confounded by string length—number words contain more characters than digits. We therefore conducted a second experiment in which string length was systematically controlled. Experiment 2 revealed that the findings of the first experiment were task dependent (as it was only observed in a task in which numerosity was relevant) or stimulus dependent (as it was only observed when the number of characters of a stimulus was not controlled). We further explored the characteristics of the activation patterns for digit and letter strings across the ventral visual processing stream through multi-voxel pattern analyses. We found an alteration in representations throughout the ventral processing stream from clustering based on amount of visual information in primary visual cortex (V1) towards clustering based on symbolic stimulus category higher in the visual hierarchy. The present findings converge to the conclusion that in the ventral visual system, as far as can be detected with fMRI, the distinction between Arabic digits and letter strings is represented in terms of distributed patterns rather than separate regions. PMID:26441613

  11. A multi-stage model for fundamental functional properties in primary visual cortex.

    Directory of Open Access Journals (Sweden)

    Nastaran Hesam Shariati

    Full Text Available Many neurons in mammalian primary visual cortex have properties such as sharp tuning for contour orientation, strong selectivity for motion direction, and insensitivity to stimulus polarity, that are not shared with their sub-cortical counterparts. Successful models have been developed for a number of these properties but in one case, direction selectivity, there is no consensus about underlying mechanisms. We here define a model that accounts for many of the empirical observations concerning direction selectivity. The model describes a single column of cat primary visual cortex and comprises a series of processing stages. Each neuron in the first cortical stage receives input from a small number of on-centre and off-centre relay cells in the lateral geniculate nucleus. Consistent with recent physiological evidence, the off-centre inputs to cortex precede the on-centre inputs by a small (∼4 ms interval, and it is this difference that confers direction selectivity on model neurons. We show that the resulting model successfully matches the following empirical data: the proportion of cells that are direction selective; tilted spatiotemporal receptive fields; phase advance in the response to a stationary contrast-reversing grating stepped across the receptive field. The model also accounts for several other fundamental properties. Receptive fields have elongated subregions, orientation selectivity is strong, and the distribution of orientation tuning bandwidth across neurons is similar to that seen in the laboratory. Finally, neurons in the first stage have properties corresponding to simple cells, and more complex-like cells emerge in later stages. The results therefore show that a simple feed-forward model can account for a number of the fundamental properties of primary visual cortex.

  12. Relationship of Visual Cortex Function and Visual Acuity in Anisometropic Amblyopic Children

    Directory of Open Access Journals (Sweden)

    Chuanming Li, Lin Cheng, Qiongwu Yu, Bing Xie, Jian Wang

    2012-01-01

    Full Text Available Purpose: To detect the functional deficit of the visual cortex in anisometropic amblyopia children using functional magnetic resonance imaging (fMRI technique, and investigate the relationship between visual acuity and visual cortex function.Methods: Blood oxygenation level-dependent fMRI (BOLD-fMRI was performed in ten monocular anisometropic amblyopia children and ten normal controls. fMRI images were acquired in two runs with visual stimulation delivered separately through the sound and amblyopic eyes. Measurements were performed in cortical activation of striate and extrastriate areas at the occipital lobe. The relationship between cortex function and visual acuity was analyzed by Pearson partial analysis.Results: The activation areas of both the striate and extrastriate cortices in the amblyopic eyes were significantly lower than that of the sound fellow eyes. No relationship was found between the striate and extrastriate cortex activation. No relationship was found between the visual cortical activation of striate, extrastriate areas and visual acuity of anisometropic amblyopes.Conclusions: BOLD-fMRI revealed the independent striate and extrastriate cortical deficits in anisometropic amblyopes. In addition, the visual acuity lesion and the striate and extrastriate cortical deficits were not parallel, and results of fMRI examination have much potential value in the evaluation of amblyopia.

  13. 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

  14. Individual differences in visual and olfactory cue preference and use by cats (Felis catus)

    OpenAIRE

    Mayes, Evely.-Rose E.; Wilkinson, Anna; Pike, Thomas W; Mills, Daniel S.

    2015-01-01

    Highlights • Eight cats were trained in a T-maze using a two-alternative forced choice procedure. • Cats could use either an olfactory or visual cue to locate a food reward. • Cues were then put in conflict to determine which was preferred for the task. • Most cats used the visual cue to learn the location of the food. • Preferences were stable, repeatable and rapidly learned. -------------------------------------------------------------------------------- ...

  15. Higher Order Spike Synchrony in Prefrontal Cortex during visual memory

    Directory of Open Access Journals (Sweden)

    Gordon ePipa

    2011-06-01

    Full Text Available Precise temporal synchrony of spike firing has been postulated as an important neuronal mechanism for signal integration and the induction of plasticity in neocortex. As prefrontal cortex plays an important role in organizing memory and executive functions, the convergence of multiple visual pathways onto PFC predicts that neurons should preferentially synchronize their spiking when stimulus information is processed. Furthermore, synchronous spike firing should intensify if memory processes require the induction of neuronal plasticity, even if this is only for short-term. Here we show with multiple simultaneously recorded units in ventral prefrontal cortex that neurons participate in 3 ms precise synchronous discharges distributed across multiple sites separated by at least 500 µm. The frequency of synchronous firing is modulated by behavioral performance and is specific for the memorized visual stimuli. In particular, during the memory period in which activity is not stimulus driven, larger groups of up to 7 sites exhibit performance dependent modulation of their spike synchronization.

  16. Distinct mechanisms for size tuning in primate visual cortex

    OpenAIRE

    Briggs, Farran; Usrey, W. Martin

    2011-01-01

    Most neurons in primary visual cortex (V1) are selective for stimulus size, a property with important implications for salient feature detection. Size selectivity involves dynamic interactions between neuronal circuits that establish the classical (center) and extraclassical (surround) of a neuron’s receptive field. Although much is known about the tuning properties and stimulus selectivity of the center and surround subunits, relatively little is known about how these subunits interact to ac...

  17. Input and output gain modulation by the lateral interhemispheric network in early visual cortex.

    Science.gov (United States)

    Wunderle, Thomas; Eriksson, David; Peiker, Christiane; Schmidt, Kerstin E

    2015-05-20

    Neurons in the cerebral cortex are constantly integrating different types of inputs. Dependent on their origin, these inputs can be modulatory in many ways and, for example, change the neuron's responsiveness, sensitivity, or selectivity. To investigate the modulatory role of lateral input from the same level of cortical hierarchy, we recorded in the primary visual cortex of cats while controlling synaptic input from the corresponding contralateral hemisphere by reversible deactivation. Most neurons showed a pronounced decrease in their response to a visual stimulus of different contrasts and orientations. This indicates that the lateral network acts via an unspecific gain-setting mechanism, scaling the output of a neuron. However, the interhemispheric input also changed the contrast sensitivity of many neurons, thereby acting on the input. Such a contrast gain mechanism has important implications because it extends the role of the lateral network from pure response amplification to the modulation of a specific feature. Interestingly, for many neurons, we found a mixture of input and output gain modulation. Based on these findings and the known physiology of callosal connections in the visual system, we developed a simple model of lateral interhemispheric interactions. We conclude that the lateral network can act directly on its target, leading to a sensitivity change of a specific feature, while at the same time it also can act indirectly, leading to an unspecific gain setting. The relative contribution of these direct and indirect network effects determines the outcome for a particular neuron.

  18. Learning a New Selection Rule in Visual and Frontal Cortex.

    Science.gov (United States)

    van der Togt, Chris; Stănişor, Liviu; Pooresmaeili, Arezoo; Albantakis, Larissa; Deco, Gustavo; Roelfsema, Pieter R

    2016-08-01

    How do you make a decision if you do not know the rules of the game? Models of sensory decision-making suggest that choices are slow if evidence is weak, but they may only apply if the subject knows the task rules. Here, we asked how the learning of a new rule influences neuronal activity in the visual (area V1) and frontal cortex (area FEF) of monkeys. We devised a new icon-selection task. On each day, the monkeys saw 2 new icons (small pictures) and learned which one was relevant. We rewarded eye movements to a saccade target connected to the relevant icon with a curve. Neurons in visual and frontal cortex coded the monkey's choice, because the representation of the selected curve was enhanced. Learning delayed the neuronal selection signals and we uncovered the cause of this delay in V1, where learning to select the relevant icon caused an early suppression of surrounding image elements. These results demonstrate that the learning of a new rule causes a transition from fast and random decisions to a more considerate strategy that takes additional time and they reveal the contribution of visual and frontal cortex to the learning process. PMID:27269960

  19. Audiovisual Association Learning in the Absence of Primary Visual Cortex.

    Science.gov (United States)

    Seirafi, Mehrdad; De Weerd, Peter; Pegna, Alan J; de Gelder, Beatrice

    2015-01-01

    Learning audiovisual associations is mediated by the primary cortical areas; however, recent animal studies suggest that such learning can take place even in the absence of the primary visual cortex. Other studies have demonstrated the involvement of extra-geniculate pathways and especially the superior colliculus (SC) in audiovisual association learning. Here, we investigated such learning in a rare human patient with complete loss of the bilateral striate cortex. We carried out an implicit audiovisual association learning task with two different colors of red and purple (the latter color known to minimally activate the extra-genicular pathway). Interestingly, the patient learned the association between an auditory cue and a visual stimulus only when the unseen visual stimulus was red, but not when it was purple. The current study presents the first evidence showing the possibility of audiovisual association learning in humans with lesioned striate cortex. Furthermore, in line with animal studies, it supports an important role for the SC in audiovisual associative learning.

  20. On the Nature of the Intrinsic Connectivity of the Cat Motor Cortex: Evidence for a Recurrent Neural Network Topology

    DEFF Research Database (Denmark)

    Capaday, Charles; Ethier, C; Brizzi, L;

    2009-01-01

    Capaday C, Ethier C, Brizzi L, Sik A, van Vreeswijk C, Gingras D. On the nature of the intrinsic connectivity of the cat motor cortex: evidence for a recurrent neural network topology. J Neurophysiol 102: 2131-2141, 2009. First published July 22, 2009; doi: 10.1152/jn.91319.2008. The details...... and functional significance of the intrinsic horizontal connections between neurons in the motor cortex (MCx) remain to be clarified. To further elucidate the nature of this intracortical connectivity pattern, experiments were done on the MCx of three cats. The anterograde tracer biocytin was ejected...

  1. Changing Human Visual Field Organization from Early Visual to Extra-Occipital Cortex

    OpenAIRE

    Anthony I Jack; Gaurav H Patel; Astafiev, Serguei V.; Snyder, Abraham Z.; Erbil Akbudak; Shulman, Gordon L.; Maurizio Corbetta

    2007-01-01

    BACKGROUND: The early visual areas have a clear topographic organization, such that adjacent parts of the cortical surface represent distinct yet adjacent parts of the contralateral visual field. We examined whether cortical regions outside occipital cortex show a similar organization. METHODOLOGY/PRINCIPAL FINDINGS: The BOLD responses to discrete visual field locations that varied in both polar angle and eccentricity were measured using two different tasks. As described previously, numerous ...

  2. Preferential encoding of visual categories in parietal cortex compared with prefrontal cortex.

    Science.gov (United States)

    Swaminathan, Sruthi K; Freedman, David J

    2012-02-01

    The ability to recognize the behavioral relevance, or category membership, of sensory stimuli is critical for interpreting the meaning of events in our environment. Neurophysiological studies of visual categorization have found categorical representations of stimuli in prefrontal cortex (PFC), an area that is closely associated with cognitive and executive functions. Recent studies have also identified neuronal category signals in parietal areas that are typically associated with visual-spatial processing. It has been proposed that category-related signals in parietal cortex and other visual areas may result from 'top-down' feedback from PFC. We directly compared neuronal activity in the lateral intraparietal (LIP) area and PFC in monkeys performing a visual motion categorization task. We found that LIP showed stronger, more reliable and shorter latency category signals than PFC. These findings suggest that LIP is strongly involved in visual categorization and argue against the idea that parietal category signals arise as a result of feedback from PFC during this task. PMID:22246435

  3. Avalanche Analysis from Multielectrode Ensemble Recordings in Cat, Monkey, and Human Cerebral Cortex during Wakefulness and Sleep

    OpenAIRE

    Nima eDehghani; Hatsopoulos, Nicholas G.; Haga, Zach D.; Rebecca eParker; Bradley eGreger; Eric eHalgren; Sydney S Cash; Alain eDestexhe

    2012-01-01

    Self-organized critical states are found in many natural systems, from earthquakes to forest fires, they have also been observed in neural systems, particularly, in neuronal cultures. However, the presence of critical states in the awake brain remains controversial. Here, we compared avalanche analyses performed on different in vivo preparations during wakefulness, slow-wave sleep, and REM sleep, using high density electrode arrays in cat motor cortex (96 electrodes), monkey motor cortex and ...

  4. Morphological dissociation between visual pathways and cortex: MRI of visually-deprived patients with congenital peripheral blindness

    International Nuclear Information System (INIS)

    MRI was used to study possible morphological changes in the visual system in 12 patients suffering from congenital blindness of peripheral (ocular) origin. While their optical pathways showed degeneration, hypoplasia or atrophy in 7 out of 12 cases, the occipital cortex appeared normal in all cases. This dissociation between afferent pathways and the cortex is contrary to the assumption that visually deprived cortex may undergo degeneration. The finding is congruent with evidence that the occipital cortex is used for other, nonvisual functions. (orig.)

  5. 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.

  6. Optogenetic Activation of Normalization in Alert Macaque Visual Cortex.

    Science.gov (United States)

    Nassi, Jonathan J; Avery, Michael C; Cetin, Ali H; Roe, Anna W; Reynolds, John H

    2015-06-17

    Normalization has been proposed as a canonical computation that accounts for a variety of nonlinear neuronal response properties associated with sensory processing and higher cognitive functions. A key premise of normalization is that the excitability of a neuron is inversely proportional to the overall activity level of the network. We tested this by optogenetically activating excitatory neurons in alert macaque primary visual cortex and measuring changes in neuronal activity as a function of stimulation intensity, with or without variable-contrast visual stimulation. Optogenetic depolarization of excitatory neurons either facilitated or suppressed baseline activity, consistent with indirect recruitment of inhibitory networks. As predicted by the normalization model, neurons exhibited sub-additive responses to optogenetic and visual stimulation, which depended lawfully on stimulation intensity and luminance contrast. We conclude that the normalization computation persists even under the artificial conditions of optogenetic stimulation, underscoring the canonical nature of this form of neural computation.

  7. Retinotopically defined primary visual cortex in Williams syndrome.

    Science.gov (United States)

    Olsen, Rosanna K; Kippenhan, J Shane; Japee, Shruti; Kohn, Philip; Mervis, Carolyn B; Saad, Ziad S; Morris, Colleen A; Meyer-Lindenberg, Andreas; Berman, Karen Faith

    2009-03-01

    Williams syndrome, caused by a hemizygous microdeletion on chromosome 7q11.23, is characterized by severe impairment in visuospatial construction. To examine potential contributions of early visual processing to this cognitive problem, we functionally mapped the size and neuroanatomical variability of primary visual cortex (V1) in high-functioning adults with Williams syndrome and age- and IQ-matched control participants from the general population by using fMRI-based retinotopic mapping and cortical surface models generated from high-resolution structural MRI. Visual stimulation, consisting of rotating hemicircles and expanding rings, was used to retinotopically define early visual processing areas. V1 boundaries based on computed phase and field sign maps were used to calculate the functional area of V1. Neuroanatomical variability was assessed by computing overlap maps of V1 location for each group on standardized cortical surfaces, and non-parametric permutation test methods were used for statistical inference. V1 did not differ in size between groups, although its anatomical boundaries were more variable in the group with Williams syndrome. V1 overlap maps showed that the average centres of gravity for the two groups were similarly located near the fundus of the calcarine fissure, approximately 25 mm away from the most posterior aspect of the occipital lobe. In summary, our functional definition of V1 size and location indicates that recruitment of primary visual cortex is grossly normal in Williams syndrome, consistent with the notion that neural abnormalities underlying visuospatial construction arise at later stages in the visual processing hierarchy. PMID:19255058

  8. Characterizing synaptic protein development in human visual cortex enables alignment of synaptic age with rat visual cortex

    Directory of Open Access Journals (Sweden)

    Joshua G.A Pinto

    2015-02-01

    Full Text Available Although many potential neuroplasticity based therapies have been developed in the lab, few have translated into established clinical treatments for human neurologic or neuropsychiatric diseases. Animal models, especially of the visual system, have shaped our understanding of neuroplasticity by characterizing the mechanisms that promote neural changes and defining timing of the sensitive period. The lack of knowledge about development of synaptic plasticity mechanisms in human cortex, and about alignment of synaptic age between animals and humans, has limited translation of neuroplasticity therapies. In this study, we quantified expression of a set of highly conserved pre- and post-synaptic proteins (Synapsin, Synaptophysin, PSD-95, Gephyrin and found that synaptic development in human primary visual cortex continues into late childhood. Indeed, this is many years longer than suggested by neuroanatomical studies and points to a prolonged sensitive period for plasticity in human sensory cortex. In addition, during childhood we found waves of inter-individual variability that are different for the 4 proteins and include a stage during early development (<1 year when only Gephyrin has high inter-individual variability. We also found that pre- and post-synaptic protein balances develop quickly, suggesting that maturation of certain synaptic functions happens within the first year or two of life. A multidimensional analysis (principle component analysis showed that most of the variance was captured by the sum of the 4 synaptic proteins. We used that sum to compare development of human and rat visual cortex and identified a simple linear equation that provides robust alignment of synaptic age between humans and rats. Alignment of synaptic ages is important for age-appropriate targeting and effective translation of neuroplasticity therapies from the lab to the clinic.

  9. Neurometabolic coupling between neural activity, glucose, and lactate in activated visual cortex.

    Science.gov (United States)

    Li, Baowang; Freeman, Ralph D

    2015-11-01

    Neural activity is closely coupled with energy metabolism but details of the association remain to be identified. One basic area involves the relationships between neural activity and the main supportive substrates of glucose and lactate. This is of fundamental significance for the interpretation of non-invasive neural imaging. Here, we use microelectrodes with high spatial and temporal resolution to determine simultaneous co-localized changes in glucose, lactate, and neural activity during visual activation of the cerebral cortex in the cat. Tissue glucose and lactate concentration levels are measured with electrochemical microelectrodes while neural spiking activity and local field potentials are sampled by a microelectrode. These measurements are performed simultaneously while neurons are activated by visual stimuli of different contrast levels, orientations, and sizes. We find immediate decreases in tissue glucose concentration and simultaneous increases in lactate during neural activation. Both glucose and lactate signals return to their baseline levels instantly as neurons cease firing. No sustained changes or initial dips in glucose or lactate signals are elicited by visual stimulation. However, co-localized measurements of cerebral blood flow and neural activity demonstrate a clear delay in the cerebral blood flow signal such that it does not correlate temporally with the neural response. These results provide direct real-time evidence regarding the coupling between co-localized energy metabolism and neural activity during physiological stimulation. They are also relevant to a current question regarding the role of lactate in energy metabolism in the brain during neural activation. Dynamic changes in energy metabolites can be measured directly with high spatial and temporal resolution by use of enzyme-based microelectrodes. Here, to examine neuro-metabolic coupling during brain activation, we use combined microelectrodes to simultaneously measure

  10. Neural mechanism of activity spread in the cat motor cortex and its relation to the intrinsic connectivity

    DEFF Research Database (Denmark)

    Capaday, Charles; van Vreeswijk, Carl; Ethier, Christian;

    2011-01-01

    to be determined. To address these issues, an 8 x 8 microelectrode array was inserted in the forelimb area of the cat motor cortex (MCx). The centre of the array had a laser etched hole ∼500 {#956}m in diameter. A microiontophoretic pipette, with a tip diameter of 2–3 {#956}m, containing bicuculline methiodide...

  11. Effects of deafness and cochlear implant use on temporal response characteristics in cat primary auditory cortex.

    Science.gov (United States)

    Fallon, James B; Shepherd, Robert K; Nayagam, David A X; Wise, Andrew K; Heffer, Leon F; Landry, Thomas G; Irvine, Dexter R F

    2014-09-01

    We have previously shown that neonatal deafness of 7-13 months duration leads to loss of cochleotopy in the primary auditory cortex (AI) that can be reversed by cochlear implant use. Here we describe the effects of a similar duration of deafness and cochlear implant use on temporal processing. Specifically, we compared the temporal resolution of neurons in AI of young adult normal-hearing cats that were acutely deafened and implanted immediately prior to recording with that in three groups of neonatally deafened cats. One group of neonatally deafened cats received no chronic stimulation. The other two groups received up to 8 months of either low- or high-rate (50 or 500 pulses per second per electrode, respectively) stimulation from a clinical cochlear implant, initiated at 10 weeks of age. Deafness of 7-13 months duration had no effect on the duration of post-onset response suppression, latency, latency jitter, or the stimulus repetition rate at which units responded maximally (best repetition rate), but resulted in a statistically significant reduction in the ability of units to respond to every stimulus in a train (maximum following rate). None of the temporal response characteristics of the low-rate group differed from those in acutely deafened controls. In contrast, high-rate stimulation had diverse effects: it resulted in decreased suppression duration, longer latency and greater jitter relative to all other groups, and an increase in best repetition rate and cut-off rate relative to acutely deafened controls. The minimal effects of moderate-duration deafness on temporal processing in the present study are in contrast to its previously-reported pronounced effects on cochleotopy. Much longer periods of deafness have been reported to result in significant changes in temporal processing, in accord with the fact that duration of deafness is a major factor influencing outcome in human cochlear implantees.

  12. Distributed fading memory for stimulus properties in the primary visual cortex.

    Directory of Open Access Journals (Sweden)

    Danko Nikolić

    2009-12-01

    Full Text Available It is currently not known how distributed neuronal responses in early visual areas carry stimulus-related information. We made multielectrode recordings from cat primary visual cortex and applied methods from machine learning in order to analyze the temporal evolution of stimulus-related information in the spiking activity of large ensembles of around 100 neurons. We used sequences of up to three different visual stimuli (letters of the alphabet presented for 100 ms and with intervals of 100 ms or larger. Most of the information about visual stimuli extractable by sophisticated methods of machine learning, i.e., support vector machines with nonlinear kernel functions, was also extractable by simple linear classification such as can be achieved by individual neurons. New stimuli did not erase information about previous stimuli. The responses to the most recent stimulus contained about equal amounts of information about both this and the preceding stimulus. This information was encoded both in the discharge rates (response amplitudes of the ensemble of neurons and, when using short time constants for integration (e.g., 20 ms, in the precise timing of individual spikes (

  13. Images of Illusory Motion in Primary Visual Cortex

    DEFF Research Database (Denmark)

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

    2006-01-01

    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...... cortex in response to real and apparent motion. The images show that during apparent motion, a path connecting the cortical representations of the stimulus locations is filled in by activation. The activation along the path of apparent motion is similar to the activation found when a stimulus is...

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

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    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.

  15. Optimization of Visual Tasks for Detecting Visual Cortex Activity in fMRI Studies

    Directory of Open Access Journals (Sweden)

    "A. Mirzajani

    2005-08-01

    Full Text Available Introduction: functional magnetic resonance imaging is a useful non-invasive technique for the evaluation and mapping of human brain, especially the visual cortex. One of the most important subjects in this background is optimizing visual stimuli in various forms of visual tasks for acquiring significant and ro-bust signals. Materials and methods: The effects of physical pa-rameters of visual stimuli on 14 healthy volunteers for detecting visual cortical activity were evaluated by functional magnetic resonance imaging. These pa-rameters were temporal frequency (TF, different pat-terns of activation including, square wave and sine wave grating, and two different states of rest includ-ing black and white screens. Results: The results showed that BOLD signal will be maximally in the TF of 8 Hz, and use the black screen in the rest state. However there was not significant difference between square-¬wave and sine-wave grat-ings in producing visual activation in the cortex. Conclusion: Physical parameters of visual tasks are effective in detecting visual cortical activity, and it is necessary to pay attention to them in order to get sig-nificant and robust signal. Visual tasks with TF of 8 Hz and one pattern of square-wave or sine-wave in activation state, and black screen in rest state are op-timally suitable for fMRI studies.

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

    Directory of Open Access Journals (Sweden)

    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.

  17. Spectrotemporal receptive fields during spindling and non-spindling epochs in cat primary auditory cortex.

    Science.gov (United States)

    Britvina, T; Eggermont, J J

    2008-07-17

    It was often thought that synchronized rhythmic epochs of spindle waves disconnect thalamo-cortical system from incoming sensory signals. The present study addresses this issue by simultaneous extracellular action potential and local field potential (LFP) recordings from primary auditory cortex of ketamine-anesthetized cats during spindling activity. We compared cortical spectrotemporal receptive fields (STRF) obtained during spindling and non-spindling epochs. The basic spectro-temporal parameters of "spindling" and "non-spindling" STRFs were similar. However, the peak-firing rate at the best frequency was significantly enhanced during spindling epochs. This enhancement was mainly caused by the increased probability of a stimulus to evoke spikes (effectiveness of stimuli) during spindling as compared with non-spindling epochs. Augmented LFPs associated with effective stimuli and increased single-unit pair correlations during spindling epochs suggested higher synchrony of thalamo-cortical inputs during spindling that resulted in increased effectiveness of stimuli presented during spindling activity. The neuronal firing rate, both stimulus-driven and spontaneous, was higher during spindling as compared with non-spindling epochs. Overall, our results suggests that thalamic cells during spindling respond to incoming stimuli-related inputs and, moreover, cause more powerful stimulus-related or spontaneous activation of the cortex. PMID:18515012

  18. Categorically distinct types of receptive fields in early visual cortex.

    Science.gov (United States)

    Talebi, Vargha; Baker, Curtis L

    2016-05-01

    In the visual cortex, distinct types of neurons have been identified based on cellular morphology, response to injected current, or expression of specific markers, but neurophysiological studies have revealed visual receptive field (RF) properties that appear to be on a continuum, with only two generally recognized classes: simple and complex. Most previous studies have characterized visual responses of neurons using stereotyped stimuli such as bars, gratings, or white noise and simple system identification approaches (e.g., reverse correlation). Here we estimate visual RF models of cortical neurons using visually rich natural image stimuli and regularized regression system identification methods and characterize their spatial tuning, temporal dynamics, spatiotemporal behavior, and spiking properties. We quantitatively demonstrate the existence of three functionally distinct categories of simple cells, distinguished by their degree of orientation selectivity (isotropic or oriented) and the nature of their output nonlinearity (expansive or compressive). In addition, these three types have differing average values of several other properties. Cells with nonoriented RFs tend to have smaller RFs, shorter response durations, no direction selectivity, and high reliability. Orientation-selective neurons with an expansive output nonlinearity have Gabor-like RFs, lower spontaneous activity and responsivity, and spiking responses with higher sparseness. Oriented RFs with a compressive nonlinearity are spatially nondescript and tend to show longer response latency. Our findings indicate multiple physiologically defined types of RFs beyond the simple/complex dichotomy, suggesting that cortical neurons may have more specialized functional roles rather than lying on a multidimensional continuum. PMID:26936978

  19. Cross-correlations between three units in cat primary auditory cortex.

    Science.gov (United States)

    Eggermont, Jos J; Munguia, Raymundo; Shaw, Gregory

    2013-10-01

    Here we use a modification of the Joint-Peri-Stimulus-Time histogram (JPSTH) to investigate triple correlations between cat auditory cortex neurons. The modified procedure allowed the decomposition of the xy-pair correlation into a part that is due to the correlation of the x and y units with the trigger unit, and a remaining 'pair correlation'. We analyzed 16 sets of 15-minute duration stationary spontaneous recordings in primary auditory cortex (AI) with between 11 and 14 electrodes from 2 arrays of 8 electrodes each that provided spontaneous firing rates above 0.22 sp/s and for which reliable frequency-tuning curves could be obtained and the characteristic frequency (CF) was estimated. Thus we evaluated 11,282 conditional cross-correlation functions. The predictor for the conditional cross-correlation, calculated on the assumption that the trigger unit had no effect on the xy-pair correlation but using the same fraction of xy spikes, was equal to the conventional pair-wise correlation function between units xy. The conditional correlation of the xy-pair due to correlation of the x and/or y unit with the trigger unit decreased with the geometric mean distance of the xy pair to the trigger unit, but was independent of the pair cross-correlation coefficient. The conditional pair correlation coefficient was estimated at 78% of the measured pair correlation coefficient. Assuming a geometric decreasing effect of activities of units on other electrodes on the conditional correlation, we estimated the potential contribution of a large number of contributing units on the measured pair correlation at 35-50 of that correlation. This suggests that conventionally measured pair correlations in auditory cortex under ketamine anesthesia overestimate the 'true pair correlation', likely resulting from massive common input, by potentially up to a factor 2. PMID:23933479

  20. Functional connectivity within the visual cortex of the rat shows state changes.

    NARCIS (Netherlands)

    C. van der Togt; V.A.F. Lamme; H. Spekreijse

    1998-01-01

    The aim of this study was to investigate the dynamics of the horizontal functional connectivity within the visual cortex during spontaneous activity or during visual stimulation. Two arrays of 16 electrodes were inserted in the visual cortex of a rat. From these electrodes a depth profile was Obtain

  1. A disinhibitory microcircuit initiates critical period plasticity in visual cortex

    Science.gov (United States)

    Kuhlman, Sandra J.; Olivas, Nicholas D.; Tring, Elaine; Ikrar, Taruna; Xu, Xiangmin; Trachtenberg, Joshua T.

    2014-01-01

    Early sensory experience instructs the maturation of neural circuitry in cortex 1,2. This has been extensively studied in the primary visual cortex where loss of vision to one eye permanently degrades cortical responsiveness to that eye 3,4, a phenomenon known as ocular dominance plasticity (ODP). Cortical inhibition mediates this process 4-6, but the precise role of specific classes of inhibitory neurons in ODP is controversial. Here we report that evoked firing rates of binocular excitatory neurons in primary visual cortex immediately drop by half when vision is restricted to one eye, but gradually return to normal over the following 24 hours, despite the fact that vision remains restricted to one eye. This restoration of binocular-like excitatory firing rates following monocular deprivation results from a rapid, though transient reduction in the firing rates of fast-spiking, parvalbumin-positive (PV) interneurons, which in turn can be attributed to a decrease in local excitatory circuit input onto PV interneurons. This reduction in PV cell evoked responses following monocular lid suture is restricted to the critical period for ODP and appears to be necessary for subsequent shifts in excitatory ODP. Pharmacologically enhancing inhibition at the time of sight deprivation blocks ODP and, conversely, pharmaco-genetic reduction of PV cell firing rates can extend the critical period for ODP. These findings define the microcircuit changes initiating competitive plasticity during critical periods of cortical development. Moreover, they show that the restoration of evoked firing rates of L2/3 pyramidal neurons by PV-specific disinhibition is a key step in the progression of ocular dominance plasticity. PMID:23975100

  2. Online learning and stimulus-driven responses of neurons in visual cortex

    OpenAIRE

    Tang, Huajin; Li, Haizhou; Yi, Zhang

    2010-01-01

    In understanding how visual scene is processed in visual cortex, it has been an intriguing problem for theoretical and experimental neuroscientists to examine the relationship between visual stimuli and the induced responses of visual cortex. In particular, it is less explored whether and how the collective responses of visual neurons are patterned to reflect the geometrical regularities. In this paper, through a computation model and statistical analysis, we show that the orientation prefere...

  3. Perceptual Learning Increases The Strength of The Earliest Signals in Visual Cortex

    OpenAIRE

    Bao, Min; Yang, Lin; Rios, Cristina; He, Bin; Engel, Stephen A.

    2010-01-01

    Training improves performance on most visual tasks. Such perceptual learning can modify how information is read out from, and represented in, later visual areas, but effects on early visual cortex are controversial. In particular, it remains unknown whether learning can reshape neural response properties in early visual areas independent from feedback arising in later cortical areas. Here, we tested whether learning can modify feed-forward signals in early visual cortex as measured by the hum...

  4. Boosting visual cortex function and plasticity with acetylcholine to enhance visual perception

    Directory of Open Access Journals (Sweden)

    Jun-Il eKang

    2014-09-01

    Full Text Available The cholinergic system is a potent neuromodulatory system that plays critical roles in cortical plasticity, attention and learning. In this review, we propose that the cellular effects of acetylcholine in the primary visual cortex during the processing of visual inputs might induce perceptual learning; i.e., long-term changes in visual perception. Specifically, the pairing of cholinergic activation with visual stimulation increases the signal-to-noise ratio, cue detection ability and long-term facilitation in the primary visual cortex. This cholinergic enhancement would increasesthe strength of thalamocortical afferents to facilitate the treatment of a novel stimulus while decreasing the cortico-cortical signaling to reduce recurrent or top-down modulation. This balance would be mediated by different cholinergic receptor subtypes that are located on both glutamatergic and GABAergic neurons of the different cortical layers. The mechanisms of cholinergic enhancement are closely linked to attentional processes, long-term potentiation and modulation of the excitatory/inhibitory balance. Recently, it was found that boosting this system during visual training robustly enhances sensory perception in a long-term manner. Our hypothesis is that repetitive pairing of cholinergic and sensory stimulation over a long period of time induces long-term changes in the processing of trained stimuli that might improve perceptual ability. Various non-invasive approaches to the activation of the cholinergic neurons have strong potential to improve visual perception.

  5. Intrinsic inter- and intralaminar connections and their relationship to the tonotopic map in cat primary auditory cortex.

    Science.gov (United States)

    Wallace, M N; Kitzes, L M; Jones, E G

    1991-01-01

    Small iontophoretic injections of the lectin, Phaseolus vulgaris leucoagglutinin (PHA-L), were made into different layers of the primary auditory cortex (AI) of cats. Injections in layer I labeled two types of morphologically distinct fibers in layer I as well as a smaller number of axons in layers II and III. Layer II injections labeled descending axons that produced a dense plexus of terminal fibers in layers I-III of both AI and adjacent auditory fields. Injections in layer III also labeled a dense plexus of axon collaterals at the junction of layers V and VI and labeled patches of terminal fibers in both AI and adjacent auditory fields. These were densest in layers I-III but usually extended into layers IV and V as well. The patches were partly formed by axon collaterals of layer III pyramidal cells that traveled for over 4 mm in the gray matter. Injections confined to layer IV labeled axons in all layers of the cortex but none of these axons appeared to reach the white matter. The axons spread laterally in layer IV and up into the superficial layers and ramified especially layer I. Injections in layers V and VI labeled axons in all layers' of the cortex but these were densest in the deep layers where labeling was fairly homogeneous. In the upper layers the labeling was arranged in semi-discrete patches. Large injections involving layers I-III were studied in tangential sections. Between 3 and 8 patches of terminal labeling were observed in AI and these were mainly arranged in a band with its long axis aligned approximately in the dorsoventral direction. However dense patches of terminal labeling also occurred both anterior and posterior to the injection site. In selected experiments portions of the tonotopic map in AI were mapped by single unit recording and subsequently the map was related to patches of anterogradely labeled fibers that surrounded injections of PHA-L. Rows of dorsoventrally oriented patches were among cells with a similar best frequency to

  6. Patterns of axon collateralization of identified supragranular pyramidal neurons in the cat auditory cortex.

    Science.gov (United States)

    Ojima, H; Honda, C N; Jones, E G

    1991-01-01

    Nine pyramidal neurons in layers II and III of cat primary auditory cortex (AI) were fully reconstructed after intracellular injections of horseradish peroxidase or biocytin. Each neuron was functionally characterized according to its position relative to an anteroposterior sequence of best frequency responses. All labeled somata were in layers II or III and gave rise to typical apical and basal dendritic arbors as well as to extensive systems of axon collaterals. The primary axon of all except 1 cell entered the white matter and was probably directed toward other cortical areas ipsi- or contralaterally. Two major intracortical collateral systems emerged from the main axon in AI, one ending in the vicinity of the cell and the second at a distance. (1) Many local and recurrent collaterals, given off in layers III and V, contributed terminal branches to the formation of a columnar pattern of terminations extending superficially and deeply into the soma. The column extended through layers I-V, with some constriction in the middle portion corresponding to layer IV. (2) The axon of each cell also gave rise to 2-5 thick, long-range collaterals in layers III and/or V. These ran parallel to the pial surface for several millimeters. At several points along these long horizontal collaterals, vertically directed branches emerged to form columnar terminations, again extending through layers I-V. These columns did not overlap with that formed in the vicinity of the cell, and were situated at distances 500-1200 microns from the cell body. When viewed in the tangential plane, horizontal collaterals were oriented, on the whole, dorsoventrally with respect to the surface of the cortex. This may correspond to the organization of isofrequency bands previously described in cats. The results suggest that the major spread of excitation in AI is mediated by horizontal collaterals of pyramidal cells and that it occurs along the lines of isofrequency domains. Within the latter the

  7. Spontaneous pattern formation and pinning in the visual cortex

    Science.gov (United States)

    Baker, Tanya I.

    Bifurcation theory and perturbation theory can be combined with a knowledge of the underlying circuitry of the visual cortex to produce an elegant story explaining the phenomenon of visual hallucinations. A key insight is the application of an important set of ideas concerning spontaneous pattern formation introduced by Turing in 1952. The basic mechanism is a diffusion driven linear instability favoring a particular wavelength that determines the size of the ensuing stripe or spot periodicity of the emerging spatial pattern. Competition between short range excitation and longer range inhibition in the connectivity profile of cortical neurons provides the difference in diffusion length scales necessary for the Turing mechanism to occur and has been proven by Ermentrout and Cowan to be sufficient to explain the generation of a subset of reported geometric hallucinations. Incorporating further details of the cortical circuitry, namely that neurons are also weakly connected to other neurons sharing a particular stimulus orientation or spatial frequency preference at even longer ranges and the resulting shift-twist symmetry of the neuronal connectivity, improves the story. We expand this approach in order to be able to include the tuned responses of cortical neurons to additional visual stimulus features such as motion, color and disparity. We apply a study of nonlinear dynamics similar to the analysis of wave propagation in a crystalline lattice to demonstrate how a spatial pattern formed through the Turing instability can be pinned to the geometric layout of various feature preferences. The perturbation analysis is analogous to solving the Schrodinger equation in a weak periodic potential. Competition between the local isotropic connections which produce patterns of activity via the Turing mechanism and the weaker patchy lateral connections that depend on a neuron's particular set of feature preferences create long wavelength affects analogous to commensurate

  8. Radiographically visualized skeletal changes associated with mucopolysaccharidosis VI in cats

    International Nuclear Information System (INIS)

    The radiographic skeletal form and structure of all cats with mucopolysaccharidosis VI is described. Common manifestations included epiphyseal dysplasia, generalized osteoporosis, abnormal nasal turbinate development, his subluxation, impaired development of skeletal growth, pectus excavatum, hyoid hypoplasia, aplasia, hypoplasia and fragmentation or abnormal ossification of the dens, and aplasia or hypoplasia of frontal and sphenoid sinuses. The skeletal measurements of two affected cats were compared with those of normal, sex-matched littermates, and the measurements of two affected female cats were compared with those of a normal male littermate

  9. Response of SII cortex to ipsilateral, contralateral and bilateral flutter stimulation in the cat

    Directory of Open Access Journals (Sweden)

    Favorov Oleg

    2005-02-01

    Full Text Available Abstract Background A distinctive property of SII is that it is the first cortical stage of the somatosensory projection pathway that integrates information arising from both sides of the body. However, there is very little known about how inputs across the body mid-line are processed within SII. Results Optical intrinsic signal imaging was used to evaluate the response of primary somatosensory cortex (SI and SII in the same hemisphere to 25 Hz sinusoidal vertical skin displacement stimulation ("skin flutter" applied contralaterally, ipsilaterally, and bilaterally to the central pads of the forepaws. A localized increase in absorbance in both SI and SII was evoked by both contralateral and bilateral flutter stimulation. Ipsilateral flutter stimulation evoked a localized increase in absorbance in SII, but not in SI. The SII region that responded with an increase in absorbance to ipsilateral stimulation was posterior to the region in which absorbance increased maximally in response to stimulation of the contralateral central pad. Additionally, in the posterior SII region that responded maximally to ipsilateral stimulation of the central pad, bilateral central pad stimulation approximated a linear summation of the SII responses to independent stimulation of the contralateral and ipsilateral central pads. Conversely, in anterior SII (the region that responded maximally to contralateral stimulation, bilateral stimulation was consistently less than the response evoked from the contralateral central pad. Conclusions The results indicate that two regions located at neighboring, but distinctly different A-P levels of the anterior ectosylvian gyrus process input from opposite sides of the body midline in very different ways. The results suggest that the SII cortex, in the cat, can be subdivided into at least two functionally distinct regions and that these functionally distinct regions demonstrate a laterality preference within SII.

  10. The speed of context integration in the visual cortex.

    Science.gov (United States)

    Sugihara, Tadashi; Qiu, Fangtu T; von der Heydt, Rüdiger

    2011-07-01

    The observation of figure-ground selectivity in neurons of the visual cortex shows that these neurons can be influenced by the image context far beyond the classical receptive field. To clarify the nature of the context integration mechanism, we studied the latencies of neural edge signals, comparing the emergence of context-dependent definition of border ownership with the onset of local edge definition (contrast polarity; stereoscopic depth order). Single-neuron activity was recorded in areas V1 and V2 of Macaca mulatta under behaviorally induced fixation. Whereas local edge definition emerged immediately (predicted from horizontal signal propagation. The prediction was based on the increase in cortical distance, computed from the mapping of the test stimuli in the cortex, and the known conduction velocities of horizontal fibers. The measured latencies increased with cortical distance, but much less than predicted by the horizontal propagation hypothesis. Probability calculations showed that an explanation of the context influence by horizontal signal propagation alone is highly unlikely, whereas mechanisms involving back projections from other extrastriate areas are plausible.

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

    Science.gov (United States)

    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.

  12. 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.

  13. Oxidative metabolic activity of cerebral cortex after fluid-percussion head injury in the cat.

    Science.gov (United States)

    Duckrow, R B; LaManna, J C; Rosenthal, M; Levasseur, J E; Patterson, J L

    1981-05-01

    To assess the metabolic and vascular effects of head trauma, fluid-percussion pressure waves were transmitted to the brains of anesthetized, paralyzed, and artificially ventilated cats. Changes in the redox state of cytochrome a,a3, and relative local blood volume were measured in situ by dual-wavelength reflection spectrophotometry of the cortical surface viewed through an acrylic cranial window implanted within the closed skull. Initial fluid-percussion impacts of 0.5 to 2.8 atm peak pressure produced consistent transient oxidation of cytochrome a,a3 and increases of cortical blood volume. These changes occurred despite the presence of transient posttraumatic hypotension i some cases. Also, impact-induced alterations of vascular tone occurred, independent of the presence or absence of transient hypertension in the posttraumatic period. These data demonstrate that hypoxia does not play a role in the immediate posttraumatic period in cerebral cortex, and are consistent with the idea that after injury there is increased cortical energy conservation. These data also support the concept that head trauma alters the relationship of metabolism and cerebral circulation in the period immediately after injury. PMID:7229699

  14. Effects of weak amplitude-modulated microwave fields on calcium efflux from awake cat cerebral cortex

    International Nuclear Information System (INIS)

    Calcium (45Ca2+) efflux was studied from preloaded cortex in cats immobilized under local anesthesia, and exposed to a 3.0-mW/cm2 450-MHz field, sinusoidally amplitude modulated at 16 Hz modulation depth 85%). Tissue dosimetry showed a field of 33 V/m in the interhemispheric fissure (rate of energy deposition 0.29 W/kg). Field exposure lasted 60 min. By comparison with controls, efflux curves from field exposed brains were disrupted by waves of increased 45Ca2+ efflux. These waves were irregular in amplitude and duration, but many exhibited periods of 20-30 min. They continued into the postexposure period. Binomial probability analysis indicates that the field-exposed efflux curves constitute a different population from controls at a confidence level of 0.96. In about 70% of cases, initiation of field exposure was followed by increased end-tidal CO2 excretion for about 5 min. However, hypercapnea induced by hypoventilation did not elicit increased 45Ca2+ efflux. Thus this increase with exposure does not appear to arise as a secondary effect of raised cerebral CO2 levels. Radioactivity measurements in cortical samples after superfusion showed 45Ca2+ penetration at about 1.7 mm/hr, consistent with diffusion of the ion in free solution

  15. The role of visual cortex acetylcholine in learning to discriminate temporally modulated visual stimuli

    Directory of Open Access Journals (Sweden)

    Victor H Minces

    2013-03-01

    Full Text Available Cholinergic neurons in the basal forebrain innervate discrete regions of the cortical mantle, bestowing the cholinergic system with the potential to dynamically modulate sub-regions of the cortex according to behavioral demands. Cortical cholinergic activity has been shown to facilitate learning and modulate attention. Experiments addressing these issues have primarily focused on widespread cholinergic depletions, extending to areas involved in general cognitive processes and sleep cycle regulation, making a definitive interpretation of the behavioral role of cholinergic projections difficult. Furthermore, a review of the electrophysiological literature suggests that cholinergic modulation is particularly important in representing the fine temporal details of stimuli, an issue rarely addressed in behavioral experimentation. The goal of this work is to understand the role cholinergic projections, specific to the sensory cortex, in learning to discriminate fine differences in the temporal structure of stimuli. A novel visual Go/No-Go task was developed to assess the ability of rats to learn and discriminate fine differences in the temporal structure of visual stimuli (lights flashing at various frequencies. The cholinergic contribution to this task was examined by selectively eliminating acetylcholine projections to visual cortex (using 192 IgG-saporin, either before or after discrimination training.We find that in the face of compromised cholinergic input to the visual cortex, the rats’ ability to learn to perform fine discriminations is impaired, whereas their ability to perform discriminations remains unaffected.These results suggest that acetylcholine serves the role of facilitating plastic changes in the sensory cortices that are needed for an animal to refine their sensitivity to the temporal characteristics of relevant stimuli.

  16. Spatial phase sensitivity of complex cells in primary visual cortex depends on stimulus contrast.

    Science.gov (United States)

    Meffin, H; Hietanen, M A; Cloherty, S L; Ibbotson, M R

    2015-12-01

    Neurons in primary visual cortex are classified as simple, which are phase sensitive, or complex, which are significantly less phase sensitive. Previously, we have used drifting gratings to show that the phase sensitivity of complex cells increases at low contrast and after contrast adaptation while that of simple cells remains the same at all contrasts (Cloherty SL, Ibbotson MR. J Neurophysiol 113: 434-444, 2015; Crowder NA, van Kleef J, Dreher B, Ibbotson MR. J Neurophysiol 98: 1155-1166, 2007; van Kleef JP, Cloherty SL, Ibbotson MR. J Physiol 588: 3457-3470, 2010). However, drifting gratings confound the influence of spatial and temporal summation, so here we have stimulated complex cells with gratings that are spatially stationary but continuously reverse the polarity of the contrast over time (contrast-reversing gratings). By varying the spatial phase and contrast of the gratings we aimed to establish whether the contrast-dependent phase sensitivity of complex cells results from changes in spatial or temporal processing or both. We found that most of the increase in phase sensitivity at low contrasts could be attributed to changes in the spatial phase sensitivities of complex cells. However, at low contrasts the complex cells did not develop the spatiotemporal response characteristics of simple cells, in which paired response peaks occur 180° out of phase in time and space. Complex cells that increased their spatial phase sensitivity at low contrasts were significantly overrepresented in the supragranular layers of cortex. We conclude that complex cells in supragranular layers of cat cortex have dynamic spatial summation properties and that the mechanisms underlying complex cell receptive fields differ between cortical layers.

  17. Oculomotor Remapping of Visual Information to Foveal Retinotopic Cortex.

    Science.gov (United States)

    Knapen, Tomas; Swisher, Jascha D; Tong, Frank; Cavanagh, Patrick

    2016-01-01

    Our eyes continually jump around the visual scene to bring the high-resolution, central part of our vision onto objects of interest. We are oblivious to these abrupt shifts, perceiving the visual world to appear reassuringly stable. A process called remapping has been proposed to mediate this perceptual stability for attended objects by shifting their retinotopic representation to compensate for the effects of the upcoming eye movement. In everyday vision, observers make goal-directed eye movements towards items of interest bringing them to the fovea and, for these items, the remapped activity should impinge on foveal regions of the retinotopic maps in visual cortex. Previous research has focused instead on remapping for targets that were not saccade goals, where activity is remapped to a new peripheral location rather than to the foveal representation. We used functional magnetic resonance imaging (fMRI) and a phase-encoding design to investigate remapping of spatial patterns of activity towards the fovea/parafovea for saccade targets that were removed prior to completion of the eye movement. We found strong evidence of foveal remapping in retinotopic visual areas, which failed to occur when observers merely attended to the same peripheral target without making eye movements towards it. Significantly, the spatial profile of the remapped response matched the orientation and size of the saccade target, and was appropriately scaled to reflect the retinal extent of the stimulus had it been foveated. We conclude that this remapping of spatially structured information to the fovea may serve as an important mechanism to support our world-centered sense of location across goal-directed eye movements under natural viewing conditions. PMID:27445715

  18. 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

    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...... 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...

  19. Avalanche analysis from multi-electrode ensemble recordings in cat, monkey and human cerebral cortex during wakefulness and sleep.

    Directory of Open Access Journals (Sweden)

    Nima eDehghani

    2012-08-01

    Full Text Available Self-organized critical states are found in many natural systems, from earthquakes to forest fires, they have also been observed in neural systems, particularly, in neuronal cultures. However, the presence of critical states in the awake brain remains controversial. Here, we compared avalanche analyses performed on different in vivo preparations during wakefulness, slow-wave sleep and REM sleep, using high-density electrode arrays in cat motor cortex (96 electrodes, monkey motor cortex and premotor cortex and human temporal cortex (96 electrodes in epileptic patients. In neuronal avalanches defined from units (up to 160 single units, the size of avalanches never clearly scaled as power-law, but rather scaled exponentially or displayed intermediate scaling. We also analyzed the dynamics of local field potentials (LFPs and in particular LFP negative peaks (nLFPs among the different electrodes (up to 96 sites in temporal cortex or up to 128 sites in adjacent motor and pre-motor cortices. In this case, the avalanches defined from nLFPs displayed power-law scaling in double logarithmic representations, as reported previously in monkey. However, avalanche defined as positive LFP (pLFP peaks, which are less directly related to neuronal firing, also displayed apparent power-law scaling. Closer examination of this scaling using the more reliable cumulative distribution function (CDF and other rigorous statistical measures, did not confirm power-law scaling. The same pattern was seen for cats, monkey and human, as well as for different brain states of wakefulness and sleep. We also tested other alternative distributions. Multiple exponential fitting yielded optimal fits of the avalanche dynamics with bi-exponential distributions. Collectively, these results show no clear evidence for power-law scaling or self-organized critical states in the awake and sleeping brain of mammals, from cat to man.

  20. Can retinal ganglion cell dipoles seed iso-orientation domains in the visual cortex?

    Directory of Open Access Journals (Sweden)

    Manuel Schottdorf

    Full Text Available It has been argued that the emergence of roughly periodic orientation preference maps (OPMs in the primary visual cortex (V1 of carnivores and primates can be explained by a so-called statistical connectivity model. This model assumes that input to V1 neurons is dominated by feed-forward projections originating from a small set of retinal ganglion cells (RGCs. The typical spacing between adjacent cortical orientation columns preferring the same orientation then arises via Moiré-Interference between hexagonal ON/OFF RGC mosaics. While this Moiré-Interference critically depends on long-range hexagonal order within the RGC mosaics, a recent statistical analysis of RGC receptive field positions found no evidence for such long-range positional order. Hexagonal order may be only one of several ways to obtain spatially repetitive OPMs in the statistical connectivity model. Here, we investigate a more general requirement on the spatial structure of RGC mosaics that can seed the emergence of spatially repetitive cortical OPMs, namely that angular correlations between so-called RGC dipoles exhibit a spatial structure similar to that of OPM autocorrelation functions. Both in cat beta cell mosaics as well as primate parasol receptive field mosaics we find that RGC dipole angles are spatially uncorrelated. To help assess the level of these correlations, we introduce a novel point process that generates mosaics with realistic nearest neighbor statistics and a tunable degree of spatial correlations of dipole angles. Using this process, we show that given the size of available data sets, the presence of even weak angular correlations in the data is very unlikely. We conclude that the layout of ON/OFF ganglion cell mosaics lacks the spatial structure necessary to seed iso-orientation domains in the primary visual cortex.

  1. The effects of prefrontal cortex inactivation on object responses of single neurons in the inferotemporal cortex during visual search

    OpenAIRE

    Monosov, Ilya E.; David L Sheinberg; Thompson, Kirk G.

    2011-01-01

    Inferotemporal cortex (IT) is believed to be directly involved in object processing and necessary for accurate and efficient object recognition. The frontal eye field (FEF) is an area in the primate prefrontal cortex that is involved in visual spatial selection and is thought to guide spatial attention and eye movements. We show that object selective responses of IT neurons and behavioral performance are affected by changes in frontal eye field activity. This was found in monkeys performing a...

  2. Deviations in cortex sulcation associated with visual hallucinations in schizophrenia.

    Science.gov (United States)

    Cachia, A; Amad, A; Brunelin, J; Krebs, M-O; Plaze, M; Thomas, P; Jardri, R

    2015-09-01

    Hallucinations, and auditory hallucinations (AH) in particular, constitute the most typical and disabling schizophrenia symptoms. Although visual hallucinations (VH) have been largely neglected in psychiatric disorders, a recent review reported a 27% mean prevalence of VH in schizophrenia patients. The pathophysiology underlying VH in schizophrenia remains elusive. Several schizophrenia studies reported a significant effect of age on VH; therefore, we tested the hypothesis that the neurodevelopmental model of schizophrenia may explain VH occurrence. We analyzed cortex sulcation, a marker of brain development, in healthy controls (HCs) and two subgroups of carefully selected schizophrenia patients suffering from hallucinations: patients with only AH (that is, patients who never reported VH) and patients with audio-visual hallucinations (A+VH). Different cortical sulcation and left-right sulcal asymmetry were found between A+VH and AH patients, with decreased sulcation in both A+VH and AH patients in comparison with the HCs. Although a specific association between VH and neurodegenerative mechanisms, for example, in Body-Lewy Dementia or Parkinson's Disease, has previously been reported in the literature, the current study provides the first neuroimaging evidence of an association between VH and neurodevelopmental mechanisms.

  3. Morphological properties of nociceptive and non-nociceptive neurons in primary somatic cerebral cortex (SI) of cat

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    With the techniques of intracellular recording and labelling, we investigated pain sensation and modulation of the somatic cortical cortex at the neuron's level. After observing the evoked potentials from stimulating the saphenous nerves (SN) of 654 neurons in SI area of the cats, we labelled 30 of the neurons with Neurobiotin to preserve the distribution and the morphologic characteristics of the neurons in the cortex. Based on the tridimensional reconstruction in addition to the eletrophysiological functions, we found clear morphological distinctions between nociceptive and non-nociceptive neurons (P<0.01). This result provided new experimental material to illustrate the function of nociceptive neurons in somatosensory cortex (SI) and presented further evidence to support the "specificity theory" of pain sensation in terms of morphology.

  4. 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.

  5. 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.

  6. Cats

    Science.gov (United States)

    ... those experienced by humans. Cats that hunt wild rodents and rabbits in the western, particularly the southwestern, ... caused by a fungus that can infect skin, hair, and nails of both people and animals. Ringworm ...

  7. The perceptual grouping criterion of colinearity is reflected by anisotropies of connections in the primary visual cortex.

    Science.gov (United States)

    Schmidt, K E; Goebel, R; Löwel, S; Singer, W

    1997-05-01

    An important step in the processing of visual patterns is the segmentation of the retinal image. Neuronal responses evoked by the contours of individual objects need to be identified and associated for further joint processing. These grouping operations are based on a number of Gestalt criteria. Here we report that connections in the visual cortex of the cat exhibit a highly significant anisotropy, preferentially linking neurons activated by contours that have similar orientation and are aligned colinearly. These anatomical data suggest a close relation between the perceptual grouping criterion of colinearity and the topology of tangential intracortical connections. We propose that tangential intracortical connections support perceptual grouping by modulating the saliency of distributed cortical responses in a context-dependent way. The present data are compatible with the hypothesis that the criteria for this grouping operation are determined by the architecture of the tangential connections.

  8. Repetitive Transcranial Direct Current Stimulation Induced Excitability Changes of Primary Visual Cortex and Visual Learning Effects—A Pilot Study

    OpenAIRE

    Sczesny-Kaiser, Matthias; Beckhaus, Katharina; Dinse, Hubert R.; Schwenkreis, Peter; Tegenthoff, Martin; Höffken, Oliver

    2016-01-01

    Studies on noninvasive motor cortex stimulation and motor learning demonstrated cortical excitability as a marker for a learning effect. Transcranial direct current stimulation (tDCS) is a non-invasive tool to modulate cortical excitability. It is as yet unknown how tDCS-induced excitability changes and perceptual learning in visual cortex correlate. Our study aimed to examine the influence of tDCS on visual perceptual learning in healthy humans. Additionally, we measured excitability in prim...

  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

    . The more symmetrical visual acuity became after unilateral cataract surgery, the more pronounced was the grey matter increase in visual cortex. Conclusion:  The data suggest that cataract surgery triggered a use-dependent structural plasticity in V2 presumably through improved binocular integration......Purpose:  The developing visual cortex has a strong potential to undergo plastic changes. Little is known about the potential of the ageing visual cortex to express plasticity. A pertinent question is whether therapeutic interventions can trigger plastic changes in the ageing visual cortex...... 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. 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.

  11. Surface-Based Analyses of Anatomical Properties of the Visual Cortex in Macular Degeneration.

    Directory of Open Access Journals (Sweden)

    Doety Prins

    Full Text Available Macular degeneration (MD can cause a central visual field defect. In a previous study, we found volumetric reductions along the entire visual pathways of MD patients, possibly indicating degeneration of inactive neuronal tissue. This may have important implications. In particular, new therapeutic strategies to restore retinal function rely on intact visual pathways and cortex to reestablish visual function. Here we reanalyze the data of our previous study using surface-based morphometry (SBM rather than voxel-based morphometry (VBM. This can help determine the robustness of the findings and will lead to a better understanding of the nature of neuroanatomical changes associated with MD.The metrics of interest were acquired by performing SBM analysis on T1-weighted MRI data acquired from 113 subjects: patients with juvenile MD (JMD; n = 34, patients with age-related MD (AMD; n = 24 and healthy age-matched controls (HC; n = 55.Relative to age-matched controls, JMD patients showed a thinner cortex, a smaller cortical surface area and a lower grey matter volume in V1 and V2, while AMD patients showed thinning of the cortex in V2. Neither patient group showed a significant difference in mean curvature of the visual cortex.The thinner cortex, smaller surface area and lower grey matter volume in the visual cortex of JMD patients are consistent with our previous results showing a volumetric reduction in their visual cortex. Finding comparable results using two rather different analysis techniques suggests the presence of marked cortical degeneration in the JMD patients. In the AMD patients, we found a thinner cortex in V2 but not in V1. In contrast to our previous VBM analysis, SBM revealed no volumetric reductions of the visual cortex. This suggests that the cortical changes in AMD patients are relatively subtle, as they apparently can be missed by one of the methods.

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

    Directory of Open Access Journals (Sweden)

    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.

  13. Differential visually-induced gamma-oscillations in human cerebral cortex

    OpenAIRE

    Asano, Eishi; Nishida, Masaaki; Fukuda, Miho; Rothermel, Robert; Juhasz, Csaba; Sood, Sandeep

    2008-01-01

    Using intracranial electrocorticography, we determined how cortical gamma-oscillations (50–150Hz) were induced by different visual tasks in nine children with focal epilepsy. In all children, full-field stroboscopic flash-stimuli induced gamma-augmentation in the anterior-medial occipital cortex (starting on average at 31-msec after stimulus presentation) and subsequently in the lateral-polar occipital cortex; minimal gamma-augmentation was noted in the inferior occipital-temporal cortex; occ...

  14. Characteristics of intracellularly injected infragranular pyramidal neurons in cat primary auditory cortex.

    Science.gov (United States)

    Ojima, H; Honda, C N; Jones, E G

    1992-01-01

    Pyramidal neurons in layers V and VI of cat primary auditory cortex (AI) were intracellularly injected with biocytin after functional characterization according to a position relative to an anteroposterior sequence of best-frequency responses. A sample of 19 completely filled neurons was analyzed, and a preliminary classification was made on the basis of dendritic morphology and axon collateral distribution. Layer V cells could be divided into two types. Cells in the upper part of layer V and projecting toward the diencephalon had a large cell body and an apical dendrite with extensive branches in layer I. These cells had few recurrent axon collaterals, and no terminal axonal bushes were formed in the vicinity of the dendritic field. Long horizontal collaterals with many boutons, however, extended in various directions parallel to the cortical surface. By contrast, cells in the lower part of layer V and sending an axon into the putamen, or without an obvious subcortical axon, had a medium soma and an apical dendrite with few branches in layer I. These cells had a dense bush of recurrent collaterals extending into layers II and III and surrounding the dendritic field, but few or no horizontal collaterals. Layer VI injected neurons were more heterogeneous. All had a thin ascending dendrite with oblique branches both ending in layer III. Axon collateral distributions varied from cell to cell. Relatively small cells with an apical dendrite that branched frequently in layers III and IV had a dense network of recurrent collaterals in the dendritic field, but virtually no horizontal collaterals. This type projected toward the diencephalon. Cells with relatively long horizontal collaterals and a weak recurrent system confined to layers V and VI had a unique arborization pattern of basal dendrites. This type may have projected to the claustrum or other cortical areas. One cell with dendritic branches restricted to layer VI had horizontal collaterals predominantly in layer

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

    Directory of Open Access Journals (Sweden)

    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.

  16. 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.

  17. Reduction in the retinotopic early visual cortex with normal aging and magnitude of perceptual learning

    Science.gov (United States)

    Chang, Li-Hung; Yotsumoto, Yuko; Salat, David H.; Andersen, George J.; Watanabe, Takeo; Sasaki, Yuka

    2014-01-01

    While normal aging is known to reduce cortical structures globally, the effects of aging on local structures and functions of early visual cortex are less understood. Here, using standard retinotopic mapping and magnetic resonance imaging (MRI) morphological analyses, we investigated whether aging affects areal size of the early visual cortex, which were retinotopically localized, and whether those morphological measures were associated with individual performance on visual perceptual learning. First, significant age-associated reduction was found in the areal size of V1, V2, and V3. Second, individual ability of visual perceptual learning was significantly correlated with areal size of V3 in older adults. These results demonstrate that aging changes local structures of the early visual cortex and the degree of change may be associated with individual visual plasticity. PMID:25277041

  18. Disconnection of the amygdala from visual association cortex impairs visual reward-association learning in monkeys.

    Science.gov (United States)

    Gaffan, E A; Gaffan, D; Harrison, S

    1988-09-01

    Cynomolgus monkeys (Macaca fascicularis) were trained in a task that assessed their ability to associate visual stimuli with food reward. Acquisition of stimulus-reward associations was measured under 2 conditions, a 2-stimuli acquisition condition and a 1-stimulus acquisition condition. On each trial in the 2-stimuli condition, the positive (correct) and negative (incorrect) stimuli were presented side by side and the animal chose one by touching it; if the choice was correct, a food reward was dispensed. On each trial in the 1-stimulus condition, either the positive or the negative stimulus was presented alone; if the stimulus was the positive, it was followed by reward delivery, regardless of the animal's response to it, and if it was the negative, it was not followed by reward delivery. Thus, reward delivery was contingent upon the animal's response to the stimuli in the 2-stimuli condition but not in the 1-stimulus condition. The effect of acquisition trials under these 2 conditions was measured, in both conditions, by the animal's subsequent choice when presented with the 2 stimuli side by side. Following preoperative training in this task, the animals were first subjected to unilateral ablation of the inferotemporal cortex. This operation had little effect on the animals' learning ability. Then, the amygdala was ablated in the hemisphere contralateral to that in which the unilateral inferotemporal ablation had been carried out. This combination of crossed unilateral lesions of the amygdala and of the inferotemporal cortex, which disconnects the amygdala from the output of visual association cortex, produced a profound impairment in stimulus-reward-associative learning.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3171671

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

    Directory of Open Access Journals (Sweden)

    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

  20. Activity of Caudate Nucleus Neurons in a Visual Fixation Paradigm in Behaving Cats

    OpenAIRE

    Tamás Nagypál; Péter Gombkötő; Balázs Barkóczi; György Benedek; Attila Nagy

    2015-01-01

    Beside its motor functions, the caudate nucleus (CN), the main input structure of the basal ganglia, is also sensitive to various sensory modalities. The goal of the present study was to investigate the effects of visual stimulation on the CN by using a behaving, head-restrained, eye movement-controlled feline model developed recently for this purpose. Extracellular multielectrode recordings were made from the CN of two cats in a visual fixation paradigm applying static and dynamic stimuli. T...

  1. The role of visual cortex acetylcholine in learning to discriminate temporally modulated visual stimuli.

    Science.gov (United States)

    Minces, V H; Alexander, A S; Datlow, M; Alfonso, S I; Chiba, A A

    2013-01-01

    Cholinergic neurons in the basal forebrain innervate discrete regions of the cortical mantle, bestowing the cholinergic system with the potential to dynamically modulate sub-regions of the cortex according to behavioral demands. Cortical cholinergic activity has been shown to facilitate learning and modulate attention. Experiments addressing these issues have primarily focused on widespread cholinergic depletions, extending to areas involved in general cognitive processes and sleep cycle regulation, making a definitive interpretation of the behavioral role of cholinergic projections difficult. Furthermore, a review of the electrophysiological literature suggests that cholinergic modulation is particularly important in representing the fine temporal details of stimuli, an issue rarely addressed in behavioral experimentation. The goal of this work is to understand the role of cholinergic projections, specific to the sensory cortices, in learning to discriminate fine differences in the temporal structure of stimuli. A novel visual Go/No-Go task was developed to assess the ability of rats to learn to discriminate fine differences in the temporal structure of visual stimuli (lights flashing at various frequencies). The cholinergic contribution to this task was examined by selective reduction of acetylcholine projections to visual cortex (VCx) (using 192 IgG-saporin), either before or after discrimination training. We find that in the face of compromised cholinergic input to the VCx, the rats' ability to learn to perform fine discriminations is impaired, whereas their ability to perform previously learned discriminations remains unaffected. These results suggest that acetylcholine serves the role of facilitating plastic changes in the sensory cortices that are necessary for an animal to refine its sensitivity to the temporal characteristics of relevant stimuli. PMID:23519084

  2. A Major Human White Matter Pathway Between Dorsal and Ventral Visual Cortex.

    Science.gov (United States)

    Takemura, Hiromasa; Rokem, Ariel; Winawer, Jonathan; Yeatman, Jason D; Wandell, Brian A; Pestilli, Franco

    2016-05-01

    Human visual cortex comprises many visual field maps organized into clusters. A standard organization separates visual maps into 2 distinct clusters within ventral and dorsal cortex. We combined fMRI, diffusion MRI, and fiber tractography to identify a major white matter pathway, the vertical occipital fasciculus (VOF), connecting maps within the dorsal and ventral visual cortex. We use a model-based method to assess the statistical evidence supporting several aspects of the VOF wiring pattern. There is strong evidence supporting the hypothesis that dorsal and ventral visual maps communicate through the VOF. The cortical projection zones of the VOF suggest that human ventral (hV4/VO-1) and dorsal (V3A/B) maps exchange substantial information. The VOF appears to be crucial for transmitting signals between regions that encode object properties including form, identity, and color and regions that map spatial information. PMID:25828567

  3. Positive affect modulates activity in the visual cortex to images of high calorie foods.

    Science.gov (United States)

    Killgore, William D S; Yurgelun-Todd, Deborah A

    2007-05-01

    Activity within the visual cortex can be influenced by the emotional salience of a stimulus, but it is not clear whether such cortical activity is modulated by the affective status of the individual. This study used functional magnetic resonance imaging (fMRI) to examine the relationship between affect ratings on the Positive and Negative Affect Schedule and activity within the occipital cortex of 13 normal-weight women while viewing images of high calorie and low calorie foods. Regression analyses revealed that when participants viewed high calorie foods, Positive Affect correlated significantly with activity within the lingual gyrus and calcarine cortex, whereas Negative Affect was unrelated to visual cortex activity. In contrast, during presentations of low calorie foods, affect ratings, regardless of valence, were unrelated to occipital cortex activity. These findings suggest a mechanism whereby positive affective state may affect the early stages of sensory processing, possibly influencing subsequent perceptual experience of a stimulus. PMID:17464782

  4. Role of the cerebellum and motor cortex in the regulation of visually controlled locomotion.

    Science.gov (United States)

    Armstrong, D M; Marple-Horvat, D E

    1996-04-01

    An account is given of the current state of knowledge of the contributions of the cerebellum and the forelimb motor cortex (MC) to the neural control of walking movements in the cat. The main emphasis is on information obtained by recording from single MC and cerebellar neurones in chronically instrumented cats engaged in walking on the rungs of a horizontal ladder, a form of locomotion that is heavily dependent on visual input and for which the integrity of MC is essential. Evidence from the authors' laboratory and from other studies is presented which establishes that MC neurones, including pyramidal tract neurones, show higher levels of activity during ladder walking than during overground walking (i.e., when less constraint exists over the locus of footfall) and that this increase is greatest in late swing-early stance in the contralateral forelimb, consistent with one role of MC being to help determine the locus of footfall. However, many MC neurones develop peak activity at other times in the step cycle, and a comparison with recordings during treadmill walking suggests MC may also help regulate stance duration when walking speed is an important performance variable. Recordings from Purkinje cells and cerebellar nuclear neurones show that during ladder walking step-related activity is widespread in the vermal, paravermal, and crural regions of cortex and in the interposed and dentate nuclei. Nuclear cell activity is so timed that it could be contributing to producing the locomotor rhythms evident in MC cells, although this is not yet proven. Results are also presented and discussed relating to MC and cerebellar neuronal responses that occur when a step onto an unstable rung results in an unexpected external perturbation of the forelimb step cycle. MC responses begin with onset latency as short as 20 ms so that MC may assist spinal reflex mechanisms to produce a post hoc compensatory change in motor output. However, work in progress suggests that corresponding

  5. Effects of cholinergic deafferentation of the rhinal cortex on visual recognition memory in monkeys

    Science.gov (United States)

    Turchi, Janita; Saunders, Richard C.; Mishkin, Mortimer

    2005-01-01

    Excitotoxic lesion studies have confirmed that the rhinal cortex is essential for visual recognition ability in monkeys. To evaluate the mnemonic role of cholinergic inputs to this cortical region, we compared the visual recognition performance of monkeys given rhinal cortex infusions of a selective cholinergic immunotoxin, ME20.4-SAP, with the performance of monkeys given control infusions into this same tissue. The immunotoxin, which leads to selective cholinergic deafferentation of the infused cortex, yielded recognition deficits of the same magnitude as those produced by excitotoxic lesions of this region, providing the most direct demonstration to date that cholinergic activation of the rhinal cortex is essential for storing the representations of new visual stimuli and thereby enabling their later recognition. PMID:15684066

  6. Microarray profiles on age-related genes in the earlier postnatal rat visual cortex

    Institute of Scientific and Technical Information of China (English)

    YANG Liu; NIE Yu-hong; ZHOU Li-hua; LIN Shao-chun; WU Kai-li

    2011-01-01

    Background Accumulating evidence indicates that both innate and adaptive mechanisms are responsible for the postnatal development of the mammalian visual cortex. Most of the studies, including gene expression analysis, were performed on the visual cortex during the critical period; few efforts were made to elucidate the molecular changes in the visual cortex during much earlier postnatal stages. The current study aimed to gain a general insight into the molecular mechanisms in the developmental process of the rat visual cortex using microarray to display the gene expression profiles of the visual cortex on postnatal days.Methods All age-matched Sprague-Dawley rats in various groups including postnatal day 0 (PO, n=20), day 10 (P10,n=15), day 20 (P20, n=15) and day 45 (P45, n=10) were sacrificed respectively. Fresh visual cortex from the binocular area (Area 17) was dissected for extraction of total RNA for microarray analyses. Taking advantage of annotation information from the gene ontology and pathway database, the gene expression profiles were systematically and globally analyzed.Results Of the 31 042 gene sequences represented on the rat expression microarray, more than 4000 of the transcripts significantly altered at days 45,20 or 10 compared to day 0. The most obvious alteration of gene expression occurred in the first ten days of the postnatal period and the genomic activities of the visual cortex maintained a high level from birth to day 45. Compared to the gene expression at birth, there were 2630 changed transcripts that shared in three postnatal periods.The up-regulated genes in most signaling pathways were more than those of the down-regulated genes.Conclusions Analyzing gene expression patterns, we provide a detailed insight into the molecular organization of the developing visual cortex in the earlier postnatal rat. The most obvious alteration of gene expression in visual cortex occurred in the first ten days. Our data were a basis to identify new

  7. 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

    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...... included high-order interactions between modality, selection and regional activity. There was greater coupling between prefrontal cortex and motor cortex during free selection and action tasks, and between prefrontal cortex and visual cortex during free selection of colours. The results suggest that the...

  8. Frequency-band signatures of visual responses to naturalistic input in ferret primary visual cortex during free viewing.

    Science.gov (United States)

    Sellers, Kristin K; Bennett, Davis V; Fröhlich, Flavio

    2015-02-19

    Neuronal firing responses in visual cortex reflect the statistics of visual input and emerge from the interaction with endogenous network dynamics. Artificial visual stimuli presented to animals in which the network dynamics were constrained by anesthetic agents or trained behavioral tasks have provided fundamental understanding of how individual neurons in primary visual cortex respond to input. In contrast, very little is known about the mesoscale network dynamics and their relationship to microscopic spiking activity in the awake animal during free viewing of naturalistic visual input. To address this gap in knowledge, we recorded local field potential (LFP) and multiunit activity (MUA) simultaneously in all layers of primary visual cortex (V1) of awake, freely viewing ferrets presented with naturalistic visual input (nature movie clips). We found that naturalistic visual stimuli modulated the entire oscillation spectrum; low frequency oscillations were mostly suppressed whereas higher frequency oscillations were enhanced. In average across all cortical layers, stimulus-induced change in delta and alpha power negatively correlated with the MUA responses, whereas sensory-evoked increases in gamma power positively correlated with MUA responses. The time-course of the band-limited power in these frequency bands provided evidence for a model in which naturalistic visual input switched V1 between two distinct, endogenously present activity states defined by the power of low (delta, alpha) and high (gamma) frequency oscillatory activity. Therefore, the two mesoscale activity states delineated in this study may define the degree of engagement of the circuit with the processing of sensory input.

  9. Research progress of functional magnetic resonance imaging in cross-modal activation of visual cortex during tactile perception

    International Nuclear Information System (INIS)

    An increasing amount of neuroimaging studies recently demonstrated activation of visual cortex in both blind and sighted participants when performing a variety of tactile tasks such as Braille reading and tactile object recognition, which indicates that visual cortex not only receives visual information, but may participate in tactile perception. To address these cross-modal changes of visual cortex and the neurophysiological mechanisms, many researchers conducted explosive studies using functional magnetic resonance imaging (fMRI) and have made some achievements. This review focuses on cross-modal activation of visual cortex and the underlying mechanisms during tactile perception in both blind and sighted individuals. (authors)

  10. 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...

  11. Predictive coding for motion stimuli in human early visual cortex

    NARCIS (Netherlands)

    Schellekens, Wouter; van Wezel, Richard J A; Petridou, Natalia; Ramsey, Nick F.; Raemaekers, Mathijs

    2016-01-01

    The current study investigates if early visual cortical areas, V1, V2 and V3, use predictive coding to process motion information. Previous studies have reported biased visual motion responses at locations where novel visual information was presented (i.e., the motion trailing edge), which is plausi

  12. Predictive coding for motion stimuli in human early visual cortex

    NARCIS (Netherlands)

    Schellekens, Wouter; Wezel, van Richard J.A.; Petridou, Natalia; Ramsey, Nick F.; Raemeakers, Mathijs; Zaborszky, L.; Zilles, K.

    2014-01-01

    The current study investigates if early visual cortical areas, V1, V2 and V3, use predictive coding to process motion information. Previous studies have reported biased visual motion responses at locations where novel visual information was presented (i.e., the motion trailing edge), which is plausi

  13. 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.

  14. Developmental continuity and change in responses to social and nonsocial categories in human extrastriate visual cortex

    OpenAIRE

    Pelphrey, Kevin A.; Juliana Lopez; James P. Morris

    2009-01-01

    It is well known that adult human extrastriate visual cortex contains areas that respond in a selective fashion to specific categories of visual stimuli. Three regions have been identified with particular regularity: the fusiform face area (FFA), which responds to faces more than to other objects; the parahippocampal place area (PPA), which responds selectively to images of houses, places, and visual scenes; and the extrastriate body area (EBA), which responds specifically to images of bodies...

  15. Sparse representation of global features of visual images in human primary visual cortex: Evidence from fMRI

    Institute of Scientific and Technical Information of China (English)

    ZHAO SongNian; YAO Li; JIN Zhen; XIONG XiaoYun; WU Xia; ZOU Qi; YAO GuoZheng; CAI XiaoHong; LIU YiJun

    2008-01-01

    In fMRI experiments on object representation in visual cortex, we designed two types of stimuli: one is the gray face image and its line drawing, and the other is the illusion and its corresponding completed illusion. Both of them have the same global features with different minute details so that the results of fMRI experiments can be compared with each other. The first kind of visual stimuli was used in a block design fMRI experiment, and the second was used in an event-related fMRI experiment. Comparing and analyzing interesting visual cortex activity patterns and blood oxygenation level dependent (BOLD)-fMRI signal, we obtained results to show some invariance of global features of visual images. A plau-sible explanation about the invariant mechanism is related with the cooperation of synchronized re-sponse to the global features of the visual image with a feedback of shape perception from higher cortex to cortex V1, namely the integration of global features and embodiment of sparse representation and distributed population code.

  16. Golgi Analysis of Neuron Morphology in the Presumptive Somatosensory Cortex and Visual Cortex of the Florida Manatee (Trichechus manatus latirostris).

    Science.gov (United States)

    Reyes, Laura D; Harland, Tessa; Reep, Roger L; Sherwood, Chet C; Jacobs, Bob

    2016-01-01

    The current study investigates neuron morphology in presumptive primary somatosensory (S1) and primary visual (V1) cortices of the Florida manatee (Trichechus manatus latirostris) as revealed by Golgi impregnation. Sirenians, including manatees, have an aquatic lifestyle, a large body size, and a relatively large lissencephalic brain. The present study examines neuron morphology in 3 cortical areas: in S1, dorsolateral cortex area 1 (DL1) and cluster cortex area 2 (CL2) and in V1, dorsolateral cortex area 4 (DL4). Neurons exhibited a variety of morphological types, with pyramidal neurons being the most common. The large variety of neuron types present in the manatee cortex was comparable to that seen in other eutherian mammals, except for rodents and primates, where pyramid-shaped neurons predominate. A comparison between pyramidal neurons in S1 and V1 indicated relatively greater dendritic branching in S1. Across all 3 areas, the dendritic arborization pattern of pyramidal neurons was also similar to that observed previously in the afrotherian rock hyrax, cetartiodactyls, opossums, and echidnas but did not resemble the widely bifurcated dendrites seen in the large-brained African elephant. Despite adaptations for an aquatic environment, manatees did not share specific neuron types such as tritufted and star-like neurons that have been found in cetaceans. Manatees exhibit an evolutionarily primitive pattern of cortical neuron morphology shared with most other mammals and do not appear to have neuronal specializations for an aquatic niche.

  17. Golgi Analysis of Neuron Morphology in the Presumptive Somatosensory Cortex and Visual Cortex of the Florida Manatee (Trichechus manatus latirostris).

    Science.gov (United States)

    Reyes, Laura D; Harland, Tessa; Reep, Roger L; Sherwood, Chet C; Jacobs, Bob

    2016-01-01

    The current study investigates neuron morphology in presumptive primary somatosensory (S1) and primary visual (V1) cortices of the Florida manatee (Trichechus manatus latirostris) as revealed by Golgi impregnation. Sirenians, including manatees, have an aquatic lifestyle, a large body size, and a relatively large lissencephalic brain. The present study examines neuron morphology in 3 cortical areas: in S1, dorsolateral cortex area 1 (DL1) and cluster cortex area 2 (CL2) and in V1, dorsolateral cortex area 4 (DL4). Neurons exhibited a variety of morphological types, with pyramidal neurons being the most common. The large variety of neuron types present in the manatee cortex was comparable to that seen in other eutherian mammals, except for rodents and primates, where pyramid-shaped neurons predominate. A comparison between pyramidal neurons in S1 and V1 indicated relatively greater dendritic branching in S1. Across all 3 areas, the dendritic arborization pattern of pyramidal neurons was also similar to that observed previously in the afrotherian rock hyrax, cetartiodactyls, opossums, and echidnas but did not resemble the widely bifurcated dendrites seen in the large-brained African elephant. Despite adaptations for an aquatic environment, manatees did not share specific neuron types such as tritufted and star-like neurons that have been found in cetaceans. Manatees exhibit an evolutionarily primitive pattern of cortical neuron morphology shared with most other mammals and do not appear to have neuronal specializations for an aquatic niche. PMID:27166161

  18. Visual cortex as a depth computer: Grossberg's LAMINART or how we see the world in depth

    OpenAIRE

    Dresp, Birgitta

    2014-01-01

    The laminar structure of cortex was first described by Ramón y Cajal (1899). It consists of six different layers, each containing a characteristic distribution of neurons and cell types connecting with other cortical and sub-cortical regions. These extensive connections form microcircuits that group into functionally distinct columns (e.g. Mountcastle, 1997). To account for the Venetian Blind Effect, Cao and Grossberg propose a model which exploits the functional organization of visual cortex...

  19. The Effects of Context and Attention on Spiking Activity in Human Early Visual Cortex

    Science.gov (United States)

    Reithler, Joel; Goebel, Rainer; Ris, Peterjan; Jeurissen, Danique; Reddy, Leila; Claus, Steven; Baayen, Johannes C.; Roelfsema, Pieter R.

    2016-01-01

    Here we report the first quantitative analysis of spiking activity in human early visual cortex. We recorded multi-unit activity from two electrodes in area V2/V3 of a human patient implanted with depth electrodes as part of her treatment for epilepsy. We observed well-localized multi-unit receptive fields with tunings for contrast, orientation, spatial frequency, and size, similar to those reported in the macaque. We also observed pronounced gamma oscillations in the local-field potential that could be used to estimate the underlying spiking response properties. Spiking responses were modulated by visual context and attention. We observed orientation-tuned surround suppression: responses were suppressed by image regions with a uniform orientation and enhanced by orientation contrast. Additionally, responses were enhanced on regions that perceptually segregated from the background, indicating that neurons in the human visual cortex are sensitive to figure-ground structure. Spiking responses were also modulated by object-based attention. When the patient mentally traced a curve through the neurons’ receptive fields, the accompanying shift of attention enhanced neuronal activity. These results demonstrate that the tuning properties of cells in the human early visual cortex are similar to those in the macaque and that responses can be modulated by both contextual factors and behavioral relevance. Our results, therefore, imply that the macaque visual system is an excellent model for the human visual cortex. PMID:27015604

  20. 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.

  1. Visual cortex activity predicts subjective experience after reading books with colored letters.

    Science.gov (United States)

    Colizoli, Olympia; Murre, Jaap M J; Scholte, H Steven; van Es, Daniel M; Knapen, Tomas; Rouw, Romke

    2016-07-29

    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 areas can be directly related to letter-color associations acquired by training. Non-synesthetes read specially prepared books with colored letters for several weeks and were scanned using functional magnetic resonance imaging. If the acquired letter-color associations were visual in nature, then brain activation in visual cortex while viewing the trained black letters (compared to untrained black letters) should predict the strength of the associations, the quality of the color experience, or the vividness of visual mental imagery. Results showed that training-related activation of area V4 was correlated with differences in reported subjective color experience. Trainees who were classified as having stronger 'associator' types of color experiences also had more negative activation for trained compared to untrained achromatic letters in area V4. In contrast, the strength of the acquired associations (measured as the Stroop effect) was not reliably reflected in visual cortex activity. The reported vividness of visual mental imagery was related to veridical color activation in early visual cortex, but not to the acquired color associations. We show for the first time that subjective experience related to a synesthesia-training paradigm was reflected in visual brain activation.

  2. Visual cortex activity predicts subjective experience after reading books with colored letters.

    Science.gov (United States)

    Colizoli, Olympia; Murre, Jaap M J; Scholte, H Steven; van Es, Daniel M; Knapen, Tomas; Rouw, Romke

    2016-07-29

    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 areas can be directly related to letter-color associations acquired by training. Non-synesthetes read specially prepared books with colored letters for several weeks and were scanned using functional magnetic resonance imaging. If the acquired letter-color associations were visual in nature, then brain activation in visual cortex while viewing the trained black letters (compared to untrained black letters) should predict the strength of the associations, the quality of the color experience, or the vividness of visual mental imagery. Results showed that training-related activation of area V4 was correlated with differences in reported subjective color experience. Trainees who were classified as having stronger 'associator' types of color experiences also had more negative activation for trained compared to untrained achromatic letters in area V4. In contrast, the strength of the acquired associations (measured as the Stroop effect) was not reliably reflected in visual cortex activity. The reported vividness of visual mental imagery was related to veridical color activation in early visual cortex, but not to the acquired color associations. We show for the first time that subjective experience related to a synesthesia-training paradigm was reflected in visual brain activation. PMID:26162617

  3. Planning Movements in Visual and Physical Space in Monkey Posterior Parietal Cortex.

    Science.gov (United States)

    Kuang, Shenbing; Morel, Pierre; Gail, Alexander

    2016-02-01

    Neurons in the posterior parietal cortex respond selectively for spatial parameters of planned goal-directed movements. Yet, it is still unclear which aspects of the movement the neurons encode: the spatial parameters of the upcoming physical movement (physical goal), or the upcoming visual limb movement (visual goal). To test this, we recorded neuronal activity from the parietal reach region while monkeys planned reaches under either normal or prism-reversed viewing conditions. We found predominant encoding of physical goals while fewer neurons were selective for visual goals during planning. In contrast, local field potentials recorded in the same brain region exhibited predominant visual goal encoding, similar to previous imaging data from humans. The visual goal encoding in individual neurons was neither related to immediate visual input nor to visual memory, but to the future visual movement. Our finding suggests that action planning in parietal cortex is not exclusively a precursor of impending physical movements, as reflected by the predominant physical goal encoding, but also contains spatial kinematic parameters of upcoming visual movement, as reflected by co-existing visual goal encoding in neuronal spiking. The co-existence of visual and physical goals adds a complementary perspective to the current understanding of parietal spatial computations in primates.

  4. Visual and eye movement functions of the posterior parietal cortex

    OpenAIRE

    Andersen, Richard A.

    1989-01-01

    Lesions of the posterior parietal area in humans produce interesting spatial-perceptual and spatial-behavioral deficits. Among the more important deficits observed are loss of spatial memories, problems representing spatial relations in models or drawings, disturbances in the spatial distribution of attention, and the inability to localize visual targets. Posterior parietal lesions in nonhuman primates also produce visual spatial deficits not unlike those found in humans. Mountcastle and his ...

  5. Postnatal development of NADPH-diaphorase expression in the visual cortex of the golden hamster

    Institute of Scientific and Technical Information of China (English)

    Ying Xu; Yuemei Xiao; Yuncheng Diao; Kwok-Fai So

    2011-01-01

    Nitric oxide is an important neuromodulator in the brain and is involved in the development of visual system. But it is not clear how nitric oxide and nitric oxide synthase (NOS) are involved in the developing visual cortex of rodents. Thus we examined the expression of NOS activity in the postnatal developing visual cortex of the golden hamster by using histochemical technique for NADPH-diaphorase (NADPH-d). A heavily stained NADPH-d band was observed in the neuropil of the visual cortex. This NADPH-d band initially appeared in the cortical plate from the day of birth (P0) to postnatal day 4 (P4). From P7 to P21, this band was confined to area 17 and migrated to the deeper layers III-IV and V-VI before it eventually disappeared at P28. Such developmental trends of the band correlated well with the process of formation and establishment of the geniculo-cortical projection patterns. Thus, the areal specific development of the band suggests that NOS is closely related to the cortical differentiation and synaptic formation of the primary visual cortex. On the other hand, monocular eye enucleation on P1 could not alter the appearance of this NADPH-d positive band, indicating a non-activity dependant role of NOS. In addition, differences in the laminar distributions and developmental sequence between the heavily and lightly stained NADPH-d positive neurons during development suggest that they play different roles in the development.

  6. Vestibular activation differentially modulates human early visual cortex and V5/MT excitability and response entropy.

    Science.gov (United States)

    Seemungal, Barry M; 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.

  7. 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

  8. Age-related changes in the attentional control of visual cortex: A selective problem in the left visual hemifield

    OpenAIRE

    Nagamatsu, Lindsay S.; Carolan, Patrick; Liu-Ambrose, Teresa Y L; Handy, Todd C

    2011-01-01

    To what extent does our visual-spatial attention change with age? In this regard, it has been previously reported that relative to young controls, seniors show delays in attention-related sensory facilitation. Given this finding, our study was designed to examine two key questions regarding age-related changes in the effect of spatial attention on sensory-evoked responses in visual cortex –– are there visual field differences in the age-related impairments in sensory processing, and do these ...

  9. The disorganized visual cortex in reelin-deficient mice is functional and allows for enhanced plasticity.

    Science.gov (United States)

    Pielecka-Fortuna, Justyna; Wagener, Robin Jan; Martens, Ann-Kristin; Goetze, Bianka; Schmidt, Karl-Friedrich; Staiger, Jochen F; Löwel, Siegrid

    2015-11-01

    A hallmark of neocortical circuits is the segregation of processing streams into six distinct layers. The importance of this layered organization for cortical processing and plasticity is little understood. We investigated the structure, function and plasticity of primary visual cortex (V1) of adult mice deficient for the glycoprotein reelin and their wild-type littermates. In V1 of rl-/- mice, cells with different laminar fates are present at all cortical depths. Surprisingly, the (vertically) disorganized cortex maintains a precise retinotopic (horizontal) organization. Rl-/- mice have normal basic visual capabilities, but are compromised in more challenging perceptual tasks, such as orientation discrimination. Additionally, rl-/- animals learn and memorize a visual task as well as their wild-type littermates. Interestingly, reelin deficiency enhances visual cortical plasticity: juvenile-like ocular dominance plasticity is preserved into late adulthood. The present data offer an important insight into the capabilities of a disorganized cortical system to maintain basic functional properties.

  10. Theta coupling between V4 and prefrontal cortex predicts visual short-term memory performance.

    Science.gov (United States)

    Liebe, Stefanie; Hoerzer, Gregor M; Logothetis, Nikos K; Rainer, Gregor

    2012-03-01

    Short-term memory requires communication between multiple brain regions that collectively mediate the encoding and maintenance of sensory information. It has been suggested that oscillatory synchronization underlies intercortical communication. Yet, whether and how distant cortical areas cooperate during visual memory remains elusive. We examined neural interactions between visual area V4 and the lateral prefrontal cortex using simultaneous local field potential (LFP) recordings and single-unit activity (SUA) in monkeys performing a visual short-term memory task. During the memory period, we observed enhanced between-area phase synchronization in theta frequencies (3-9 Hz) of LFPs together with elevated phase locking of SUA to theta oscillations across regions. In addition, we found that the strength of intercortical locking was predictive of the animals' behavioral performance. This suggests that theta-band synchronization coordinates action potential communication between V4 and prefrontal cortex that may contribute to the maintenance of visual short-term memories. PMID:22286175

  11. Hemodynamic responses in human multisensory and auditory association cortex to purely visual stimulation

    Directory of Open Access Journals (Sweden)

    Baumann Simon

    2007-02-01

    Full Text Available Abstract Background Recent findings of a tight coupling between visual and auditory association cortices during multisensory perception in monkeys and humans raise the question whether consistent paired presentation of simple visual and auditory stimuli prompts conditioned responses in unimodal auditory regions or multimodal association cortex once visual stimuli are presented in isolation in a post-conditioning run. To address this issue fifteen healthy participants partook in a "silent" sparse temporal event-related fMRI study. In the first (visual control habituation phase they were presented with briefly red flashing visual stimuli. In the second (auditory control habituation phase they heard brief telephone ringing. In the third (conditioning phase we coincidently presented the visual stimulus (CS paired with the auditory stimulus (UCS. In the fourth phase participants either viewed flashes paired with the auditory stimulus (maintenance, CS- or viewed the visual stimulus in isolation (extinction, CS+ according to a 5:10 partial reinforcement schedule. The participants had no other task than attending to the stimuli and indicating the end of each trial by pressing a button. Results During unpaired visual presentations (preceding and following the paired presentation we observed significant brain responses beyond primary visual cortex in the bilateral posterior auditory association cortex (planum temporale, planum parietale and in the right superior temporal sulcus whereas the primary auditory regions were not involved. By contrast, the activity in auditory core regions was markedly larger when participants were presented with auditory stimuli. Conclusion These results demonstrate involvement of multisensory and auditory association areas in perception of unimodal visual stimulation which may reflect the instantaneous forming of multisensory associations and cannot be attributed to sensation of an auditory event. More importantly, we are able

  12. Dissociation of object and spatial visual processing pathways in human extrastriate cortex

    Energy Technology Data Exchange (ETDEWEB)

    Haxby, J.V.; Grady, C.L.; Horwitz, B.; Ungerleider, L.G.; Mishkin, M.; Carson, R.E.; Herscovitch, P.; Schapiro, M.B.; Rapoport, S.I. (National Institutes of Health, Bethesda, MD (USA))

    1991-03-01

    The existence and neuroanatomical locations of separate extrastriate visual pathways for object recognition and spatial localization were investigated in healthy young men. Regional cerebral blood flow was measured by positron emission tomography and bolus injections of H2(15)O, while subjects performed face matching, dot-location matching, or sensorimotor control tasks. Both visual matching tasks activated lateral occipital cortex. Face discrimination alone activated a region of occipitotemporal cortex that was anterior and inferior to the occipital area activated by both tasks. The spatial location task alone activated a region of lateral superior parietal cortex. Perisylvian and anterior temporal cortices were not activated by either task. These results demonstrate the existence of three functionally dissociable regions of human visual extrastriate cortex. The ventral and dorsal locations of the regions specialized for object recognition and spatial localization, respectively, suggest some homology between human and nonhuman primate extrastriate cortex, with displacement in human brain, possibly related to the evolution of phylogenetically newer cortical areas.

  13. Dissociation of object and spatial visual processing pathways in human extrastriate cortex.

    Science.gov (United States)

    Haxby, J V; Grady, C L; Horwitz, B; Ungerleider, L G; Mishkin, M; Carson, R E; Herscovitch, P; Schapiro, M B; Rapoport, S I

    1991-01-01

    The existence and neuroanatomical locations of separate extrastriate visual pathways for object recognition and spatial localization were investigated in healthy young men. Regional cerebral blood flow was measured by positron emission tomography and bolus injections of H2(15)O, while subjects performed face matching, dot-location matching, or sensorimotor control tasks. Both visual matching tasks activated lateral occipital cortex. Face discrimination alone activated a region of occipitotemporal cortex that was anterior and inferior to the occipital area activated by both tasks. The spatial location task alone activated a region of lateral superior parietal cortex. Perisylvian and anterior temporal cortices were not activated by either task. These results demonstrate the existence of three functionally dissociable regions of human visual extrastriate cortex. The ventral and dorsal locations of the regions specialized for object recognition and spatial localization, respectively, suggest some homology between human and nonhuman primate extrastriate cortex, with displacement in human brain, possibly related to the evolution of phylogenetically newer cortical areas. Images PMID:2000370

  14. Dissociation of object and spatial visual processing pathways in human extrastriate cortex

    International Nuclear Information System (INIS)

    The existence and neuroanatomical locations of separate extrastriate visual pathways for object recognition and spatial localization were investigated in healthy young men. Regional cerebral blood flow was measured by positron emission tomography and bolus injections of H2(15)O, while subjects performed face matching, dot-location matching, or sensorimotor control tasks. Both visual matching tasks activated lateral occipital cortex. Face discrimination alone activated a region of occipitotemporal cortex that was anterior and inferior to the occipital area activated by both tasks. The spatial location task alone activated a region of lateral superior parietal cortex. Perisylvian and anterior temporal cortices were not activated by either task. These results demonstrate the existence of three functionally dissociable regions of human visual extrastriate cortex. The ventral and dorsal locations of the regions specialized for object recognition and spatial localization, respectively, suggest some homology between human and nonhuman primate extrastriate cortex, with displacement in human brain, possibly related to the evolution of phylogenetically newer cortical areas

  15. Chimera in a neuronal network model of the cat brain

    OpenAIRE

    Santos, M. S.; Szezech Jr., J. D.; Borges, F. S.; Iarosz, K. C.; Caldas, I. L.; Batista, A. M.; Viana, R. L.; Kurths, J.

    2016-01-01

    Neuronal systems have been modeled by complex networks in different description levels. Recently, it has been verified that networks can simultaneously exhibit one coherent and other incoherent domain, known as chimera states. In this work, we study the existence of chimera states in a network considering the connectivity matrix based on the cat cerebral cortex. The cerebral cortex of the cat can be separated in 65 cortical areas organised into the four cognitive regions: visual, auditory, so...

  16. The responses to illusory contours of neurons in cortex areas 17 and 18 of the cats

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Responses to illusory contours (ICs) were sampled from neurons incortical areas 17 and 18 of the anesthetized cats. For ICs sensitive cells, the differences of receptive field properties were compared when ICs and real contour stimuli were applied. Two hundred orientation or direction selective cells were studied. We find that about 42 percent of these cells were the ICs sensitive cells. Although their orientation or direction tuning curves to ICs bar and real bars were similar, the response modes (especially latency and time course) were different. The cells' responses to ICs were independent of the spatial phases of sinusoidal gratings, which composed the ICs. The cells' optimal spatial frequency to composing gratings the ICs was much higher than the one to moving gratings. Therefore, these cells really responded to the ICs rather than the line ends of composing gratings. For some kinds of velocity-tuning cells, the optimal velocity to moving ICs bar was much lower than the optimal velocity to moving bars. The present results demonstrate that some cells in areas 17 and 18 of cats have the ability to respond to ICs and have different response properties of the receptive fields to ICs and luminance boundaries via different neural mechanisms.

  17. The linearity and selectivity of neuronal responses in awake visual cortex

    OpenAIRE

    Chen, Yao; Anand, Sanjiv; Martinez-Conde, Susana; Macknik, Stephen L.; Bereshpolova, Yulia; Swadlow, Harvey A.; Alonso, Jose-Manuel

    2009-01-01

    Neurons in primary visual cortex (V1) are frequently classified based on their response linearity: the extent in which their visual responses to drifting gratings resemble a linear replica of the stimulus. This classification is supported by the finding that response linearity is bimodally distributed across neurons in area V1 of anesthetized animals. However, recent studies suggest that such bimodal distribution may not reflect two neuronal types but a nonlinear relationship between the memb...

  18. Theta coupling between V4 and prefrontal cortex predicts visual short-term memory performance

    OpenAIRE

    Liebe S.; Hoerzer G.,; Logothetis N.K.; Rainer G.

    2012-01-01

    Short-term memory requires communication between multiple brain regions that collectively mediate the encoding and maintenance of sensory information. It has been suggested that oscillatory synchronization underlies intercortical communication. Yet, whether and how distant cortical areas cooperate during visual memory remains elusive. We examined neural interactions between visual area V4 and the lateral prefrontal cortex using simultaneous local field potential (LFP) recordings and single-un...

  19. Contributions of early parallel pathways to extrastriate visual cortex in macaque monkey

    OpenAIRE

    Nassi, Jonathan J.

    2007-01-01

    Parallel Processing is a commonly used strategy in sensory systems of the mammalian brain. In the primate visual system, information is relayed from the retina to primary visual cortex (V1) along three parallel pathways: magnocellular (M), parvocellular (P), and koniocellular (K). These three pathways remain anatomically and physiologically distinct as they pass through M, P, and K layers of the lateral geniculate nucleus (LGN) of the thalamus and into V1, with the M pathway terminating prima...

  20. Perceptual expertise and top-down expectation of musical notation engages the primary visual cortex

    OpenAIRE

    Wong, Yetta Kwailing; Peng, Cynthia; Fratus, Kristyn N.; Woodman, Geoffrey F.; Gauthier, Isabel

    2014-01-01

    Most theories of visual processing propose that object recognition is achieved in higher visual cortex. However, we show that category selectivity for musical notation can be observed in the first event-related potential component called the C1 (measured 40-60ms after stimulus onset) with music-reading expertise. Moreover, the C1 note selectivity was observed only when the stimulus category was blocked but not when the stimulus category was randomized. Under blocking, the C1 activity for note...

  1. 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.

  2. Travelling waves of activity in primary visual cortex during binocular rivalry

    OpenAIRE

    Lee, Sang-Hun; Blake, Randolph; Heeger, David J.

    2004-01-01

    When the two eyes view large dissimilar patterns that induce binocular rivalry, alternating waves of visibility are experienced, as one pattern sweeps the other out of conscious awareness. Here we show tight linkage between dynamics of perceptual waves during rivalry and neural events in human primary visual cortex (V1).

  3. Multivoxel fMRI analysis of color tuning in human primary visual cortex

    NARCIS (Netherlands)

    Parkes, Laura M.; Marsman, Jan-Bernard C.; Oxley, David C.; Goulermas, John Y.; Wuerger, Sophie M.

    2009-01-01

    We use multivoxel pattern analysis (MVPA) to study the spatial clustering of color-selective neurons in the human brain. Our main objective was to investigate whether MVPA reveals the spatial arrangements of color-selective neurons in human primary visual cortex (V1). We measured the distributed fMR

  4. 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…

  5. 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…

  6. Response of SI cortex to ipsilateral, contralateral and bilateral flutter stimulation in the cat

    Directory of Open Access Journals (Sweden)

    Favorov Oleg

    2005-04-01

    Full Text Available Abstract Background While SII cortex is considered to be the first cortical stage of the pathway that integrates tactile information arising from both sides of the body, SI cortex is generally not considered as a region in which neuronal response is modulated by simultaneous stimulation of bilateral (and mirror-image skin sites. Results Optical intrinsic signal imaging was used to evaluate the response of SI and SII in the same hemisphere to 25 Hz sinusoidal vertical skin displacement stimulation ("skin flutter" applied contralaterally, ipsilaterally, and bilaterally (simultaneously to the central pads of the forepaws. A localized increase in absorbance in both SI and SII occurred in response to both contralateral and bilateral flutter stimulation. Ipsilateral flutter stimulation evoked a localized increase in absorbance in SII, but little or no change in SI absorbance. In the forepaw representational region of SI, however, bilateral stimulation of the central pads evoked a response substantially smaller (approximately 30–35% smaller than the response to flutter stimulation of the contralateral central pad. Conclusion The finding that the response of SI cortex to bilateral central pad flutter stimulation is substantially smaller than the response evoked by a contralateral flutter stimulus, together with the recently published observation that a region located posteriorly in SII responds with a substantially larger response to a bilateral flutter stimulus than the response evoked from the contralateral central pad, lead us to propose that the SI activity evoked by contralateral skin stimulation is suppressed/inhibited (via corticocortical connections between SII and SI in the same hemisphere by the activity a simultaneous ipsilateral skin stimulus evokes in posterior SII.

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

    Science.gov (United States)

    Shimada, Koji; Takiguchi, Shinichiro; Mizushima, Sakae; Fujisawa, Takashi X.; Saito, Daisuke N.; Kosaka, Hirotaka; Okazawa, Hidehiko; Tomoda, Akemi

    2015-01-01

    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. PMID:26288752

  8. 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.

  9. Developmental changes in GABAergic mechanisms in human visual cortex across the lifespan

    Directory of Open Access Journals (Sweden)

    Joshua G A Pinto

    2010-06-01

    Full Text Available Functional maturation of visual cortex is linked with dynamic changes in synaptic expression of GABAergic mechanisms. These include setting the excitation-inhibition balance required for experience-dependent plasticity, as well as, intracortical inhibition underlying development and aging of receptive field properties. Animal studies have shown developmental regulation of GABAergic mechanisms in visual cortex. In this study, we show for the first time how these mechanisms develop in the human visual cortex across the lifespan. We used Western blot analysis of postmortem tissue from human primary visual cortex (n=30, range: 20 days to 80 years to quantify expression of 8 pre- and post-synaptic GABAergic markers. We quantified the inhibitory modulating cannabinoid receptor (CB1, GABA vesicular transporter (VGAT, GABA synthesizing enzymes (GAD65/GAD67, GABAA receptor anchoring protein (Gephyrin, and GABAA receptor subunits (GABAA∝1, GABAA∝2, GABAA∝3. We found a complex pattern of changes, many of which were prolonged and continued well into into the teen, young adult, and even older adult years. These included a monotonic increase or decrease (GABAA∝1, GABAA∝2, a biphasic increase then decrease (GAD65, Gephyrin, or multiple increases and decreases (VGAT, CB1 across the lifespan. Comparing the balances between the pre- and post-synaptic markers we found 3 main transitions (early childhood, early teen years, aging when there were rapid switches in the composition of the GABAergic signaling system, indicating that functioning of the GABAergic system must change as the visual cortex develops and ages. Furthermore, these results provide key information for translating therapies developed in animal models into effective treatments for amblyopia in humans.

  10. Four-Month-Old Infants' Visual Investigation of Cats and Dogs: Relations with Pet Experience and Attentional Strategy

    Science.gov (United States)

    Kovack-Lesh, Kristine A.; McMurray, Bob; Oakes, Lisa M.

    2014-01-01

    We assessed the eye-movements of 4-month-old infants (N = 38) as they visually inspected pairs of images of cats or dogs. In general, infants who had previous experience with pets exhibited more sophisticated inspection than did infants without pet experience, both directing more visual attention to the informative head regions of the animals,…

  11. Methylmercury intoxication and histochemical demonstration of NADPH-diaphorase activity in the striate cortex of adult cats

    Directory of Open Access Journals (Sweden)

    Oliveira R.B.

    1998-01-01

    Full Text Available The effects of methylmercury (MeHg on histochemical demonstration of the NADPH-diaphorase (NADPH-d activity in the striate cortex were studied in 4 adult cats. Two animals were used as control. The contaminated animals received 50 ml milk containing 0.42 µg MeHg and 100 g fish containing 0.03 µg MeHg daily for 2 months. The level of MeHg in area 17 of intoxicated animals was 3.2 µg/g wet weight brain tissue. Two cats were perfused 24 h after the last dose (group 1 and the other animals were perfused 6 months later (group 2. After microtomy, sections were processed for NADPHd histochemistry procedures using the malic enzyme method. Dendritic branch counts were performed from camera lucida drawings for control and intoxicated animals (N = 80. Average, standard deviation and Student t-test were calculated for each data group. The concentrations of mercury (Hg in milk, fish and brain tissue were measured by acid digestion of samples, followed by reduction of total Hg in the digested sample to metallic Hg using stannous chloride followed by atomic fluorescence analysis. Only group 2 revealed a reduction of the neuropil enzyme activity and morphometric analysis showed a reduction in dendritic field area and in the number of distal dendrite branches of the NADPHd neurons in the white matter (P<0.05. These results suggest that NADPHd neurons in the white matter are more vulnerable to the long-term effects of MeHg than NADPHd neurons in the gray matter.

  12. Partial dissociation in the neural bases of VSTM and imagery in the early visual cortex

    Science.gov (United States)

    Saad, Elyana; Wojciechowska, Maria; Silvanto, Juha

    2015-01-01

    Visual short-term memory (VSTM) and visual imagery are believed to involve overlapping neuronal representations in the early visual cortex. While a number of studies have provided evidence for this overlap, at the behavioral level VSTM and imagery are dissociable processes; this begs the question of how their neuronal mechanisms differ. Here we used transcranial magnetic stimulation (TMS) to examine whether the neural bases of imagery and VSTM maintenance are dissociable in the early visual cortex (EVC). We intentionally used a similar task for VSTM and imagery in order to equate their assessment. We hypothesized that any differential effect of TMS on VSTM and imagery would indicate that their neuronal bases differ at the level of EVC. In the “alone” condition, participants were asked to engage either in VSTM or imagery, whereas in the “concurrent” condition, each trial required both VSTM maintenance and imagery simultaneously. A dissociation between VSTM and imagery was observed for reaction times: TMS slowed down responses for VSTM but not for imagery. The impact of TMS on sensitivity did not differ between VSTM and imagery, but did depend on whether the tasks were carried concurrently or alone. This study shows that neural processes associated with VSTM and imagery in the early visual cortex can be partially dissociated. PMID:26026256

  13. The stimulus-evoked population response in visual cortex of awake monkey is a propagating wave.

    Science.gov (United States)

    Muller, Lyle; Reynaud, Alexandre; Chavane, Frédéric; Destexhe, Alain

    2014-04-28

    Propagating waves occur in many excitable media and were recently found in neural systems from retina to neocortex. While propagating waves are clearly present under anaesthesia, whether they also appear during awake and conscious states remains unclear. One possibility is that these waves are systematically missed in trial-averaged data, due to variability. Here we present a method for detecting propagating waves in noisy multichannel recordings. Applying this method to single-trial voltage-sensitive dye imaging data, we show that the stimulus-evoked population response in primary visual cortex of the awake monkey propagates as a travelling wave, with consistent dynamics across trials. A network model suggests that this reliability is the hallmark of the horizontal fibre network of superficial cortical layers. Propagating waves with similar properties occur independently in secondary visual cortex, but maintain precise phase relations with the waves in primary visual cortex. These results show that, in response to a visual stimulus, propagating waves are systematically evoked in several visual areas, generating a consistent spatiotemporal frame for further neuronal interactions.

  14. Attention enhances stimulus representations in macaque visual cortex without affecting their signal-to-noise level

    Science.gov (United States)

    Daliri, Mohammad Reza; Kozyrev, Vladislav; Treue, Stefan

    2016-01-01

    The magnitude of the attentional modulation of neuronal responses in visual cortex varies with stimulus contrast. Whether the strength of these attentional influences is similarly dependent on other stimulus properties is unknown. Here we report the effect of spatial attention on responses in the medial-temporal area (MT) of macaque visual cortex to moving random dots pattern of various motion coherences, i.e. signal-to-noise ratios. Our data show that allocating spatial attention causes a gain change in MT neurons. The magnitude of this attentional modulation is independent of the attended stimulus’ motion coherence, creating a multiplicative scaling of the neuron’s coherence-response function. This is consistent with the characteristics of gain models of attentional modulation and suggests that attention strengthens the neuronal representation of behaviorally relevant visual stimuli relative to unattended stimuli, but without affecting their signal-to-noise ratios. PMID:27283275

  15. Category-Selectivity in Human Visual Cortex Follows Cortical Topology: A Grouped icEEG Study.

    Directory of Open Access Journals (Sweden)

    Cihan Mehmet Kadipasaoglu

    Full Text Available Neuroimaging studies suggest that category-selective regions in higher-order visual cortex are topologically organized around specific anatomical landmarks: the mid-fusiform sulcus (MFS in the ventral temporal cortex (VTC and lateral occipital sulcus (LOS in the lateral occipital cortex (LOC. To derive precise structure-function maps from direct neural signals, we collected intracranial EEG (icEEG recordings in a large human cohort (n = 26 undergoing implantation of subdural electrodes. A surface-based approach to grouped icEEG analysis was used to overcome challenges from sparse electrode coverage within subjects and variable cortical anatomy across subjects. The topology of category-selectivity in bilateral VTC and LOC was assessed for five classes of visual stimuli-faces, animate non-face (animals/body-parts, places, tools, and words-using correlational and linear mixed effects analyses. In the LOC, selectivity for living (faces and animate non-face and non-living (places and tools classes was arranged in a ventral-to-dorsal axis along the LOS. In the VTC, selectivity for living and non-living stimuli was arranged in a latero-medial axis along the MFS. Written word-selectivity was reliably localized to the intersection of the left MFS and the occipito-temporal sulcus. These findings provide direct electrophysiological evidence for topological information structuring of functional representations within higher-order visual cortex.

  16. 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.

  17. 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.

  18. 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. PMID:27125770

  19. A computational model as neurodecoder based on synchronous oscillation in the visual cortex.

    Science.gov (United States)

    Songnian, Zhao; Xiaoyun, Xiong; Guozheng, Yao; Zhi, Fu

    2003-10-01

    Based on synchronized responses of neuronal populations in the visual cortex to external stimuli, we proposed a computational model consisting primarily of a neuronal phase-locked loop (NPLL) and multiscaled operator. The former reveals the function of synchronous oscillations in the visual cortex. Regardless of which of these patterns of the spike trains may be an average firing-rate code, a spike-timing code, or a rate-time code, the NPLL can decode original visual information from neuronal spike trains modulated with patterns of external stimuli, because a voltage-controlled oscillator (VCO), which is included in the NPLL, can precisely track neuronal spike trains and instantaneous variations, that is, VCO can make a copy of an external stimulus pattern. The latter, however, describes multi-scaled properties of visual information processing, but not merely edge and contour detection. In this study, in which we combined NPLL with a multiscaled operator and maximum likelihood estimation, we proved that the model, as a neurodecoder, implements optimum algorithm decoding visual information from neuronal spike trains at the system level. At the same time, the model also obtains increasingly important supports, which come from a series of experimental results of neurobiology on stimulus-specific neuronal oscillations or synchronized responses of the neuronal population in the visual cortex. In addition, the problem of how to describe visual acuity and multiresolution of vision by wavelet transform is also discussed. The results indicate that the model provides a deeper understanding of the role of synchronized responses in decoding visual information.

  20. Encoding of temporal information by timing, rate, and place in cat auditory cortex.

    Directory of Open Access Journals (Sweden)

    Kazuo Imaizumi

    Full Text Available A central goal in auditory neuroscience is to understand the neural coding of species-specific communication and human speech sounds. Low-rate repetitive sounds are elemental features of communication sounds, and core auditory cortical regions have been implicated in processing these information-bearing elements. Repetitive sounds could be encoded by at least three neural response properties: 1 the event-locked spike-timing precision, 2 the mean firing rate, and 3 the interspike interval (ISI. To determine how well these response aspects capture information about the repetition rate stimulus, we measured local group responses of cortical neurons in cat anterior auditory field (AAF to click trains and calculated their mutual information based on these different codes. ISIs of the multiunit responses carried substantially higher information about low repetition rates than either spike-timing precision or firing rate. Combining firing rate and ISI codes was synergistic and captured modestly more repetition information. Spatial distribution analyses showed distinct local clustering properties for each encoding scheme for repetition information indicative of a place code. Diversity in local processing emphasis and distribution of different repetition rate codes across AAF may give rise to concurrent feed-forward processing streams that contribute differently to higher-order sound analysis.

  1. Consolidation of visual associative long-term memory in the temporal cortex of primates.

    Science.gov (United States)

    Miyashita, Y; Kameyama, M; Hasegawa, I; Fukushima, T

    1998-01-01

    Neuropsychological theories have proposed a critical role for the interaction between the medial temporal lobe and the neocortex in the formation of long-term memory for facts and events, which has often been tested by learning of a series of paired words or figures in humans. We have examined neural mechanisms underlying the memory "consolidation" process by single-unit recording and molecular biological methods in an animal model of a visual pair-association task in monkeys. In our previous studies, we found that long-term associative representations of visual objects are acquired through learning in the neural network of the anterior inferior temporal (IT) cortex. In this article, we propose the hypothesis that limbic neurons undergo rapid modification of synaptic connectivity and provide backward signals that guide the reorganization of neocortical neural circuits. Two experiments tested this hypothesis: (1) we examined the role of the backward connections from the medial temporal lobe to the IT cortex by injecting ibotenic acid into the entorhinal and perirhinal cortices, which provided massive backward projections ipsilaterally to the IT cortex. We found that the limbic lesion disrupted the associative code of the IT neurons between the paired associates, without impairing the visual response to each stimulus. (2) We then tested the first half of this hypothesis by detecting the expression of immediate-early genes in the monkey temporal cortex. We found specific expression of zif268 during the learning of a new set of paired associates in the pair-association task, most intensively in area 36 of the perirhinal cortex. All these results with the visual pair-association task support our hypothesis and demonstrate that the consolidation process, which was first proposed on the basis of clinico-psychological evidence, can now be examined in primates using neurophysiolocical and molecular biological approaches.

  2. The effects of background noise on the neural responses to natural sounds in cat primary auditory cortex

    Directory of Open Access Journals (Sweden)

    Omer Bar-Yosef

    2007-11-01

    Full Text Available Animal vocalizations in natural settings are invariably accompanied by an acoustic background with a complex statistical structure. We have previously demonstrated that neuronal responses in primary auditory cortex of halothane-anesthetized cats depend strongly on the natural background. Here, we study in detail the neuronal responses to the background sounds and their relationships to the responses to the foreground sounds. Natural bird chirps as well as modifications of these chirps were used. The chirps were decomposed into three components: the clean chirps, their echoes, and the background noise. The last two were weaker than the clean chirp by 13 and 29 dB on average respectively. The test stimuli consisted of the full natural stimulus, the three basic components, and their three pairwise combinations. When the level of the background components (echoes and background noise presented alone was sufficiently loud to evoke neuronal activity, these background components had an unexpectedly strong effect on the responses of the neurons to the main bird chirp. In particular, the responses to the original chirps were more similar on average to the responses evoked by the two background components than to the responses evoked by the clean chirp, both in terms of the evoked spike count and in terms of the temporal pattern of the responses. These results suggest that some of the neurons responded specifically to the acoustic background even when presented together with the substantially louder main chirp, and may imply that neurons in A1 already participate in auditory source segregation.

  3. Comparison of LFP-Based and Spike-Based Spectro-Temporal Receptive Fields and Cross-Correlation in Cat Primary Auditory Cortex

    OpenAIRE

    Eggermont, Jos J.; Munguia, Raymundo; Pienkowski, Martin; Shaw, Greg

    2011-01-01

    Multi-electrode array recordings of spike and local field potential (LFP) activity were made from primary auditory cortex of 12 normal hearing, ketamine-anesthetized cats. We evaluated 259 spectro-temporal receptive fields (STRFs) and 492 frequency-tuning curves (FTCs) based on LFPs and spikes simultaneously recorded on the same electrode. We compared their characteristic frequency (CF) gradients and their cross-correlation distances. The CF gradient for spike-based FTCs was about twice that ...

  4. Top-Down-Mediated Facilitation in the Visual Cortex Is Gated by Subcortical Neuromodulation.

    Science.gov (United States)

    Pafundo, Diego E; Nicholas, Mark A; Zhang, Ruilin; Kuhlman, Sandra J

    2016-03-01

    Response properties in primary sensory cortices are highly dependent on behavioral state. For example, the nucleus basalis of the forebrain plays a critical role in enhancing response properties of excitatory neurons in primary visual cortex (V1) during active exploration and learning. Given the strong reciprocal connections between hierarchically arranged cortical regions, how are increases in sensory response gain constrained to prevent runaway excitation? To explore this, we used in vivo two-photon guided cell-attached recording in conjunction with spatially restricted optogenetic photo-inhibition of higher-order visual cortex in mice. We found that the principle feedback projection to V1 originating from the lateral medial area (LM) facilitated visual responses in layer 2/3 excitatory neurons by ∼20%. This facilitation was reduced by half during basal forebrain activation due to differential response properties between LM and V1. Our results demonstrate that basal-forebrain-mediated increases in response gain are localized to V1 and are not propagated to LM and establish that subcortical modulation of visual cortex is regionally distinct. PMID:26961946

  5. A computational study of how orientation bias in the lateral geniculate nucleus can give rise to orientation selectivity in primary visual cortex

    Directory of Open Access Journals (Sweden)

    Levin eKuhlmann

    2011-10-01

    Full Text Available Controversy remains about how orientation selectivity emerges in simple cells of the mammalian primary visual cortex. In this paper, we present a computational model of how the orientation-biased responses of cells in lateral geniculate nucleus can contribute to the orientation selectivity in simple cells in cats. We propose that simple cells are excited by lateral geniculate fields with an orientation-bias and disynaptically inhibited by unoriented lateral geniculate fields (or biased fields pooled across orientations, both at approximately the same retinotopic co-ordinates. This interaction, combined with recurrent cortical excitation and inhibition, helps to create the sharp orientation tuning seen in simple cell responses. Along with describing orientation selectivity, the model also accounts for the spatial frequency and length response functions in simple cells, in normal conditions as well as under the influence of the GABAA antagonist, bicuculline. In addition, the model captures the response properties of LGN and simple cells to simultaneous visual stimulation and electrical stimulation of the LGN. We show that the sharp selectivity for stimulus orientation seen in primary visual cortical cells can be achieved without the excitatory convergence of the lateral geniculate nucleus input cells with receptive fields along a line in visual space, which has been a core assumption in classical models of visual cortex. We have also simulated how the full range of orientations seen in the cortex can emerge from the activity among broadly tuned channels tuned to a limited number of optimum orientations, just as in the classical case of coding for colour in trichromatic primates.

  6. The sparseness of neuronal responses in ferret primary visual cortex.

    Science.gov (United States)

    Tolhurst, David J; Smyth, Darragh; Thompson, Ian D

    2009-02-25

    Various arguments suggest that neuronal coding of natural sensory stimuli should be sparse (i.e., individual neurons should respond rarely but should respond reliably). We examined sparseness of visual cortical neurons in anesthetized ferret to flashed natural scenes. Response behavior differed widely between neurons. The median firing rate of 4.1 impulses per second was slightly higher than predicted from consideration of metabolic load. Thirteen percent of neurons (12 of 89) responded to 25% of images. Multivariate analysis of the range of sparseness values showed that 67% of the variance was accounted for by differing response patterns to moving gratings. Repeat presentation of images showed that response variance for natural images exaggerated sparseness measures; variance was scaled with mean response, but with a lower Fano factor than for the responses to moving gratings. This response variability and the "soft" sparse responses (Rehn and Sommer, 2007) raise the question of what constitutes a reliable neuronal response and imply parallel signaling by multiple neurons. We investigated whether the temporal structure of responses might be reliable enough to give additional information about natural scenes. Poststimulus time histogram shape was similar for "strong" and "weak" stimuli, with no systematic change in first-spike latency with stimulus strength. The variance of first-spike latency for repeat presentations of the same image was greater than the latency variance between images. In general, responses to flashed natural scenes do not seem compatible with a sparse encoding in which neurons fire rarely but reliably. PMID:19244512

  7. A neural network model on self-organizing emergence of simple-cell receptive field with orientation selectivity in visual cortex

    Institute of Scientific and Technical Information of China (English)

    YANG; Qian(

    2001-01-01

    [1]Hubel, D. H.. Wiesel. T. N., Receptive fields of single neuron in the cat striate cortex, Journal of Physiology, 1959, 148:574-591.[2]Hubel. D. H.. Wiesel, T. N., Functional architecture macaque monkey visual cortexm, Proc. Roy. Soc. B, 1977, 198: 1-59.[3]Shou. T. D., Brain Mechanisms of Visual Information Processing (in Chinese), Shanghai: Shanghai Science-Technology and Education Press, 1997, 188-197.[4]Ferster, D., Chung, S., Wheat, H., Orientation selectivity of thalamic input to simple cells of cat visual cortex, Nature,1996, 380: 249-252.[5]Vidyasagar. T. R., Pei, X., Volgushev, M., Multiple mechanisms underlying the orientation selectivity of visual cortical neurons. TINS, 1996, 19: 272-277.[6]Artun, O. B., Shouval, H. Z., Cooper, L. N., The effect of dynamic synapses on spatiotemporal receptive fields in visual cortex, Proc. Natl. Acad. Sci. USA, 1998, 95:11999-12003.[7]Rolls, E. T.. Tovee, M. J., Sparseness of the neuronal representation of stimuli in the primate temporal visual cortex, J.Neurophysiology, 1995,73: 713-726.[8]Olshausen. B. A.. Field, D. J., Sparse coding with an overcomplete basis set: A strategy employed by V 1 ? Vision Research,1997.37: 3311-3325.[9]Bell. A. J., Sejnoswski, T. J., The "Independent components" of natural scenes are edge filters, Vision Research, 1997, 37:3327-3338.[10]Dan, Y., Atick, J. J., Reid, R. C., Efficient coding of natural scenes in the lateral geniculate nucleus: experimental test of a computational theory, Journal of Neuroscience, 1996, 16:3351-3362.[11]Field. D. J., Relations between the statistics of natural images and the response properties of cortical cells, Journal of the Optical Society of America A, 1987, 4: 2379-2394.[12]DeAngelis, G. C., Ohzawa, I., Freeman, R. D., Receptive filed dynamics in the central visual pathway, TINS, 1995,18:451-458.[13]Wang, Y. J., Qi, X. L., Chen, Y. Z., Simulations of receptive fields dynamics, TINS, 1996, 19: 385-386.

  8. Tilt aftereffects in a self-organizing model of the primary visual cortex.

    Science.gov (United States)

    Bednar, J A; Miikkulainen, R

    2000-07-01

    RF-LISSOM, a self-organizing model of laterally connected orientation maps in the primary visual cortex, was used to study the psychological phenomenon known as the tilt aftereffect. The same self-organizing processes that are responsible for the long-term development of the map are shown to result in tilt aftereffects over short timescales in the adult. The model permits simultaneous observation of large numbers of neurons and connections, making it possible to relate high-level phenomena to low-level events, which is difficult to do experimentally. The results give detailed computational support for the long-standing conjecture that the direct tilt aftereffect arises from adaptive lateral interactions between feature detectors. They also make a new prediction that the indirect effect results from the normalization of synaptic efficacies during this process. The model thus provides a unified computational explanation of self-organization and both the direct and indirect tilt aftereffect in the primary visual cortex.

  9. 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…

  10. Response Selectivity Is Correlated to Dendritic Structure in Parvalbumin-Expressing Inhibitory Neurons in Visual Cortex

    OpenAIRE

    Runyan, Caroline A.; Sur, Mriganka

    2013-01-01

    Inhibitory neurons have been shown to perform a variety of functions within brain circuits, including shaping response functions in target cells. Still, how the properties of specific inhibitory neuron classes relate to their local circuits remains unclear. To better understand the distribution and origins of orientation selectivity in inhibitory neurons expressing the calcium binding protein parvalbumin (PV) in the mouse primary visual cortex, we labeled PV+ neurons with red fluorescent prot...

  11. GAD67-mediated GABA Synthesis and Signaling Regulate Inhibitory Synaptic Innervation in the Visual Cortex

    OpenAIRE

    Chattopadhyaya, Bidisha; Di Cristo, Graziella; Wu, Cai Zhi; Knott, Graham; Kuhlman, Sandra; Fu, Yu; Palmiter, Richard D; Huang, Z. Josh

    2007-01-01

    The development of GABAergic inhibitory circuits is shaped by neural activity, but the underlying mechanisms are unclear. we demonstrate a novel function of GABA in regulating GABAergic innervation in the adolescent brain, when GABA is mainly known as an inhibitory transmitter. Conditional knockdown of the rate-limiting synthetic enzyme GAD67 in basket interneurons in adolescent visual cortex resulted in cell autonomous deficits in axon branching, perisomatic synapse formation around pyramida...

  12. Integration of Auditory and Visual Communication Information in the Primate Ventrolateral Prefrontal Cortex

    OpenAIRE

    Sugihara, T.; Diltz, M. D.; Averbeck, B. B.; Romanski, L. M.

    2006-01-01

    The integration of auditory and visual stimuli is crucial for recognizing objects, communicating effectively, and navigating through our complex world. Although the frontal lobes are involved in memory, communication, and language, there has been no evidence that the integration of communication information occurs at the single-cell level in the frontal lobes. Here, we show that neurons in the macaque ventrolateral prefrontal cortex (VLPFC) integrate audiovisual communication stimuli. The mul...

  13. A precise form of divisive suppression supports population coding in primary visual cortex

    OpenAIRE

    MacEvoy, Sean P.; Tucker, Thomas R.; Fitzpatrick, David

    2009-01-01

    The responses of neurons in the primary visual cortex (V1) to an optimally-oriented grating are suppressed when a non-optimal grating is superimposed. Although cross-orientation suppression is thought to reflect mechanisms that maintain a distributed code for orientation, the impact of superimposed gratings upon V1 populations is unknown. Using intrinsic signal optical imaging, we find that patterns of tree shrew V1 activity evoked by superimposed equal-contrast gratings were predicted by the...

  14. The Role of the Human Extrastriate Visual Cortex in Mirror Symmetry Discrimination: A TMS-Adaptation Study

    Science.gov (United States)

    Cattaneo, Zaira; Mattavelli, Giulia; Papagno, Costanza; Herbert, Andrew; Silvanto, Juha

    2011-01-01

    The human visual system is able to efficiently extract symmetry information from the visual environment. Prior neuroimaging evidence has revealed symmetry-preferring neuronal representations in the dorsolateral extrastriate visual cortex; the objective of the present study was to investigate the necessity of these representations in symmetry…

  15. Basic level category structure emerges gradually across human ventral visual cortex.

    Science.gov (United States)

    Iordan, Marius Cătălin; Greene, Michelle R; Beck, Diane M; Fei-Fei, Li

    2015-07-01

    Objects can be simultaneously categorized at multiple levels of specificity ranging from very broad ("natural object") to very distinct ("Mr. Woof"), with a mid-level of generality (basic level: "dog") often providing the most cognitively useful distinction between categories. It is unknown, however, how this hierarchical representation is achieved in the brain. Using multivoxel pattern analyses, we examined how well each taxonomic level (superordinate, basic, and subordinate) of real-world object categories is represented across occipitotemporal cortex. We found that, although in early visual cortex objects are best represented at the subordinate level (an effect mostly driven by low-level feature overlap between objects in the same category), this advantage diminishes compared to the basic level as we move up the visual hierarchy, disappearing in object-selective regions of occipitotemporal cortex. This pattern stems from a combined increase in within-category similarity (category cohesion) and between-category dissimilarity (category distinctiveness) of neural activity patterns at the basic level, relative to both subordinate and superordinate levels, suggesting that successive visual areas may be optimizing basic level representations.

  16. 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.

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

    Directory of Open Access Journals (Sweden)

    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.

  18. Basic level category structure emerges gradually across human ventral visual cortex.

    Science.gov (United States)

    Iordan, Marius Cătălin; Greene, Michelle R; Beck, Diane M; Fei-Fei, Li

    2015-07-01

    Objects can be simultaneously categorized at multiple levels of specificity ranging from very broad ("natural object") to very distinct ("Mr. Woof"), with a mid-level of generality (basic level: "dog") often providing the most cognitively useful distinction between categories. It is unknown, however, how this hierarchical representation is achieved in the brain. Using multivoxel pattern analyses, we examined how well each taxonomic level (superordinate, basic, and subordinate) of real-world object categories is represented across occipitotemporal cortex. We found that, although in early visual cortex objects are best represented at the subordinate level (an effect mostly driven by low-level feature overlap between objects in the same category), this advantage diminishes compared to the basic level as we move up the visual hierarchy, disappearing in object-selective regions of occipitotemporal cortex. This pattern stems from a combined increase in within-category similarity (category cohesion) and between-category dissimilarity (category distinctiveness) of neural activity patterns at the basic level, relative to both subordinate and superordinate levels, suggesting that successive visual areas may be optimizing basic level representations. PMID:25811711

  19. A two-stage cascade model of BOLD responses in human visual cortex.

    Directory of Open Access Journals (Sweden)

    Kendrick N Kay

    Full Text Available Visual neuroscientists have discovered fundamental properties of neural representation through careful analysis of responses to controlled stimuli. Typically, different properties are studied and modeled separately. To integrate our knowledge, it is necessary to build general models that begin with an input image and predict responses to a wide range of stimuli. In this study, we develop a model that accepts an arbitrary band-pass grayscale image as input and predicts blood oxygenation level dependent (BOLD responses in early visual cortex as output. The model has a cascade architecture, consisting of two stages of linear and nonlinear operations. The first stage involves well-established computations-local oriented filters and divisive normalization-whereas the second stage involves novel computations-compressive spatial summation (a form of normalization and a variance-like nonlinearity that generates selectivity for second-order contrast. The parameters of the model, which are estimated from BOLD data, vary systematically across visual field maps: compared to primary visual cortex, extrastriate maps generally have larger receptive field size, stronger levels of normalization, and increased selectivity for second-order contrast. Our results provide insight into how stimuli are encoded and transformed in successive stages of visual processing.

  20. Learning Enhances Sensory and Multiple Non-sensory Representations in Primary Visual Cortex.

    Science.gov (United States)

    Poort, Jasper; Khan, Adil G; Pachitariu, Marius; Nemri, Abdellatif; Orsolic, Ivana; Krupic, Julija; Bauza, Marius; Sahani, Maneesh; Keller, Georg B; Mrsic-Flogel, Thomas D; Hofer, Sonja B

    2015-06-17

    We determined how learning modifies neural representations in primary visual cortex (V1) during acquisition of a visually guided behavioral task. We imaged the activity of the same layer 2/3 neuronal populations as mice learned to discriminate two visual patterns while running through a virtual corridor, where one pattern was rewarded. Improvements in behavioral performance were closely associated with increasingly distinguishable population-level representations of task-relevant stimuli, as a result of stabilization of existing and recruitment of new neurons selective for these stimuli. These effects correlated with the appearance of multiple task-dependent signals during learning: those that increased neuronal selectivity across the population when expert animals engaged in the task, and those reflecting anticipation or behavioral choices specifically in neuronal subsets preferring the rewarded stimulus. Therefore, learning engages diverse mechanisms that modify sensory and non-sensory representations in V1 to adjust its processing to task requirements and the behavioral relevance of visual stimuli.

  1. Callosal connections of primary visual cortex predict the spatial spreading of binocular rivalry across the visual hemifields

    Directory of Open Access Journals (Sweden)

    Erhan eGenc

    2011-12-01

    Full Text Available In binocular rivalry, presentation of different images to the separate eyes leads to conscious perception alternating between the two possible interpretations every few seconds. During perceptual transitions, a stimulus emerging into dominance can spread in a wave-like manner across the visual field. These traveling waves of rivalry dominance have been successfully related to the cortical magnification properties and functional activity of early visual areas, including the primary visual cortex (V1. Curiously however, these traveling waves undergo a delay when passing from one hemifield to another. In the current study, we used diffusion tensor imaging (DTI to investigate whether the strength of interhemispheric connections between the left and right visual cortex might be related to the delay of traveling waves across hemifields. We measured the delay in traveling-wave times (ΔTWT in nineteen participants and repeated this test 6 weeks later to evaluate the reliability of our behavioral measures. We found large interindividual variability but also good test-retest reliability for individual measures of ΔTWT. Using DTI in connection with fiber tractography, we identified parts of the corpus callosum connecting functionally defined visual areas V1-V3. We found that individual differences in ΔTWT was reliably predicted by the diffusion properties of transcallosal fibers connecting left and right V1, but observed no such effect for neighboring transcallosal visual fibers connecting V2 and V3. Our results demonstrate that the anatomical characteristics of topographically specific transcallosal connections predict the individual delay of interhemispheric traveling waves, providing further evidence that V1 is an important site for neural processes underlying binocular rivalry.

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

    Directory of Open Access Journals (Sweden)

    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. 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

    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......Whereas the links between eye movements and the shifts in visual attention are well established, less is known about how eye position affects the prioritization of visual space. It was recently observed that visual sensitivity varies with the direction of gaze and the level of excitability...... detectability observed previously, but not from the location of the visual targets relative to the body. These results strongly argue for a modulatory connection from the eye proprioceptive area in the somatosensory cortex to the higher-order visual cortex. This connection may contribute to flexibly allocate...

  4. Brain polarization of parietal cortex augments training-induced improvement of visual exploratory and attentional skills.

    Science.gov (United States)

    Bolognini, Nadia; Fregni, Felipe; Casati, Carlotta; Olgiati, Elena; Vallar, Giuseppe

    2010-08-19

    Recent evidence suggests that behavioural gains induced by behavioural training are maximized when combined with techniques of cortical neuromodulation, such as transcranial Direct Current Stimulation (tDCS). Here we address the validity of this appealing approach by investigating the effect of coupling a multisensory visual field exploration training with tDCS of the posterior parietal cortex (PPC). The multisensory visual field exploration training consisted in the practice of visual search through the systematic audio-visual stimulation of the visual field. Neurologically unimpaired participants performed a bimodal exploration training for 30 min, while simultaneously receiving anodal-excitatory PPC tDCS or sham tDCS. In two different experiments, the left and the right hemisphere were stimulated. Outcome measures included visual exploration speed at different time intervals during the training, and the post-training effects on tests assessing visual scanning and visuo-spatial orienting. Results show that PPC tDCS applied to the right, but not to the left, hemisphere increases the training-induced behavioural improvement of visual exploration, as compared to sham tDCS. In addition, right PPC tDCS brings about an improvement of covert visual orienting, in a task different from the visual search practice. In an additional experiment, we confirm that right parietal tDCS by itself, even without the associated training, can lead to enhancement of visual search. Overall, anodal PPC tDCS is a promising technique to enhance visuo-spatial abilities, when combined to a visual field exploration training task. PMID:20599813

  5. Comparing development of synaptic proteins in rat visual, somatosensory, and frontal cortex

    Directory of Open Access Journals (Sweden)

    Joshua G A Pinto

    2013-05-01

    Full Text Available Two theories have influenced our understanding of cortical development: the integrated network theory, where synaptic development is coordinated across areas; and the cascade theory, where the cortex develops in a wave-like manner from sensory to non-sensory areas. These different views on cortical development raise challenges for current studies aimed at comparing detailed maturation of the connectome among cortical areas. We have taken a different approach to compare synaptic development in rat visual, somatosensory, and frontal cortex by measuring expression of pre-synaptic (Synapsin and Synaptophysin proteins that regulate vesicle cycling, and post-synaptic (PSD-95 and Gephyrin proteins that anchor excitatory or inhibitory (E-I receptors. We also compared development of the balances between the pairs of pre- or post-synaptic proteins, and the overall pre-to-post-synaptic balance, to address functional maturation and emergence of the E-I balance. We found that development of the individual proteins and the post-synaptic index overlapped among the 3 cortical areas, but the pre-synaptic index matured later in frontal cortex. Finally, we applied a neuroinformatics approach using principal component analysis (PCA and found that 3 components captured development of the synaptic proteins. The first component accounted for 64% of the variance in protein expression and reflected total protein expression, which overlapped among the 3 cortical areas. The second component was Gephyrin and the E-I balance, it emerged as sequential waves starting in somatosensory, then frontal, and finally visual cortex. The third component was the balance between pre- and post-synaptic proteins, and this followed a different developmental trajectory in somatosensory cortex. Together, these results give the most support to an integrated network of synaptic development, but also highlight more complex patterns of development that vary in timing and end point among the

  6. Metabolic changes in the visual cortex of binocular blindness macaque monkeys: a proton magnetic resonance spectroscopy study.

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    Lingjie Wu

    Full Text Available PURPOSE: To evaluate proton magnetic resonance spectroscopy ((1H-MRS in a study of cross-modal plasticity in the visual cortex of binocular blindness macaque monkeys. MATERIALS AND METHODS: Four healthy neonatal macaque monkeys were randomly divided into 2 groups, with 2 in each group. Optic nerve transection was performed in both monkeys in the experimental group (group B to obtain binocular blindness. Two healthy macaque monkeys served as a control group (group A. After sixteen months post-procedure, (1H-MRS was performed in the visual cortex of all monkeys. We compared the peak areas of NAA, Cr, Cho, Glx and Ins and the ratios of NAA/Cr, Cho/Cr, Glx/Cr and Ins/Cr of each monkey in group B with group A. RESULTS: The peak area of NAA and the NAA/Cr ratio in the visual cortex of monkey 4 in group B were found to be dramatically decreased, the peak area of NAA slightly decreased and the NAA/Cr ratio clearly decreased in visual cortex of monkey 3 in group B than those in group A. The peak area of Ins and the Ins/Cr ratio in the visual cortex of monkey 4 in group B slightly increased. The peak area of Cho and the Cho/Cr ratio in the visual cortex of all monkeys in group B dramatically increased compared with group A. The peak area of Glx in the visual cortex of all monkeys in group B slightly increased compared with group A. CONCLUSIONS: (1H-MRS could detect biochemical and metabolic changes in the visual cortex and therefore this technique can be used to provide valuable information for investigating the mechanisms of cross-modal plasticity of binocular blindness in a macaque monkey model.

  7. The Development of Dominance Stripes and Orientation Maps in a Self-Organising Visual Cortex Network (VICON)

    OpenAIRE

    Luttrell, Stephen

    2010-01-01

    A self-organising neural network is presented that is based on a rigorous Bayesian analysis of the information contained in individual neural firing events. This leads to a visual cortex network (VICON) that has many of the properties emerge when a mammalian visual cortex is exposed to data arriving from two imaging sensors (i.e. the two retinae), such as dominance stripes and orientation maps.

  8. Characterization of visual percepts evoked by noninvasive stimulation of the human posterior parietal cortex.

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    Peter J Fried

    Full Text Available Phosphenes are commonly evoked by transcranial magnetic stimulation (TMS to study the functional organization, connectivity, and excitability of the human visual brain. For years, phosphenes have been documented only from stimulating early visual areas (V1-V3 and a handful of specialized visual regions (V4, V5/MT+ in occipital cortex. Recently, phosphenes were reported after applying TMS to a region of posterior parietal cortex involved in the top-down modulation of visuo-spatial processing. In the present study, we systematically characterized parietal phosphenes to determine if they are generated directly by local mechanisms or emerge through indirect activation of other visual areas. Using technology developed in-house to record the subjective features of phosphenes, we found no systematic differences in the size, shape, location, or frame-of-reference of parietal phosphenes when compared to their occipital counterparts. In a second experiment, discrete deactivation by 1 Hz repetitive TMS yielded a double dissociation: phosphene thresholds increased at the deactivated site without producing a corresponding change at the non-deactivated location. Overall, the commonalities of parietal and occipital phosphenes, and our ability to independently modulate their excitability thresholds, lead us to conclude that they share a common neural basis that is separate from either of the stimulated regions.

  9. The role of visual cortex acetylcholine in learning to discriminate temporally modulated visual stimuli

    OpenAIRE

    Minces, V. H.; Alexander, A.S.; Datlow, M.; Alfonso, S. I.; Chiba, A. A.

    2013-01-01

    Cholinergic neurons in the basal forebrain innervate discrete regions of the cortical mantle, bestowing the cholinergic system with the potential to dynamically modulate sub-regions of the cortex according to behavioral demands. Cortical cholinergic activity has been shown to facilitate learning and modulate attention. Experiments addressing these issues have primarily focused on widespread cholinergic depletions, extending to areas involved in general cognitive processes and sleep cycle regu...

  10. A hierarchy of timescales explains distinct effects of local inhibition of primary visual cortex and frontal eye fields.

    Science.gov (United States)

    Cocchi, Luca; Sale, Martin V; L Gollo, Leonardo; Bell, Peter T; Nguyen, Vinh T; Zalesky, Andrew; Breakspear, Michael; Mattingley, Jason B

    2016-09-06

    Within the primate visual system, areas at lower levels of the cortical hierarchy process basic visual features, whereas those at higher levels, such as the frontal eye fields (FEF), are thought to modulate sensory processes via feedback connections. Despite these functional exchanges during perception, there is little shared activity between early and late visual regions at rest. How interactions emerge between regions encompassing distinct levels of the visual hierarchy remains unknown. Here we combined neuroimaging, non-invasive cortical stimulation and computational modelling to characterize changes in functional interactions across widespread neural networks before and after local inhibition of primary visual cortex or FEF. We found that stimulation of early visual cortex selectively increased feedforward interactions with FEF and extrastriate visual areas, whereas identical stimulation of the FEF decreased feedback interactions with early visual areas. Computational modelling suggests that these opposing effects reflect a fast-slow timescale hierarchy from sensory to association areas.

  11. A hierarchy of timescales explains distinct effects of local inhibition of primary visual cortex and frontal eye fields.

    Science.gov (United States)

    Cocchi, Luca; Sale, Martin V; L Gollo, Leonardo; Bell, Peter T; Nguyen, Vinh T; Zalesky, Andrew; Breakspear, Michael; Mattingley, Jason B

    2016-01-01

    Within the primate visual system, areas at lower levels of the cortical hierarchy process basic visual features, whereas those at higher levels, such as the frontal eye fields (FEF), are thought to modulate sensory processes via feedback connections. Despite these functional exchanges during perception, there is little shared activity between early and late visual regions at rest. How interactions emerge between regions encompassing distinct levels of the visual hierarchy remains unknown. Here we combined neuroimaging, non-invasive cortical stimulation and computational modelling to characterize changes in functional interactions across widespread neural networks before and after local inhibition of primary visual cortex or FEF. We found that stimulation of early visual cortex selectively increased feedforward interactions with FEF and extrastriate visual areas, whereas identical stimulation of the FEF decreased feedback interactions with early visual areas. Computational modelling suggests that these opposing effects reflect a fast-slow timescale hierarchy from sensory to association areas. PMID:27596931

  12. Reduced myelin basic protein and actin-related gene expression in visual cortex in schizophrenia.

    Science.gov (United States)

    Matthews, Paul R; Eastwood, Sharon L; Harrison, Paul J

    2012-01-01

    Most brain gene expression studies of schizophrenia have been conducted in the frontal cortex or hippocampus. The extent to which alterations occur in other cortical regions is not well established. We investigated primary visual cortex (Brodmann area 17) from the Stanley Neuropathology Consortium collection of tissue from 60 subjects with schizophrenia, bipolar disorder, major depression, or controls. We first carried out a preliminary array screen of pooled RNA, and then used RT-PCR to quantify five mRNAs which the array identified as differentially expressed in schizophrenia (myelin basic protein [MBP], myelin-oligodendrocyte glycoprotein [MOG], β-actin [ACTB], thymosin β-10 [TB10], and superior cervical ganglion-10 [SCG10]). Reduced mRNA levels were confirmed by RT-PCR for MBP, ACTB and TB10. The MBP reduction was limited to transcripts containing exon 2. ACTB and TB10 mRNAs were also decreased in bipolar disorder. None of the transcripts were altered in subjects with major depression. Reduced MBP mRNA in schizophrenia replicates findings in other brain regions and is consistent with oligodendrocyte involvement in the disorder. The decreases in expression of ACTB, and the actin-binding protein gene TB10, suggest changes in cytoskeletal organisation. The findings confirm that the primary visual cortex shows molecular alterations in schizophrenia and extend the evidence for a widespread, rather than focal, cortical pathophysiology.

  13. Reduced myelin basic protein and actin-related gene expression in visual cortex in schizophrenia.

    Directory of Open Access Journals (Sweden)

    Paul R Matthews

    Full Text Available Most brain gene expression studies of schizophrenia have been conducted in the frontal cortex or hippocampus. The extent to which alterations occur in other cortical regions is not well established. We investigated primary visual cortex (Brodmann area 17 from the Stanley Neuropathology Consortium collection of tissue from 60 subjects with schizophrenia, bipolar disorder, major depression, or controls. We first carried out a preliminary array screen of pooled RNA, and then used RT-PCR to quantify five mRNAs which the array identified as differentially expressed in schizophrenia (myelin basic protein [MBP], myelin-oligodendrocyte glycoprotein [MOG], β-actin [ACTB], thymosin β-10 [TB10], and superior cervical ganglion-10 [SCG10]. Reduced mRNA levels were confirmed by RT-PCR for MBP, ACTB and TB10. The MBP reduction was limited to transcripts containing exon 2. ACTB and TB10 mRNAs were also decreased in bipolar disorder. None of the transcripts were altered in subjects with major depression. Reduced MBP mRNA in schizophrenia replicates findings in other brain regions and is consistent with oligodendrocyte involvement in the disorder. The decreases in expression of ACTB, and the actin-binding protein gene TB10, suggest changes in cytoskeletal organisation. The findings confirm that the primary visual cortex shows molecular alterations in schizophrenia and extend the evidence for a widespread, rather than focal, cortical pathophysiology.

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

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    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.

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

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    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.

  16. 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

    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......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.......99-2.93), respectively. Thus, in the children, an rCBF increase could not be detected by perfusion MRI, but indications of a FAIR signal decrease were found. An rCBF decrease in the primary visual cortex during stimulation has not been reported previously, but it is a possible explanation for the negative BOLD response...

  17. Playing the electric light orchestra--how electrical stimulation of visual cortex elucidates the neural basis of perception.

    Science.gov (United States)

    Cicmil, Nela; Krug, Kristine

    2015-09-19

    Vision research has the potential to reveal fundamental mechanisms underlying sensory experience. Causal experimental approaches, such as electrical microstimulation, provide a unique opportunity to test the direct contributions of visual cortical neurons to perception and behaviour. But in spite of their importance, causal methods constitute a minority of the experiments used to investigate the visual cortex to date. We reconsider the function and organization of visual cortex according to results obtained from stimulation techniques, with a special emphasis on electrical stimulation of small groups of cells in awake subjects who can report their visual experience. We compare findings from humans and monkeys, striate and extrastriate cortex, and superficial versus deep cortical layers, and identify a number of revealing gaps in the 'causal map' of visual cortex. Integrating results from different methods and species, we provide a critical overview of the ways in which causal approaches have been used to further our understanding of circuitry, plasticity and information integration in visual cortex. Electrical stimulation not only elucidates the contributions of different visual areas to perception, but also contributes to our understanding of neuronal mechanisms underlying memory, attention and decision-making.

  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. Temporal response properties to second-order visual stimuli in the LGN of cats

    Institute of Scientific and Technical Information of China (English)

    XU PengJing; YE Xiang; ZHOU Yifeng

    2007-01-01

    Visual stimuli occurring naturally are rich in instances of objects delineated from the backgrounds only by differences in luminance, which is called first-order stimuli, as well as those defined by differences of contrast or texture, referred to as second-order stimuli.The neuronal mechanism for processing second-order stimuli is still unclear.In this study, we compared the responses of cat LGN (lateral geniculate nucleus) cells to second-order stimuli at five temporal frequencies to their responses to first-order stimuli.Our results showed that most LGN cells can be evoked by second-order stimuli, and their firing rates to second-order stimuli decreased relative to first-order stimuli as temporal frequency increased from 0.5 to 8 Hz; moreover the ratio of a nonlinear to linear factor had a higher value in the responses to second-order stimuli than to first-order stimuli.We also found that the responses of Y-cells to second-order stimuli were significantly higher than the responses of X-cells, suggesting the Y-cells have a more important role in the processing of second-order stimuli.All these results reveal that first-order and second-order signals might be processed in separate 'streams' of the visual system.

  20. 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.

  1. A small-world-based population encoding model of the primary visual cortex.

    Science.gov (United States)

    Shi, Li; Niu, Xiaoke; Wan, Hong; Shang, Zhigang; Wang, Zhizhong

    2015-06-01

    A wide range of evidence has shown that information encoding performed by the visual cortex involves complex activities of neuronal populations. However, the effects of the neuronal connectivity structure on the population's encoding performance remain poorly understood. In this paper, a small-world-based population encoding model of the primary visual cortex (V1) is established on the basis of the generalized linear model (GLM) to describe the computation of the neuronal population. The model mainly consists of three sets of filters, including a spatiotemporal stimulus filter, a post-spike history filter, and a set of coupled filters with the coupling neurons organizing as a small-world network. The parameters of the model were fitted with neuronal data of the rat V1 recorded with a micro-electrode array. Compared to the traditional GLM, without considering the small-world structure of the neuronal population, the proposed model was proved to produce more accurate spiking response to grating stimuli and enhance the capability of the neuronal population to carry information. The comparison results proved the validity of the proposed model and further suggest the role of small-world structure in the encoding performance of local populations in V1, which provides new insights for understanding encoding mechanisms of a small scale population in visual system.

  2. Comparative study on direction selectivity and functional organization of the primary visual cortical cells in monkeys and cats

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Although the directionally selective cells in many visual cortical areas are organized in columnar manner, the functional organization of direction selectivity of area Vl in the monkey still remains unclear. We quantitatively studied the proportion of directionally selective cells, direction selectivity and the functional organization of the striate cortical cells in the monkey and compared those with the cat. The results show that the direction selectivity and directional organization of striate cortical cells in the monkey are significantly weaker than those in the cat, suggesting that the species difference between the two kinds of animal is related to their different anatomic pathways.

  3. Comparative study on direction selectivity and functional organization of the primary visual cortical cells in monkeys and cats

    Institute of Scientific and Technical Information of China (English)

    寿天德; 周逸峰; 俞洪波

    2000-01-01

    Although the directionally selective cells in many visual cortical areas are organized in columnar manner, the functional organization of direction selectivity of area VI in the monkey still remains unclear. We quantitatively studied the proportion of directionally selective cells, direction selectivity and the functional organization of the striate cortical cells in the monkey and compared those with the cat. The results show that the direction selectivity and directional organization of striate cortical cells in the monkey are significantly weaker than those in the cat, suggesting that the species difference between the two kinds of animal is related to their different anatomic pathways.

  4. 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)

  5. Cortical and thalamic connectivity of the auditory anterior ectosylvian cortex of early-deaf cats: Implications for neural mechanisms of crossmodal plasticity.

    Science.gov (United States)

    Meredith, M Alex; Clemo, H Ruth; Corley, Sarah B; Chabot, Nicole; Lomber, Stephen G

    2016-03-01

    Early hearing loss leads to crossmodal plasticity in regions of the cerebrum that are dominated by acoustical processing in hearing subjects. Until recently, little has been known of the connectional basis of this phenomenon. One region whose crossmodal properties are well-established is the auditory field of the anterior ectosylvian sulcus (FAES) in the cat, where neurons are normally responsive to acoustic stimulation and its deactivation leads to the behavioral loss of accurate orienting toward auditory stimuli. However, in early-deaf cats, visual responsiveness predominates in the FAES and its deactivation blocks accurate orienting behavior toward visual stimuli. For such crossmodal reorganization to occur, it has been presumed that novel inputs or increased projections from non-auditory cortical areas must be generated, or that existing non-auditory connections were 'unmasked.' These possibilities were tested using tracer injections into the FAES of adult cats deafened early in life (and hearing controls), followed by light microscopy to localize retrogradely labeled neurons. Surprisingly, the distribution of cortical and thalamic afferents to the FAES was very similar among early-deaf and hearing animals. No new visual projection sources were identified and visual cortical connections to the FAES were comparable in projection proportions. These results support an alternate theory for the connectional basis for cross-modal plasticity that involves enhanced local branching of existing projection terminals that originate in non-auditory as well as auditory cortices. PMID:26724756

  6. 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.

  7. Posttraining transcranial magnetic stimulation of striate cortex disrupts consolidation early in visual skill learning.

    Science.gov (United States)

    De Weerd, Peter; Reithler, Joel; van de Ven, Vincent; Been, Marin; Jacobs, Christianne; Sack, Alexander T

    2012-02-01

    Practice-induced improvements in skilled performance reflect "offline " consolidation processes extending beyond daily training sessions. According to visual learning theories, an early, fast learning phase driven by high-level areas is followed by a late, asymptotic learning phase driven by low-level, retinotopic areas when higher resolution is required. Thus, low-level areas would not contribute to learning and offline consolidation until late learning. Recent studies have challenged this notion, demonstrating modified responses to trained stimuli in primary visual cortex (V1) and offline activity after very limited training. However, the behavioral relevance of modified V1 activity for offline consolidation of visual skill memory in V1 after early training sessions remains unclear. Here, we used neuronavigated transcranial magnetic stimulation (TMS) directed to a trained retinotopic V1 location to test for behaviorally relevant consolidation in human low-level visual cortex. Applying TMS to the trained V1 location within 45 min of the first or second training session strongly interfered with learning, as measured by impaired performance the next day. The interference was conditional on task context and occurred only when training in the location targeted by TMS was followed by training in a second location before TMS. In this condition, high-level areas may become coupled to the second location and uncoupled from the previously trained low-level representation, thereby rendering consolidation vulnerable to interference. Our data show that, during the earliest phases of skill learning in the lowest-level visual areas, a behaviorally relevant form of consolidation exists of which the robustness is controlled by high-level, contextual factors.

  8. Contributions of cortical feedback to sensory processing in primary visual cortex

    Directory of Open Access Journals (Sweden)

    Lucy S. Petro

    2014-11-01

    Full Text Available Closing the structure-function divide is more challenging in the brain than in any other organ (Lichtman and Denk, 2011. For example, in early visual cortex, feedback projections to V1 can be quantified (e.g. Budd, 1998 but the understanding of feedback function is comparatively rudimentary (Muckli and Petro, 2013. Focusing on the function of feedback, we discuss how textbook descriptions mask the complexity of V1 responses, and how feedback and local activity reflects not only sensory processing but internal brain states.

  9. Contributions of cortical feedback to sensory processing in primary visual cortex.

    Science.gov (United States)

    Petro, Lucy S; Vizioli, Luca; Muckli, Lars

    2014-01-01

    Closing the structure-function divide is more challenging in the brain than in any other organ (Lichtman and Denk, 2011). For example, in early visual cortex, feedback projections to V1 can be quantified (e.g., Budd, 1998) but the understanding of feedback function is comparatively rudimentary (Muckli and Petro, 2013). Focusing on the function of feedback, we discuss how textbook descriptions mask the complexity of V1 responses, and how feedback and local activity reflects not only sensory processing but internal brain states. PMID:25414677

  10. Ocular dominance patterns in mammalian visual cortex: A wire length minimization approach

    OpenAIRE

    Chklovskii, Dmitri B.; Koulakov, Alexei A.

    1999-01-01

    We propose a theory for ocular dominance (OD) patterns in mammalian primary visual cortex. This theory is based on the premise that OD pattern is an adaptation to minimize the length of intra-cortical wiring. Thus we can understand the existing OD patterns by solving a wire length minimization problem. We divide all the neurons into two classes: left-eye dominated and right-eye dominated. We find that segregation of neurons into monocular regions reduces wire length if the number of connectio...

  11. 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

    Regional cerebral blood flow (CBF) was studied tomographically with 133Xe administered by inhalation over a 1-min period at a concentration of 10 mCi/l. A fast rotating ("dynamic') single-photon emission computed tomograph with four detector heads was used, an instrument that has been found......% 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...

  12. Synaptic output of individual layer 4 neurons in guinea pig visual cortex

    OpenAIRE

    Sáez, Ignacio; Friedlander, Michael J.

    2009-01-01

    More than 90% of geniculocortical axons from the dorsal lateral geniculate nucleus of the thalamus innervate layer 4 (L4) of the primary visual cortex (V1). Excitatory neurons, which comprise over 80% of the neuronal population in L4, synapse mainly onto adjacent L4 neurons and layer 2/3 (L2/3) neurons. It has been suggested that intra-laminar L4-L4 connections contribute to amplifying and refining thalamocortical signals before routing to L2/3. In order to unambiguously probe the properties ...

  13. Levodopa methyl ester increases nerve growth factor expression in visual cortex area 17 in a feline model of strabismic amblyopia

    Institute of Scientific and Technical Information of China (English)

    Yongwen Li; Xing Lin; Shijun Zhang; Rong Li; Weizhe Jiang; Renbin Huang

    2011-01-01

    In the present study, a feline model of strabismic amblyopia was established during a sensitive developmental period, and the influence of levodopa methyl ester and levodopa on nerve growth factor expression in the visual cortex (area 17) was compared. Pattern visual-evoked potential and immunohistochemistry results showed that levodopa methyl ester and levodopa treatment shortened P100 wave latency, increased P100 amplitude, and increased the number of endogenous nerve growth factor-positive cells in visual cortex levels. In particular, the effects of levodopa methyl ester were superior to levodopa treatment.

  14. The role of primary visual cortex (V1) in visual awareness.

    NARCIS (Netherlands)

    V.A.F. Lamme; H. Super; R. Landman; P.R. Roelfsema; H. Spekreijse

    2000-01-01

    Neurophysiological data from V1 recordings in awake monkeys were examined in light of 2 general classes of visual awareness (VA)models. In model type 1, VA is seen as being mediated either by a particular set of areas or pathways, or alternatively by a specific set of neurons. In these models, the r

  15. 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

  16. 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.

  17. Surface area of early visual cortex predicts individual speed of traveling waves during binocular rivalry.

    Science.gov (United States)

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

    2015-06-01

    Binocular rivalry ensues when different images are presented to the 2 eyes with conscious perception alternating between the possible interpretations. For large rivalry displays, perceptual transitions are initiated at one location and spread to other parts of the visual field, a phenomenon termed "traveling wave." Previous studies investigated the underlying neural mechanisms of the traveling wave and surmised that primary visual cortex might play an important role. We used magnetic resonance imaging and behavioral measures in humans to explore how interindividual differences in observers' subjective experience of the wave are related to anatomical characteristics of cortical regions. We measured wave speed in participants and confirmed the long-term stability of the individual values. Retinotopic mapping was employed to delineate borders of visual areas V1-V3 in order to determine surface area and cortical thickness in those regions. Only the surface areas of V1 and V2, but not V3 showed a correlation with wave speed. For individuals with larger V1/V2 area, the traveling wave needed longer to spread across the same distance in visual space. Our results highlight the role of early visual areas in mediating binocular rivalry and suggest possible mechanisms for the correlation between surface area and the traveling waves. PMID:24334918

  18. 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.

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

    Directory of Open Access Journals (Sweden)

    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.

  20. 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...

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

    Directory of Open Access Journals (Sweden)

    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.

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

    Directory of Open Access Journals (Sweden)

    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.

  3. The effect of electrode return configuration on multi-unit activity of the visual cortex from supra choroidal electrical stimulation

    International Nuclear Information System (INIS)

    Full text: To compare differences in thresholds and spatial selec tivity of various electrode return configurations using multi-unit cortical activity in response to electrical stimulation of a supracho roidal retinal prosthesis. Methods A polyimide substrate flexible platinum electrode array was inserted into the suprachoroidal space of normally sighted anaesthe tised cats (n 8). lndividual electrodes were electrically stimulated with biphasic, cathodic first CUITent pulses (500 lS per phase, 0-725 pAl using monopolar, hexagonal and common ground stimulation. Multi-unit activity was recorded with a 32-channel array inserted into the exposed primary visual cortex. Results Both, monopolar and hexagonal stimulation elicited cortical activity with significantly lower thresholds (monopolar, 69 27 nC; hexagonal, 86 15 nC) than common ground stimulation (J 53 15 nC), however no significant difference was found between the thresholds for monopolar and hexagonal stimulation (One way RM-ANOYA, p < 0.00 I; Pairwise multiple comparisons, Tukey test). Further, cortical thresholds increased by 58 nC for the mon polar return, 79 nC for the hexagonal return, and II nC for the common ground return for every I mm change in retinal stimulating position from the retinal position that elicited the lowest cortical threshold. Conclusion A successful retinal prosthesis will need to produce discrete phosphenes at charge levels which will not harm the retina or the stimulating electrodes. Our data shows that hexagonal stimulation is efficient in inducing cortical activity both with lower charge thresholds and a higher degree of spatial selectivity compared to monopolar and common ground stimulation. Our results suggest that hexagonal stimulation is the ideal mode of stimulation for a retinal prosthesis.

  4. Similar adaptation effects in primary visual cortex and area MT of the macaque monkey under matched stimulus conditions

    OpenAIRE

    Patterson, Carlyn A.; Duijnhouwer, Jacob; Wissig, Stephanie C.; Krekelberg, Bart; Kohn, Adam

    2013-01-01

    Recent stimulus history, or adaptation, can alter neuronal response properties. Adaptation effects have been characterized in a number of visually responsive structures, from the retina to higher visual cortex. However, it remains unclear whether adaptation effects across stages of the visual system take a similar form in response to a particular sensory event. This is because studies typically probe a single structure or cortical area, using a stimulus ensemble chosen to provide potent drive...

  5. Visual Cortex Inspired CNN Model for Feature Construction in Text Analysis

    Science.gov (United States)

    Fu, Hongping; Niu, Zhendong; Zhang, Chunxia; Ma, Jing; Chen, Jie

    2016-01-01

    Recently, biologically inspired models are gradually proposed to solve the problem in text analysis. Convolutional neural networks (CNN) are hierarchical artificial neural networks, which include a various of multilayer perceptrons. According to biological research, CNN can be improved by bringing in the attention modulation and memory processing of primate visual cortex. In this paper, we employ the above properties of primate visual cortex to improve CNN and propose a biological-mechanism-driven-feature-construction based answer recommendation method (BMFC-ARM), which is used to recommend the best answer for the corresponding given questions in community question answering. BMFC-ARM is an improved CNN with four channels respectively representing questions, answers, asker information and answerer information, and mainly contains two stages: biological mechanism driven feature construction (BMFC) and answer ranking. BMFC imitates the attention modulation property by introducing the asker information and answerer information of given questions and the similarity between them, and imitates the memory processing property through bringing in the user reputation information for answerers. Then the feature vector for answer ranking is constructed by fusing the asker-answerer similarities, answerer's reputation and the corresponding vectors of question, answer, asker, and answerer. Finally, the Softmax is used at the stage of answer ranking to get best answers by the feature vector. The experimental results of answer recommendation on the Stackexchange dataset show that BMFC-ARM exhibits better performance. PMID:27471460

  6. 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.

  7. 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

    2016-01-01

    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. PMID:27435679

  8. Visual cortex inspired CNN model for feature construction in text analysis

    Directory of Open Access Journals (Sweden)

    Hongping Fu

    2016-07-01

    Full Text Available Recently, biologically inspired models are gradually proposed to solve the problem in text analysis. Convolutional neural networks (CNN are hierarchical artificial neural networks, which include a various of multilayer perceptrons. According to biological research, CNN can be improved by bringing in the attention modulation and memory processing of primate visual cortex. In this paper, we employ the above properties of primate visual cortex to improve CNN and propose a biological-mechanism-driven-feature-construction based answer recommendation method (BMFC-ARM, which is used to recommend the best answer for the corresponding given questions in community question answering. BMFC-ARM is an improved CNN with four channels respectively representing questions, answers, asker information and answerer information, and mainly contains two stages: biological mechanism driven feature construction (BMFC and answer ranking. BMFC imitates the attention modulation property by introducing the asker information and answerer information of given questions and the similarity between them, and imitates the memory processing property through bringing in the user reputation information for answerers. Then the feature vector for answer ranking is constructed by fusing the asker-answerer similarities, answerer's reputation and the corresponding vectors of question, answer, asker and answerer. Finally, the Softmax is used at the stage of answer ranking to get best answers by the feature vector. The experimental results of answer recommendation on the Stackexchange dataset show that BMFC-ARM exhibits better performance.

  9. 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.

  10. Postnatal expression and distribution of Refsum disease gene associated protein in the rat retina and visual cortex: effect of binocular visual deprivation.

    Science.gov (United States)

    Ahn, Kyu Youn; Nam, Kwang Il; Kim, Baik Yoon; Cho, Chul Woong; Jeong, Sang Ki; Yang, Kun Jin; Kim, Kyung Keun

    2002-04-01

    Previously, phytanoyl-CoA alpha-hydroxylase-associated protein 1 (PAHX-AP1) was isolated as a novel neuron-specific protein to interact with Refsum disease (RfD) gene PAHX. Its expression in the brain increased after eyelid opening, and the elevated level was maintained through adulthood. In this report, to verify the hypothesis that light could trigger this increase, we have examined the developmental distribution pattern of PAHX-AP1 in rat retina and visual cortex, and changes of its expression by binocular deprivation. Northern blot analyses demonstrated PAHX-AP1 expression reached its highest level in the visual cortex and eyeball at 4 weeks after birth, and these levels were maintained through adult life. Two weeks after visual deprivation, its expression in the eyeball and visual cortex decreased compared with the control. In situ hybridization analyses of the retina showed that PAHX-AP1 expression was limited to the ganglionic cell layer at 10 days after birth, but expressed in the inner nuclear cell layer and extended to the outer nuclear cell layer at 2 and 3 weeks after birth, respectively. Two weeks after visual deprivation, however, it decreased in the ganglionic and inner nuclear cell layer, and disappeared in the rod and cone cell layers. In the visual cortex, strong signals of PAHX-AP1 were detected in layers IV and VI, and II-VI at 10 days and 2 weeks after birth, respectively. Its expression decreased after 2 weeks of visual deprivation. These results indicate that visual stimulation is essential for the maintenance of PAHX-AP1 expressions in the retina, especially in the rod and cone cell layers, and visual cortex, and suggest that PAHX-AP1 may be involved in the developmental regulation of the photoreceptor's function.

  11. Spontaneous and visually-driven high-frequency oscillations in the occipital cortex: Intracranial recording in epileptic patients

    OpenAIRE

    Nagasawa, Tetsuro; Juhász, Csaba; Rothermel, Robert; Hoechstetter, Karsten; Sood, Sandeep; Asano, Eishi

    2011-01-01

    High-frequency oscillations (HFOs) at ≧80 Hz of nonepileptic nature spontaneously emerge from human cerebral cortex. In 10 patients with extra-occipital lobe epilepsy, we compared the spectral-spatial characteristics of HFOs spontaneously arising from the nonepileptic occipital cortex with those of HFOs driven by a visual task as well as epileptogenic HFOs arising from the extra-occipital seizure focus. We identified spontaneous HFOs at ≧80 Hz with a mean duration of 330 msec intermittently e...

  12. Response features of parvalbumin-expressing interneurons suggest precise roles for subtypes of inhibition in visual cortex

    OpenAIRE

    Runyan, Caroline A.; Schummers, James; Van Wart, Audra; Kuhlman, Sandra J.; Nathan R. Wilson; Huang, Z. Josh; Sur, Mriganka

    2010-01-01

    Inhibitory interneurons in the cerebral cortex include a vast array of subtypes, varying in their molecular signatures, electrophysiological properties, and connectivity patterns. This diversity suggests that individual inhibitory classes have unique roles in cortical circuits; however, their characterization to date has been limited to broad classifications including many subtypes. We used the Cre/LoxP system, specifically labeling parvalbumin(PV)-expressing interneurons in visual cortex of ...

  13. 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. PMID:27582714

  14. Dopamine-induced dissociation of BOLD and neural activity in macaque visual cortex.

    Science.gov (United States)

    Zaldivar, Daniel; Rauch, Alexander; Whittingstall, Kevin; Logothetis, Nikos K; Goense, Jozien

    2014-12-01

    Neuromodulators determine how neural circuits process information during cognitive states such as wakefulness, attention, learning, and memory. fMRI can provide insight into their function and dynamics, but their exact effect on BOLD responses remains unclear, limiting our ability to interpret the effects of changes in behavioral state using fMRI. Here, we investigated the effects of dopamine (DA) injections on neural responses and haemodynamic signals in macaque primary visual cortex (V1) using fMRI (7T) and intracortical electrophysiology. Aside from DA's involvement in diseases such as Parkinson's and schizophrenia, it also plays a role in visual perception. We mimicked DAergic neuromodulation by systemic injection of L-DOPA and Carbidopa (LDC) or by local application of DA in V1 and found that systemic application of LDC increased the signal-to-noise ratio (SNR) and amplitude of the visually evoked neural responses in V1. However, visually induced BOLD responses decreased, whereas cerebral blood flow (CBF) responses increased. This dissociation of BOLD and CBF suggests that dopamine increases energy metabolism by a disproportionate amount relative to the CBF response, causing the reduced BOLD response. Local application of DA in V1 had no effect on neural activity, suggesting that the dopaminergic effects are mediated by long-range interactions. The combination of BOLD-based and CBF-based fMRI can provide a signature of dopaminergic neuromodulation, indicating that the application of multimodal methods can improve our ability to distinguish sensory processing from neuromodulatory effects. PMID:25456449

  15. 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.

  16. Learning Enhances Sensory and Multiple Non-sensory Representations in Primary Visual Cortex.

    Science.gov (United States)

    Poort, Jasper; Khan, Adil G; Pachitariu, Marius; Nemri, Abdellatif; Orsolic, Ivana; Krupic, Julija; Bauza, Marius; Sahani, Maneesh; Keller, Georg B; Mrsic-Flogel, Thomas D; Hofer, Sonja B

    2015-06-17

    We determined how learning modifies neural representations in primary visual cortex (V1) during acquisition of a visually guided behavioral task. We imaged the activity of the same layer 2/3 neuronal populations as mice learned to discriminate two visual patterns while running through a virtual corridor, where one pattern was rewarded. Improvements in behavioral performance were closely associated with increasingly distinguishable population-level representations of task-relevant stimuli, as a result of stabilization of existing and recruitment of new neurons selective for these stimuli. These effects correlated with the appearance of multiple task-dependent signals during learning: those that increased neuronal selectivity across the population when expert animals engaged in the task, and those reflecting anticipation or behavioral choices specifically in neuronal subsets preferring the rewarded stimulus. Therefore, learning engages diverse mechanisms that modify sensory and non-sensory representations in V1 to adjust its processing to task requirements and the behavioral relevance of visual stimuli. PMID:26051421

  17. Disentangling Representations of Object Shape and Object Category in Human Visual Cortex: The Animate-Inanimate Distinction.

    Science.gov (United States)

    Proklova, Daria; Kaiser, Daniel; Peelen, Marius V

    2016-05-01

    Objects belonging to different categories evoke reliably different fMRI activity patterns in human occipitotemporal cortex, with the most prominent distinction being that between animate and inanimate objects. An unresolved question is whether these categorical distinctions reflect category-associated visual properties of objects or whether they genuinely reflect object category. Here, we addressed this question by measuring fMRI responses to animate and inanimate objects that were closely matched for shape and low-level visual features. Univariate contrasts revealed animate- and inanimate-preferring regions in ventral and lateral temporal cortex even for individually matched object pairs (e.g., snake-rope). Using representational similarity analysis, we mapped out brain regions in which the pairwise dissimilarity of multivoxel activity patterns (neural dissimilarity) was predicted by the objects' pairwise visual dissimilarity and/or their categorical dissimilarity. Visual dissimilarity was measured as the time it took participants to find a unique target among identical distractors in three visual search experiments, where we separately quantified overall dissimilarity, outline dissimilarity, and texture dissimilarity. All three visual dissimilarity structures predicted neural dissimilarity in regions of visual cortex. Interestingly, these analyses revealed several clusters in which categorical dissimilarity predicted neural dissimilarity after regressing out visual dissimilarity. Together, these results suggest that the animate-inanimate organization of human visual cortex is not fully explained by differences in the characteristic shape or texture properties of animals and inanimate objects. Instead, representations of visual object properties and object category may coexist in more anterior parts of the visual system. PMID:26765944

  18. Determinants of motion response anisotropies in human early visual cortex: the role of configuration and eccentricity.

    Science.gov (United States)

    Maloney, Ryan T; Watson, Tamara L; Clifford, Colin W G

    2014-10-15

    Anisotropies in the cortical representation of various stimulus parameters can reveal the fundamental mechanisms by which sensory properties are analysed and coded by the brain. One example is the preference for motion radial to the point of fixation (i.e. centripetal or centrifugal) exhibited in mammalian visual cortex. In two experiments, this study used functional magnetic resonance imaging (fMRI) to explore the determinants of these radial biases for motion in functionally-defined areas of human early visual cortex, and in particular their dependence upon eccentricity which has been indicated in recent reports. In one experiment, the cortical response to wide-field random dot kinematograms forming 16 different complex motion patterns (including centrifugal, centripetal, rotational and spiral motion) was measured. The response was analysed according to preferred eccentricity within four different eccentricity ranges. Response anisotropies were characterised by enhanced activity for centripetal or centrifugal patterns that changed systematically with eccentricity in visual areas V1-V3 and hV4 (but not V3A/B or V5/MT+). Responses evolved from a preference for centrifugal over centripetal patterns close to the fovea, to a preference for centripetal over centrifugal at the most peripheral region stimulated, in agreement with previous work. These effects were strongest in V2 and V3. In a second experiment, the stimuli were restricted to within narrow annuli either close to the fovea (0.75-1.88°) or further in the periphery (4.82-6.28°), in a way that preserved the local motion information available in the first experiment. In this configuration a preference for radial motion (centripetal or centrifugal) persisted but the dependence upon eccentricity disappeared. Again this was clearest in V2 and V3. A novel interpretation of the dependence upon eccentricity of motion anisotropies in early visual cortex is offered that takes into account the spatiotemporal

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

    Science.gov (United States)

    Ward, Laura McKernan; Aitchison, Ross Thomas; Tawse, Melisa; Simmers, Anita Jane; Shahani, Uma

    2015-01-01

    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. PMID:25909849

  20. 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.

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

    Science.gov (United States)

    Siu, Caitlin R; Balsor, Justin L; Jones, David G; Murphy, Kathryn M

    2015-01-01

    Traditionally, myelin is viewed as insulation around axons, however, more recent studies have shown it also plays an important role in plasticity, axonal metabolism, and neuroimmune signaling. 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. Furthermore, Golli-MBP has been called a "molecular link" between the nervous and immune systems. In visual cortex specifically, 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 early developmental changes that are coincident with milestones in visual system sensitive period, and gradually increases into aging. There are three 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.

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

    Directory of Open Access Journals (Sweden)

    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.

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

    Directory of Open Access Journals (Sweden)

    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.

  4. Sex differences in interactions between nucleus accumbens and visual cortex by explicit visual erotic stimuli: an fMRI study.

    Science.gov (United States)

    Lee, S W; Jeong, B S; Choi, J; Kim, J-W

    2015-01-01

    Men tend to have greater positive responses than women to explicit visual erotic stimuli (EVES). However, it remains unclear, which brain network makes men more sensitive to EVES and which factors contribute to the brain network activity. In this study, we aimed to assess the effect of sex difference on brain connectivity patterns by EVES. We also investigated the association of testosterone with brain connection that showed the effects of sex difference. During functional magnetic resonance imaging scans, 14 males and 14 females were asked to see alternating blocks of pictures that were either erotic or non-erotic. Psychophysiological interaction analysis was performed to investigate the functional connectivity of the nucleus accumbens (NA) as it related to EVES. Men showed significantly greater EVES-specific functional connection between the right NA and the right lateral occipital cortex (LOC). In addition, the right NA and the right LOC network activity was positively correlated with the plasma testosterone level in men. Our results suggest that the reason men are sensitive to EVES is the increased interaction in the visual reward networks, which is modulated by their plasma testosterone level. PMID:25971857

  5. Attention Modulates TMS-Locked Alpha Oscillations in the Visual Cortex.

    Science.gov (United States)

    Herring, Jim D; Thut, Gregor; Jensen, Ole; Bergmann, Til O

    2015-10-28

    Cortical oscillations, such as 8-12 Hz alpha-band activity, are thought to subserve gating of information processing in the human brain. While most of the supporting evidence is correlational, causal evidence comes from attempts to externally drive ("entrain") these oscillations by transcranial magnetic stimulation (TMS). Indeed, the frequency profile of TMS-evoked potentials (TEPs) closely resembles that of oscillations spontaneously emerging in the same brain region. However, it is unclear whether TMS-locked and spontaneous oscillations are produced by the same neuronal mechanisms. If so, they should react in a similar manner to top-down modulation by endogenous attention. To test this prediction, we assessed the alpha-like EEG response to TMS of the visual cortex during periods of high and low visual attention while participants attended to either the visual or auditory modality in a cross-modal attention task. We observed a TMS-locked local oscillatory alpha response lasting several cycles after TMS (but not after sham stimulation). Importantly, TMS-locked alpha power was suppressed during deployment of visual relative to auditory attention, mirroring spontaneous alpha amplitudes. In addition, the early N40 TEP component, located at the stimulation site, was amplified by visual attention. The extent of attentional modulation for both TMS-locked alpha power and N40 amplitude did depend, with opposite sign, on the individual ability to modulate spontaneous alpha power at the stimulation site. We therefore argue that TMS-locked and spontaneous oscillations are of common neurophysiological origin, whereas the N40 TEP component may serve as an index of current cortical excitability at the time of stimulation.

  6. 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.

  7. Enhanced awareness followed reversible inhibition of human visual cortex: a combined TMS, MRS and MEG study.

    Directory of Open Access Journals (Sweden)

    Christopher P G Allen

    Full Text Available This series of experiments investigated the neural basis of conscious vision in humans using a form of transcranial magnetic stimulation (TMS known as continuous theta burst stimulation (cTBS. Previous studies have shown that occipital TMS, when time-locked to the onset of visual stimuli, can induce a phenomenon analogous to blindsight in which conscious detection is impaired while the ability to discriminate 'unseen' stimuli is preserved above chance. Here we sought to reproduce this phenomenon using offline occipital cTBS, which has been shown to induce an inhibitory cortical aftereffect lasting 45-60 minutes. Contrary to expectations, our first experiment revealed the opposite effect: cTBS enhanced conscious vision relative to a sham control. We then sought to replicate this cTBS-induced potentiation of consciousness in conjunction with magnetoencephalography (MEG and undertook additional experiments to assess its relationship to visual cortical excitability and levels of the inhibitory neurotransmitter γ-aminobutyric acid (GABA; via magnetic resonance spectroscopy, MRS. Occipital cTBS decreased cortical excitability and increased regional GABA concentration. No significant effects of cTBS on MEG measures were observed, although the results provided weak evidence for potentiation of event related desynchronisation in the β band. Collectively these experiments suggest that, through the suppression of noise, cTBS can increase the signal-to-noise ratio of neural activity underlying conscious vision. We speculate that gating-by-inhibition in the visual cortex may provide a key foundation of consciousness.

  8. 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

    To test the hypothesis that calcitonin gene-related peptide (CGRP) modulates brain activity, we investigated the effect of intravenous CGRP on brain activity in response to a visual stimulus. In addition, we examined if possible alteration in brain activity was reversed by the anti-migraine drug......% 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...... sumatriptan. Eighteen healthy volunteers were randomly allocated to receive CGRP infusion (1.5 µg/min for 20 min) or placebo. In vivo activity in the visual cortex was recorded before, during and after infusion and after 6 mg subcutaneous sumatriptan by functional magnetic resonance imaging (3 T). 77...

  9. 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.

  10. Dissociable neural responses to hands and non-hand body parts in human left extrastriate visual cortex.

    Science.gov (United States)

    Bracci, Stefania; Ietswaart, Magdalena; Peelen, Marius V; Cavina-Pratesi, Cristiana

    2010-06-01

    Accumulating evidence points to a map of visual regions encoding specific categories of objects. For example, a region in the human extrastriate visual cortex, the extrastriate body area (EBA), has been implicated in the visual processing of bodies and body parts. Although in the monkey, neurons selective for hands have been reported, in humans it is unclear whether areas selective for individual body parts such as the hand exist. Here, we conducted two functional MRI experiments to test for hand-preferring responses in the human extrastriate visual cortex. We found evidence for a hand-preferring region in left lateral occipitotemporal cortex in all 14 participants. This region, located in the lateral occipital sulcus, partially overlapped with left EBA, but could be functionally and anatomically dissociated from it. In experiment 2, we further investigated the functional profile of hand- and body-preferring regions by measuring responses to hands, fingers, feet, assorted body parts (arms, legs, torsos), and non-biological handlike stimuli such as robotic hands. The hand-preferring region responded most strongly to hands, followed by robotic hands, fingers, and feet, whereas its response to assorted body parts did not significantly differ from baseline. By contrast, EBA responded most strongly to body parts, followed by hands and feet, and did not significantly respond to robotic hands or fingers. Together, these results provide evidence for a representation of the hand in extrastriate visual cortex that is distinct from the representation of other body parts.

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

    Directory of Open Access Journals (Sweden)

    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.

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

    OpenAIRE

    Honda Manabu; Okada Tomohisa; Saito Daisuke N; Yonekura Yoshiharu; Sadato Norihiro

    2006-01-01

    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 ...

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

    Directory of Open Access Journals (Sweden)

    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.

  14. The universal fuzzy logical framework of neural circuits and its application in modeling primary visual cortex.

    Science.gov (United States)

    Hu, Hong; Li, Su; Wang, YunJiu; Qi, XiangLin; Shi, ZhongZhi

    2008-10-01

    Analytical study of large-scale nonlinear neural circuits is a difficult task. Here we analyze the function of neural systems by probing the fuzzy logical framework of the neural cells' dynamical equations. Although there is a close relation between the theories of fuzzy logical systems and neural systems and many papers investigate this subject, most investigations focus on finding new functions of neural systems by hybridizing fuzzy logical and neural system. In this paper, the fuzzy logical framework of neural cells is used to understand the nonlinear dynamic attributes of a common neural system by abstracting the fuzzy logical framework of a neural cell. Our analysis enables the educated design of network models for classes of computation. As an example, a recurrent network model of the primary visual cortex has been built and tested using this approach.

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

    Directory of Open Access Journals (Sweden)

    Andreia Martins Rosa

    2013-01-01

    Full Text Available 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.

  16. The universal fuzzy logical framework of neural circuits and its application in modeling primary visual cortex

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Analytical study of large-scale nonlinear neural circuits is a difficult task. Here we analyze the function of neural systems by probing the fuzzy logical framework of the neural cells’ dynamical equations. Al- though there is a close relation between the theories of fuzzy logical systems and neural systems and many papers investigate this subject, most investigations focus on finding new functions of neural systems by hybridizing fuzzy logical and neural system. In this paper, the fuzzy logical framework of neural cells is used to understand the nonlinear dynamic attributes of a common neural system by abstracting the fuzzy logical framework of a neural cell. Our analysis enables the educated design of network models for classes of computation. As an example, a recurrent network model of the primary visual cortex has been built and tested using this approach.

  17. The universal fuzzy Logical framework of neural circuits and its application in modeling primary visual cortex

    Institute of Scientific and Technical Information of China (English)

    HU Hong; LI Su; WANG YunJiu; QI XiangLin; SHI ZhongZhi

    2008-01-01

    Analytical study of large-scale nonlinear neural circuits is a difficult task. Here we analyze the function of neural systems by probing the fuzzy logical framework of the neural cells' dynamical equations. Al-though there is a close relation between the theories of fuzzy logical systems and neural systems and many papers investigate this subject, most investigations focus on finding new functions of neural systems by hybridizing fuzzy logical and neural system. In this paper, the fuzzy logical framework of neural cells is used to understand the nonlinear dynamic attributes of a common neural system by abstracting the fuzzy logical framework of a neural cell. Our analysis enables the educated design of network models for classes of computation. As an example, a recurrent network model of the primary visual cortex has been built and tested using this approach.

  18. 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.

  19. Mixed functional microarchitectures for orientation selectivity in the mouse primary visual cortex

    Science.gov (United States)

    Kondo, Satoru; Yoshida, Takashi; Ohki, Kenichi

    2016-01-01

    A minicolumn is the smallest anatomical module in the cortical architecture, but it is still in debate whether it serves as functional units for cortical processing. In the rodent primary visual cortex (V1), neurons with different preferred orientations are mixed horizontally in a salt and pepper manner, but vertical functional organization was not examined. In this study, we found that neurons with similar orientation preference are weakly but significantly clustered vertically in a short length and horizontally in the scale of a minicolumn. Interestingly, the vertical clustering is found only in a part of minicolumns, and others are composed of neurons with a variety of orientation preferences. Thus, the mouse V1 is a mixture of vertical clusters of neurons with various degrees of orientation similarity, which may be the compromise between the brain size and keeping the vertical clusters of similarly tuned neurons at least in a subset of clusters. PMID:27767032

  20. Immunocytochemical expression of monocarboxylate transporters in the human visual cortex at midgestation.

    Science.gov (United States)

    Fayol, Laurence; Baud, Olivier; Monier, Anne; Pellerin, Luc; Magistretti, Pierre; Evrard, Philippe; Verney, Catherine

    2004-01-31

    Lactate and the other monocarboxylates are a major energy source for the developing brain. We investigated the immunocytochemical expression of two monocarboxylate transporters, MCT1 and MCT2, in the human visual cortex between 13 and 26 post-ovulatory weeks. We used immunoperoxidase and immunofluorescence techniques to determine whether these transporters co-localized with markers for blood vessels (CD34), neurons (microtubule-associated protein 2 [MAP2], SMI 311), radial glia (vimentin), or astrocytes (glial fibrillary acidic protein [GFAP], S100beta protein). MCT1 immunoreactivity was visible in blood vessel walls as early as the 13th week of gestation mainly in the cortical plate and subplate. At this stage, less than 10% of vessels in the ventricular layer expressed MCT1, whereas all blood vessels walls showed this immunoreactivity at the 26th gestational week. Starting at the 19th week of gestation, sparse MCT1 positive cell bodies were detected, some of them co-localized with MAP2 immunoreactivity. MCT2 immunoreactivity was noted in astrocytic cell bodies from week 19 and spread subsequently to the astrocyte end-feet in contact with blood vessels. MCTs immunoreactivities were most marked in the subplate and deep cortical plate, where the most differentiated neurons were located. Our findings suggest that monocarboxylate trafficking between vessels (MCT1), astrocytes (MCT2) and some postmitotic neurons (MCT1) could develop gradually toward 20 gestational weeks (g.w.). These data suggest that lactate or other monocarboxylates could represent a significant energy source for the human visual cortex at this early stage. PMID:14757520

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

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    Geoffrey K Aguirre

    2007-06-01

    Full Text Available BACKGROUND: 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. METHODS AND FINDINGS: 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

  2. Repeatability of Detecting Visual Cortex Activity in Functional Magnetic Resonance Imaging

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    Mahboubeh Ma'soumbeigi

    2012-03-01

    Full Text Available Introduction As functional magnetic resonance imaging (fMRI is too expensive and time consuming, its frequent implementation is difficult. The aim of this study is to evaluate repeatability of detecting visual cortex activity in fMRI. Materials and Methods In this study, 15 normal volunteers (10 female, 5 male; Mean age±SD: 24.7±3.8 years attended. Functional magnetic resonance images were obtained during a visual task of sine-wave with spatial frequency of 1.84 cpd and temporal frequency of 8 Hz in three scan runs. Two runs of functional images were provided consecutively in a session, and the third run was provided 1-6 weeks later. The activation map was created using the data obtained from the block-designed fMRI study. Voxels whose Z value was above a threshold of 2.3, at a significance level p=0.05, were considered activated. After image processing, the blood oxygen level dependent (BOLD signal changes and the number of activated voxels in response to visual stimuli were compared in different runs. Results The results of this study demonstrate no significant difference between the number of activated voxels and BOLD signal in first and second runs in one session (Paired t-test, p>0.05. Moreover, there is a considerable correlation between first and second scan runs (rsignal=0.74, p=0.006 and rvoxel=0.62, p=0.03, while the correlation between the runs in separate sessions is weak (rsignal=0.28, p=0.38 and rvoxel=0.32, p=0.31. Conclusion Since the repeatability of BOLD signal and number of activated voxels in one session is considerably better than that in the separate sessions, it is suggested that in fMRI visual studies that need repeated scanning, scans should be acquired during a single session.

  3. Effect of epileptogenic agents on the incorporation of /sup 3/H-glycine into proteins in the cat's cerebral cortex

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    Rojik, I.; Feher, O.

    1982-06-01

    Filter paper strips soaked in /sup 3/H-glycine solution were applied to acoustic cortex of cats, anaesthetized with Nembutal and pretreated with epileptogenic agents (Metrazol, G-penicillin, and 3-amino-pyridine) and cycloheximide. The untreated contralateral hemisphere served as control. After 1 h incubation, both cortical samples were excised simultaneously and fixed in Bouin solution for autoradiography. Incorporation was blocked by cycloheximide. There was no glycine incorporation on the penicillin-treated side, while pyramidal cells were intensively labelled in layers II-V of the mirror focus. 3-Aminopyridine produced the same result. Metrazol as convulsant proved to be far weaker than the previous two. The intensity of incorporation was significantly more intensive in the mirror focus than in the primary one. Penicillin and 3-aminopyridine, while provoking cortical seizures, seem to inhibit glycine incorporation into a neuron-specific, function-dependent protein contained by the labelled cells in the autoradiogram.

  4. 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.

  5. 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

    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.......99-2.93), respectively. Thus, in the children, an rCBF increase could not be detected by perfusion MRI, but indications of a FAIR signal decrease were found. An rCBF decrease in the primary visual cortex during stimulation has not been reported previously, but it is a possible explanation for the negative BOLD response...

  6. Binocular robot vision emulating disparity computation in the primary visual cortex.

    Science.gov (United States)

    Shimonomura, Kazuhiro; Kushima, Takayuki; Yagi, Tetsuya

    2008-01-01

    We designed a VLSI binocular vision system that emulates the disparity computation in the primary visual cortex (V1). The system consists of two silicon retinas, orientation chips, and field programmable gate array (FPGA), mimicking a hierarchical architecture of visual information processing in the disparity energy model. The silicon retinas emulate a Laplacian-Gaussian-like receptive field of the vertebrate retina. The orientation chips generate an orientation-selective receptive field by aggregating multiple pixels of the silicon retina, mimicking the Hubel-Wiesel-type feed-forward model in order to emulate a Gabor-like receptive field of simple cells. The FPGA receives outputs from the orientation chips corresponding to the left and right eyes and calculates the responses of the complex cells based on the disparity energy model. The system can provide the responses of complex cells tuned to five different disparities and a disparity map obtained by comparing these energy outputs. Owing to the combination of spatial filtering by analog parallel circuits and pixel-wise computation by hard-wired digital circuits, the present system can execute the disparity computation in real time using compact hardware.

  7. [Retinotopic mapping of the human visual cortex with functional magnetic resonance imaging - basic principles, current developments and ophthalmological perspectives].

    Science.gov (United States)

    Hoffmann, M B; Kaule, F; Grzeschik, R; Behrens-Baumann, W; Wolynski, B

    2011-07-01

    Since its initial introduction in the mid-1990 s, retinotopic mapping of the human visual cortex, based on functional magnetic resonance imaging (fMRI), has contributed greatly to our understanding of the human visual system. Multiple cortical visual field representations have been demonstrated and thus numerous visual areas identified. The organisation of specific areas has been detailed and the impact of pathophysiologies of the visual system on the cortical organisation uncovered. These results are based on investigations at a magnetic field strength of 3 Tesla or less. In a field-strength comparison between 3 and 7 Tesla, it was demonstrated that retinotopic mapping benefits from a magnetic field strength of 7 Tesla. Specifically, the visual areas can be mapped with high spatial resolution for a detailed analysis of the visual field maps. Applications of fMRI-based retinotopic mapping in ophthalmological research hold promise to further our understanding of plasticity in the human visual cortex. This is highlighted by pioneering studies in patients with macular dysfunction or misrouted optic nerves.

  8. Study on Long-term Potentiation in Developing Rat Visual Cortex during the Critical Period of Plasticity

    Institute of Scientific and Technical Information of China (English)

    Pengfen Gao; Zhengqin Yin; Yingbing Liu; Shijun Wang; Huimin Fan

    2005-01-01

    Purpose: To study the property of LTP in layers Ⅱ~Ⅳof the rats visual cortex at different postnatal days induced by pairing low-frequency stimulation at layer Ⅳ with post synaptic depolarization in order to explore the synaptic and cellular mechanism of experience-dependent plasticity in the visual cortex.Methods: Postsynaptic currents (PSCs) of layers Ⅱ~Ⅳ in visual cortex slices of Wistar rats aged P0-29 d were recorded by patch-clamp whole cell recording method. Long-term potentiation (LTP) was induced by low-frequency stimulation (LFS) at 1Hz for 60~90 s.Each pulse of the LFS paired with depolarization of post-synaptic neurons to -20 mV.100μM APV, a kind of competitive N-methyl-d-aspartate (NMDA) receptor antagonist, was both applied to some slices to test the property of LTP.Results: 1. The LTP incidence was very low before P10d (5/34), and increased rapidly to the top at P15-24 d (17/28), then decreased sharply to 1/5 at P25-29 d, coinciding well with the critical period of plasticity of rat visual cortex. The LTP incidence of P15-29d (after eye opening, 18/33) was significantly higher than that of P0-14 d (before eye opening, 12/43, P < 0.05). 2. Compared with non-APV applied group (30/76), LTP incidence of APV applied group (4/33) was significantly decreased (P < 0.01 ). There were 4 Ⅳ-Ⅳ horizontal synapses. APV application could not block the LTP induction.Conclusions: 1. LTP was a reflection of naturally occurring, experience-dependent plasticity in rat visual cortex. The patterned visual stimuli received after eye opening might be an activation factor of the synaptic plasticity. 2. LTP of visual cortex induced by LFS in layer Ⅳ paired with postsynaptic depolarization was NMDA receptor dependent during the critical period of visual plasticity. However, there were LTP existed in Ⅳ-Ⅳ horizontal synapses which could not be blocked by 100μM APV.

  9. 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.

  10. Prediction of the main cortical areas and connections involved in the tactile function of the visual cortex by network analysis.

    Science.gov (United States)

    Négyessy, László; Nepusz, Tamás; Kocsis, László; Bazsó, Fülöp

    2006-04-01

    We explored the cortical pathways from the primary somatosensory cortex to the primary visual cortex (V1) by analysing connectional data in the macaque monkey using graph-theoretical tools. Cluster analysis revealed the close relationship of the dorsal visual stream and the sensorimotor cortex. It was shown that prefrontal area 46 and parietal areas VIP and 7a occupy a central position between the different clusters in the visuo-tactile network. Among these structures all the shortest paths from primary somatosensory cortex (3a, 1 and 2) to V1 pass through VIP and then reach V1 via MT, V3 and PO. Comparison of the input and output fields suggested a larger specificity for the 3a/1-VIP-MT/V3-V1 pathways among the alternative routes. A reinforcement learning algorithm was used to evaluate the importance of the aforementioned pathways. The results suggest a higher role for V3 in relaying more direct sensorimotor information to V1. Analysing cliques, which identify areas with the strongest coupling in the network, supported the role of VIP, MT and V3 in visuo-tactile integration. These findings indicate that areas 3a, 1, VIP, MT and V3 play a major role in shaping the tactile information reaching V1 in both sighted and blind subjects. Our observations greatly support the findings of the experimental studies and provide a deeper insight into the network architecture underlying visuo-tactile integration in the primate cerebral cortex.

  11. Suppressive responses by visual food cues in postprandial activities of insular cortex as revealed by magnetoencephalography.

    Science.gov (United States)

    Yoshikawa, Takahiro; Tanaka, Masaaki; Ishii, Akira; Watanabe, Yasuyoshi

    2014-06-01

    'Hara-Hachibu' in Japanese means a subjective sense by which we stop eating just before the motivation to eat is completely lost, a similar concept to caloric restriction (CR). Insular cortex is a critical platform which integrates sensory information into decision-making processes in eating behavior. We compared the responses of insular cortex, as assessed by magnetoencephalography (MEG), immediately after presentation of food images in the Fasting condition with those in the 'Hara-Hachibu' condition. Eleven healthy, right-handed males [age, 27.2±9.6 years; body mass index, 22.6±2.1kg/m(2) (mean±SD)] were enrolled in a randomized, two-crossover experiment (Fasting and 'Hara-Hachibu' conditions). Before the MEG recordings in the 'Hara-Hachibu' condition, the participants consumed rice balls as much as they judged themselves to have consumed shortly before reaching satiety. During the MEG recordings, they viewed food pictures projected on a screen. The intensities of MEG responses to viewing food pictures were significantly lower in the 'Hara-Hachibu' condition than those in the Fasting condition (P<0.05). The intensities of the MEG responses to the visual food stimuli in the 'Hara-Hachibu' condition was positively associated with the factor-3 (food tasted) (r=0.693, P=0.018) and aggregated scores (r=0.659, P=0.027) of the Power of Food Scale, a self-report measure of hedonic hunger. These findings may help to elucidate the neural basis of variability of appetite phenotypes under the condition of CR among individuals, and to develop possible strategies for the maintenance of adequate CR in daily life.

  12. 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.

  13. Modified areal cartography in auditory cortex following early- and late-onset deafness.

    Science.gov (United States)

    Wong, Carmen; Chabot, Nicole; Kok, Melanie A; Lomber, Stephen G

    2014-07-01

    Cross-modal plasticity following peripheral sensory loss enables deprived cortex to provide enhanced abilities in remaining sensory systems. These functional adaptations have been demonstrated in cat auditory cortex following early-onset deafness in electrophysiological and psychophysical studies. However, little information is available concerning any accompanying structural compensations. To examine the influence of sound experience on areal cartography, auditory cytoarchitecture was examined in hearing cats, early-deaf cats, and cats with late-onset deafness. Cats were deafened shortly after hearing onset or in adulthood. Cerebral cytoarchitecture was revealed immunohistochemically using SMI-32, a monoclonal antibody used to distinguish auditory areas in many species. Auditory areas were delineated in coronal sections and their volumes measured. Staining profiles observed in hearing cats were conserved in early- and late-deaf cats. In all deaf cats, dorsal auditory areas were the most mutable. Early-deaf cats showed further modifications, with significant expansions in second auditory cortex and ventral auditory field. Borders between dorsal auditory areas and adjacent visual and somatosensory areas were shifted ventrally, suggesting expanded visual and somatosensory cortical representation. Overall, this study shows the influence of acoustic experience in cortical development, and suggests that the age of auditory deprivation may significantly affect auditory areal cartography.

  14. A preliminary study on visual cortex and optic radiation with diabetic retinopathy by 1H-MR spectroscopy

    International Nuclear Information System (INIS)

    Objective: To study the metabolic change of proton magnetic resonance spectroscopy (1H-MRS) in the visual cortex and optic radiation region of patients with diabetic retinopathy (DR). Methods: 1H-MRS was performed in 20 patients with DR and 20 healthy volunteers on GE 1.5 T MR system respectively. Metabolic peaks of N-acetylasparte (NAA), creatine (Cr, in 3.02 and 3.94 ppm), choline-containing compounds (Cho) and myo-inositol (mi) were observed, and the ratios were analyzed by each other. Independent-samples t test was performed between two sets of data. Results: In both visual cortex and optic radiation, the ratios of mI/Cr and mI/Crsec in DR group (0.664±0.052 and 1.453± 0.068 in visual cortex, 0.717±0.074 and 1.484±0.114 in optic radiation) were significant higher than those in normal group (0.602±0.047 and 1.249±0.044 in visual cortex, 0.679±0.075 and 1.334± 0.089 in optic radiation, Psec/Cr, Cho/Cr and NAA/Cr in visual cortex and optic radiation were 0.458±0.043 and 0.488±0.052, 0.481±0.057 and 0.807±0.110, 1.633±0.105 and 1.709±0.140 respectively. In control group, the ratios of those were 0.484±0.041 and 0.502±0.056, 0.471±0.065 and 0.786±0.109, 1.625±0.098 and 1.716±0.135 respectively. The ratios of Crsec/Cr, Cho/Cr and NAA/Cr had no statistic difference between two groups (Psec is a typical change in the visual cortex and optic radiation region, 1H-MRS as a noninvasive examination could provide biochemical and metabolic informations for diabetic patients. (authors)

  15. Increased amygdala and visual cortex activity and functional connectivity towards stimulus novelty is associated with state anxiety.

    Directory of Open Access Journals (Sweden)

    Olga T Ousdal

    Full Text Available Novel stimuli often require a rapid reallocation of sensory processing resources to determine the significance of the event, and the appropriate behavioral response. Both the amygdala and the visual cortex are central elements of the neural circuitry responding to novelty, demonstrating increased activity to new as compared to highly familiarized stimuli. Further, these brain areas are intimately connected, and thus the amygdala may be a key region for directing sensory processing resources to novel events. Although knowledge regarding the neurocircuit of novelty detection is gradually increasing, we still lack a basic understanding of the conditions that are necessary and sufficient for novelty-specific responses in human amygdala and the visual cortices, and if these brain areas interact during detection of novelty. In the present study, we investigated the response of amygdala and the visual cortex to novelty, by comparing functional MRI activity between 1st and 2nd time presentation of a series of emotional faces in an event-related task. We observed a significant decrease in amygdala and visual cortex activity already after a single stimulus exposure. Interestingly, this decrease in responsiveness was less for subjects with a high score on state anxiety. Further, novel faces stimuli were associated with a relative increase in the functional coupling between the amygdala and the inferior occipital gyrus (BA 18. Thus, we suggest that amygdala is involved in fast sensory boosting that may be important for attention reallocation to novel events, and that the strength of this response depends on individual state anxiety.

  16. 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.

  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. GAD67-mediated GABA Synthesis and Signaling Regulate Inhibitory Synaptic Innervation in the Visual Cortex

    Science.gov (United States)

    Chattopadhyaya, Bidisha; Di Cristo, Graziella; Wu, Cai Zhi; Knott, Graham; Kuhlman, Sandra; Fu, Yu; Palmiter, Richard D.; Huang, Z. Josh

    2007-01-01

    The development of GABAergic inhibitory circuits is shaped by neural activity, but the underlying mechanisms are unclear. we demonstrate a novel function of GABA in regulating GABAergic innervation in the adolescent brain, when GABA is mainly known as an inhibitory transmitter. Conditional knockdown of the rate-limiting synthetic enzyme GAD67 in basket interneurons in adolescent visual cortex resulted in cell autonomous deficits in axon branching, perisomatic synapse formation around pyramidal neurons, and complexity of the innervation fields; the same manipulation had little influence on the subsequent maintenance of perisomatic synapses. These effects of GABA deficiency were rescued by suppressing GABA re-uptake and by GABA receptor agonists. Germ-line knockdown of GAD67 but not GAD65 showed similar deficits, suggesting a specific role of GAD67 in the maturation of perisomatic innervation. Since intracellular GABA levels are modulated by neuronal activity, our results implicate GAD67-mediated GABA synthesis in activity-dependent regulation of inhibitory innervation patterns. PMID:17582330

  19. Population coding in mouse visual cortex: response reliability and dissociability of stimulus tuning and noise correlation.

    Science.gov (United States)

    Montijn, Jorrit S; Vinck, Martin; Pennartz, Cyriel M A

    2014-01-01

    The primary visual cortex is an excellent model system for investigating how neuronal populations encode information, because of well-documented relationships between stimulus characteristics and neuronal activation patterns. We used two-photon calcium imaging data to relate the performance of different methods for studying population coding (population vectors, template matching, and Bayesian decoding algorithms) to their underlying assumptions. We show that the variability of neuronal responses may hamper the decoding of population activity, and that a normalization to correct for this variability may be of critical importance for correct decoding of population activity. Second, by comparing noise correlations and stimulus tuning we find that these properties have dissociated anatomical correlates, even though noise correlations have been previously hypothesized to reflect common synaptic input. We hypothesize that noise correlations arise from large non-specific increases in spiking activity acting on many weak synapses simultaneously, while neuronal stimulus response properties are dependent on more reliable connections. Finally, this paper provides practical guidelines for further research on population coding and shows that population coding cannot be approximated by a simple summation of inputs, but is heavily influenced by factors such as input reliability and noise correlation structure.

  20. The predictive value of white matter organization in posterior parietal cortex for spatial visualization ability.

    Science.gov (United States)

    Wolbers, Thomas; Schoell, Eszter D; Büchel, Christian

    2006-09-01

    Humans differ substantially in their ability to imagine spatial transformations of novel stimuli (i.e., mental rotation). Whereas "high-spatial" individuals are able to maintain high-quality representations even after complex mental transformations, "low-spatial" individuals often experience substantial degradation of the initial representation. Even though subdivisions of the posterior parietal cortex are known to instantiate the necessary spatial transformations, a direct demonstration of neuroanatomical differences predicting this behavioral variability is currently missing. Because recent evidence suggests that interindividual differences on the behavioral level might be related to regionally specific white matter organization, we addressed this question using diffusion tensor imaging in combination with well-established psychometric tests. As expected, behavioral results revealed a substantial disparity in mental rotation performance. Most importantly, despite controlling for differences in spatial short-term memory capacity, we observed a tight relationship between mental rotation proficiency and white matter organization near the anterior part of the intraparietal sulcus. Whereas high-level proficiency was paralleled by high fractional anisotropy (FA) values, the opposite pattern was observed in "low spatials". The present results strongly indicate that the efficiency of information transfer between posterior parietal regions involved in the mental transformation process could be one decisive factor in individual spatial visualization proficiency. PMID:16793288

  1. Lesions to right posterior parietal cortex impair visual depth perception from disparity but not motion cues

    Science.gov (United States)

    Leopold, David A.; Humphreys, Glyn W.; Welchman, Andrew E.

    2016-01-01

    The posterior parietal cortex (PPC) is understood to be active when observers perceive three-dimensional (3D) structure. However, it is not clear how central this activity is in the construction of 3D spatial representations. Here, we examine whether PPC is essential for two aspects of visual depth perception by testing patients with lesions affecting this region. First, we measured subjects' ability to discriminate depth structure in various 3D surfaces and objects using binocular disparity. Patients with lesions to right PPC (N = 3) exhibited marked perceptual deficits on these tasks, whereas those with left hemisphere lesions (N = 2) were able to reliably discriminate depth as accurately as control subjects. Second, we presented an ambiguous 3D stimulus defined by structure from motion to determine whether PPC lesions influence the rate of bistable perceptual alternations. Patients' percept durations for the 3D stimulus were generally within a normal range, although the two patients with bilateral PPC lesions showed the fastest perceptual alternation rates in our sample. Intermittent stimulus presentation reduced the reversal rate similarly across subjects. Together, the results suggest that PPC plays a causal role in both inferring and maintaining the perception of 3D structure with stereopsis supported primarily by the right hemisphere, but do not lend support to the view that PPC is a critical contributor to bistable perceptual alternations. This article is part of the themed issue ‘Vision in our three-dimensional world’. PMID:27269606

  2. Primary visual cortex excitability in migraine: a systematic review with meta-analysis.

    Science.gov (United States)

    Brigo, Francesco; Storti, Monica; Tezzon, Frediano; Manganotti, Paolo; Nardone, Raffaele

    2013-06-01

    The objective is to update and extend previous results of a systematic review of the literature with meta-analysis performed to determine the prevalence of phosphenes and the phosphene threshold (PT) values obtained during single-pulse transcranial magnetic stimulation (TMS) in adults with migraine. Both published and unpublished controlled studies measuring PT by single-pulse TMS in adults with migraine with or without aura (MA, MwA) were systematically reviewed. Prevalence of phosphenes and PT values were assessed calculating mean difference (MD) and odds ratio (OR) with 95 % confidence intervals (CI). Fifteen trials (369 migraine patients and 269 controls), were included. Patients with MA had a statistically significant lower PT compared with controls when a circular coil was used (MD: -22.27, 95 % CI -33.44 to -11.10); with a figure-of-eight coil the difference was not statistically significant. There was a significant higher phosphene prevalence in MA compared with controls (OR: 3.57, 95 % CI 1.16-10.94). No significant differences were found either in phosphene reporting between patients with MwA and controls, or in PT values obtained by figure-of-eight coil in subjects with MwA versus controls. In general, these results slightly support the hypothesis of a primary visual cortex hyper-excitability in MA, providing not enough evidence for MwA. A significant heterogeneity across studies probably reflects relevant clinical and methodological heterogeneity.

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

    Science.gov (United States)

    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. The Invariance Hypothesis Implies Domain-Specific Regions in Visual Cortex.

    Directory of Open Access Journals (Sweden)

    Joel Z Leibo

    2015-10-01

    Full Text Available Is visual cortex made up of general-purpose information processing machinery, or does it consist of a collection of specialized modules? If prior knowledge, acquired from learning a set of objects is only transferable to new objects that share properties with the old, then the recognition system's optimal organization must be one containing specialized modules for different object classes. Our analysis starts from a premise we call the invariance hypothesis: that the computational goal of the ventral stream is to compute an invariant-to-transformations and discriminative signature for recognition. The key condition enabling approximate transfer of invariance without sacrificing discriminability turns out to be that the learned and novel objects transform similarly. This implies that the optimal recognition system must contain subsystems trained only with data from similarly-transforming objects and suggests a novel interpretation of domain-specific regions like the fusiform face area (FFA. Furthermore, we can define an index of transformation-compatibility, computable from videos, that can be combined with information about the statistics of natural vision to yield predictions for which object categories ought to have domain-specific regions in agreement with the available data. The result is a unifying account linking the large literature on view-based recognition with the wealth of experimental evidence concerning domain-specific regions.

  5. Effects of Long-term Visual Experience on Responses of Distinct Classes of Single Units in Inferior Temporal Cortex

    OpenAIRE

    Woloszyn, Luke; David L Sheinberg

    2012-01-01

    Primates can learn to recognize a virtually limitless number of visual objects. A candidate neural substrate for this adult plasticity is the inferior temporal cortex (ITC). Using a large stimulus set, we explored the impact that long-term experience has on the response properties of two classes of neurons in ITC, broad-spiking (putative excitatory) cells and narrow-spiking (putative inhibitory) cells. We found that experience increased maximum responses of putative excitatory neurons but had...

  6. Relationship between BOLD amplitude and pattern classification of orientation-selective activity in the human visual cortex

    OpenAIRE

    Tong, Frank; Harrison, Stephenie A.; Dewey, John A.; Kamitani, Yukiyasu

    2012-01-01

    Orientation-selective responses can be decoded from fMRI activity patterns in the human visual cortex, using multivariate pattern analysis (MVPA). To what extent do these feature-selective activity patterns depend on the strength and quality of the sensory input, and might the reliability of these activity patterns be predicted by the gross amplitude of the stimulus-driven BOLD response? Observers viewed oriented gratings that varied in luminance contrast (4, 20 or 100%) or spatial frequency ...

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

    Directory of Open Access Journals (Sweden)

    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.

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

    Science.gov (United States)

    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.

  9. Cross-adaptation combined with TMS reveals a functional overlap between vision and imagery in the early visual cortex.

    Science.gov (United States)

    Cattaneo, Zaira; Bona, Silvia; Silvanto, Juha

    2012-02-01

    The extent to which the generation of mental images draws on the neuronal representations involved in visual perception has been the subject of much debate. To investigate this overlap, we assessed whether adaptation to visual stimuli affects the ability to generate visual mental images; such cross-adaptation would indicate shared neural representations between visual perception and imagery. Mental imagery was tested using a modified version of the clock task, in which subjects are presented with a digital time (e.g. "2.15") and are asked to generate a mental image of the clock hands displaying this time on an empty clock face. Participants were adapted to oriented lines either on the upper or lower side of the clock face prior to the mental image generation. The results showed that mental imagery was impaired when the mental image had to be generated in the adapted region of visual space (Experiment 1). In Experiment 2, we used TMS to determine whether this adaptation effect occurs in the early visual cortex (EVC; V1/V2). Relative to control conditions (No TMS and Vertex TMS), EVC TMS facilitated mental imagery generation when the mental image spatially overlapped with the adapter. Our results thus show that neuronal representations in the EVC which encode (and are suppressed by) visual input play a causal role in visual mental imagery.

  10. Transcranial magnetic stimulation of visual cortex in migraine patients: a systematic review with meta-analysis.

    Science.gov (United States)

    Brigo, Francesco; Storti, Monica; Nardone, Raffaele; Fiaschi, Antonio; Bongiovanni, Luigi Giuseppe; Tezzon, Frediano; Manganotti, Paolo

    2012-07-01

    We systematically reviewed the literature to evaluate the prevalence of phosphenes and the phosphene threshold (PT) values obtained during single-pulse transcranial magnetic stimulation (TMS) in adults with migraine. Controlled studies measuring PT by single-pulse TMS in adults with migraine with or without aura (MA, MwA) were systematically searched. Prevalence of phosphenes and PT values were assessed calculating mean difference (MD) and odds ratio (OR) with 95 % confidence intervals (CI). Ten trials (277 migraine patients and 193 controls) were included. Patients with MA had statistically significant lower PT compared with controls when a circular coil was used (MD -28.33; 95 % CI -36.09 to -20.58); a similar result was found in MwA patients (MD -17.12; 95 % CI -23.81 to -10.43); using a figure-of-eight coil the difference was not statistically significant. There was a significantly higher phosphene prevalence in MA patients compared with control subjects (OR 4.21; 95 % CI 1.18-15.01). No significant differences were found either in phosphene reporting between patients with MwA and controls, or in PT values obtained with a figure-of-eight coil in MA and MwA patients versus controls. Overall considered, these results support the hypothesis of a primary visual cortex hyper-excitability in MA, providing not enough evidence for MwA. A significant statistical heterogeneity reflects clinical and methodological differences across studies, and higher temporal variabilities among PT measurements over time, related to unstable excitability levels. Patients should therefore be evaluated in the true interictal period with an adequate headache-free interval. Furthermore, skull thickness and ovarian cycle should be assessed as possible confounding variables, and sham stimulation should be performed to reduce the rate of false positives. Phosphene prevalence alone cannot be considered a measure of cortical excitability, but should be integrated with PT evaluation.

  11. Dissociable effects of natural image structure and color on LFP and spiking activity in the lateral prefrontal cortex and extrastriate visual area V4

    OpenAIRE

    Liebe, Stefanie; Logothetis, Nikos K.; Rainer, Gregor

    2011-01-01

    Visual perception is mediated by unique contributions of the numerous brain regions that constitute the visual system. We performed simultaneous recordings of local field potentials (LFPs) and single unit activity (SUA) in areas V4 and lateral prefrontal cortex to characterize their contribution to visual processing. Here, we trained monkeys to identify natural images at different degradation levels in a visual recognition task. We parametrically varied color and structural information of nat...

  12. Aging Affects on the Response Irregularity of Cells in Different Visual Areas of Cats%老化对猫视觉区域细胞反应不规则性的影响

    Institute of Scientific and Technical Information of China (English)

    周保琢; 姚志模; 梁振; 王正春; 袁妮妮; 刘治国; 周逸峰

    2013-01-01

    Department of Bio-Medial Engineering, School of Li fe Science, Anhui Medical University, Hefei 230032, China In this research, we compared the visual neuron responses for LGN, A18 and PMLS of old and young cats with extracellular single-neuron recording techniques. We used firing rate vector to characterize information, and response irregularity of cells to evaluate the degeneration of visual characters. Response irregularity is characterized by means of the two coefficients of variation of firing rate vectors: Cv and Cv2. We found that there was no significant change of the response irregularity in LGN areas during the aging process from young to old cats. But in the other two areas, neurons of old cats exhibited significantly larger response irregularity than those of young cats. The result indicated that the information processing function of advanced visual cortex was impaired by aging. This result also provids a reference for the research of the other neuronal system changes during aging process.%采用在体单细胞胞外记录的方法对比记录了老年猫及青年猫LGN、A18和PMLS区的细胞反应.使用发放率向量的方法表征神经元在多次Trial中一次的发放信息,同时采用视觉皮层细胞的一个重要的特性指标—反应不规则性,来衡量其在衰老过程中的变化情况,其中反应不规则性采用发放率向量的两种变异系数Cv和Cv2的平均值表示.结果发现,老化过程中LGN区细胞没有显著的变化,而其他两个区域的反应不规则性都受到衰老不同程度的影响,表现为反应不规则性的增大,说明老化对猫视皮层信息处理带来了损伤,本研究为其他神经体系在动物衰老过程中的变化研究提供实验依据.

  13. Fractal features of dark, maintained, and driven neural discharges in the cat visual system

    CERN Document Server

    Lowen, S B; Kaplan, E; Saleh, B E A; Teich, M C; Lowen, Steven B.; Ozaki, Tsuyoshi; Kaplan, Ehud; Saleh, Bahaa E. A.; Teich, Malvin C.

    1999-01-01

    We employ a number of statistical measures to characterize neural discharge activity in cat retinal ganglion cells (RGCs) and in their target lateral geniculate nucleus (LGN) neurons under various stimulus conditions, and we develop a new measure to examine correlations in fractal activity between spike-train pairs. In the absence of stimulation (i.e., in the dark), RGC and LGN discharges exhibit similar properties. The presentation of a constant, uniform luminance to the eye reduces the fractal fluctuations in the RGC maintained discharge but enhances them in the target LGN discharge, so that neural activity in the pair no longer mirror each other. A drifting-grating stimulus yields RGC and LGN driven spike trains similar in character to those observed in the maintained discharge, with two notable distinctions: action potentials are reorganized along the time axis so that they occur only during certain phases of the stimulus waveform, and fractal activity is suppressed. Under both uniform-luminance and drift...

  14. Differential effects of m1 and m2 receptor antagonists in perirhinal cortex on visual recognition memory in monkeys.

    Science.gov (United States)

    Wu, Wei; Saunders, Richard C; Mishkin, Mortimer; Turchi, Janita

    2012-07-01

    Microinfusions of the nonselective muscarinic antagonist scopolamine into perirhinal cortex impairs performance on visual recognition tasks, indicating that muscarinic receptors in this region play a pivotal role in recognition memory. To assess the mnemonic effects of selective blockade in perirhinal cortex of muscarinic receptor subtypes, we locally infused either the m1-selective antagonist pirenzepine or the m2-selective antagonist methoctramine in animals performing one-trial visual recognition, and compared these scores with those following infusions of equivalent volumes of saline. Compared to these control infusions, injections of pirenzepine, but not of methoctramine, significantly impaired recognition accuracy. Further, similar doses of scopolamine and pirenzepine yielded similar deficits, suggesting that the deficits obtained earlier with scopolamine were due mainly, if not exclusively, to blockade of m1 receptors. The present findings indicate that m1 and m2 receptors have functionally dissociable roles, and that the formation of new visual memories is critically dependent on the cholinergic activation of m1 receptors located on perirhinal cells. PMID:22561485

  15. Response features of parvalbumin-expressing interneurons suggest precise roles for subtypes of inhibition in visual cortex

    Science.gov (United States)

    Runyan, Caroline A.; Schummers, James; Wart, Audra Van; Kuhlman, Sandra J.; Wilson, Nathan R.; Huang, Z. Josh; Sur, Mriganka

    2010-01-01

    Summary Inhibitory interneurons in the cerebral cortex include a vast array of subtypes, varying in their molecular signatures, electrophysiological properties, and connectivity patterns. This diversity suggests that individual inhibitory classes have unique roles in cortical circuits; however, their characterization to date has been limited to broad classifications including many subtypes. We used the Cre/LoxP system, specifically labeling parvalbumin(PV)-expressing interneurons in visual cortex of PV-Cre mice with red fluorescent protein (RFP), followed by targeted loose-patch recordings and two-photon imaging of calcium responses in vivo to characterize the visual receptive field properties of these cells. Despite their relative molecular and morphological homogeneity, we find that PV+ neurons have a diversity of feature-specific visual responses that include sharp orientation and direction-selectivity, small receptive fields, and bandpass spatial frequency tuning. These results suggest that subsets of parvalbumin interneurons are components of specific cortical networks, and that perisomatic inhibition contributes to the generation of precise response properties. PMID:20826315

  16. Effect of the small-world structure on encoding performance in the primary visual cortex: an electrophysiological and modeling analysis.

    Science.gov (United States)

    Shi, Li; Niu, Xiaoke; Wan, Hong

    2015-05-01

    The biological networks have been widely reported to present small-world properties. However, the effects of small-world network structure on population's encoding performance remain poorly understood. To address this issue, we applied a small world-based framework to quantify and analyze the response dynamics of cell assemblies recorded from rat primary visual cortex, and further established a population encoding model based on small world-based generalized linear model (SW-GLM). The electrophysiological experimental results show that the small world-based population responses to different topological shapes present significant variation (t test, p 0.8), while no significant variation was found for control networks without considering their spatial connectivity (t test, p > 0.05; effect size: Hedge's g numerical experimental results show that the predicted response under SW-GLM is more accurate and reliable compared to the control model without small-world structure, and the decoding performance is also improved about 10 % by taking the small-world structure into account. The above results suggest the important role of the small-world neural structure in encoding visual information for the neural population by providing electrophysiological and theoretical evidence, respectively. The study helps greatly to well understand the population encoding mechanisms of visual cortex. PMID:25764307

  17. Visual experience and subsequent sleep induce sequential plastic changes in putative inhibitory and excitatory cortical neurons

    OpenAIRE

    Aton, Sara J.; Broussard, Christopher; Dumoulin, Michelle; Seibt, Julie; Watson, Adam; Coleman, Tammi; Frank, Marcos G.

    2013-01-01

    Ocular dominance plasticity in the developing primary visual cortex is initiated by monocular deprivation (MD) and consolidated during subsequent sleep. To clarify how visual experience and sleep affect neuronal activity and plasticity, we continuously recorded extragranular visual cortex fast-spiking (FS) interneurons and putative principal (i.e., excitatory) neurons in freely behaving cats across periods of waking MD and post-MD sleep. Consistent with previous reports in mice, MD induces tw...

  18. Comparison of LFP-based and spike-based spectro-temporal receptive fields and cross-correlation in cat primary auditory cortex.

    Directory of Open Access Journals (Sweden)

    Jos J Eggermont

    Full Text Available Multi-electrode array recordings of spike and local field potential (LFP activity were made from primary auditory cortex of 12 normal hearing, ketamine-anesthetized cats. We evaluated 259 spectro-temporal receptive fields (STRFs and 492 frequency-tuning curves (FTCs based on LFPs and spikes simultaneously recorded on the same electrode. We compared their characteristic frequency (CF gradients and their cross-correlation distances. The CF gradient for spike-based FTCs was about twice that for 2-40 Hz-filtered LFP-based FTCs, indicating greatly reduced frequency selectivity for LFPs. We also present comparisons for LFPs band-pass filtered between 4-8 Hz, 8-16 Hz and 16-40 Hz, with spike-based STRFs, on the basis of their marginal frequency distributions. We find on average a significantly larger correlation between the spike based marginal frequency distributions and those based on the 16-40 Hz filtered LFP, compared to those based on the 4-8 Hz, 8-16 Hz and 2-40 Hz filtered LFP. This suggests greater frequency specificity for the 16-40 Hz LFPs compared to those of lower frequency content. For spontaneous LFP and spike activity we evaluated 1373 pair correlations for pairs with >200 spikes in 900 s per electrode. Peak correlation-coefficient space constants were similar for the 2-40 Hz filtered LFP (5.5 mm and the 16-40 Hz LFP (7.4 mm, whereas for spike-pair correlations it was about half that, at 3.2 mm. Comparing spike-pairs with 2-40 Hz (and 16-40 Hz LFP-pair correlations showed that about 16% (9% of the variance in the spike-pair correlations could be explained from LFP-pair correlations recorded on the same electrodes within the same electrode array. This larger correlation distance combined with the reduced CF gradient and much broader frequency selectivity suggests that LFPs are not a substitute for spike activity in primary auditory cortex.

  19. Comparison of LFP-based and spike-based spectro-temporal receptive fields and cross-correlation in cat primary auditory cortex.

    Science.gov (United States)

    Eggermont, Jos J; Munguia, Raymundo; Pienkowski, Martin; Shaw, Greg

    2011-01-01

    Multi-electrode array recordings of spike and local field potential (LFP) activity were made from primary auditory cortex of 12 normal hearing, ketamine-anesthetized cats. We evaluated 259 spectro-temporal receptive fields (STRFs) and 492 frequency-tuning curves (FTCs) based on LFPs and spikes simultaneously recorded on the same electrode. We compared their characteristic frequency (CF) gradients and their cross-correlation distances. The CF gradient for spike-based FTCs was about twice that for 2-40 Hz-filtered LFP-based FTCs, indicating greatly reduced frequency selectivity for LFPs. We also present comparisons for LFPs band-pass filtered between 4-8 Hz, 8-16 Hz and 16-40 Hz, with spike-based STRFs, on the basis of their marginal frequency distributions. We find on average a significantly larger correlation between the spike based marginal frequency distributions and those based on the 16-40 Hz filtered LFP, compared to those based on the 4-8 Hz, 8-16 Hz and 2-40 Hz filtered LFP. This suggests greater frequency specificity for the 16-40 Hz LFPs compared to those of lower frequency content. For spontaneous LFP and spike activity we evaluated 1373 pair correlations for pairs with >200 spikes in 900 s per electrode. Peak correlation-coefficient space constants were similar for the 2-40 Hz filtered LFP (5.5 mm) and the 16-40 Hz LFP (7.4 mm), whereas for spike-pair correlations it was about half that, at 3.2 mm. Comparing spike-pairs with 2-40 Hz (and 16-40 Hz) LFP-pair correlations showed that about 16% (9%) of the variance in the spike-pair correlations could be explained from LFP-pair correlations recorded on the same electrodes within the same electrode array. This larger correlation distance combined with the reduced CF gradient and much broader frequency selectivity suggests that LFPs are not a substitute for spike activity in primary auditory cortex. PMID:21625385

  20. Experience-dependent plasticity without long-term depression by type 2 metabotropic glutamate receptors in developing visual cortex

    OpenAIRE

    Renger, John J.; Hartman, Kenichi N.; Tsuchimoto, Yoshiko; Yokoi, Mineto; Nakanishi, Shigetada; Hensch, Takao K.

    2002-01-01

    Synaptic depression is thought to underlie the loss of cortical responsiveness to an eye deprived of vision. Here, we establish a fundamental role for type 2 metabotropic glutamate receptors (mGluR2) in long-term depression (LTD) of synaptic transmission within primary visual cortex. Direct mGluR2 activation by (2S,2′R,3′R-2-(2′,3′-dicarboxycyclopropyl)glycine (DCG-IV) persistently depressed layer 2/3 field potentials in slices of mouse binocular zone when stimulated concomitantly. Chemical L...

  1. Single-unit studies of visual motion processing in cat extrastriate areas

    NARCIS (Netherlands)

    Vajda, Ildiko

    2003-01-01

    Motion vision has high survival value and is a fundamental property of all visual systems. The old Greeks already studied motion vision, but the physiological basis of it first came under scrutiny in the late nineteenth century. Later, with the introduction of single-cell (single-unit) recordings ar

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

    NARCIS (Netherlands)

    N.T. Markov; J. Vezoli; P. Chameau; A. Falchier; R. Quilodran; C. Huissoud; C. Lamy; P. Misery; P. Giroud; S. Ullman; P. Barone; C. Dehay; K. Knoblauch; H. Kennedy

    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

  3. Investigation of the metabolic changes in visual cortex due to visual stimulation using high field magnetic resonance spectroscopy at 7.0 T

    International Nuclear Information System (INIS)

    Objective: To investigate the metabolic changes in the visual cortex due to visual stimulation using high field functional proton magnetic resonance spectroscopy at 7.0 T. A clear picture of brain metabolism and neurotransmitter activity during activation was expected to be established. Methods: Nine healthy subjects participated in this study. All MR measurements were acquired using a 7.0 T MR system and a 16-channel SENSE head coil. An initial fMRI scan was performed prior to spectroscopic acquisition in order to determine the activated region in the visual cortex. A cubic ROI of 2 cm× 2 cm × 2 cm was positioned inside the activated region for functional MRS acquisition. A short TE STEAM sequence was used for acquiring the MRS data. The functional paradigm comprised 6.6 min baseline followed by 13.2 min of visual stimulation and 19.8 min recovery. Summed averaged spectra for visual stimulus off and visual stimulus on were analyzed separately using LC Model and internal reference of water. A Wilcoxon signed rank test was conducted to compare the metabolite changes. Results During stimulation, concentration in Asp [(3.20 ± 0.28) μmol/g], Gln [(2.07 ± 0.10) μmol/g] and Gly [(1.65 ± 0.11)μmol/g] was found to be significantly decreased,compared with that of (3.52 ± 0.28), (2.25 ± 0.10) and (1.85 ± 0.11) μmol/g in rest (Z=-2.073, -2.073 and -2.429, respectively, P<0.05). The level in Glu [(11.50 ± 0.11) μmol/g], GSH [(2.45 ± 0.10) μmol/g] and Lac [(0.89 ± 0.05) μmol/g] due to neuronal activation was found to be significantly increased,versus resting concentration of (11.28 ± 0.11), (2.28 ± 0.10) and (0.79 ± 0.05) μmol/g,respectively (Z=2.521, 2.310, 2.016, respectively, P<0.05). Glc level [(1.54 ± 0.23)μmol/g] exhibited a tendency to decrease throughout the period of stimulation, compared with that of [(1.78 ± 0.28) μmol/g] in rest,but the decrease did not reach statistical significance (Z=-1.897, P>0.05). Conclusions: Using a novel visual

  4. Physical Exercise Preserves Adult Visual Plasticity in Mice and Restores it after a Stroke in the Somatosensory Cortex

    Science.gov (United States)

    Kalogeraki, Evgenia; Pielecka-Fortuna, Justyna; Hüppe, Janika M.; Löwel, Siegrid

    2016-01-01

    The primary visual cortex (V1) is widely used to study brain plasticity, which is not only crucial for normal brain function, such as learning and memory, but also for recovery after brain injuries such as stroke. In standard cage (SC) raised mice, experience-dependent ocular dominance (OD) plasticity in V1 declines with age and is compromised by a lesion in adjacent and distant cortical regions. In contrast, mice raised in an enriched environment (EE), exhibit lifelong OD plasticity and are protected from losing OD plasticity after a stroke-lesion in the somatosensory cortex. Since SC mice with an access to a running wheel (RW) displayed preserved OD plasticity during aging, we investigated whether physical exercise might also provide a plasticity promoting effect after a cortical stroke. To this end, we tested if adult RW-raised mice preserved OD plasticity after stroke and also if short-term running after stroke restored OD plasticity to SC mice. Indeed, unlike mice without a RW, adult RW mice continued to show OD plasticity even after stroke, and a 2 weeks RW experience after stroke already restored lost OD plasticity. Additionally, the experience-enabled increase of the spatial frequency and contrast threshold of the optomotor reflex of the open eye, normally lost after a stroke, was restored in both groups of RW mice. Our data suggest that physical exercise alone can not only preserve visual plasticity into old age, but also restore it after a cortical stroke. PMID:27708575

  5. Top-down inputs enhance orientation selectivity in neurons of the primary visual cortex during perceptual learning.

    Directory of Open Access Journals (Sweden)

    Samat Moldakarimov

    2014-08-01

    Full Text Available Perceptual learning has been used to probe the mechanisms of cortical plasticity in the adult brain. Feedback projections are ubiquitous in the cortex, but little is known about their role in cortical plasticity. Here we explore the hypothesis that learning visual orientation discrimination involves learning-dependent plasticity of top-down feedback inputs from higher cortical areas, serving a different function from plasticity due to changes in recurrent connections within a cortical area. In a Hodgkin-Huxley-based spiking neural network model of visual cortex, we show that modulation of feedback inputs to V1 from higher cortical areas results in shunting inhibition in V1 neurons, which changes the response properties of V1 neurons. The orientation selectivity of V1 neurons is enhanced without changing orientation preference, preserving the topographic organizations in V1. These results provide new insights to the mechanisms of plasticity in the adult brain, reconciling apparently inconsistent experiments and providing a new hypothesis for a functional role of the feedback connections.

  6. The effect of unpredicted visual feedback on activation in the secondary somatosensory cortex during movement execution

    Directory of Open Access Journals (Sweden)

    Wasaka Toshiaki

    2012-11-01

    Full Text Available Abstract Background A mechanism that monitors the congruence between sensory inputs and motor outputs is necessary to control voluntary movement. The representation of limb position is constantly updated on the basis of somatosensory and visual information and efference copy from motor areas. However, the cortical mechanism underlying detection of limb position using somatosensory and visual information has not been elucidated. This study investigated the influence of visual feedback on information processing in somatosensory areas during movement execution using magnetoencephalography. We used an experimental condition in which the visual information was incongruent despite the motor execution and somatosensory feedback being congruent. Subjects performed self-paced bimanual movements of both thumbs, either symmetric or asymmetric, under normal visual and mirrored conditions. The mirror condition provided a visual feedback by showing a reflection of the subject’s right hand in place of the left hand. Therefore, in the Asymmetric task of the Mirror condition, subjects saw symmetric movements despite performing asymmetric movements. Results Activation in the primary somatosensory area (SI revealed inhibition of neural activity and that in the secondary somatosensory area (SII showed enhancement with voluntary movement. In addition, the SII contralateral to the side of stimulation was significantly enhanced in the Asymmetric task of the Mirror condition, which provided non-veridical visual feedback. Conclusions These results suggested that visual information influenced the neuronal activity concerning sensorimotor interaction in the SII during motor execution. The SII contributes to the detection of unpredicted visual feedback of movement execution.

  7. The Right Frontopolar Cortex Is Involved in Visual-Spatial Prospective Memory

    OpenAIRE

    Alberto Costa; Massimiliano Oliveri; Francesco Barban; Sonia Bonnì; Giacomo Koch; Carlo Caltagirone; 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...

  8. 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

  9. 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.

  10. Relationship between BOLD amplitude and pattern classification of orientation-selective activity in the human visual cortex.

    Science.gov (United States)

    Tong, Frank; Harrison, Stephenie A; Dewey, John A; Kamitani, Yukiyasu

    2012-11-15

    Orientation-selective responses can be decoded from fMRI activity patterns in the human visual cortex, using multivariate pattern analysis (MVPA). To what extent do these feature-selective activity patterns depend on the strength and quality of the sensory input, and might the reliability of these activity patterns be predicted by the gross amplitude of the stimulus-driven BOLD response? Observers viewed oriented gratings that varied in luminance contrast (4, 20 or 100%) or spatial frequency (0.25, 1.0 or 4.0 cpd). As predicted, activity patterns in early visual areas led to better discrimination of orientations presented at high than low contrast, with greater effects of contrast found in area V1 than in V3. A second experiment revealed generally better decoding of orientations at low or moderate as compared to high spatial frequencies. Interestingly however, V1 exhibited a relative advantage at discriminating high spatial frequency orientations, consistent with the finer scale of representation in the primary visual cortex. In both experiments, the reliability of these orientation-selective activity patterns was well predicted by the average BOLD amplitude in each region of interest, as indicated by correlation analyses, as well as decoding applied to a simple model of voxel responses to simulated orientation columns. Moreover, individual differences in decoding accuracy could be predicted by the signal-to-noise ratio of an individual's BOLD response. Our results indicate that decoding accuracy can be well predicted by incorporating the amplitude of the BOLD response into simple simulation models of cortical selectivity; such models could prove useful in future applications of fMRI pattern classification. PMID:22917989

  11. Comparative morphology of three types of projection-identified pyramidal neurons in the superficial layers of cat visual cortex.

    Science.gov (United States)

    Matsubara, J A; Chase, R; Thejomayen, M

    1996-02-26

    The morphology and dendritic organization of corticocortical neurons in the superficial layers of area 18 that project to area 17 were studied by intracellular injection of lucifer yellow in the fixed-slice preparation. This corticocortical population contains primarily standard pyramidal cells, but occasional nonpyramidal, modified, fusiform, star, and inverted pyramidal cells were also seen. All cell types were present throughout layer 2 and in the upper and middle parts of layer 3. Standard pyramidal cells were found exclusively in lower layer 3. The mean somatic area of the area 17 projecting neurons was 251 microns 2. The width of basal dendritic fields was correlated to cell size for standard pyramidal cells but not for the other cell types. Next, the morphology and dendritic organization of the area 17 projecting neurons were compared to the pyramidal cells of the local horizontal patch networks and of the callosal system. The depth profile of the area 17 projecting and callosal pyramidal groups was virtually identical, peaking at 400 microns from the pial surface, whereas the local patch pyramidal group peaked at 281 microns. The local patch, area 17 projecting, and callosal pyramidal cells displayed increasingly larger mean somatic areas and basilar dendritic field width measurements. The number of basal dendritic branch points was greatest for callosal cells, and it was indistinguishable between local patch and area 17 projecting neurons. In the tangential plane, circular dendritic fields were observed on all callosal cells, but they were found on only approximately half of the local patch and area 17 projecting neurons. The remaining local patch and area 17 projecting neurons displayed mediolaterally and anteroposteriorly elongated basal dendritic fields, respectively. PMID:8866848

  12. Herding Cats: Geocuration Practices Employed for Field Research Data Collection Activities and Visualization by Blueprint Earth

    Science.gov (United States)

    Hoover, R.; Harrison, M.; Sonnenthal, N.; Hernandez, A.; Pelaez, J.

    2015-12-01

    Researchers investigating interdisciplinary topics must work to understand the barriers created by information siloes in order to productively collaborate on complex Earth science questions. These barriers create acute challenges when research is driven by observations rather than hypotheses, as communication between collaborators hinges on data synthesis techniques that often vary greatly between disciplines. Field data collection across disciplines creates even more challenges, and employing student researchers of varying abilities demands an approach that is structured, and yet still flexible enough to accommodate inherent differences in the subjective portions of student data collection. Blueprint Earth is performing system-level environmental observations in the broad areas of geology, biology, hydrology, and atmospheric science. Traditional field data collection methodologies are employed for ease of reproducibility, but must translate across disciplinary information siloes. Information collected must be readily useable in the formulation of hypotheses based on field observations, which necessitates an understanding of key metrics by all investigators involved in data analysis. Blueprint Earth demonstrates the ability to create clear data standards across several disciplines while incorporating a quality control process and this allows for conversion of data into functional visualizations. Additionally, geocuration is organized such that data will be ready for public dissemination upon completion of field research.

  13. fMRI activation of visual cortex to brightness change by the visual stimulating without form information

    International Nuclear Information System (INIS)

    Visual information is of various types and includes form, color and motion. There have been no studies that have only measured just the responses to visual stimuli of luminance change without form information in area V1. To achieve a spatially uniform brightness change that excluded color and form, such as Ganzfeld stimuli, subjects wore semi-transparent covers on their eyes. Through the use of functional magnetic resonance imaging (fMRI), we were able to measure the V1 responses while subjects viewed instantaneous or gradual brightness changes. Our results indicated that responses to temporal contrast changes of brightness without spatial contrast in area V1 do exist. These results must have been caused by responses in area V1 that were a combination of the transient responses to the instantaneous brightness change and the sustained responses to the value of luminance. (author)

  14. Processing of visual gravitational motion in the peri-sylvian cortex: Evidence from brain-damaged patients.

    Science.gov (United States)

    Maffei, Vincenzo; Mazzarella, Elisabetta; Piras, Fabrizio; Spalletta, Gianfranco; Caltagirone, Carlo; Lacquaniti, Francesco; Daprati, Elena

    2016-05-01

    Rich behavioral evidence indicates that the brain estimates the visual direction and acceleration of gravity quite accurately, and the underlying mechanisms have begun to be unraveled. While the neuroanatomical substrates of gravity direction processing have been studied extensively in brain-damaged patients, to our knowledge no such study exists for the processing of visual gravitational motion. Here we asked 31 stroke patients to intercept a virtual ball moving along the vertical under either natural gravity or artificial reversed gravity. Twenty-seven of them also aligned a luminous bar to the vertical direction (subjective visual vertical, SVV). Using voxel-based lesion-symptom mapping as well as lesion subtraction analysis, we found that lesions mainly centered on the posterior insula are associated with greater deviations of SVV, consistent with several previous studies. Instead, lesions mainly centered on the parietal operculum decrease the ability to discriminate natural from unnatural gravitational acceleration with a timed motor response in the interception task. Both the posterior insula and the parietal operculum belong to the vestibular cortex, and presumably receive multisensory information about the gravity vector. We speculate that an internal model estimating the effects of gravity on visual objects is constructed by transforming the vestibular estimates of mechanical gravity, which are computed in the brainstem and cerebellum, into internalized estimates of virtual gravity, which are stored in the cortical vestibular network. The present lesion data suggest a specific role for the parietal operculum in detecting the mismatch between predictive signals from the internal model and the online visual signals. PMID:27007069

  15. Early depolarizing GABA controls critical period plasticity in the rat visual cortex

    OpenAIRE

    Deidda, Gabriele; Allegra, Manuela; Cerri, Chiara; Naskar, Shovan; Bony, Guillaume; Zunino, Giulia; Bozzi, Yuri; Caleo, Matteo; Cancedda, Laura

    2014-01-01

    SUMMARY Hyperpolarizing and inhibitory GABA regulates “critical periods” for plasticity in sensory cortices. Here, we examine the role of early, depolarizing GABA in controlling plasticity mechanisms. We report that brief interference with depolarizing GABA during early development prolonged critical period plasticity in visual cortical circuits, without affecting overall development of the visual system. The effects on plasticity were accompanied by dampened inhibitory neurotransmission, dow...

  16. Electrophysiology Alterations in Primary Visual Cortex Neurons of Retinal Degeneration (S334ter-line-3) Rats.

    Science.gov (United States)

    Chen, Ke; Wang, Yi; Liang, Xiaohua; Zhang, Yihuai; Ng, Tsz Kin; Chan, Leanne Lai Hang

    2016-01-01

    The dynamic nature of the brain is critical for the success of treatments aimed at restoring vision at the retinal level. The success of these treatments relies highly on the functionality of the surviving neurons along the entire visual pathway. Electrophysiological properties at the retina level have been investigated during the progression of retinal degeneration; however, little is known about the changes in electrophysiological properties that occur in the primary visual cortex (V1) during the course of retinal degeneration. By conducting extracellular recording, we examined the electrophysiological properties of V1 in S334ter-line-3 rats (a transgenic model of retinal degeneration developed to express a rhodopsin mutation similar to that found in human retinitis pigmentosa patients). We measured the orientation tuning, spatial and temporal frequency tunings and the receptive field (RF) size for 127 V1 neurons from 11 S334ter-3 rats and 10 Long-Evans (LE) rats. V1 neurons in the S334ter-3 rats showed weaker orientation selectivity, lower optimal spatial and temporal frequency values and a smaller receptive field size compared to the LE rats. These results suggest that the visual cognitive ability significantly changes during retinal degeneration. PMID:27225415

  17. Behavioral-state modulation of inhibition is context-dependent and cell type specific in mouse visual cortex

    Science.gov (United States)

    Pakan, Janelle MP; Lowe, Scott C; Dylda, Evelyn; Keemink, Sander W; Currie, Stephen P; Coutts, Christopher A; Rochefort, Nathalie L

    2016-01-01

    Cortical responses to sensory stimuli are modulated by behavioral state. In the primary visual cortex (V1), visual responses of pyramidal neurons increase during locomotion. This response gain was suggested to be mediated through inhibitory neurons, resulting in the disinhibition of pyramidal neurons. Using in vivo two-photon calcium imaging in layers 2/3 and 4 in mouse V1, we reveal that locomotion increases the activity of vasoactive intestinal peptide (VIP), somatostatin (SST) and parvalbumin (PV)-positive interneurons during visual stimulation, challenging the disinhibition model. In darkness, while most VIP and PV neurons remained locomotion responsive, SST and excitatory neurons were largely non-responsive. Context-dependent locomotion responses were found in each cell type, with the highest proportion among SST neurons. These findings establish that modulation of neuronal activity by locomotion is context-dependent and contest the generality of a disinhibitory circuit for gain control of sensory responses by behavioral state. DOI: http://dx.doi.org/10.7554/eLife.14985.001 PMID:27552056

  18. Anodal Transcranial Direct Current Stimulation Reduces Psychophysically Measured Surround Suppression in the Human Visual Cortex

    OpenAIRE

    Daniel P. Spiegel; Hansen, Bruce C.; Byblow, Winston D.; Benjamin Thompson

    2012-01-01

    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, therefor...

  19. [Multiscale functional imaging: reconstructing network dynamics from the synaptic echoes recorded in a single visual cortex neuron].

    Science.gov (United States)

    Fregnac, Yves; Baudot, Pierre; Chavane, Frédéric; Marre, Olivier; Monier, Cyril; Pananceau, Marc; Sadoc, Gérard

    2009-04-01

    In vivo intracellular electrophysiology offers the unique possibility of listening to the "synaptic rumor " of the cortical network, captured by a recording electrode in a single V1 cell. It allows one to reconstruct the distribution of input sources in space and time, i.e. the effective network dynamics. We have used a reverse engineering method to demonstrate the propagation of visually evoked activity through lateral (and feedback) connectivity in the primary cortex of higher mammals. This approach, based on synaptic echography, is compared here with a real-time brain imaging technique based on voltage-sensitive dye imaging. The former method gives access to the microscopic convergence processes of single neurons, whereas the latter describes the macroscopic divergence process on the neuronal map. A combination of the two techniques can be used to elucidate the cortical origin of low-level (non attentive) binding processes participating in the emergence of Gestalt percepts. PMID:20120274

  20. Cell-Targeted Optogenetics and Electrical Microstimulation Reveal the Primate Koniocellular Projection to Supra-granular Visual Cortex.

    Science.gov (United States)

    Klein, Carsten; Evrard, Henry C; Shapcott, Katharine A; Haverkamp, Silke; Logothetis, Nikos K; Schmid, Michael C

    2016-04-01

    Electrical microstimulation and more recently optogenetics are widely used to map large-scale brain circuits. However, the neuronal specificity achieved with both methods is not well understood. Here we compare cell-targeted optogenetics and electrical microstimulation in the macaque monkey brain to functionally map the koniocellular lateral geniculate nucleus (LGN) projection to primary visual cortex (V1). Selective activation of the LGN konio neurons with CamK-specific optogenetics caused selective electrical current inflow in the supra-granular layers of V1. Electrical microstimulation targeted at LGN konio layers revealed the same supra-granular V1 activation pattern as the one elicited by optogenetics. Taken together, these findings establish a selective koniocellular LGN influence on V1 supra-granular layers, and they indicate comparable capacities of both stimulation methods to isolate thalamo-cortical circuits in the primate brain.

  1. 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.

  2. 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.

  3. Lateral occipitotemporal cortex (LOTC) activity is greatest while viewing dance compared to visualization and movement: learning and expertise effects.

    Science.gov (United States)

    Di Nota, Paula M; Levkov, Gabriella; Bar, Rachel; DeSouza, Joseph F X

    2016-07-01

    The lateral occipitotemporal cortex (LOTC) is comprised of subregions selectively activated by images of human bodies (extrastriate body area, EBA), objects (lateral occipital complex, LO), and motion (MT+). However, their role in motor imagery and movement processing is unclear, as are the influences of learning and expertise on its recruitment. The purpose of our study was to examine putative changes in LOTC activation during action processing following motor learning of novel choreography in professional ballet dancers. Subjects were scanned with functional magnetic resonance imaging up to four times over 34 weeks and performed four tasks: viewing and visualizing a newly learned ballet dance, visualizing a dance that was not being learned, and movement of the foot. EBA, LO, and MT+ were activated most while viewing dance compared to visualization and movement. Significant increases in activation were observed over time in left LO only during visualization of the unlearned dance, and all subregions were activated bilaterally during the viewing task after 34 weeks of performance, suggesting learning-induced plasticity. Finally, we provide novel evidence for modulation of EBA with dance experience during the motor task, with significant activation elicited in a comparison group of novice dancers only. These results provide a composite of LOTC activation during action processing of newly learned ballet choreography and movement of the foot. The role of these areas is confirmed as primarily subserving observation of complex sequences of whole-body movement, with new evidence for modification by experience and over the course of real world ballet learning. PMID:26960739

  4. Explaining neural signals in human visual cortex with an associative learning model.

    Science.gov (United States)

    Jiang, Jiefeng; Schmajuk, Nestor; Egner, Tobias

    2012-08-01

    "Predictive coding" models posit a key role for associative learning in visual cognition, viewing perceptual inference as a process of matching (learned) top-down predictions (or expectations) against bottom-up sensory evidence. At the neural level, these models propose that each region along the visual processing hierarchy entails one set of processing units encoding predictions of bottom-up input, and another set computing mismatches (prediction error or surprise) between predictions and evidence. This contrasts with traditional views of visual neurons operating purely as bottom-up feature detectors. In support of the predictive coding hypothesis, a recent human neuroimaging study (Egner, Monti, & Summerfield, 2010) showed that neural population responses to expected and unexpected face and house stimuli in the "fusiform face area" (FFA) could be well-described as a summation of hypothetical face-expectation and -surprise signals, but not by feature detector responses. Here, we used computer simulations to test whether these imaging data could be formally explained within the broader framework of a mathematical neural network model of associative learning (Schmajuk, Gray, & Lam, 1996). Results show that FFA responses could be fit very closely by model variables coding for conditional predictions (and their violations) of stimuli that unconditionally activate the FFA. These data document that neural population signals in the ventral visual stream that deviate from classic feature detection responses can formally be explained by associative prediction and surprise signals.

  5. Dissociable effects of natural image structure and color on LFP and spiking activity in the lateral prefrontal cortex and extrastriate visual area V4.

    Science.gov (United States)

    Liebe, Stefanie; Logothetis, Nikos K; Rainer, Gregor

    2011-07-13

    Visual perception is mediated by unique contributions of the numerous brain regions that constitute the visual system. We performed simultaneous recordings of local field potentials (LFPs) and single unit activity (SUA) in areas V4 and lateral prefrontal cortex to characterize their contribution to visual processing. Here, we trained monkeys to identify natural images at different degradation levels in a visual recognition task. We parametrically varied color and structural information of natural images while the animals were performing the task. We show that the visual-evoked potential (VEP) of the LFP in V4 is highly sensitive to color, whereas the VEP in prefrontal cortex predominantly depends on image structure. When examining the relationship between VEP and SUA, we found that stimulus sensitivity for SUA was well predicted by the VEP in PF cortex but not in V4. Our results first reveal a functional specialization in both areas at the level of the LFP and further suggest that the degree to which mesoscopic signals, such as the VEP, are representative of the underlying SUA neural processing may be brain region specific within the context of visual recognition. PMID:21752998

  6. Differential processing of binocular and monocular gloss cues in human visual cortex

    Science.gov (United States)

    Di Luca, Massimiliano; Ban, Hiroshi; Muryy, Alexander; Fleming, Roland W.

    2016-01-01

    The visual impression of an object's surface reflectance (“gloss”) relies on a range of visual cues, both monocular and binocular. Whereas previous imaging work has identified processing within ventral visual areas as important for monocular cues, little is known about cortical areas involved in processing binocular cues. Here, we used human functional MRI (fMRI) to test for brain areas selectively involved in the processing of binocular cues. We manipulated stereoscopic information to create four conditions that differed in their disparity structure and in the impression of surface gloss that they evoked. We performed multivoxel pattern analysis to find areas whose fMRI responses allow classes of stimuli to be distinguished based on their depth structure vs. material appearance. We show that higher dorsal areas play a role in processing binocular gloss information, in addition to known ventral areas involved in material processing, with ventral area lateral occipital responding to both object shape and surface material properties. Moreover, we tested for similarities between the representation of gloss from binocular cues and monocular cues. Specifically, we tested for transfer in the decoding performance of an algorithm trained on glossy vs. matte objects defined by either binocular or by monocular cues. We found transfer effects from monocular to binocular cues in dorsal visual area V3B/kinetic occipital (KO), suggesting a shared representation of the two cues in this area. These results indicate the involvement of mid- to high-level visual circuitry in the estimation of surface material properties, with V3B/KO potentially playing a role in integrating monocular and binocular cues. PMID:26912596

  7. Visual Tuning Properties of Genetically Identified Layer 2/3 Neuronal Types in the Primary Visual Cortex of Cre-Transgenic Mice

    Directory of Open Access Journals (Sweden)

    Hatim A Zariwala

    2011-01-01

    Full Text Available The putative excitatory and inhibitory cell classes within the mouse primary visual cortex V1 have different functional properties as studied using recording microelectrode. Excitatory neurons show high selectivity for the orientation angle of moving gratings while the putative inhibitory neurons show poor selectivity. However, the study of selectivity of the genetically identified interneurons and their subtypes remain controversial. Here we use novel Cre-driver and reporter mice to identify genetic subpopulations in vivo for two photon calcium dye imaging: Wfs1(+ / Gad1(- mice that labels layer 2/3 excitatory cell population and Pvalb(+ / Gad1(+ mice that labels a genetic subpopulation of inhibitory neurons. The cells in both mice were identically labeled with a tdTomato protein, visible in vivo, using a Cre-reporter line. We found that the Wfs1(+ cells exhibited visual tuning properties comparable to the excitatory population, i.e. high selectivity and tuning to the angle, direction and spatial frequency of oriented moving gratings. The functional tuning of Pvalb(+ neurons was consistent with previously reported narrow spiking interneurons in microelectrode studies, exhibiting poorer selectivity than the excitatory neurons. This study demonstrates the utility of Cre-transgenic mouse technology in selective targeting of subpopulations of neurons and makes them amenable to structural, functional and connectivity studies.

  8. Texture Segregation Causes Early Figure Enhancement and Later Ground Suppression in Areas V1 and V4 of Visual Cortex

    Science.gov (United States)

    Poort, Jasper; Self, Matthew W.; van Vugt, Bram; Malkki, Hemi; Roelfsema, Pieter R.

    2016-01-01

    Segregation of images into figures and background is fundamental for visual perception. Cortical neurons respond more strongly to figural image elements than to background elements, but the mechanisms of figure–ground modulation (FGM) are only partially understood. It is unclear whether FGM in early and mid-level visual cortex is caused by an enhanced response to the figure, a suppressed response to the background, or both. We studied neuronal activity in areas V1 and V4 in monkeys performing a texture segregation task. We compared texture-defined figures with homogeneous textures and found an early enhancement of the figure representation, and a later suppression of the background. Across neurons, the strength of figure enhancement was independent of the strength of background suppression. We also examined activity in the different V1 layers. Both figure enhancement and ground suppression were strongest in superficial and deep layers and weaker in layer 4. The current–source density profiles suggested that figure enhancement was caused by stronger synaptic inputs in feedback-recipient layers 1, 2, and 5 and ground suppression by weaker inputs in these layers, suggesting an important role for feedback connections from higher level areas. These results provide new insights into the mechanisms for figure–ground organization. PMID:27522074

  9. 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.

  10. Contrast-sensitive perceptual grouping and object-based attention in the laminar circuits of primary visual cortex.

    Science.gov (United States)

    Grossberg, S; Raizada, R D

    2000-01-01

    Recent neurophysiological studies have shown that primary visual cortex, or V1, does more than passively process image features using the feedforward filters suggested by Hubel and Wiesel. It also uses horizontal interactions to group features preattentively into object representations, and feedback interactions to selectively attend to these groupings. All neocortical areas, including V1, are organized into layered circuits. We present a neural model showing how the layered circuits in areas V1 and V2 enable feedforward, horizontal, and feedback interactions to complete perceptual groupings over positions that do not receive contrastive visual inputs, even while attention can only modulate or prime positions that do not receive such inputs. Recent neurophysiological data about how grouping and attention occur and interact in V1 are simulated and explained, and testable predictions are made. These simulations show how attention can selectively propagate along an object grouping and protect it from competitive masking, and how contextual stimuli can enhance or suppress groupings in a contrast-sensitive manner. PMID:10788649

  11. Where practice makes perfect in texture discrimination: evidence for primary visual cortex plasticity.

    OpenAIRE

    Karni, A; Sagi, D

    1991-01-01

    In terms of functional anatomy, where does learning occur when, for a basic visual discrimination task, performance improves with practice (perceptual learning)? We report remarkable long-term learning in a simple texture discrimination task where learning is specific for retinal input. This learning is (i) local (in a retinotopic sense), (ii) orientation specific but asymmetric (it is specific for background but not for target-element orientation), and (iii) strongly monocular (there is litt...

  12. Geometry and dimensionality reduction of feature spaces in primary visual cortex

    OpenAIRE

    Barbieri, Davide

    2015-01-01

    Copyright 2015 Society of Photo Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic electronic or print reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited http://dx.doi.org/10.1117/12.2187026 Some geometric properties of the wavelet analysis performed by visual neurons are discussed and compared with experimenta...

  13. Alfred Walter Campbell and the visual functions of the occipital cortex.

    Science.gov (United States)

    Macmillan, Malcolm

    2014-07-01

    In his pioneering cytoarchitectonic studies of the human brain, Alfred Walter Campbell identified two structurally different areas in the occipital lobes and assigned two different kinds of visual functions to them. The first area, the visuosensory, was essentially on the mesial surface of the calcarine fissure. It was the terminus of nervous impulses generated in the retina and was where simple visual sensations arose. The second area, the visuopsychic, which surrounded or invested the first, was where sensations were interpreted and elaborated into visual perceptions. I argue that Campbell's distinction between the two areas was the starting point for the eventual differentiation of areas V1-V5. After a brief outline of Campbell's early life and education in Australia and of his Scottish medical education and early work as a pathologist at the Lancashire County Lunatic Asylum at Rainhill near Liverpool, I summarise his work on the human brain. In describing the structures he identified in the occipital lobes, I analyse the similarities and differences between them and the related structures identified by Joseph Shaw Bolton. I conclude by proposing some reasons for how that work came to be overshadowed by the later studies of Brodmann and for the more general lack of recognition given Campbell and his work. Those reasons include the effect of the controversies precipitated by Campbell's alliance with Charles Sherrington over the functions of the sensory and motor cortices.

  14. 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. PMID:26994832

  15. Response properties of cat AMLS neurons to optic flow stimuli

    Institute of Scientific and Technical Information of China (English)

    LI; Baowang(李宝旺); LI; Bing(李兵); CHEN; Hui(陈辉); XU; Ying(徐颖); DIAO; Yuncheng(刁云程)

    2002-01-01

    Spiral and translation stimuli were used to investigate the response properties of cat AMLS (anteromedial lateral suprasylvian area) neurons to optic flow. The overwhelming majority of cells could be significantly excited by the two modes of stimuli and most responsive cells displayed obvious direction selectivity. It is the first time to find a visual area in mammalian brain preferring rotation stimuli. Two representative hypotheses are discussed here on the neural mechanism of optic flow analysis in visual cortex, and some new viewpoints are proposed to explain the experimental results.

  16. Spatial Frequency Dependence of the Human Visual Cortex Response on Temporal Frequency Modulation Studied by fMRI

    Directory of Open Access Journals (Sweden)

    A. Mirzajani

    2006-07-01

    Full Text Available Background/Objective: The brain response to temporal frequencies (TF has been already reported. However, there is no study on different TF with respect to various spatial frequencies (SF. Materials and Methods: Functional magnetic resonance imaging (fMRI was done by a 1.5 T General Electric system for 14 volunteers (9 males and 5 females, aged 19–26 years during square-wave reversal checkerboard visual stimulation with different temporal frequencies of 4, 6, 8 and 10 Hz in 2 states of low SF of 0.4 and high SF of 8 cycles/degree (cpd. All subjects had normal visual acuity of 20/20 based on Snellen’s fraction in each eye with good binocular vision and normal visual field based on confrontation test. The mean luminance of the entire checkerboard was 161.4 cd/m2 and the black and white check contrast was 96%. The activation map was created using the data obtained from the block designed fMRI study. Pixels with a Z score above a threshold of 2.3, at a statistical significance level of 0.05, were considered activated. The average percentage blood oxygenation level dependent (BOLD signal change for all activated pixels within the occipital lobe, multiplied by the total number of activated pixels within the occipital lobe, was used as an index for the magnitude of the fMRI signal at each state of TF&SF. Results: The magnitude of the fMRI signal in response to different TF’s was maximum at 6 Hz for a high SF value of 8 cpd; it was however, maximum at a TF of 8 Hz for a low SF of 0.4 cpd. Conclusion: The results of this study agree with those of animal invasive neurophysiologic studies showing SF and TF selectivity of neurons in visual cortex. These results can be useful for vision therapy and selecting visual tasks in fMRI studies.

  17. Retinotopy and attention to the face and house images in the human visual cortex.

    Science.gov (United States)

    Wang, Bin; Yan, Tianyi; Ohno, Seiichiro; Kanazawa, Susumu; Wu, Jinglong

    2016-06-01

    Attentional modulation of the neural activities in human visual areas has been well demonstrated. However, the retinotopic activities that are driven by face and house images and attention to face and house images remain unknown. In the present study, we used images of faces and houses to estimate the retinotopic activities that were driven by both the images and attention to the images, driven by attention to the images, and driven by the images. Generally, our results show that both face and house images produced similar retinotopic activities in visual areas, which were only observed in the attention + stimulus and the attention conditions, but not in the stimulus condition. The fusiform face area (FFA) responded to faces that were presented on the horizontal meridian, whereas parahippocampal place area (PPA) rarely responded to house at any visual field. We further analyzed the amplitudes of the neural responses to the target wedge. In V1, V2, V3, V3A, lateral occipital area 1 (LO-1), and hV4, the neural responses to the attended target wedge were significantly greater than those to the unattended target wedge. However, in LO-2, ventral occipital areas 1 and 2 (VO-1 and VO-2) and FFA and PPA, the differences were not significant. We proposed that these areas likely have large fields of attentional modulation for face and house images and exhibit responses to both the target wedge and the background stimuli. In addition, we proposed that the absence of retinotopic activity in the stimulus condition might imply no perceived difference between the target wedge and the background stimuli.

  18. Prior Knowledge about Objects Determines Neural Color Representation in Human Visual Cortex.

    Science.gov (United States)

    Vandenbroucke, A R E; Fahrenfort, J J; Meuwese, J D I; Scholte, H S; Lamme, V A F

    2016-04-01

    To create subjective experience, our brain must translate physical stimulus input by incorporating prior knowledge and expectations. For example, we perceive color and not wavelength information, and this in part depends on our past experience with colored objects ( Hansen et al. 2006; Mitterer and de Ruiter 2008). Here, we investigated the influence of object knowledge on the neural substrates underlying subjective color vision. In a functional magnetic resonance imaging experiment, human subjects viewed a color that lay midway between red and green (ambiguous with respect to its distance from red and green) presented on either typical red (e.g., tomato), typical green (e.g., clover), or semantically meaningless (nonsense) objects. Using decoding techniques, we could predict whether subjects viewed the ambiguous color on typical red or typical green objects based on the neural response of veridical red and green. This shift of neural response for the ambiguous color did not occur for nonsense objects. The modulation of neural responses was observed in visual areas (V3, V4, VO1, lateral occipital complex) involved in color and object processing, as well as frontal areas. This demonstrates that object memory influences wavelength information relatively early in the human visual system to produce subjective color vision. PMID:25323417

  19. Somatostatin Interneurons Control a Key Component of Mismatch Negativity in Mouse Visual Cortex.

    Science.gov (United States)

    Hamm, Jordan P; Yuste, Rafael

    2016-07-19

    Patients with schizophrenia have deficient sensory processing, undermining how they perceive and relate to a changing environment. This impairment can be captured by the reduced mismatch negativity (MMN) index, an electroencephalographic biomarker of psychosis. The biological factors contributing to MMN are unclear, though mouse research, in which genetic and optical methods could be applied, has given some insight. Using fast two-photon calcium imaging and multielectrode recordings in awake mice, we find that visual cortical circuits display adapted (decreased) responses to repeated stimuli and amplified responses to a deviant stimulus, the key component of human MMN. Moreover, pharmacogenetic silencing of somatostatin-containing interneurons specifically eliminated this amplification, along with its associated theta/alpha-band response, leaving stimulus-specific adaption and related gamma-band modulations intact. Our results validate a mouse model of MMN and suggest that abnormalities in somatostatin-containing interneurons cause sensory deficits underlying MMN and schizophrenia.

  20. Gravity influences the visual representation of object tilt in parietal cortex.

    Science.gov (United States)

    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.

  1. Collinear stimuli induce local and cross-areal coherence in the visual cortex of behaving monkeys.

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    Ariel Gilad

    Full Text Available BACKGROUND: Collinear patterns of local visual stimuli are used to study contextual effects in the visual system. Previous studies have shown that proximal collinear flankers, unlike orthogonal, can enhance the detection of a low contrast central element. However, the direct neural interactions between cortical populations processing the individual flanker elements and the central element are largely unknown. METHODOLOGY/PRINCIPAL FINDINGS: Using voltage-sensitive dye imaging (VSDI we imaged neural population responses in V1 and V2 areas in fixating monkeys while they were presented with collinear or orthogonal arrays of Gabor patches. We then studied the spatio-temporal interactions between neuronal populations processing individual Gabor patches in the two conditions. Time-frequency analysis of the stimulus-evoked VSDI signal showed power increase mainly in low frequencies, i.e., the alpha band (α; 7-14 Hz. Power in the α-band was more discriminative at a single trial level than other neuronal population measures. Importantly, the collinear condition showed an increased intra-areal (V1-V1 and V2-V2 and inter-areal (V1-V2 α-coherence with shorter latencies than the orthogonal condition, both before and after the removal of the stimulus contribution. α-coherence appeared between discrete neural populations processing the individual Gabor patches: the central element and the flankers. CONCLUSIONS/SIGNIFICANCE: Our findings suggest that collinear effects are mediated by synchronization in a distributed network of proximal and distant neuronal populations within and across V1 and V2.

  2. Localization of Nitric Oxide Synthase-containing Neurons in the Bat Visual Cortex and Co-localization with Calcium-binding Proteins

    International Nuclear Information System (INIS)

    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

  3. 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

    2015-10-05

    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.

  4. Sensory experience differentially modulates the mRNA expression of the polysialyltransferases ST8SiaII and ST8SiaIV in postnatal mouse visual cortex.

    Directory of Open Access Journals (Sweden)

    Marie-Claude Bélanger

    Full Text Available Polysialic acid (PSA is a unique carbohydrate composed of a linear homopolymer of α-2,8 linked sialic acid, and is mainly attached to the fifth immunoglobulin-like domain of the neural cell adhesion molecule (NCAM in vertebrate neural system. In the brain, PSA is exclusively synthesized by the two polysialyltransferases ST8SiaII (also known as STX and ST8SiaIV (also known as PST. By modulating adhesive property of NCAM, PSA plays a critical role in several neural development processes such as cell migration, neurite outgrowth, axon pathfinding, synaptogenesis and activity-dependent plasticity. The expression of PSA is temporally and spatially regulated during neural development and a tight regulation of PSA expression is essential to its biological function. In mouse visual cortex, PSA is downregulated following eye opening and its decrease allows the maturation of GABAergic synapses and the opening of the critical period for ocular dominance plasticity. Relatively little is known about how PSA levels are regulated by sensory experience and neuronal activity. Here, we demonstrate that while both ST8SiaII and ST8SiaIV mRNA levels decrease around the time of eye opening in mouse visual cortex, only ST8SiaII mRNA level reduction is regulated by sensory experience. Using an organotypic culture system from mouse visual cortex, we further show that ST8SiaII gene expression is regulated by spiking activity and NMDA-mediated excitation. Further, we show that both ST8SiaII and ST8SiaIV mRNA levels are positively regulated by PKC-mediated signaling. Therefore, sensory experience-dependent ST8SiaII gene expression regulates PSA levels in postnatal visual cortex, thus acting as molecular link between visual activity and PSA expression.

  5. An uncertainty principle underlying the pinwheel structure in the primary visual cortex

    CERN Document Server

    Barbieri, Davide; Sanguinetti, Gonzalo; Sarti, Alessandro

    2010-01-01

    The visual information in V1 is processed by an array of modules called orientation preference columns. In some species including humans, orientation columns are radially arranged around singular points like the spokes of a wheel, that are called pinwheels. The pinwheel structure has been observed first with optical imaging techniques and more recently by in vivo two-photon imaging proving their organization with single cell precision. In this research we provide evidence that pinwheels are de facto optimal distributions for coding at the best angular position and momentum. In the last years many authors have recognized that the functional architecture of V1 is locally invariant with respect to the symmetry group of rotations and translations SE(2). In the present study we show that the orientation cortical maps used to construct pinwheels can be modeled as coherent states, i.e. the configurations best localized both in angular position and angular momentum. The theory we adopt is based on the well known unce...

  6. Population response to natural images in the primary visual cortex encodes local stimulus attributes and perceptual processing.

    Science.gov (United States)

    Ayzenshtat, Inbal; Gilad, Ariel; Zurawel, Guy; Slovin, Hamutal

    2012-10-01

    The primary visual cortex (V1) is extensively studied with a large repertoire of stimuli, yet little is known about its encoding of natural images. Using voltage-sensitive dye imaging in behaving monkeys, we measured neural population response evoked in V1 by natural images presented during a face/scramble discrimination task. The population response showed two distinct phases of activity: an early phase that was spread over most of the imaged area, and a late phase that was spatially confined. To study the detailed relation between the stimulus and the population response, we used a simple encoding model to compute a continuous map of the expected neural response based on local attributes of the stimulus (luminance and contrast), followed by an analytical retinotopic transformation. Then, we computed the spatial correlation between the maps of the expected and observed response. We found that the early response was highly correlated with the local luminance of the stimulus and was sufficient to effectively discriminate between stimuli at the single trial level. The late response, on the other hand, showed a much lower correlation to the local luminance, was confined to central parts of the face images, and was highly correlated with the animal's perceptual report. Our study reveals a continuous spatial encoding of low- and high-level features of natural images in V1. The low level is directly linked to the stimulus basic local attributes and the high level is correlated with the perceptual outcome of the stimulus processing.

  7. 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)

    Raudies, Florian; Hasselmo, Michael E

    2015-11-01

    Firing fields of grid cells in medial entorhinal cortex show compression or expansion after manipulations of the location of environmental barriers. This compression or expansion could be selective for individual grid cell modules with particular properties of spatial scaling. We present a model for differences in the response of modules to barrier location that arise from different mechanisms for the influence of visual features on the computation of location that drives grid cell firing patterns. These differences could arise from differences in the position of visual features within the visual field. When location was computed from the movement of visual features on the ground plane (optic flow) in the ventral visual field, this resulted in grid cell spatial firing that was not sensitive to barrier location in modules modeled with small spacing between grid cell firing fields. In contrast, when location was computed from static visual features on walls of barriers, i.e. in the more dorsal visual field, this resulted in grid cell spatial firing that compressed or expanded based on the barrier locations in modules modeled with large spacing between grid cell firing fields. This indicates that different grid cell modules might have differential properties for computing location based on visual cues, or the spatial radius of sensitivity to visual cues might differ between modules. PMID:26584432

  8. Rapid eye movement sleep deprivation revives a form of developmentally regulated synaptic plasticity in the visual cortex of post-critical period rats.

    Science.gov (United States)

    Shaffery, James P; Lopez, Jorge; Bissette, Garth; Roffwarg, Howard P

    2006-01-01

    The critical period for observing a developmentally regulated form of synaptic plasticity in the visual cortex of young rats normally ends at about postnatal day 30. This developmentally regulated form of in vitro long-term potentiation (LTP) can be reliably induced in layers II-III by aiming high frequency, theta burst stimulation (TBS) at the white matter situated directly below visual cortex (LTPWM-III). Previous work has demonstrated that suppression of sensory activation of visual cortex, achieved by rearing young rats in total darkness from birth, delays termination of the critical period for inducing LTPWM-III. Subsequent data also demonstrated that when rapid eye movement sleep (REMS) is suppressed, thereby reducing REMS cortical activation, just prior to the end of the critical period, termination of this developmental phase is delayed, and LTPWM-III can still be reliably produced in the usual post-critical period. Here, we report that for approximately 3 weeks immediately following the usual end of the critical period, suppression of REMS disrupts the maturational processes that close the critical period, and LTPWM-III is readily induced in brain slices taken from these somewhat older animals. Insofar as in vitro LTP is a model for the cellular and molecular changes that underlie developmental synaptic plasticity, these results suggest that mechanisms of synaptic plasticity, which participate in brain development and perhaps also in learning and memory processes, remain susceptible to the effects of REMS deprivation during the general period of adolescence in the rat.

  9. Alternating Periods of High and Low-Entropy Neural Ensemble Activity During Image Processing in the Primary Visual Cortex of Rats.

    Science.gov (United States)

    Li, Xiaoyuan; Li, Qiwei; Shi, Li; Jiao, Liucheng

    2016-01-01

    The response properties of individual neurons in the primary visual cortex (V1) are among the most thoroughly described in the mammalian central nervous system, but they reveal less about higher-order processes like visual perception. Neural activity is highly nonlinear and non-stationary over time, greatly complicating the relationships among the spatiotemporal characteristics of visual stimuli, local field potential (LFP) signal components, and the underlying neuronal activity patterns. We applied discrete wavelet transformation to detect new features of the LFP that may better describe the association between visual input and neural ensemble activity. The relative wavelet energy (RWE), wavelet entropy (WS), and the mean WS were computed from LFPs recorded in rat V1 during three distinct visual stimuli: low ambient light, a uniform grey computer screen, and simple pictures of common scenes. The time evolution of the RWE within the γ band (31-62.5 Hz) was the dominant component over certain periods during visual stimulation. Mean WS decreased with increasing complexity of the visual image, and the time-dependent WS alternated between periods of highly ordered and disordered population activity. In conclusion, these alternating periods of high and low WS may correspond to different aspects of visual processing, such as feature extraction and perception. PMID:27347219

  10. Schroedinger's cat

    International Nuclear Information System (INIS)

    The issue is to seek quantum interference effects in an arbitrary field, in particular in psychology. For this a digest of quantum mechanics over finite-n-dimensional Hilbert space is invented. In order to match crude data not only von Neumann's mixed states are used but also a parallel notion of unsharp tests. The mathematically styled text (and earlier work on multibin tests, designated MB) deals largely with these new tests. Quantum psychology itself is only given a foundation. It readily engenders objections; its plausibility is developed gradually, in interlocking essays. There is also the empirically definite proposal that (state, test, outcome)-indexed counts be gathered to record data, then fed to a 'matrix format' (MF) search for quantum models. A previously proposed experiment in visual perception which has since failed to find significant quantum correlations, is discussed. The suspicion that quantum mechanics is all around goes beyond MF, and 'Schroedinger's cat' symbolizes this broader perspective. (author)

  11. Functional Architecture of Noise Correlations in Human Early Visual Cortex and its Relationship with Coherent Spontaneous Activity

    Directory of Open Access Journals (Sweden)

    Jungwon Ryu

    2012-10-01

    Full Text Available Responses of single sensory neurons to stimuli are ‘noisy’, varying substantially across repeated trials of identical stimulation. Intriguingly, these individual ‘noise responses’ (NR—deviations from their means—are not isolated; rather they are highly correlated, referred to as ‘noise correlation’ (NC. From a computational viewpoint, the presence and nature of NC exert great impacts on the information processing capacity of neurons as they encode sensory events as a population, decode those encoded neural responses, and contribute to perceptual choices for action. Regarding the origin of NR, on the other hand, there has been growing evidence pointing to its tight linkage with ‘spontaneous responses’ (SR—fluctuations of neural activity in the absence of external input or tasks. To investigate the functional structure of NC and its relationship with ‘correlations in SR’ (SC, we defined population receptive fields (pRFs of unit volumes of gray matter (UV in human early visual cortex and computed NRs and SRs using fMRI. NC increased with an increasing degree of similarity in pRF tuning properties such as orientation, spatial frequency, and visuotopic position, particularly between UV pairs close in cortical distance. This ‘like-to-like’ structure of NC remained unaltered across scan runs with different stimuli, even among between-area UV pairs. SC was higher than NC, and its functional and temporal structures were quite similar to those of NC. Furthermore, the partial correlation analysis revealed that NC between a given pair of UVs was best predicted by their SC than by any other factors examined in the current study.

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

    Science.gov (United States)

    Battaglia, Demian; Hansel, David

    2011-10-01

    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

  13. Layer- and cell-type-specific subthreshold and suprathreshold effects of long-term monocular deprivation in rat visual cortex.

    Science.gov (United States)

    Medini, Paolo

    2011-11-23

    Connectivity and dendritic properties are determinants of plasticity that are layer and cell-type specific in the neocortex. However, the impact of experience-dependent plasticity at the level of synaptic inputs and spike outputs remains unclear along vertical cortical microcircuits. Here I compared subthreshold and suprathreshold sensitivity to prolonged monocular deprivation (MD) in rat binocular visual cortex in layer 4 and layer 2/3 pyramids (4Ps and 2/3Ps) and in thick-tufted and nontufted layer 5 pyramids (5TPs and 5NPs), which innervate different extracortical targets. In normal rats, 5TPs and 2/3Ps are the most binocular in terms of synaptic inputs, and 5NPs are the least. Spike responses of all 5TPs were highly binocular, whereas those of 2/3Ps were dominated by either the contralateral or ipsilateral eye. MD dramatically shifted the ocular preference of 2/3Ps and 4Ps, mostly by depressing deprived-eye inputs. Plasticity was profoundly different in layer 5. The subthreshold ocular preference shift was sevenfold smaller in 5TPs because of smaller depression of deprived inputs combined with a generalized loss of responsiveness, and was undetectable in 5NPs. Despite their modest ocular dominance change, spike responses of 5TPs consistently lost their typically high binocularity during MD. The comparison of MD effects on 2/3Ps and 5TPs, the main affected output cells of vertical microcircuits, indicated that subthreshold plasticity is not uniquely determined by the initial degree of input binocularity. The data raise the question of whether 5TPs are driven solely by 2/3Ps during MD. The different suprathreshold plasticity of the two cell populations could underlie distinct functional deficits in amblyopia.

  14. 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

  15. Combination of blood oxygen level–dependent functional magnetic resonance imaging and visual evoked potential recordings for abnormal visual cortex in two types of amblyopia

    Science.gov (United States)

    Wang, Xinmei; Cui, Dongmei; Zheng, Ling; Yang, Xiao; Yang, Hui

    2012-01-01

    Purpose To elucidate the different neuromechanisms of subjects with strabismic and anisometropic amblyopia compared with normal vision subjects using blood oxygen level–dependent functional magnetic resonance imaging (BOLD-fMRI) and pattern-reversal visual evoked potential (PR-VEP). Methods Fifty-three subjects, age range seven to 12 years, diagnosed with strabismic amblyopia (17 cases), anisometropic amblyopia (20 cases), and normal vision (16 cases), were examined using the BOLD-fMRI and PR-VEP of UTAS-E3000 techniques. Cortical activation by binocular viewing of reversal checkerboard patterns was examined in terms of the calcarine region of interest (ROI)-based and spatial frequency–dependent analysis. The correlation of cortical activation in fMRI and the P100 amplitude in VEP were analyzed using the SPSS 12.0 software package. Results In the BOLD-fMRI procedure, reduced areas and decreased activation levels were found in Brodmann area (BA) 17 and other extrastriate areas in subjects with amblyopia compared with the normal vision group. In general, the reduced areas mainly resided in the striate visual cortex in subjects with anisometropic amblyopia. In subjects with strabismic amblyopia, a more significant cortical impairment was found in bilateral BA 18 and BA 19 than that in subjects with anisometropic amblyopia. The activation by high-spatial-frequency stimuli was reduced in bilateral BA 18 and 19 as well as BA 17 in subjects with anisometropic amblyopia, whereas the activation was mainly reduced in BA 18 and BA 19 in subjects with strabismic amblyopia. These findings were further confirmed by the ROI-based analysis of BA 17. During spatial frequency–dependent VEP detection, subjects with anisometropic amblyopia had reduced sensitivity for high spatial frequency compared to subjects with strabismic amblyopia. The cortical activation in fMRI with the calcarine ROI-based analysis of BA 17 was significantly correlated with the P100 amplitude in VEP

  16. The effects of AMPA blockade on the spectral profile of human early visual cortex recordings studied with non-invasive MEG.

    Science.gov (United States)

    Muthukumaraswamy, Suresh D; Routley, Bethany; Droog, Wouter; Singh, Krish D; Hamandi, Khalid

    2016-08-01

    The generation of gamma-band (>30 Hz) cortical activity is thought to depend on the reciprocal connections of excitatory glutamatergic principal cells with inhibitory GABAergic interneurons. Both in vitro and in vivo animal studies have shown that blockade of glutamatergic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors reduces the amplitude of gamma-band activity. In this registered report, we hypothesised that similar effects would be observed in humans following administration of perampanel, a first in class AMPA antagonist, used in the treatment of epilepsy. In a single-blind placebo-controlled crossover study, 20 healthy male participants completed two study days. On one day participants were given a 6 mg dose of perampanel and on the other an inactive placebo. magnetoencephalography (MEG) recordings of brain activity were taken before and two hours after drug administration, with activity in the visual cortex probed using a stimulation protocol known to induce gamma-band activity in the primary visual cortex. As hypothesised, our results indicated a decrease in gamma-band amplitudes following perampanel administration. The decreases in gamma-band amplitudes observed were temporally restricted to the early time-period of stimulus presentation (up to 400 msec) with no significant effects observed on early evoked responses or alpha rhythms. This suggests that the early time-window of induced visual gamma-band activity, thought to reflect input to the visual cortex from the lateral geniculate nucleus, is most sensitive to AMPA blocking drugs. PMID:27209006

  17. A neural network model on self-organizing emergence of simple-cell receptive field with orientation selectivity in visual cortex

    Institute of Scientific and Technical Information of China (English)

    杨谦; 齐翔林; 汪云九

    2001-01-01

    In order to probe into the self-organizing emergence of simple cell orientation selectivity,we tried to construct a neural network model that consists of LGN neurons and simple cells in visual cortex and obeys the Hebbian learning rule. We investigated the neural coding and representation of simple cells to a natural image by means of this model. The results show that the structures of their receptive fields are determined by the preferred orientation selectivity of simple cells.However, they are also decided by the emergence of self-organization in the unsupervision learning process. This kind of orientation selectivity results from dynamic self-organization based on the interactions between LGN and cortex.

  18. Functional specialization and convergence in the occipito-temporal cortex supporting haptic and visual identification of human faces and body parts: an fMRI study.

    Science.gov (United States)

    Kitada, Ryo; Johnsrude, Ingrid S; Kochiyama, Takanori; Lederman, Susan J

    2009-10-01

    Humans can recognize common objects by touch extremely well whenever vision is unavailable. Despite its importance to a thorough understanding of human object recognition, the neuroscientific study of this topic has been relatively neglected. To date, the few published studies have addressed the haptic recognition of nonbiological objects. We now focus on haptic recognition of the human body, a particularly salient object category for touch. Neuroimaging studies demonstrate that regions of the occipito-temporal cortex are specialized for visual perception of faces (fusiform face area, FFA) and other body parts (extrastriate body area, EBA). Are the same category-sensitive regions activated when these components of the body are recognized haptically? Here, we use fMRI to compare brain organization for haptic and visual recognition of human body parts. Sixteen subjects identified exemplars of faces, hands, feet, and nonbiological control objects using vision and haptics separately. We identified two discrete regions within the fusiform gyrus (FFA and the haptic face region) that were each sensitive to both haptically and visually presented faces; however, these two regions differed significantly in their response patterns. Similarly, two regions within the lateral occipito-temporal area (EBA and the haptic body region) were each sensitive to body parts in both modalities, although the response patterns differed. Thus, although the fusiform gyrus and the lateral occipito-temporal cortex appear to exhibit modality-independent, category-sensitive activity, our results also indicate a degree of functional specialization related to sensory modality within these structures.

  19. Action word Related to Walk Heard by the Ears Activates Visual Cortex and Superior Temporal Gyrus: An fMRI Study

    Directory of Open Access Journals (Sweden)

    Naoyuki Osaka

    2012-10-01

    Full Text Available Cognitive neuroscience of language of action processing is one of the interesting issues on the cortical “seat” of word meaning and related action (Pulvermueller, 1999 Behavioral Brain Sciences 22 253–336. For example, generation of action verbs referring to various arm or leg actions (e.g., pick or kick differentially activate areas along the motor strip that overlap with those areas activated by actual movement of the fingers or feet (Hauk et al., 2004 Neuron 41 301–307. Meanwhile, mimic words like onomatopoeia have the other potential to selectively and strongly stimulate specific brain regions having a specified “seat” of action meaning. In fact, mimic words highly suggestive of laughter and gaze significantly activated the extrastriate visual /premotor cortices and the frontal eye field, respectively (Osaka et al., 2003 Neuroscience Letters 340 127–130; 2009 Neuroscience Letters 461 65–68. However, the role of a mimic word related to walk on specific brain regions has not yet been investigated. The present study showed that a mimic word highly suggestive of human walking, heard by the ears with eyes closed, significantly activated the visual cortex located in extrastriate cortex and superior temporal gyrus while hearing non-sense words that did not imply walk under the same task did not activate these areas. These areas would be a critical region for generating visual images of walking and related action.

  20. Three-dimensional visualization of functional brain tissue and functional magnetic resonance imaging-integrated neuronavigation in the resection of brain tumor adjacent to motor cortex

    International Nuclear Information System (INIS)

    Objective: To assess the value of three -dimensional visualization of functional brain tissue and the functional magnetic resonance imaging (fMRI)-integrated neuronavigation in the resection of brain tumor adjacent to motor cortex. Method: Sixty patients with tumor located in the central sulcus were enrolled. Thirty patients were randomly assigned to function group and 30 to control group. Patients in function group underwent fMRI to localize the functional brain tissues. Then the function information was transferred to the neurosurgical navigator. The patients in control group underwent surgery with navigation without function information. The therapeutic effect, excision rate. improvement of motor function, and survival quality during follow-up were analyzed. Result: All patients in function group were accomplished visualization of functional brain tissues and fMRI-integrated neuronavigation. The locations of tumors, central sulcus and motor cortex were marked during the operation. The fMRI -integrated information played a great role in both pre- and post-operation. Pre-operation: designing the location of the skin flap and window bone, determining the relationship between the tumor and motor cortex, and designing the pathway for the resection. Post- operation: real-time navigation of relationship between the tumor and motor cortex, assisting to localize the motor cortex using interoperation ultra-sound for correcting the displacement by the CSF outflow and collapsing tumor. The patients in the function group had better results than the patients in the control group in therapeutic effect (u=2.646, P=0.008), excision rate (χ=7.200, P<0.01), improvement of motor function (u=2.231, P=0.026), and survival quality (KPS uc= 2.664, P=0.008; Zubrod -ECOG -WHO uc=2.135, P=0.033). Conclusions: Using preoperative three -dimensional visualization of cerebral function tissue and the fMRI-integrated neuronavigation technology, combining intraoperative accurate positioning

  1. The combined effects of unilateral enucleation and rearing in a 'dim' red light on synapse-to-neuron ratios in the rat visual cortex.

    OpenAIRE

    Bedi, K S

    1989-01-01

    One day old rats had their right eyes removed and together with non-enucleated controls were raised in either 'light' or 'dark' (red light) conditions from birth until 39 days of age. This resulted in four groups of animals: light-reared enucleated, light-reared non-enucleated, dark-reared enucleated and dark-reared non-enucleated. All animals were killed by intracardiac perfusion with 2.5% sodium cacodylate-buffered glutaraldehyde at 39 days of age. Pieces of visual cortex (Area 17) from bot...

  2. 盲人视皮层重塑的探讨%Plasticity of visual cortex of blind person

    Institute of Scientific and Technical Information of China (English)

    邹叶青; 邹怀宇; 甘瑞华; 柳丰萍; 邹彤

    2013-01-01

    大脑可塑性是大脑的主要属性之一,研究大脑可塑性对于揭示大脑活动的规律具有十分重要的意义.很早以前,人们就发现盲人虽然视觉缺失,但是他们的其他功能,如触觉、听觉等都好于正常人,为什么盲人这些方面的功能会好于正常人?研究盲人视皮层重塑对于了解大脑可塑性有着十分重要的作用.20世纪末,学者们开始利用正电子发射断层扫描(PET)、透颅磁刺激(transcranial magnetic stimulation,TMS)、功能磁共振成像(functional magnetic resonance imaging,FMRI)等技术研究盲人视皮层重塑,发现盲人在阅读盲文时,视皮层会被激活,由此得出盲人视皮层重塑的理论依据.但是,目前关于盲人视皮层重塑的机制尚不清楚,如在盲人视皮层重塑的过程中大脑的结构和功能到底发生了哪些变化?诱导大脑结构和功能发生变化的内在机制是什么?本文将结合神经解剖学、神经组织学、神经生理学、认知神经科学等学科的理论探讨盲人视皮层重塑的机制.%Plasticity was one of the most important traits of brain and quite vital for exploring the law of brain activity. Previous studies showed that it was worth considering that blind person with better touching and listening ability than healthy person. Therefore, the plasticity of blind person' s brain was valuabe for study. At the end of 20th centurary, the study results showed that plasticity occurred in blind person' s brain with the technology of positron emission tomography, transcranial magnetic stimulation, functional magnetic resonance imaging. Their visual cortex was activated while reading, however, it was ambiguous. What happened in the brain' s structure during the plasticity process? What was the mechanics? So the changes of neuron-anatomy structure, neuron-histology, neuron-physiology and cognitive neuroscience would be discussed in this article.

  3. Feedback from visual cortical area 7 to areas 17 and 18 in cats: How neural web is woven during feedback.

    Science.gov (United States)

    Yang, X; Ding, H; Lu, J

    2016-01-15

    To investigate the feedback effect from area 7 to areas 17 and 18, intrinsic signal optical imaging combined with pharmacological, morphological methods and functional magnetic resonance imaging (fMRI) was employed. A spatial frequency-dependent decrease in response amplitude of orientation maps was observed in areas 17 and 18 when area 7 was inactivated by a local injection of GABA, or by a lesion induced by liquid nitrogen freezing. The pattern of orientation maps of areas 17 and 18 after the inactivation of area 7, if they were not totally blurred, paralleled the normal one. In morphological experiments, after one point at the shallow layers within the center of the cat's orientation column of area 17 was injected electrophoretically with HRP (horseradish peroxidase), three sequential patches in layers 1, 2 and 3 of area 7 were observed. Employing fMRI it was found that area 7 feedbacks mainly to areas 17 and 18 on ipsilateral hemisphere. Therefore, our conclusions are: (1) feedback from area 7 to areas 17 and 18 is spatial frequency modulated; (2) feedback from area 7 to areas 17 and 18 occurs mainly ipsilaterally; (3) histological feedback pattern from area 7 to area 17 is weblike.

  4. Calcium-binding protein-containing neuronal populations in mammalian visual cortex: a comparative study in whales, insectivores, bats, rodents, and primates.

    Science.gov (United States)

    Glezer, I I; Hof, P R; Leranth, C; Morgane, P J

    1993-01-01

    This study is focused on comparative analysis of gamma-aminobutyric acid-positive (GABAergic) neuronal populations in primary visual cortex of totally aquatic toothed whales and select terrestrial mammals with different evolutionary histories and various ecological adaptations. The distribution of neuronal populations containing the calcium-binding proteins calbindin and parvalbumin, which are recognized markers for the GABAergic neurons in cerebral cortex, is compared in five species of toothed whales and in representatives (one species each) of insectivores, bats, rodents, and primates. Computerized image analysis has shown that overall quantitative characteristics of GABAergic cortical neurons in toothed whales are similar to those in other mammalian orders. Thus, GABA-positive neurons represent 26% of the total population of cortical neurons in the visual cortex of whales. Some 97% of GABA-positive cells contain calcium-binding proteins, which is numerically similar to these parameters found in primates and other mammals. On the other hand, the typology and laminar distribution of calcium-binding protein-containing neurons in the primary visual cortex of five whale species (Delphinapterus leucas, Globicephala melaena, Phocoena phocoena, Stenella coeruleoalba, and Tursiops truncatus) differ significantly from those of primates (Macaca mulatta) and rodents (Rattus rattus) and are similar to those found in insectivorous bats (Eptesicus fuscus) and hedgehogs (Erinaceus europaeus). In whales, bats, and hedgehogs a significant concentration of calbindin-positive, vertically oriented bipolar and bitufted neurons was found in layers I, II, and IIIc/V with their axons arranged in a three-dimensional network. In primates and rodents they are distributed evenly across all cortical layers and are predominantly multipolar or bitufted neurons found in all cortical layers with their axons oriented along the vertical axis of the cortical plate. The parvalbumin-positive neurons

  5. Involvement of nicotinic and muscarinic receptors in the endogenous cholinergic modulation of the balance between excitation and inhibition in the young rat visual cortex.

    Science.gov (United States)

    Lucas-Meunier, Estelle; Monier, Cyril; Amar, Muriel; Baux, Gérard; Frégnac, Yves; Fossier, Philippe

    2009-10-01

    This study aims to clarify how endogenous release of cortical acetylcholine (ACh) modulates the balance between excitation and inhibition evoked in visual cortex. We show that electrical stimulation in layer 1 produced a significant release of ACh measured intracortically by chemoluminescence and evoked a composite synaptic response recorded intracellularly in layer 5 pyramidal neurons of rat visual cortex. The pharmacological specificity of the ACh neuromodulation was determined from the continuous whole-cell voltage clamp measurement of stimulation-locked changes of the input conductance during the application of cholinergic agonists and antagonists. Blockade of glutamatergic and gamma-aminobutyric acid (GABAergic) receptors suppressed the evoked response, indicating that stimulation-induced release of ACh does not directly activate a cholinergic synaptic conductance in recorded neurons. Comparison of cytisine and mecamylamine effects on nicotinic receptors showed that excitation is enhanced by endogenous evoked release of ACh through the presynaptic activation of alpha(*)beta4 receptors located on glutamatergic fibers. DHbetaE, the selective alpha4beta2 nicotinic receptor antagonist, induced a depression of inhibition. Endogenous ACh could also enhance inhibition by acting directly on GABAergic interneurons, presynaptic to the recorded cell. We conclude that endogenous-released ACh amplifies the dominance of the inhibitory drive and thus decreases the excitability and sensory responsiveness of layer 5 pyramidal neurons. PMID:19176636

  6. 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.; Wezel, van R.J.A.; Wildt, van der G.J.; Berg, van den A.V.

    2011-01-01

    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

  7. 初级视皮层神经元对瞬态刺激响应的时间性质%The Temporal Responses of Neurons in The Primary Visual Cortex to Transient Stimuli

    Institute of Scientific and Technical Information of China (English)

    李骁健; 蒋震; 王毅

    2012-01-01

    durations reflected the evolution of responses to the static stimuli. All the data were collected from the anesthetized cat V1 with extracellular unit recording. V1 neurons showed wave-like response curves that grew up after a short latency to the stimulus onset and then dropped off gradually due to the stimulus offset. When stimulus duration prolonged, the time and width of the main peak (the first peak, the largest one, of PSTH response curve) increased and saturated at 30 ms stimulus duration that we tested. Magnitudes of most main peaks were almost equal except that the response peak to the 5 ms stimulus duration was significantly lower than those to the others. There were also offset response peaks which were evoked by the stimulus offset, but were smaller than the main peaks and contained less information about visual stimuli. The magnitude of the offset responses increased with the stimulus duration, so it could be regarded as the aftereffects of the stimulus offset. Statistically, the response durations (represented by 2 × half peak width) of V1 neurons to different stimulus durations were not shorter than 39 ms (even the stimulus duration was as short as 5 or 10 ms), which might be the physiological basis of the visual persistence (the duration of perception for a visual stimulus is longer than the physical presentation) at the primary visual cortex level. On the other hand, the time differences of the main and offset peaks were longer than the corresponding stimulus durations, suggesting that the offset responses were delayed by the onset responses. This may be a kind of mechanism to ensure that the information processed by V1 neurons is not disrupted by the offset responses or the onset responses of another stimulus. Furthermore, the similarity of the minimal response duration (39 ms) and the minimal time peak (36 ms) between the main peak and offset peak suggest that the minimal time (response duration) necessary for V1 neurons to process information is at

  8. Neural coding of image structure and contrast polarity of Cartesian, hyperbolic, and polar gratings in the primary and secondary visual cortex of the tree shrew.

    Science.gov (United States)

    Poirot, Jordan; De Luna, Paolo; Rainer, Gregor

    2016-04-01

    We comprehensively characterize spiking and visual evoked potential (VEP) activity in tree shrew V1 and V2 using Cartesian, hyperbolic, and polar gratings. Neural selectivity to structure of Cartesian gratings was higher than other grating classes in both visual areas. From V1 to V2, structure selectivity of spiking activity increased, whereas corresponding VEP values tended to decrease, suggesting that single-neuron coding of Cartesian grating attributes improved while the cortical columnar organization of these neurons became less precise from V1 to V2. We observed that neurons in V2 generally exhibited similar selectivity for polar and Cartesian gratings, suggesting that structure of polar-like stimuli might be encoded as early as in V2. This hypothesis is supported by the preference shift from V1 to V2 toward polar gratings of higher spatial frequency, consistent with the notion that V2 neurons encode visual scene borders and contours. Neural sensitivity to modulations of polarity of hyperbolic gratings was highest among all grating classes and closely related to the visual receptive field (RF) organization of ON- and OFF-dominated subregions. We show that spatial RF reconstructions depend strongly on grating class, suggesting that intracortical contributions to RF structure are strongest for Cartesian and polar gratings. Hyperbolic gratings tend to recruit least cortical elaboration such that the RF maps are similar to those generated by sparse noise, which most closely approximate feedforward inputs. Our findings complement previous literature in primates, rodents, and carnivores and highlight novel aspects of shape representation and coding occurring in mammalian early visual cortex. PMID:26843607

  9. A BOLD perspective on age-related flow-metabolism coupling and neural efficiency changes in human visual cortex

    OpenAIRE

    JoannaLynnHutchison; HanzhangLu

    2013-01-01

    Age-related performance declines in visual tasks have been attributed to reductions in processing efficiency. The neural basis of these declines has been explored by comparing the blood-oxygen-level-dependent (BOLD) index of neural activity in older and younger adults during visual task performance. However, neural activity is one of many factors that change with age and lead to BOLD signal differences. We investigated the origin of age-related BOLD changes by comparing blood-flow and oxygen-...

  10. Similarity-Based Fusion of MEG and fMRI Reveals Spatio-Temporal Dynamics in Human Cortex During Visual Object Recognition.

    Science.gov (United States)

    Cichy, Radoslaw Martin; Pantazis, Dimitrios; Oliva, Aude

    2016-08-01

    Every human cognitive function, such as visual object recognition, is realized in a complex spatio-temporal activity pattern in the brain. Current brain imaging techniques in isolation cannot resolve the brain's spatio-temporal dynamics, because they provide either high spatial or temporal resolution but not both. To overcome this limitation, we developed an integration approach that uses representational similarities to combine measurements of magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI) to yield a spatially and temporally integrated characterization of neuronal activation. Applying this approach to 2 independent MEG-fMRI data sets, we observed that neural activity first emerged in the occipital pole at 50-80 ms, before spreading rapidly and progressively in the anterior direction along the ventral and dorsal visual streams. Further region-of-interest analyses established that dorsal and ventral regions showed MEG-fMRI correspondence in representations later than early visual cortex. Together, these results provide a novel and comprehensive, spatio-temporally resolved view of the rapid neural dynamics during the first few hundred milliseconds of object vision. They further demonstrate the feasibility of spatially unbiased representational similarity-based fusion of MEG and fMRI, promising new insights into how the brain computes complex cognitive functions. PMID:27235099

  11. Inhibitory Stabilization of the Cortical Network Underlies Visual Surround Suppression

    OpenAIRE

    Ozeki, Hirofumi; Finn, Ian M.; Schaffer, Evan S.; Miller, Kenneth D.; Ferster, David

    2009-01-01

    In what regime does the cortical circuit operate? Our intracellular studies of surround suppression in cat primary visual cortex (V1) provide strong evidence on this question. Although suppression has been thought to arise from an increase in lateral inhibition, we find that the inhibition that cells receive is reduced, not increased, by a surround stimulus. Instead, suppression is mediated by a withdrawal of excitation. Thalamic recordings and previous work show that these effects cannot be ...

  12. Reduced density of geniculocortical terminals in foveal layer 4A in the macaque primary visual cortex: relationship to S-cone density.

    Science.gov (United States)

    Garcia-Marin, Virginia; Sundiang, Marina; Hawken, Michael J

    2015-09-01

    The S-cone system is closely linked to the perception of blue/yellow. The trichromatic system of Old-World monkeys and humans has relatively few S-cones in the fovea. In this study, we investigated the distribution of putative S-cone afferents in macaques primary visual cortex (V1) which form a characteristic honeycomb arrangement in layer 4A. It was hypothesized that if there were a low number of S-cone opponent projecting neurons in central vision then this would be seen as a reduction in afferents in foveal layer 4A. Recent studies have shown that the vesicular glutamate transporter 2 (VGlut2) is a marker for thalamic afferent terminals in cortex. The distribution of VGlut2-immunoreactive (-ir) terminals was studied in the foveal and perifoveal representation of V1. It was found that there was a substantial reduction in the terminal density in the foveal representation: the density was 5-6 times lower in the foveal V1 than in regions representing perifoveal eccentricities of 1°-2° and beyond. These findings may provide the cortical substrate of foveal tritanopia, the reduced blue perceptual ability for small fields in the center of gaze. PMID:25009312

  13. Effects of Unilateral Transcranial Direct Current Stimulation of Left Prefrontal Cortex on Processing and Memory of Emotional Visual Stimuli.

    Directory of Open Access Journals (Sweden)

    Stefania Balzarotti

    Full Text Available The dorsolateral prefrontal cortex (DLPFC is generally thought to be involved in affect and emotional processing; however, the specific contribution of each hemisphere continues to be debated. In the present study, we employed unilateral tDCS to test the unique contribution of left DLPFC in the encoding and retrieval of emotional stimuli in healthy subjects. Forty-two right handed undergraduate students received either anodal, cathodal or sham stimulation of left DLPFC while viewing neutral, pleasant, and unpleasant pictures. After completing a filler task, participants were asked to remember as many pictures as possible. Results showed that participants were able to remember a larger amount of emotional (both pleasant and unpleasant pictures than of neutral ones, regardless of the type of tDCS condition. Participants who received anodal stimulation recalled a significantly higher number of pleasant images than participants in the sham and cathodal conditions, while no differences emerged in the recall of neutral and unpleasant pictures. We conclude that our results provide some support to the role of left prefrontal cortex in the encoding and retrieval of pleasant stimuli.

  14. Visual agnosia.

    Science.gov (United States)

    Álvarez, R; Masjuan, J

    2016-03-01

    Visual agnosia is defined as an impairment of object recognition, in the absence of visual acuity or cognitive dysfunction that would explain this impairment. This condition is caused by lesions in the visual association cortex, sparing primary visual cortex. There are 2 main pathways that process visual information: the ventral stream, tasked with object recognition, and the dorsal stream, in charge of locating objects in space. Visual agnosia can therefore be divided into 2 major groups depending on which of the two streams is damaged. The aim of this article is to conduct a narrative review of the various visual agnosia syndromes, including recent developments in a number of these syndromes.

  15. Changes in cytochrome-oxidase oxidation in the occipital cortex during visual simulation: improvement in sensitivity by the determination of the wavelength dependence of the differential pathlength

    Science.gov (United States)

    Kohl-Bareis, Matthias; Nolte, Christian; Heekeren, Hauke R.; Horst, Susanne; Scholz, J.; Obrig, Hellmuth; Villringer, Arno

    1998-01-01

    In this study we assess changes in the hemoglobin oxygenation (oxy-Hb, deoxy-Hb) and the Cytochrome-C-Oxidase redox state (Cyt-ox) in the occipital cortex during visual stimulation by near infrared spectroscopy. For the calculation of changes in oxy-Hb, deoxy-Hb and Cyt-ox from attenuation data via a modified Beer-Lambert equation, the wavelength dependence of the differential pathlength factor (DPF), i.e. the ratio of the mean optical pathlength and the physical light-source-detector separation, has to be taken into account. The wavelength dependence of the DPF determines the crosstalk between the different concentrations and is therefore essential for a high sensitivity. Here a simple method is suggested to estimate the wavelength dependence of the DPF((lambda) ) from pulse induced attenuation changes measured on the head of adult humans. The essence is that the DPF is the ratio of the attenuation changes over absorption coefficient changes and the spectral form of the pulse correlated absorption coefficient change is proportional to the extinction coefficient of blood. Indicators for the validity of the DPF((lambda) ) derived for wavelengths between 700 and 970 nm are the stability of the calculated oxy-Hb, deoxy-Hb and Cyt-ox signals with variations of the wavelength range included for their calculation and its overall agreement with the data available from the literature. The DPF derived from pulse measurements was used for the analysis of attenuation data from cortical stimulations. We show that Cyt-ox in the occipital cortex of human subjects is transiently oxidized during visual stimulation.

  16. Interplay between non-NMDA and NMDA receptor activation during oscillatory wave propagation: Analyses of caffeine-induced oscillations in the visual cortex of rats.

    Science.gov (United States)

    Yoshimura, Hiroshi; Sugai, Tokio; Kato, Nobuo; Tominaga, Takashi; Tominaga, Yoko; Hasegawa, Takahiro; Yao, Chenjuan; Akamatsu, Tetsuya

    2016-07-01

    Generation and propagation of oscillatory activities in cortical networks are important features of the brain. However, many issues related to oscillatory phenomena are unclear. We previously reported neocortical oscillation following caffeine treatment of rat brain slices. Input to the primary visual cortex (Oc1) generates N-methyl-d-aspartate (NMDA) receptor-dependent oscillations, and we proposed that the oscillatory signals originate in the secondary visual cortex (Oc2). Because non-NMDA and NMDA receptors cooperate in synaptic transmission, non-NMDA receptors may also play an important role in oscillatory activities. Here we investigated how non-NMDA receptor activities contribute to NMDA receptor-dependent oscillations by using optical recording methods. After induction of stable oscillations with caffeine application, blockade of NMDA receptors abolished the late stable oscillatory phase, but elicited 'hidden' non-NMDA receptor-dependent oscillation during the early depolarizing phase. An interesting finding is that the origin of the non-NMDA receptor-dependent oscillation moved from the Oc1, during the early phase, toward the origin of the NMDA receptor-dependent oscillation that is fixed in the Oc2. In addition, the frequency of the non-NMDA receptor-dependent oscillation was higher than that of the NMDA receptor-dependent oscillation. Thus, in one course of spatiotemporal oscillatory activities, the relative balance in receptor activities between non-NMDA and NMDA receptors gradually changes, and this may be due to the different kinetics of the two receptor types. These results suggest that interplay between the two receptor types in the areas of Oc1 and Oc2 may play an important role in oscillatory signal communication. PMID:27136667

  17. A robust index of lexical representation in the left occipito-temporal cortex as evidenced by EEG responses to fast periodic visual stimulation.

    Science.gov (United States)

    Lochy, Aliette; Van Belle, Goedele; Rossion, Bruno

    2015-01-01

    Despite decades of research on reading, including the relatively recent contributions of neuroimaging and electrophysiology, identifying selective representations of whole visual words (in contrast to pseudowords) in the human brain remains challenging, in particular without an explicit linguistic task. Here we measured discrimination responses to written words by means of electroencephalography (EEG) during fast periodic visual stimulation. Sequences of pseudofonts, nonwords, or pseudowords were presented through sinusoidal contrast modulation at a periodic 10 Hz frequency rate (F), in which words were interspersed at regular intervals of every fifth item (i.e., F/5, 2 Hz). Participants monitored a central cross color change and had no linguistic task to perform. Within only 3 min of stimulation, a robust discrimination response for words at 2 Hz (and its harmonics, i.e., 4 and 6 Hz) was observed in all conditions, located predominantly over the left occipito-temporal cortex. The magnitude of the response was largest for words embedded in pseudofonts, and larger in nonwords than in pseudowords, showing that list context effects classically reported in behavioral lexical decision tasks are due to visual discrimination rather than decisional processes. Remarkably, the oddball response was significant even for the critical words/pseudowords discrimination condition in every individual participant. A second experiment replicated this words/pseudowords discrimination, and showed that this effect is not accounted for by a higher bigram frequency of words than pseudowords. Without any explicit task, our results highlight the potential of an EEG fast periodic visual stimulation approach for understanding the representation of written language. Its development in the scientific community might be valuable to rapidly and objectively measure sensitivity to word processing in different human populations, including neuropsychological patients with dyslexia and other reading

  18. Functional architecture for disparity in macaque inferior temporal cortex and its relationship to the architecture for faces, color, scenes, and visual field.

    Science.gov (United States)

    Verhoef, Bram-Ernst; Bohon, Kaitlin S; Conway, Bevil R

    2015-04-29

    Binocular disparity is a powerful depth cue for object perception. The computations for object vision culminate in inferior temporal cortex (IT), but the functional organization for disparity in IT is unknown. Here we addressed this question by measuring fMRI responses in alert monkeys to stimuli that appeared in front of (near), behind (far), or at the fixation plane. We discovered three regions that showed preferential responses for near and far stimuli, relative to zero-disparity stimuli at the fixation plane. These "near/far" disparity-biased regions were located within dorsal IT, as predicted by microelectrode studies, and on the posterior inferotemporal gyrus. In a second analysis, we instead compared responses to near stimuli with responses to far stimuli and discovered a separate network of "near" disparity-biased regions that extended along the crest of the superior temporal sulcus. We also measured in the same animals fMRI responses to faces, scenes, color, and checkerboard annuli at different visual field eccentricities. Disparity-biased regions defined in either analysis did not show a color bias, suggesting that disparity and color contribute to different computations within IT. Scene-biased regions responded preferentially to near and far stimuli (compared with stimuli without disparity) and had a peripheral visual field bias, whereas face patches had a marked near bias and a central visual field bias. These results support the idea that IT is organized by a coarse eccentricity map, and show that disparity likely contributes to computations associated with both central (face processing) and peripheral (scene processing) visual field biases, but likely does not contribute much to computations within IT that are implicated in processing color. PMID:25926470

  19. Cat Scan

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    <正> A man takes his motionless dog to the vet."Doc,I think my dog is dead.”The vet looks the dog over, goes into a backroom,and comes out with a cat.He places the caton the table next to the dog.The cat walks aroundand sniffs at the dog.The dog does not move.The

  20. Effects of spatial and feature attention on disparity-rendered structure-from-motion stimuli in the human visual cortex.

    Directory of Open Access Journals (Sweden)

    Ifan Betina Ip

    Full Text Available An important advance in the study of visual attention has been the identification of a non-spatial component of attention that enhances the response to similar features or objects across the visual field. Here we test whether this non-spatial component can co-select individual features that are perceptually bound into a coherent object. We combined human psychophysics and functional magnetic resonance imaging (fMRI to demonstrate the ability to co-select individual features from perceptually coherent objects. Our study used binocular disparity and visual motion to define disparity structure-from-motion (dSFM stimuli. Although the spatial attention system induced strong modulations of the fMRI response in visual regions, the non-spatial system's ability to co-select features of the dSFM stimulus was less pronounced and variable across subjects. Our results demonstrate that feature and global feature attention effects are variable across participants, suggesting that the feature attention system may be limited in its ability to automatically select features within the attended object. Careful comparison of the task design suggests that even minor differences in the perceptual task may be critical in revealing the presence of global feature attention.

  1. Short colon in a cat

    International Nuclear Information System (INIS)

    An 11-year-old male Japanese domestic cat was referred to the veterinary hospital with a chronic diarrhea and signs of pain and vocalization when defecating. The cat has discharged unformed feces throughout his life. Morphological diagnosis of short colon was made radiographically after barium enema. The ileocolic junction and cecum was located to the left of the midline at the proximal end of the descending colon. Additional endoscopic examination demonstrated the difference in visual structures of the mucosal surface and in histological structures on mucosal biopsy specimens, between the colon and ileum. This is the first report of short colon in a cat in Japan

  2. Thinking about eating food activates visual cortex with reduced bilateral cerebellar activation in females with anorexia nervosa: an fMRI study.

    Directory of Open Access Journals (Sweden)

    Samantha J Brooks

    Full Text Available BACKGROUND: Women with anorexia nervosa (AN have aberrant cognitions about food and altered activity in prefrontal cortical and somatosensory regions to food images. However, differential effects on the brain when thinking about eating food between healthy women and those with AN is unknown. METHODS: Functional magnetic resonance imaging (fMRI examined neural activation when 42 women thought about eating the food shown in images: 18 with AN (11 RAN, 7 BPAN and 24 age-matched controls (HC. RESULTS: Group contrasts between HC and AN revealed reduced activation in AN in the bilateral cerebellar vermis, and increased activation in the right visual cortex. Preliminary comparisons between AN subtypes and healthy controls suggest differences in cortical and limbic regions. CONCLUSIONS: These preliminary data suggest that thinking about eating food shown in images increases visual and prefrontal cortical neural responses in females with AN, which may underlie cognitive biases towards food stimuli and ruminations about controlling food intake. Future studies are needed to explicitly test how thinking about eating activates restraint cognitions, specifically in those with restricting vs. binge-purging AN subtypes.

  3. Combination of blood oxygen level–dependent functional magnetic resonance imaging and visual evoked potential recordings for abnormal visual cortex in two types of amblyopia

    OpenAIRE

    Wang, Xinmei; Cui, Dongmei; Zheng, Ling; Yang, Xiao; Yang, Hui; Zeng, Junwen

    2012-01-01

    Purpose To elucidate the different neuromechanisms of subjects with strabismic and anisometropic amblyopia compared with normal vision subjects using blood oxygen level–dependent functional magnetic resonance imaging (BOLD-fMRI) and pattern-reversal visual evoked potential (PR-VEP). Methods Fifty-three subjects, age range seven to 12 years, diagnosed with strabismic amblyopia (17 cases), anisometropic amblyopia (20 cases), and normal vision (16 cases), were examined using the BOLD-fMRI and PR...

  4. Adaptive learning in a compartmental model of visual cortex - how feedback enables stable category learning and refinement

    Directory of Open Access Journals (Sweden)

    Georg eLayher

    2014-12-01

    Full Text Available The categorization of real world objects is often reflected in the similarity of their visual appearances. Such categories of objects do not necessarily form disjunct sets of objects, neither semantically nor visually. The relationship between categories can often be described in terms of a hierarchical structure. For instance, tigers and leopards build two separate mammalian categories, but both belong to the category of felines. In other words, tigers and leopards are subcategories of the category Felidae. In the last decades, the unsupervised learning of categories of visual input stimuli has been addressed by numerous approaches in machine learning as well as in the computational neurosciences. However, the question of what kind of mechanisms might be involved in the process of subcategory learning, or category refinement, remains a topic of active investigation. We propose a recurrent computational network architecture for the unsupervised learning of categorial and subcategorial visual input representations. During learning, the connection strengths of bottom-up weights from input to higher-level category representations are adapted according to the input activity distribution. In a similar manner, top-down weights learn to encode the characteristics of a specific stimulus category. Feedforward and feedback learning in combination realize an associative memory mechanism, enabling the selective top-down propagation of a category's feedback weight distribution. We suggest that the difference between the expected input encoded in the projective field of a category node and the current input pattern controls the amplification of feedforward-driven representations. Large enough differences trigger the recruitment of new representational resources and the establishment of (sub- category representations. We demonstrate the temporal evolution of such learning and show how the approach successully establishes category and subcategory

  5. Coupling of cerebral blood flow and oxygen metabolism is conserved for chromatic and luminance stimuli in human visual cortex

    OpenAIRE

    Leontiev, Oleg; Buracas, Giedrius T.; Liang, Christine; Ances, Beau M.; Perthen, Joanna E.; Shmuel, Amir; Buxton, Richard B.

    2012-01-01

    The ratio of the changes in cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2) during brain activation is a critical determinant of the magnitude of the blood oxygenation level dependent (BOLD) response measured with functional magnetic resonance imaging (fMRI). Cytochrome oxidase (CO), a key component of oxidative metabolism in the mitochondria, is non-uniformly distributed in visual area V1 in distinct blob and interblob regions, suggesting significant spatial variation...

  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. Extent and time-course of competition in visual cortex between emotionally arousing distractors and a concurrent task.

    Science.gov (United States)

    Deweese, Menton M; Müller, Matthias; Keil, Andreas

    2016-04-01

    Emotionally arousing cues automatically attract attentional resources, which may be at the cost of processing task-related information. Of central importance is how the visual system resolves competition for processing resources among stimuli differing in motivational salience. Here, we assessed the extent and time-course of competition between emotionally arousing distractors and task-related stimuli in a frequency-tagging paradigm. Steady-state visual evoked potentials (ssVEPs) were evoked using random-dot kinematograms that consisted of rapidly flickering (8.57 Hz) dots, superimposed upon emotional or neutral distractor pictures flickering at 12 Hz. The time-varying amplitude of the ssVEP evoked by the motion detection task showed a significant reduction to the task-relevant stream while emotionally arousing pictures were presented as distractors. Competition between emotionally arousing pictures and moving dots began 450 ms after picture onset and persisted for an additional 2600 ms. Competitive effects of the overlapping task and picture stream revealed cost effects for the motion detection task when unpleasant pictures were presented as distractors between 450 and 1650 ms after picture onset, where an increase in ssVEP amplitude to the flickering picture stimulus was at the cost of ssVEP amplitude to the flickering dot stimulus. Cost effects were generalized to all emotionally arousing contents between 1850 and 3050 ms after picture onset, where the greatest amount of competition was evident for conditions in which emotionally arousing pictures, compared to neutral, served as distractors. In sum, the processing capacity of the visual system as measured by ssVEPs is limited, resulting in prioritized processing of emotionally relevant cues. PMID:26790572

  8. Cat Scratch Disease

    Science.gov (United States)

    Cat scratch disease (CSD) is an illness caused by the bacterium Bartonella henselae. Almost half of all cats carry ... infection does not make cats sick. However, the scratch or bite of an infected cat can cause ...

  9. A BOLD Perspective on Age-Related Neurometabolic-Flow Coupling and Neural Efficiency Changes in Human Visual Cortex.

    Science.gov (United States)

    Hutchison, Joanna Lynn; Shokri-Kojori, Ehsan; Lu, Hanzhang; Rypma, Bart

    2013-01-01

    Age-related performance declines in visual tasks have been attributed to reductions in processing efficiency. The neural basis of these declines has been explored by comparing the blood-oxygen-level-dependent (BOLD) index of neural activity in older and younger adults during visual task performance. However, neural activity is one of many factors that change with age and lead to BOLD signal differences. We investigated the origin of age-related BOLD changes by comparing blood flow and oxygen metabolic constituents of BOLD signal. Subjects periodically viewed flickering annuli and pressed a button when detecting luminance changes in a central fixation cross. Using magnetic resonance dual-echo arterial spin labeling and CO2 ingestion, we observed age-equivalent (i.e., similar in older and younger groups) fractional cerebral blood flow (ΔCBF) in the presence of age-related increases in fractional cerebral metabolic rate of oxygen (ΔCMRO2). Reductions in ΔCBF responsiveness to increased ΔCMRO2 in elderly led to paradoxical age-related BOLD decreases. Age-related ΔCBF/ΔCMRO2 ratio decreases were associated with reaction times, suggesting that age-related slowing resulted from less efficient neural activity. We hypothesized that reduced vascular responsiveness to neural metabolic demand would lead to a reduction in ΔCBF/ΔCMRO2. A simulation of BOLD relative to ΔCMRO2 for lower and higher neurometabolic-flow coupling ratios (approximating those for old and young, respectively) indicated less BOLD signal change in old than young in relatively lower CMRO2 ranges, as well as greater BOLD signal change in young compared to old in relatively higher CMRO2 ranges. These results suggest that age-comparative studies relying on BOLD signal might be misinterpreted, as age-related BOLD changes do not merely reflect neural activity changes. Age-related declines in neurometabolic-flow coupling might lead to neural efficiency reductions that can adversely affect visual task

  10. A BOLD perspective on age-related flow-metabolism coupling and neural efficiency changes in human visual cortex

    Directory of Open Access Journals (Sweden)

    Joanna Lynn Hutchison

    2013-05-01

    Full Text Available Age-related performance declines in visual tasks have been attributed to reductions in processing efficiency. The neural basis of these declines has been explored by comparing the blood-oxygen-level-dependent (BOLD index of neural activity in older and younger adults during visual task performance. However, neural activity is one of many factors that change with age and lead to BOLD signal differences. We investigated the origin of age-related BOLD changes by comparing blood-flow and oxygen-metabolic constituents of BOLD signal. Subjects periodically viewed flickering annuli and pressed a button when detecting luminance changes in a central fixation cross. Using magnetic resonance dual-echo arterial spin labeling and CO2 ingestion, we observed age-equivalent (i.e., similar in older and younger groups fractional cerebral blood flow (∆CBF in the presence of age-related increases in fractional cerebral metabolic rate of oxygen (∆CMRO2. Reductions in ∆CBF responsiveness to increased ∆CMRO2 in elderly led to paradoxical age-related BOLD decreases. Age-related ∆CBF/∆CMRO2 ratio decreases were associated with reaction times, suggesting that age-related slowing resulted from less efficient neural activity. We hypothesized that reduced vascular responsiveness to neural metabolic demand would lead to a reduction in ∆CBF/∆CMRO2. A simulation of BOLD relative to ∆CMRO2 for lower and higher neurometabolic-flow coupling ratios (approximating those for old and young, respectively indicated less BOLD signal change in old than young in relatively lower CMRO2 ranges, as well as greater BOLD signal change in young compared to old in relatively higher CMRO2 ranges. These results suggest that age-comparative studies relying on BOLD signal might be misinterpreted, as age-related BOLD changes do not merely reflect neural activity changes. Age-related declines in neurometabolic-flow coupling might lead to neural efficiency reductions that can

  11. Three dimensional visualization and fractal analysis of mosaic patches in rat chimeras: cell assortment in liver, adrenal cortex and cornea.

    Directory of Open Access Journals (Sweden)

    Stephen Iannaccone

    Full Text Available The production of organ parenchyma in a rapid and reproducible manner is critical to normal development. In chimeras produced by the combination of genetically distinguishable tissues, mosaic patterns of cells derived from the combined genotypes can be visualized. These patterns comprise patches of contiguously similar genotypes and are different in different organs but similar in a given organ from individual to individual. Thus, the processes that produce the patterns are regulated and conserved. We have previously established that mosaic patches in multiple tissues are fractal, consistent with an iterative, recursive growth model with simple stereotypical division rules. Fractal dimensions of various tissues are consistent with algorithmic models in which changing a single variable (e.g. daughter cell placement after division switches the mosaic pattern from islands to stripes of cells. Here we show that the spiral pattern previously observed in mouse cornea can also be visualized in rat chimeras. While it is generally held that the pattern is induced by stem cell division dynamics, there is an unexplained discrepancy in the speed of cellular migration and the emergence of the pattern. We demonstrate in chimeric rat corneas both island and striped patterns exist depending on the age of the animal. The patches that comprise the pattern are fractal, and the fractal dimension changes with the age of the animal and indicates the constraint in patch complexity as the spiral pattern emerges. The spiral patterns are consistent with a loxodrome. Such data are likely to be relevant to growth and cell division in organ systems and will help in understanding how organ parenchyma are generated and maintained from multipotent stem cell populations located in specific topographical locations within the organ. Ultimately, understanding algorithmic growth is likely to be essential in achieving organ regeneration in vivo or in vitro from stem cell populations.

  12. Three dimensional visualization and fractal analysis of mosaic patches in rat chimeras: cell assortment in liver, adrenal cortex and cornea.

    Science.gov (United States)

    Iannaccone, Stephen; Zhou, Yue; Walterhouse, David; Taborn, Greg; Landini, Gabriel; Iannaccone, Philip

    2012-01-01

    The production of organ parenchyma in a rapid and reproducible manner is critical to normal development. In chimeras produced by the combination of genetically distinguishable tissues, mosaic patterns of cells derived from the combined genotypes can be visualized. These patterns comprise patches of contiguously similar genotypes and are different in different organs but similar in a given organ from individual to individual. Thus, the processes that produce the patterns are regulated and conserved. We have previously established that mosaic patches in multiple tissues are fractal, consistent with an iterative, recursive growth model with simple stereotypical division rules. Fractal dimensions of various tissues are consistent with algorithmic models in which changing a single variable (e.g. daughter cell placement after division) switches the mosaic pattern from islands to stripes of cells. Here we show that the spiral pattern previously observed in mouse cornea can also be visualized in rat chimeras. While it is generally held that the pattern is induced by stem cell division dynamics, there is an unexplained discrepancy in the speed of cellular migration and the emergence of the pattern. We demonstrate in chimeric rat corneas both island and striped patterns exist depending on the age of the animal. The patches that comprise the pattern are fractal, and the fractal dimension changes with the age of the animal and indicates the constraint in patch complexity as the spiral pattern emerges. The spiral patterns are consistent with a loxodrome. Such data are likely to be relevant to growth and cell division in organ systems and will help in understanding how organ parenchyma are generated and maintained from multipotent stem cell populations located in specific topographical locations within the organ. Ultimately, understanding algorithmic growth is likely to be essential in achieving organ regeneration in vivo or in vitro from stem cell populations.

  13. Cat's Claw

    Science.gov (United States)

    ... R S T U V W X Y Z Cat's Claw Share: On This Page Introduction What the ... More Information Key References © Steven Foster Common Names: cat’s claw, uña de gato Latin Name: Uncaria tomentosa, ...

  14. My Cat

    Institute of Scientific and Technical Information of China (English)

    王悦; 李成梅

    2002-01-01

    The name of my cat is Naty. This year he is one year old. He isvery fat, but he is very nice. He has a big round white head. His mouth and nose are small. His eyes are interesting. In the day,they are small and black,but at night they are big and blue.

  15. Role of GABAA-Mediated Inhibition and Functional Assortment of Synapses onto Individual Layer 4 Neurons in Regulating Plasticity Expression in Visual Cortex.

    Science.gov (United States)

    Saez, Ignacio; Friedlander, Michael J

    2016-01-01

    Layer 4 (L4) of primary visual cortex (V1) is the main recipient of thalamocortical fibers from the dorsal lateral geniculate nucleus (LGNd). Thus, it is considered the main entry point of visual information into the neocortex and the first anatomical opportunity for intracortical visual processing before information leaves L4 and reaches supra- and infragranular cortical layers. The strength of monosynaptic connections from individual L4 excitatory cells onto adjacent L4 cells (unitary connections) is highly malleable, demonstrating that the initial stage of intracortical synaptic transmission of thalamocortical information can be altered by previous activity. However, the inhibitory network within L4 of V1 may act as an internal gate for induction of excitatory synaptic plasticity, thus providing either high fidelity throughput to supragranular layers or transmittal of a modified signal subject to recent activity-dependent plasticity. To evaluate this possibility, we compared the induction of synaptic plasticity using classical extracellular stimulation protocols that recruit a combination of excitatory and inhibitory synapses with stimulation of a single excitatory neuron onto a L4 cell. In order to induce plasticity, we paired pre- and postsynaptic activity (with the onset of postsynaptic spiking leading the presynaptic activation by 10ms) using extracellular stimulation (ECS) in acute slices of primary visual cortex and comparing the outcomes with our previously published results in which an identical protocol was used to induce synaptic plasticity between individual pre- and postsynaptic L4 excitatory neurons. Our results indicate that pairing of ECS with spiking in a L4 neuron fails to induce plasticity in L4-L4 connections if synaptic inhibition is intact. However, application of a similar pairing protocol under GABAARs inhibition by bath application of 2μM bicuculline does induce robust synaptic plasticity, long term potentiation (LTP) or long term

  16. Role of GABAA-Mediated Inhibition and Functional Assortment of Synapses onto Individual Layer 4 Neurons in Regulating Plasticity Expression in Visual Cortex.

    Directory of Open Access Journals (Sweden)

    Ignacio Saez

    Full Text Available Layer 4 (L4 of primary visual cortex (V1 is the main recipient of thalamocortical fibers from the dorsal lateral geniculate nucleus (LGNd. Thus, it is considered the main entry point of visual information into the neocortex and the first anatomical opportunity for intracortical visual processing before information leaves L4 and reaches supra- and infragranular cortical layers. The strength of monosynaptic connections from individual L4 excitatory cells onto adjacent L4 cells (unitary connections is highly malleable, demonstrating that the initial stage of intracortical synaptic transmission of thalamocortical information can be altered by previous activity. However, the inhibitory network within L4 of V1 may act as an internal gate for induction of excitatory synaptic plasticity, thus providing either high fidelity throughput to supragranular layers or transmittal of a modified signal subject to recent activity-dependent plasticity. To evaluate this possibility, we compared the induction of synaptic plasticity using classical extracellular stimulation protocols that recruit a combination of excitatory and inhibitory synapses with stimulation of a single excitatory neuron onto a L4 cell. In order to induce plasticity, we paired pre- and postsynaptic activity (with the onset of postsynaptic spiking leading the presynaptic activation by 10ms using extracellular stimulation (ECS in acute slices of primary visual cortex and comparing the outcomes with our previously published results in which an identical protocol was used to induce synaptic plasticity between individual pre- and postsynaptic L4 excitatory neurons. Our results indicate that pairing of ECS with spiking in a L4 neuron fails to induce plasticity in L4-L4 connections if synaptic inhibition is intact. However, application of a similar pairing protocol under GABAARs inhibition by bath application of 2μM bicuculline does induce robust synaptic plasticity, long term potentiation (LTP or

  17. Differential roles of delay-period neural activity in the monkey dorsolateral prefrontal cortex in visual-haptic crossmodal working memory.

    Science.gov (United States)

    Wang, Liping; Li, Xianchun; Hsiao, Steven S; Lenz, Fred A; Bodner, Mark; Zhou, Yong-Di; Fuster, Joaquín M

    2015-01-13

    Previous studies have shown that neurons of monkey dorsolateral prefrontal cortex (DLPFC) integrate information across modalities and maintain it throughout the delay period of working-memory (WM) tasks. However, the mechanisms of this temporal integration in the DLPFC are still poorly understood. In the present study, to further elucidate the role of the DLPFC in crossmodal WM, we trained monkeys to perform visuo-haptic (VH) crossmodal and haptic-haptic (HH) unimodal WM tasks. The neuronal activity recorded in the DLPFC in the delay period of both tasks indicates that the early-delay differential activity probably is related to the encoding of sample information with different strengths depending on task modality, that the late-delay differential activity reflects the associated (modality-independent) action component of haptic choice in both tasks (that is, the anticipation of the behavioral choice and/or active recall and maintenance of sample information for subsequent action), and that the sustained whole-delay differential activity likely bridges and integrates the sensory and action components. In addition, the VH late-delay differential activity was significantly diminished when the haptic choice was not required. Taken together, the results show that, in addition to the whole-delay differential activity, DLPFC neurons also show early- and late-delay differential activities. These previously unidentified findings indicate that DLPFC is capable of (i) holding the coded sample information (e.g., visual or tactile information) in the early-delay activity, (ii) retrieving the abstract information (orientations) of the sample (whether the sample has been haptic or visual) and holding it in the late-delay activity, and (iii) preparing for behavioral choice acting on that abstract information. PMID:25540412

  18. The advantage of combining MEG and EEG: comparison to fMRI in focally stimulated visual cortex.

    Science.gov (United States)

    Sharon, Dahlia; Hämäläinen, Matti S; Tootell, Roger B H; Halgren, Eric; Belliveau, John W

    2007-07-15

    To exploit the high (millisecond) temporal resolution of magnetoencephalography (MEG) and electroencephalography (EEG) for measuring neuronal dynamics within well-defined brain regions, it is important to quantitatively assess their localizing ability. Previous modeling studies and empirical data suggest that a combination of MEG and EEG signals should yield the most accurate localization, due to their complementary sensitivities. However, these two modalities have rarely been explicitly combined for source estimation in studies of recorded brain activity, and a quantitative empirical assessment of their abilities, combined and separate, is currently lacking. Here we studied early visual responses to focal Gabor patches flashed during subject fixation. MEG and EEG data were collected simultaneously and were compared with the functional MRI (fMRI) localization produced by identical stimuli in the same subjects. This allowed direct evaluation of the localization accuracy of separate and combined MEG/EEG inverse solutions. We found that the localization accuracy of the combined MEG+EEG solution was consistently better than that of either modality alone, using three different source estimation approaches. Further analysis suggests that this improved localization is due to the different properties of the two imaging modalities rather than simply due to increased total channel number. Thus, combining MEG and EEG data is important for high-resolution spatiotemporal studies of the human brain. PMID:17532230

  19. Coupling of cerebral blood flow and oxygen metabolism is conserved for chromatic and luminance stimuli in human visual cortex.

    Science.gov (United States)

    Leontiev, Oleg; Buracas, Giedrius T; Liang, Christine; Ances, Beau M; Perthen, Joanna E; Shmuel, Amir; Buxton, Richard B

    2013-03-01

    The ratio of the changes in cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO(2)) during brain activation is a critical determinant of the magnitude of the blood oxygenation level dependent (BOLD) response measured with functional magnetic resonance imaging (fMRI). Cytochrome oxidase (CO), a key component of oxidative metabolism in the mitochondria, is non-uniformly distributed in visual area V1 in distinct blob and interblob regions, suggesting significant spatial variation in the capacity for oxygen metabolism. The goal of this study was to test whether CBF/CMRO(2) coupling differed when these subpopulations of neurons were preferentially stimulated, using chromatic and luminance stimuli to preferentially stimulate either the blob or interblob regions. A dual-echo spiral arterial spin labeling (ASL) technique was used to measure CBF and BOLD responses simultaneously in 7 healthy human subjects. When the stimulus contrast levels were adjusted to evoke similar CBF responses (mean 65.4% ± 19.0% and 64.6% ± 19.9%, respectively for chromatic and luminance contrast), the BOLD responses were remarkably similar (1.57% ± 0.39% and 1.59% ± 0.35%) for both types of stimuli. We conclude that CBF-CMRO(2) coupling is conserved for the chromatic and luminance stimuli used, suggesting a consistent coupling for blob and inter-blob neuronal populations despite the difference in CO concentration. PMID:23238435

  20. black cat

    Institute of Scientific and Technical Information of China (English)

    杜铁梅

    2016-01-01

    The black cat is a masterpiece of short fiction of Poe. He successfully solved the problem of creating of the horror effect by using scene description, symbol, repetition and first-person narrative methods. And created a complete and unified mysterious terror, achieved the effect of shocking. This paper aims to discuss the mystery in-depth and to enrich the research system in Poe’s novels.

  1. Time Course of Visual Attention in Infant Categorization of Cats versus Dogs: Evidence for a Head Bias as Revealed through Eye Tracking

    Science.gov (United States)

    Quinn, Paul C.; Doran, Matthew M.; Reiss, Jason E.; Hoffman, James E.

    2009-01-01

    Previous looking time studies have shown that infants use the heads of cat and dog images to form category representations for these animal classes. The present research used an eye-tracking procedure to determine the time course of attention to the head and whether it reflects a preexisting bias or online learning. Six- to 7-month-olds were…

  2. Functional MRI activity in the thalamus and occipital cortex of anesthetized dogs induced by monocular and binocular stimulation.

    Science.gov (United States)

    Willis, C K; Quinn, R P; McDonell, W M; Gati, J; Partlow, G; Vilis, T

    2001-07-01

    The neuroanatomy of the mammalian visual system has received considerable attention through electrophysiological study of cats and non-human primates, and through neuroimaging of humans. Canine neuroanatomy, however, has received much less attention, limiting our understanding of canine vision and visual pathways. As an early step in applying blood oxygenation level dependant (BOLD) functional magnetic resonance imaging (fMRI) for veterinary use, we compared visual activity in the thalamus and occipital cortex of anesthetized dogs presented with binocular and monocular visual stimuli. Activity in the left and right thalamus and occipital cortex during monocular stimulation was also compared. Six beagles were presented with a vertical grating visual stimulus and scanned at 4 Tesla. Each dog was scanned twice under each of 3 anesthetic protocols (isoflurane, propofol, and fentanyl/midazolam). We found: 1) significant BOLD activation in the lateral geniculate nucleus (LGN) of the thalamus and the occipital cortex; 2) a significantly larger area of activation in the LGN during monocular stimulation than during binocular stimulation; and 3) that activity in the hemisphere contralateral to the stimulus was not significantly greater than that ipsilateral to it. PMID:11480525

  3. Validación de contenido de un catálogo de estímulos corporales visuales / Validity Content of Stimuli Bodily Catalog

    OpenAIRE

    Rosa Margarita Zuvirie Hernández; Rosalía Vázquez Árevalo; Juan Manuel Mancilla Díaz; Juan José Cervantes Navarrete

    2013-01-01

    Parte de la investigación en Trastornos de la Conducta Alimentaria (TCA) se ha enfocado en la exhibición experimental del ideal de delgadez, donde se han empleado diferentes estímulos (Groesz et al., 2002), sin embargo, estos pocas veces son sometidos a procesos de validación. Por esto, el presente estudio tuvo como objetivo la validación de contenido de un catálogo de imágenes de mujeres delgadas, normopeso y obesas. Participaron ocho mujeres que fueron denominadas Jueces Expertos en TCA y 3...

  4. Cat and Dog Bites

    Science.gov (United States)

    MENU Return to Web version Cat and Dog Bites Cat and Dog Bites How should I take care of a bite from a cat or a dog? Whether from a family pet or a neighborhood stray, cat and dog bites are common. Here are some things you ...

  5. 伴有视觉障碍的偏头痛患者脑枕叶皮层血流灌注研究%Study on Blood Perfusion in Occipital cortex of Migraine with Visual Disorder

    Institute of Scientific and Technical Information of China (English)

    谷涛

    2013-01-01

    Objective Using perfusion weighted imaging to study blood perfusion in occipital cortex of migraine with visual disorder Methods 30 migraine and 14 matched healthy control subjects took magnetic resonance perfusion weighted imaging examination. Flow-sensitive alternating invasion recovery mode was applied to get regional cerebral blood flow map. Perfusion of occipital cortex of brain was divided into hypo-, hyper- and normal perfusion by two radiologists. Results In migraine with aura, 9 abnormal subjects including 6 hypoperfusion and 3 hyperperfusion were found in occipital cortex. Two abnormal perfusion were observed in non-threatened migraine and with visual disorder, which showed hypoperfusion in migraine with visual disorder and hyperperfusion in migraine threatened. Conclusion There was abnormal perfusion in occipital cortex in migraine with visual disorder. Hypoperfusion was mostly found in threatened migraine.%目的 应用磁共振灌注技术来评估伴有视觉障碍的偏头痛患者脑枕叶皮质血流.方法 30例偏头痛患者及14例健康志愿者行动脉质子自旋标记磁共振灌注成像检查,采用FAIR技术获得受试者枕叶血流rCBF图,并由两名高年资放射科医生对图像进行分类,分为灌注不足、正常灌注和过度灌注三类.结果 具有视觉先兆的偏头痛患者中枕叶区域灌注表现异常的有9例:6例为低灌注、3例为高灌注;无先兆但伴有视觉障碍临床症状患者中2例为低灌注;无先兆无视觉障碍患者中2例为高灌注.结论 伴有视觉障碍的偏头痛患者存在脑枕叶皮质血流量异常,有先兆的偏头痛患者多表现低灌注.

  6. An evoked potential mapping of transcallosal projections in the cat

    Directory of Open Access Journals (Sweden)

    A. Cukiert

    1989-03-01

    Full Text Available In ten adult cats anesthetized with ketamine hydrochloride the neocortex was exposed and rectangular pulses (1msec, 0.5 Hz and variable intensity were applied to discrete points of one side and transcallosal evoked potentials were recorded from the other. The stimulation and recording positions were determined on a cartesian map of most of the exposable neocortical areas and the potentials were analysed as to their components, voltage and latency. Passive spread and electrotonic potentials and the effects of increasing frequency were also analysed. The results showed large transcallosal potentials in some areas and an increase of potentials in the caudorostral direction, attaining the highest values in anteromedial areas of the suprasylvian gyrus. Confirming anatomical studies, a few silent spots were found in the motor and somesthetic cortex and in restricted posterior regions of the visual cortex, where small or zero voltages occurred. While causing weak contralateral potentials, stimulation of some posterior sites provoked high voltage potentials in anterior regions of the side being stimulated and in the corresponding area of the opposite site. These posterior sites are. poorly interconnected by the corpus callosum. The L-shaped indirect connection described in this work may be involved in some types of epilepsy and may explain the effectiveness of partial callosotomy in their treatment.

  7. Validación de contenido de un catálogo de estímulos corporales visuales / Validity Content of Stimuli Bodily Catalog

    Directory of Open Access Journals (Sweden)

    Rosa Margarita Zuvirie Hernández

    2013-03-01

    Full Text Available Parte de la investigación en Trastornos de la Conducta Alimentaria (TCA se ha enfocado en la exhibición experimental del ideal de delgadez, donde se han empleado diferentes estímulos (Groesz et al., 2002, sin embargo, estos pocas veces son sometidos a procesos de validación. Por esto, el presente estudio tuvo como objetivo la validación de contenido de un catálogo de imágenes de mujeres delgadas, normopeso y obesas. Participaron ocho mujeres que fueron denominadas Jueces Expertos en TCA y 30 mujeres estudiantes de 19 a 25 años quienes fueron nombradas Jueces No Expertos. Se realizó una búsqueda en Internet de imágenes gratuitas de mujeres en tres categorías de peso: delgadez, normopeso y obesidad. De esta búsqueda resultaron 150 imágenes que se editaron. Posteriormente, fueron aleatorizadas en diapositivas para ser clasificadas por los jueces en delgadez, normopeso y obesidad. Se calculó el índice kappa para saber el acuerdo entre los Jueces Expertos, que reveló un nivel de coincidencia adecuado (kappa = 0.7 - 0.76, p < 0.05. A continuación, se realizó un análisis de las coincidencias entre los Jueces Expertos y No Expertos, se obtuvieron 32 imágenes de delgadez, 38 de obesidad y 12 de normopeso con un porcentaje de acuerdo del 70 al 100 %. La validación de contenido de este catálogo es una aproximación a la presentación experimental de estímulos que representan el ideal de delgadez.

  8. 出生后不同鼠龄大鼠视皮质差异基因表达谱分析%Expression profiles analysis of differential genes in rat visual cortex depending upon postnatal days by microarray

    Institute of Scientific and Technical Information of China (English)

    杨柳; 瞿远珍; 李岱; 吴开力

    2014-01-01

    Background Visual adaptive mechanism of mammalian is close responsible for the development of visual cortex.The various genes with different biological functions in different developing stages of visual cortex participate in regulation of visual development.To investigate the differential expression profiles of various genes in different ages of rat cortex can offer basis and evidence for the study of visual development.Objective Present study aimed to investigate the genes that changed continuously in the postnatal developmental process of rat visual cortex by microarray analysis of visual cortex RNA.Methods Sixty clean SD rats were grouped numbered and randomized into the postnatal day 0 group (P0,n =20),before eye opening group (postnatal day 10,P10,n =15),before the critical period of visual cortex growth group (postnatal day 20,P20,n =15) and the end of development of visual cortex group(postnatal day 45,P45,n=15).The rats were sacrificed at corresponding time point respectively,and the fresh visual cortex were obtained for the extraction of total RNA and microarray analysis.Genes exhibiting changes in expression by≥2.0 folds were further confirmed using real-time PCR(RT-PCR).In order to evaluate the association of differential gene expression with growth,the postnatal stages were paired as 36 groups with the 3 pairs for each target gene (P45/P0,P20/P0,P10/P0).Results Microarray analysis showed that the gene with differential ratio ≥ 2.0 folds in rat visual cortex included Akap7,Asam,Casp3,Cxcr4,Egr1,Ennp2,Fabp7,Gpr88,Inpp5d,Rpsa,Stk32c and Vamp1.Real-time PCR verified that 24 genes form 26 probe sets had the same-phase regulating tendency,including 20 up-regulating probe sets and 6 down-regulating probe sets.The homodromous expressing tendency was seen in Akap7,Asam,Casp3,Cxcr4,Egr1,Ennp2,Fabp7,Inpp5d,Rpsa and Vamp1 genes between microarray analysis and RT-PCR.However,reverse expressions were found in the P45/P0 of Gpr88 and Stk32c genes,showing the up

  9. Acute lesions of primary visual cortical areas in adult cats inactivate responses of neurons in higher visual cortices%急性毁损猫的初级视区使高级视区细胞失去对视觉刺激的诱发反应

    Institute of Scientific and Technical Information of China (English)

    张辉; 孟建军; 王珂; 刘瑞龙; 奚敏敏; 华田苗

    2012-01-01

    心理物理学研究提示,初级视区毁损后的视觉残留可能是通过外纹状皮层的神经网络重组介导的,但缺少支持这一假说的电生理实验证据.采用在体细胞外单细胞记录技术,该研究分别检测了初级视区(主要包括17和18区)急性毁损猫和正常对照猫的高级视区(包括19、20和21区)神经元对不同视觉刺激的反应性.结果显示,与对照相比,急性毁损初级视区使99.3%的高级视区神经元丧失对运动光栅刺激的诱发反应,93%的神经元丧失对闪光刺激的反应.该结果表明,急性毁损成年猫的初级视皮层可能会导致其绝大部分视觉能力丧失.在幼年期实施初级视皮层毁损后,成年猫出现的残留视觉可能主要是由于手术后皮层下神经核团与外纹状皮层之间的通路重组引起的.%Psychophysical studies suggest that lateral extrastriate visual cortical areas in cats may mediate the sparing of vision largely by network reorganization following lesions of early visual cortical areas.To date,however,there is little direct physiological evidence to support this hypothesis.Using in vivo single-unit recording techniques,we examined the response of neurons in areas 19,21,and 20 to different types of visual stimulation in cats with or without acute bilateral lesions in areas 17 and 18.Our results showed that,relative to the controls,acute lesions inactivated the response of 99.3% of neurons to moving gratings and 93% of neurons to flickering square stimuli in areas 19,21,and 20.These results indicated that acute lesions of primary visual areas in adult cats may impair most visual abilities.Sparing of vision in cats with neonatal lesions in early visual cortical areas may result largely from a postoperative reorganization of visual pathways from subcortical nucleus to extrastriate visual cortical areas.

  10. Chemosensory Learning in the Cortex

    Directory of Open Access Journals (Sweden)

    Edmund eRolls

    2011-09-01

    Full Text Available Taste is a primary reinforcer. Olfactory-taste and visual-taste association learning takes place in the primate including human orbitofrontal cortex to build representations of flavour. Rapid reversal of this learning can occur using a rule-based learning system that can be reset when an expected taste or flavour reward is not obtained, that is by negative reward prediction error, to which a population of neurons in the orbitofrontal cortex responds. The representation in the orbitofrontal cortex but not the primary taste or olfactory cortex is of the reward value of the visual / olfactory / taste / input as shown by devaluation experiments in which food is fed to satiety, and by correlations with the activations with subjective pleasantness ratings in humans. Sensory-specific satiety for taste, olfactory, visual, and oral somatosensory inputs produced by feeding a particular food to satiety are implemented it is proposed by medium-term synaptic adaptation in the orbitofrontal cortex. Cognitive factors, including word-level descriptions, modulate the representation of the reward value of food in the orbitofrontal cortex, and this effect is learned it is proposed by associative modification of top-down synapses onto neurons activated by bottom-up taste and olfactory inputs when both are active in the orbitofrontal cortex. A similar associative synaptic learning process is proposed to be part of the mechanism for the top-down attentional control to the reward value vs the sensory properties such as intensity of taste and olfactory inputs in the orbitofrontal cortex, as part of a biased activation theory of selective attention.

  11. Cat Scratch Disease

    Science.gov (United States)

    Cat scratch disease (CSD) is an illness caused by the bacterium Bartonella henselae. Almost half of all cats carry the infection ... symptoms of CSD, call your doctor. Centers for Disease Control and Prevention

  12. Differential Functional Roles of Slow-Wave and Oscillatory-Alpha Activity in Visual Sensory Cortex during Anticipatory Visual–Spatial Attention

    OpenAIRE

    Grent-'t-Jong, Tineke; Boehler, C. Nicolas; Kenemans, J Leon; Woldorff, Marty G.

    2011-01-01

    Markers of preparatory visual–spatial attention in sensory cortex have been described both as lateralized, slow-wave event-related potential (ERP) components and as lateralized changes in oscillatory-electroencephalography alpha power, but the roles of these markers and their functional relationship are still unclear. Here, 3 versions of a visual–spatial cueing paradigm, differing in perceptual task difficulty and/or response instructions, were used to investigate the functional relationships...

  13. The visual corticostriatal loop through the tail of the caudate: Circuitry and function

    Directory of Open Access Journals (Sweden)

    Carol A Seger

    2013-12-01

    Full Text Available Although high level visual cortex projects to a specific region of the striatum, the tail of the caudate, and participates in corticostriatal loops, the function of this visual corticostriatal system is not well understood. This article first reviews what is known about the anatomy of the visual corticostriatal loop across mammals, including rodents, cats, monkeys, and humans. Like other corticostriatal systems, the visual corticostriatal system includes both closed loop components (recurrent projections that return to the originating cortical location and open loop components (projections that terminate in other neural regions. The article then reviews what previous empircal research has shown about the function of the tail of the caudate. The article finally addresses the possible functions of the closed and open loop connections of the visual loop in the context of theories and computational models of corticostriatal function.

  14. Effects of the Bee Venom Herbal Acupuncture on the Neurotransmitters of the Rat Brain Cortex

    Directory of Open Access Journals (Sweden)

    Hyoung-Seok Yun

    2001-02-01

    Full Text Available In order to study the effects of bee venom Herbal Acupuncture on neurotransmitters in the rat brain cortex, herbal acupuncture with bee venom group and normal saline group was performed at LI4 bilaterally of the rat. the average optical density of neurotransmitters from the cerebral cortex was analysed 30 minutes after the herbal aqupuncture, by the immunohistochemistry. The results were as follows: 1. The density of NADPH-diaphorase in bee venom group was increased significantly at the motor cortex, visual cortex, auditory cortex, cingulate cortex, retrosplenial cortex and perirhinal cortex compared to the normal saline group. 2. The average optical density of vasoactive intestinal peptide in bee venom group had significant changes at the insular cortex, retrosplenial cortex and perirhinal cortex, compared to the normal saline group. 3. The average optical density of neuropeptide-Y in bee venom group increased significantly at the visual cortex and cingulate cortex, compared to the normal saline group.

  15. Getting a CAT Scan

    Medline Plus

    Full Text Available ... Crushes What's a Booger? Getting a CAT Scan (Video) KidsHealth > For Kids > Getting a CAT Scan (Video) Print A A A Text Size en español Obtención de una tomografía computada (video) CAT stands for "computerized axial tomography." Translated, that ...

  16. Getting a CAT Scan

    Medline Plus

    Full Text Available ... Here's Help White House Lunch Recipes Getting a CAT Scan (Video) KidsHealth > For Kids > Getting a CAT Scan (Video) Print A A A Text Size en español Obtención de una tomografía computada (video) CAT stands for "computerized axial tomography." Translated, that means ...

  17. Discospondylitis in a cat

    International Nuclear Information System (INIS)

    The incidence and causative agents of discospondylitis in cats are unknown. This report describes a cat with radiologic changes consistent with discospondylitis and concurrent urinary tract infection. As in dogs, discospondylitis should be the primary rule out for vertebral end plate lysis in cats

  18. Getting a CAT Scan

    Medline Plus

    Full Text Available ... Snowboarding, Skating Crushes What's a Booger? Getting a CAT Scan (Video) KidsHealth > For Kids > Getting a CAT Scan (Video) Print A A A Text Size en español Obtención de una tomografía computada (video) CAT stands for "computerized axial tomography." Translated, that means ...

  19. Pulmonary thromboembolism in cats.

    Science.gov (United States)

    Schermerhorn, Thomas; Pembleton-Corbett, Julie R; Kornreich, Bruce

    2004-01-01

    Pulmonary thromboembolism (PTE) is rarely diagnosed in cats, and the clinical features of the disease are not well known. PTE was diagnosed at postmortem examination in 17 cats, a prevalence of 0.06% over a 24-year period. The age of affected cats ranged from 10 months to 18 years, although young (10 years) cats were more commonly affected than were middle-aged cats. Males and females were equally affected. The majority of cats with PTE (n = 16) had concurrent disease, which was often severe. The most common diseases identified in association with PTE were neoplasia, anemia of unidentified cause, and pancreatitis. Cats with glomerulonephritis, encephalitis, pneumonia, heart disease, and hepatic lipidosis were also represented in this study. Most cats with PTE demonstrated dyspnea and respiratory distress before death or euthanasia, but PTE was not recognized ante mortem in any cat studied. In conclusion, PTE can affect cats of any age and is associated with a variety of systemic and inflammatory disorders. It is recommended that the same clinical criteria used to increase the suspicion of PTE in dogs should also be applied to cats. PMID:15320593

  20. An olfactory input to the hippocampus of the cat: Field potential analysis

    NARCIS (Netherlands)

    Habets, A.M.M.C.; Lopes Da Silva, F.H.; Mollevanger, W.J.

    1980-01-01

    Hippocampal responses to electrical stimulation of the prepyriform cortex in the cat were studied both in acute experiments under halothane anesthesia and in awake cats with chronically indwelling electrodes. Analysis of field potentials and unit activity indicated the extent to which different hipp

  1. The life of the cortical column: opening the domain of functional architecture of the cortex (1955-1981).

    Science.gov (United States)

    Haueis, Philipp

    2016-09-01

    The concept of the cortical column refers to vertical cell bands with similar response properties, which were initially observed by Vernon Mountcastle's mapping of single cell recordings in the cat somatic cortex. It has subsequently guided over 50 years of neuroscientific research, in which fundamental questions about the modularity of the cortex and basic principles of sensory information processing were empirically investigated. Nevertheless, the status of the column remains controversial today, as skeptical commentators proclaim that the vertical cell bands are a functionally insignificant by-product of ontogenetic development. This paper inquires how the column came to be viewed as an elementary unit of the cortex from Mountcastle's discovery in 1955 until David Hubel and Torsten Wiesel's reception of the Nobel Prize in 1981. I first argue that Mountcastle's vertical electrode recordings served as criteria for applying the column concept to electrophysiological data. In contrast to previous authors, I claim that this move from electrophysiological data to the phenomenon of columnar responses was concept-laden, but not theory-laden. In the second part of the paper, I argue that Mountcastle's criteria provided Hubel Wiesel with a conceptual outlook, i.e. it allowed them to anticipate columnar patterns in the cat and macaque visual cortex. I argue that in the late 1970s, this outlook only briefly took a form that one could call a 'theory' of the cerebral cortex, before new experimental techniques started to diversify column research. I end by showing how this account of early column research fits into a larger project that follows the conceptual development of the column into the present. PMID:27325058

  2. Simulation Study of the Effect on Visual Cortex Neural Activation during Epidural Electrical Stimulation%经硬脑膜电刺激对视皮层神经活动影响的仿真研究

    Institute of Scientific and Technical Information of China (English)

    夏楠; 侯文生; 章毅; 郑小林; 吴小鹰; 阴正勤; JIANGYingtao

    2011-01-01

    The epidural electrical stimulation applied on the visual cortex is a new tachnical idea for vision rehabilitation. Previous researches have shown that the effects on visual cortex during epidural electrical stimulation can be qualitatively described by using the activating function, but this method can not accurately describe the scope of the electrode. In this paper we introduced neuron model into original model and quantify the effect of different stimulation waveforms and parameters on the scope of the electrode. A neuron model was developed and introduced into the finite element model of visual cortex. A Fourier finite element was the used to calculate the potential distribution in the model of visual cortex which was stimulated by bipulse, exponential pulse and sinusoidal pulse. The voltages were then applied to the neuron model to determine neural activation. The number of excitatory neurons were calculated as a function of scope of the electrode. The simulation results indicated that different stimulus waveforms and parameters caused different numbers of excitatory neuron region. In addition, the stimulation result was affected by anatomic structure.%经硬脑膜对视皮层电刺激为视觉功能修复提供了一种新的技术思路.前期的仿真工作利用激活函数定性研究了经硬脑膜电刺激对视皮层的作用效果,本研究在原有模型基础上引入神经无模型,定量研究不同刺激波形及参数对电极作用范围的影响.该方法将已建立的神经元模型耦合到视皮层区域有限元模型中,利用傅里叶-有限元方法分别计算双脉冲、指数脉冲和正弦波刺激下视皮层区域模型内的场电位,将电位加载到神经元模型上,观察神经元是否发生兴奋,以神经元区域兴奋个数判定电极的作用范围.仿真结果表明,该方法能较好的表达刺激的响应范围:不同刺激波形及参数引起的神经元区域兴奋数量不同,且解剖结构会影响刺激

  3. Input-dependent wave attenuation in a critically-balanced model of cortex.

    Directory of Open Access Journals (Sweden)

    Xiao-Hu Yan

    Full Text Available A number of studies have suggested that many properties of brain activity can be understood in terms of critical systems. However it is still not known how the long-range susceptibilities characteristic of criticality arise in the living brain from its local connectivity structures. Here we prove that a dynamically critically-poised model of cortex acquires an infinitely-long ranged susceptibility in the absence of input. When an input is presented, the susceptibility attenuates exponentially as a function of distance, with an increasing spatial attenuation constant (i.e., decreasing range the larger the input. This is in direct agreement with recent results that show that waves of local field potential activity evoked by single spikes in primary visual cortex of cat and macaque attenuate with a characteristic length that also increases with decreasing contrast of the visual stimulus. A susceptibility that changes spatial range with input strength can be thought to implement an input-dependent spatial integration: when the input is large, no additional evidence is needed in addition to the local input; when the input is weak, evidence needs to be integrated over a larger spatial domain to achieve a decision. Such input-strength-dependent strategies have been demonstrated in visual processing. Our results suggest that input-strength dependent spatial integration may be a natural feature of a critically-balanced cortical network.

  4. Growth of dendritic spines and its synapses in pyramidal neurons of visual cortex in mice%小鼠视皮质锥体神经元树突棘和突触的发育

    Institute of Scientific and Technical Information of China (English)

    赵凯冰; 崔占军; 陈文静; 牛艳丽

    2012-01-01

    目的:通过观察小鼠视皮质锥体神经元正常发育过程中树突棘的形态变化,研究树突棘与突触的发生及其可塑性的关系.方法:利用DiI散射方法标记小鼠视皮质锥体神经元树突棘,使用共聚焦显微镜对其进行观察分析;同时利用透射电子显微镜技术,对树突棘的超微结构进行分析.结果:树突棘的形态大小及其密度随发育而变化;成熟树突棘内部存在滑面内质网与棘器;树突棘参与了大部分突触后成分的构成.结论:树突棘的发育过程与突触的形成以及突触可塑性密切相关.%Objective:To explore the relationship among the synaptogenesis, synaptic plasticity and dendritic spines by observing the morphological changes of dendritic spines of pyramidal neurons in the visual cortex of mice during development Methods: The dendritic spines of the pyramidal neurons of mouse visual cortex were labeled with Dil and observed under a confocal microscope. The ultrastructures of dendritic spines were observed by means of transmission electron microscopy. Results:The morphology and density of dendritic spines were changing with mouse growth in response to neuronal activity. The smooth endoplasmic reticulum and spine apparatus were detectable in matured dendritic spines. And, dendritic spines offered most parts of the postsynaptic element. Conclusion :These findings suggest that dendritic spines be close related synaptogenesis and synaptic plasticity.

  5. Geometric Representation Of Visual Data In The Cortex Of Primates: Computer Reconstruction And Modeling Of Neo-Cortical Map And Column Systems

    Science.gov (United States)

    Schwartz, Eric

    1988-08-01

    Much of vertebrate midbrain and mammalian cortex is dedicated to two-dimensional "maps" in which two or more stimulus parameters are encoded by the position of neural activation in the map. Moreover, there are a large number of such maps which interact in an unknown fashion to yield a unified perception of the world. Our research program is based on studying the structure and function of brain maps. In the present paper, we review a recently constructed system of computer aided neuro-anatomy which allows high resolution texture mapped models of cortical surfaces in two and three dimensions to be displayed and manipulated. At the same time, this work demonstrates some of the basic geometric patterns of architecture of the primate brain, such as columnar and topographic mapping.

  6. A tortoiseshell male cat

    DEFF Research Database (Denmark)

    Pedersen, A. S.; Berg, Lise Charlotte; Almstrup, Kristian;

    2014-01-01

    Tortoiseshell coat color is normally restricted to female cats due to X-linkage of the gene that encodes the orange coat color. Tortoiseshell male cats do, however, occur at a low frequency among tortoiseshell cats because of chromosome aberrations similar to the Klinefelter syndrome in man...... tissue from a tortoiseshell male cat referred to us. Chromosome analysis using RBA-banding consistently revealed a 39,XXY karyotype. Histological examinations of testis biopsies from this cat showed degeneration of the tubules, hyperplasia of the interstitial tissue, and complete loss of germ cells....... Immunostaining using anti-vimentin and anti-VASA (DDX4) showed that only Sertoli cells and no germ cells were observed in the testicular tubules. As no sign of spermatogenesis was detected, we conclude that this is a classic case of a sterile, male tortoiseshell cat with a 39,XXY chromosome complement. © 2013 S...

  7. Extrastriate cortical areas activated during visual discrimination in man

    DEFF Research Database (Denmark)

    Roland, PE

    1981-01-01

    The regional cerebral blood flow (rCBF) was measured in 254 different regions of the human extrastriate cerebral cortex during rest and during visual shape discrimination. Visual shape discrimination increased the rCBF markedly in the frontal eye fields, the upper part of the prefrontal cortex......, the lateral occipital cortex and the superior parietal cortex. Moderate increases of rCBF appeared in the inferotemporal cortex, the parietotemporo-occipital region and scattered in the lateral part of the prefrontal cortex....

  8. Computed tomography of nonanesthetized cats with upper airway obstruction.

    Science.gov (United States)

    Stadler, Krystina; O'Brien, Robert

    2013-01-01

    Upper airway obstruction is a potentially life-threatening problem in cats and for which a noninvasive, sensitive method rapid diagnosis is needed. The purposes of this prospective study were to describe a computed tomography (CT) technique for nonanesthetized cats with upper airway obstruction, CT characteristics of obstructive diseases, and comparisons between CT findings and findings from other diagnostic tests. Ten cats with clinical signs of upper airway obstruction were recruited for the study. Four cats with no clinical signs of upper airway obstruction were recruited as controls. All cats underwent computed tomography imaging without sedation or anesthesia, using a 16-slice helical CT scanner and a previously described transparent positional device. Three-dimensional (3D) internal volume rendering was performed on all CT image sets and 3D external volume rendering was also performed on cats with evidence of mass lesions. Confirmation of upper airway obstruction was based on visual laryngeal examination, endoscopy, fine-needle aspirate, biopsy, or necropsy. Seven cats were diagnosed with intramural upper airway masses, two with laryngotracheitis, and one with laryngeal paralysis. The CT and 3D volume-rendered images identified lesions consistent with upper airway disease in all cats. In cats with mass lesions, CT accurately identified the mass and location. Findings from this study supported the use of CT imaging as an effective technique for diagnosing upper airway obstruction in nonanesthetized cats. PMID:23441677

  9. Enhancement of Visual Motion Detection Thresholds in Early Deaf People

    Science.gov (United States)

    Shiell, Martha M.; Champoux, François; Zatorre, Robert J.

    2014-01-01

    In deaf people, the auditory cortex can reorganize to support visual motion processing. Although this cross-modal reorganization has long been thought to subserve enhanced visual abilities, previous research has been unsuccessful at identifying behavioural enhancements specific to motion processing. Recently, research with congenitally deaf cats has uncovered an enhancement for visual motion detection. Our goal was to test for a similar difference between deaf and hearing people. We tested 16 early and profoundly deaf participants and 20 hearing controls. Participants completed a visual motion detection task, in which they were asked to determine which of two sinusoidal gratings was moving. The speed of the moving grating varied according to an adaptive staircase procedure, allowing us to determine the lowest speed necessary for participants to detect motion. Consistent with previous research in deaf cats, the deaf group had lower motion detection thresholds than the hearing. This finding supports the proposal that cross-modal reorganization after sensory deprivation will occur for supramodal sensory features and preserve the output functions. PMID:24587381

  10. Enhancement of visual motion detection thresholds in early deaf people.

    Science.gov (United States)

    Shiell, Martha M; Champoux, François; Zatorre, Robert J

    2014-01-01

    In deaf people, the auditory cortex can reorganize to support visual motion processing. Although this cross-modal reorganization has long been thought to subserve enhanced visual abilities, previous research has been unsuccessful at identifying behavioural enhancements specific to motion processing. Recently, research with congenitally deaf cats has uncovered an enhancement for visual motion detection. Our goal was to test for a similar difference between deaf and hearing people. We tested 16 early and profoundly deaf participants and 20 hearing controls. Participants completed a visual motion detection task, in which they were asked to determine which of two sinusoidal gratings was moving. The speed of the moving grating varied according to an adaptive staircase procedure, allowing us to determine the lowest speed necessary for participants to detect motion. Consistent with previous research in deaf cats, the deaf group had lower motion detection thresholds than the hearing. This finding supports the proposal that cross-modal reorganization after sensory deprivation will occur for supramodal sensory features and preserve the output functions.

  11. Contour extracting networks in early extrastriate cortex

    NARCIS (Netherlands)

    Dumoulin, Serge O.; Hess, Robert F.; May, Keith A.; Harvey, Ben M.; Rokers, Bas; Barendregt, Martijn

    2014-01-01

    Neurons in the visual cortex process a local region of visual space, but in order to adequately analyze natural images, neurons need to interact. The notion of an ''association field'' proposes that neurons interact to extract extended contours. Here, we identify the site and properties of contour i

  12. No evidence for early modulation of evoked responses in primary visual cortex to irrelevant probe stimuli presented during the attentional blink.

    Directory of Open Access Journals (Sweden)

    Oscar Jacoby

    Full Text Available BACKGROUND: During rapid serial visual presentation (RSVP, observers often miss the second of two targets if it appears within 500 ms of the first. This phenomenon, called the attentional blink (AB, is widely held to reflect a bottleneck in the processing of rapidly sequential stimuli that arises after initial sensory registration is complete (i.e., at a relatively late, post-perceptual stage of processing. Contrary to this view, recent fMRI studies have found that activity in the primary visual area (V1, which represents the earliest cortical stage of visual processing, is attenuated during the AB. Here we asked whether such changes in V1 activity during the AB arise in the initial feedforward sweep of stimulus input, or instead reflect the influence of feedback signals from higher cortical areas. METHODOLOGY/PRINCIPAL FINDINGS: EEG signals were recorded while participants monitored a sequential stream of distractor letters for two target digits (T1 and T2. Neural responses associated with an irrelevant probe stimulus presented simultaneously with T2 were measured using an ERP marker--the C1 component--that reflects initial perceptual processing of visual information in V1. As expected, T2 accuracy was compromised when the inter-target interval was brief, reflecting an AB deficit. Critically, however, the magnitude of the early C1 component evoked by the probe was not reduced during the AB. CONCLUSIONS/SIGNIFICANCE: Our finding that early sensory processing of irrelevant probe stimuli is not suppressed during the AB is consistent with theoretical models that assume that the bottleneck underlying the AB arises at a post-perceptual stage of processing. This suggests that reduced neural activity in V1 during the AB is driven by re-entrant signals from extrastriate areas that regulate early cortical activity via feedback connections with V1.

  13. That Fat Cat

    Science.gov (United States)

    Lambert, Phyllis Gilchrist

    2012-01-01

    This activity began with a picture book, Nurit Karlin's "Fat Cat On a Mat" (HarperCollins; 1998). The author and her students started their project with a 5-inch circular template for the head of their cats. They reviewed shapes as they drew the head and then added the ears and nose, which were triangles. Details to the face were added when…

  14. Cat Scratch Colon

    Directory of Open Access Journals (Sweden)

    M. Lourdes Ruiz-Rebollo

    2011-01-01

    Full Text Available Over the past few years, we have read several publications regarding the term “cat scratch colon.” This neologism was developed to define some bright red linear markings seen in the colonic mucosa that resemble scratches made by a cat. We would like to communicate a recent case attended at our institution.

  15. Hyperadrenocorticism in a cat.

    Science.gov (United States)

    Zerbe, C A; Nachreiner, R F; Dunstan, R W; Dalley, J B

    1987-03-01

    A diabetic cat with hyperadrenocorticism had polydipsia, polyuria, ventral abdominal alopecia, thin dry skin, and a pendulous abdomen. Results of laboratory testing indicated persistent resting hypercortisolemia, hyperresponsiveness of the adrenal glands (increased cortisol concentration) to ACTH gel, and no suppression of cortisol concentrations after administration of dexamethasone at 0.01 or 1.0 mg/kg of body weight. Necropsy revealed a pituitary gland tumor, bilateral adrenal hyperplasia, hepatic neoplasia, and demodicosis. Adrenal gland function was concurrently assessed in 2 cats with diabetes mellitus. One cat had resting hypercortisolemia, and both had hyperresponsiveness to ACTH gel (increased cortisol concentration) at one hour. After administration of dexamethasone (0.01 and 1.0 mg/kg), the diabetic cats appeared to have normal suppression of cortisol concentrations. The effects of mitotane were investigated in 4 clinically normal cats. Adrenocortical suppression of cortisol production occurred in 2 of 4 cats after dosages of 25, 37, and 50 mg/kg. Three cats remained clinically normal throughout the study. One cat experienced vomiting, diarrhea, and anorexia.

  16. Getting a CAT Scan

    Medline Plus

    Full Text Available ... Dictionary of Medical Words En Español What Other Kids Are Reading Movie: Digestive System Winter Sports: Sledding, ... Booger? Getting a CAT Scan (Video) KidsHealth > For Kids > Getting a CAT Scan (Video) Print A A ...

  17. Getting a CAT Scan

    Medline Plus

    Full Text Available ... Skiing, Snowboarding, Skating Crushes What's a Booger? Getting a CAT Scan (Video) KidsHealth > For Kids > Getting a CAT Scan (Video) Print A A A Text Size en español Obtención de ...

  18. Obesity in show cats.

    Science.gov (United States)

    Corbee, R J

    2014-12-01

    Obesity is an important disease with a high prevalence in cats. Because obesity is related to several other diseases, it is important to identify the population at risk. Several risk factors for obesity have been described in the literature. A higher incidence of obesity in certain cat breeds has been suggested. The aim of this study was to determine whether obesity occurs more often in certain breeds. The second aim was to relate the increased prevalence of obesity in certain breeds to the official standards of that breed. To this end, 268 cats of 22 different breeds investigated by determining their body condition score (BCS) on a nine-point scale by inspection and palpation, at two different cat shows. Overall, 45.5% of the show cats had a BCS > 5, and 4.5% of the show cats had a BCS > 7. There were significant differences between breeds, which could be related to the breed standards. Most overweight and obese cats were in the neutered group. It warrants firm discussions with breeders and cat show judges to come to different interpretations of the standards in order to prevent overweight conditions in certain breeds from being the standard of beauty. Neutering predisposes for obesity and requires early nutritional intervention to prevent obese conditions. PMID:24612018

  19. CAT questions and answers

    International Nuclear Information System (INIS)

    This document, prepared in February 1993, addresses the most common questions asked by APS Collaborative Access Teams (CATs). The answers represent the best judgment on the part of the APS at this time. In some cases, details are provided in separate documents to be supplied by the APS. Some of the answers are brief because details are not yet available. The questions are separated into five categories representing different aspects of CAT interactions with the APS: (1) Memorandum of Understanding (MOU), (2) CAT Beamline Review and Construction, (3) CAT Beamline Safety, (4) CAT Beamline Operations, and (5) Miscellaneous. The APS plans to generate similar documents as needed to both address new questions and clarify answers to present questions

  20. State of cat genomics.

    Science.gov (United States)

    O'Brien, Stephen J; Johnson, Warren; Driscoll, Carlos; Pontius, Joan; Pecon-Slattery, Jill; Menotti-Raymond, Marilyn

    2008-06-01

    Our knowledge of cat family biology was recently expanded to include a genomics perspective with the completion of a draft whole genome sequence of an Abyssinian cat. The utility of the new genome information has been demonstrated by applications ranging from disease gene discovery and comparative genomics to species conservation. Patterns of genomic organization among cats and inbred domestic cat breeds have illuminated our view of domestication, revealing linkage disequilibrium tracks consequent of breed formation, defining chromosome exchanges that punctuated major lineages of mammals and suggesting ancestral continental migration events that led to 37 modern species of Felidae. We review these recent advances here. As the genome resources develop, the cat is poised to make a major contribution to many areas in genetics and biology.

  1. Distinct changes in CREB phosphorylation in frontal cortex and striatum during contingent and non-contingent performance of a visual attention task

    Directory of Open Access Journals (Sweden)

    Mirjana eCarli

    2011-10-01

    Full Text Available The cyclic-AMP response element binding protein (CREB family of transcription factors has been implicated in numerous forms of behavioural plasticity. We investigated CREB phosphorylation along some nodes of corticostriatal circuitry such as frontal cortex (FC and dorsal (caudate putamen, CPu and ventral (nucleus accumbens, NAC striatum in response to the contingent or non-contingent performance of the five-choice serial reaction time task (5-CSRTT used to assess visuospatial attention. Three experimental manipulations were used; an attentional performance group (contingent, master, a group trained previously on the task but for whom the instrumental contingency coupling responding with stimulus detection and reward was abolished (non-contingent, yoked and a control group matched for food deprivation and exposure to the test apparatus (untrained. Rats trained on the 5-CSRTT (both master and yoked had higher levels of CREB protein in the FC, CPu and NAC compared to untrained controls. Despite the divergent behaviour of master and yoked rats CREB activity in the FC was not substantially different. In rats performing the 5-CSRTT (master, CREB activity was completely abolished in the CPu whereas in the NAC it remained unchanged. In contrast, CREB phosphorylation in CPu and NAC increased only when the contingency changed from goal-dependent to goal-independent reinforcement (yoked. The present results indicate that up-regulation of CREB protein expression across cortical and striatal regions possibly reflects the extensive instrumental learning and performance whereas increased CREB activity in striatal regions may signal the unexpected change in the relationship between instrumental action and reinforcement.

  2. Effect of dark rearing on development of visual sense and proteomics of visual cortex in growing rat%避光对生长发育期大鼠视觉及视皮层蛋白质组学的影响

    Institute of Scientific and Technical Information of China (English)

    曲露; 张晔; 衡斌; 刘燕强

    2013-01-01

    Background Previous study on critical period plasticity in local cortical circuits primarily was only to test the role of some proteins in visual cortex on visual development based on the existed neural signals expression system,but whole containing proteins analysis in cortical circuits is lack.To perform a whole containing proteins analysis has an important significance for critical period plasticity study.Objective This study was to investigate the influence of dark rearing on visual sense and proteomics in visual cortex for growing rat.Methods Two SD female rats were fed in two cages together with 12 newborn rats on the same day respectively,and half number of newborn rats were exchanged each other from first day after delivering and marked by eartipping.The newborn rats in a cage were bred in the dark environment for 40 days,and newborn rats in other cage were bred in the nature environment as controls.The blink response of rats to nearby object was examined and compared between the two groups of rats.Then three rats from two cages were sacrificed respectively and bilateral primary visual cortex tissue was isolated.Proteomics in rat primary visual cortex was detected by two-dimensional electrophoresis and mass spectrometry and the result was checked from database.Then the survival rats in the dark environment returned to the nature environment for 10 days,and the blink response of rats to nearby object were compared with that of agematched rats in the natural environment.The use and care of experimental rats followed the instruction of Ethic Committee of Nankai University.Results The blink response of rats was (0.33 ± 0.35) times in the dark environment for 40-day group,and that in the natural environment for 40-day group was (6.42±0.68) times,with a significant difference between them (t =24.38,P<0.01).After returned to natural environment for 10 days,the blink response times of rats were less than those of the natural environment group ([5.00±1

  3. For whom the bell tolls: periodic reactivation of sensory cortex in the gamma band as a substrate of visual working memory maintenance

    Directory of Open Access Journals (Sweden)

    Marieke Karlijn Van Vugt

    2014-09-01

    Full Text Available Working memory (WM is central to human cognition as it allows information to be kept online over brief periods of time and facilitates its usage in cognitive operations (Luck & Vogel, 2013. How this information maintenance actually is implemented is still a matter of debate. Several independent theories of WM, derived, respectively, from behavioral studies and neural considerations, advance the idea that items in WM decay over time and must be periodically reactivated. In this proposal, we show how recent data from intracranial EEG and attention research naturally leads to a simple model of such reactivation in the case of sensory memories. Specifically, in our model the amplitude of high-frequency activity (>50 Hz, in the gamma-band underlies the representation of items in high-level visual areas. This activity decreases to noise-levels within 500 ms, unless it is reactivated. We propose that top-down attention, which targets multiple sensory items in a cyclical or rhythmic fashion at around 6 to 10 Hz, reactivates these decaying gamma-band representations. Therefore, working memory capacity is essentially the number of representations that can simultaneously be kept active by a rhythmically sampling attentional spotlight given the known decay rate. Since attention samples at 6-10 Hz, the predicted WM capacity is 3-5 items, in agreement with empirical findings.

  4. Changes in the axonal conduction velocity of pyramidal tract neurons in the aged cat.

    Science.gov (United States)

    Xi, M C; Liu, R H; Engelhardt, J K; Morales, F R; Chase, M H

    1999-01-01

    The present study was undertaken to determine whether age-dependent changes in axonal conduction velocity occur in pyramidal tract neurons. A total of 260 and 254 pyramidal tract neurons were recorded extracellularly in the motor cortex of adult control and aged cats, respectively. These cells were activated antidromically by electrical stimulation of the medullary pyramidal tract. Fast- and slow-conducting neurons were identified according to their axonal conduction velocity in both control and aged cats. While 51% of pyramidal tract neurons recorded in the control cats were fast conducting (conduction velocity greater than 20 m/s), only 26% of pyramidal tract neurons in the aged cats were fast conducting. There was a 43% decrease in the median conduction velocity for the entire population of pyramidal tract neurons in aged cats when compared with that of pyramidal tract neurons in the control cats (P cats. However, the regression slope was significantly reduced in aged cats. This reduction was due to the appearance of a group of pyramidal tract neurons with relatively shorter spike durations but slower axonal conduction velocities in the aged cat. Sample intracellular data confirmed the above results. These observations form the basis for the following conclusions: (i) there is a decrease in median conduction velocity of pyramidal tract neurons in aged cats; (ii) the reduction in the axonal conduction velocity of pyramidal tract neurons in aged cats is due, in part, to fibers that previously belonged to the fast-conducting group and now conduct at slower velocity. PMID:10392844

  5. IndexCat

    Data.gov (United States)

    U.S. Department of Health & Human Services — IndexCat provides access to the digitized version of the printed Index-Catalogue of the Library of the Surgeon General's Office; eTK for medieval Latin texts; and...

  6. StreamCat

    Data.gov (United States)

    U.S. Environmental Protection Agency — The StreamCat Dataset provides summaries of natural and anthropogenic landscape features for ~2.65 million streams, and their associated catchments, within the...

  7. A structured model of video reproduces primary visual cortical organisation.

    Directory of Open Access Journals (Sweden)

    Pietro Berkes

    2009-09-01

    Full Text Available The visual system must learn to infer the presence of objects and features in the world from the images it encounters, and as such it must, either implicitly or explicitly, model the way these elements interact to create the image. Do the response properties of cells in the mammalian visual system reflect this constraint? To address this question, we constructed a probabilistic model in which the identity and attributes of simple visual elements were represented explicitly and learnt the parameters of this model from unparsed, natural video sequences. After learning, the behaviour and grouping of variables in the probabilistic model corresponded closely to functional and anatomical properties of simple and complex cells in the primary visual cortex (V1. In particular, feature identity variables were activated in a way that resembled the activity of complex cells, while feature attribute variables responded much like simple cells. Furthermore, the grouping of the attributes within the model closely parallelled the reported anatomical grouping of simple cells in cat V1. Thus, this generative model makes explicit an interpretation of complex and simple cells as elements in the segmentation of a visual scene into basic independent features, along with a parametrisation of their moment-by-moment appearances. We speculate that such a segmentation may form the initial stage of a hierarchical system that progressively separates the identity and appearance of more articulated visual elements, culminating in view-invariant object recognition.

  8. Resolving Schrodinger's cat

    OpenAIRE

    Hobson, Art

    2016-01-01

    Schrodinger's famous cat has long been misunderstood. According to quantum theory and experiments with entangled systems, an entangled state such as the Schrodinger's cat state is neither a superposition of states of either subsystem nor a superposition of compound states of the composite system, but rather a nonlocal superposition of correlations between pairs of states of the two subsystems. The entangled post-measurement state that results from an ideal measurement is not paradoxical, but ...

  9. Haemobartonellosis in Van Cats

    OpenAIRE

    AKKAN, Hasan Altan; Karaca, Mehmet; TÜTÜNCÜ, Mehmet

    2005-01-01

    The present study was conducted to determine prevalence of Haemobartonella felis in Van cats. 121 Van cats (82 female, 39 male, aged 1-9 years) were the materials of the study. To determine biochemical and haematological parameters, 2 ml blood with and without anticoagulant were taken according to technique from vena cephalica antebrachii. H. felis was detected in blood smears preparations of 18 (14.88%) by Papenheim staining. Among biochemical parameters aspartate amino transferase (AST), al...

  10. Cardiac Biomarkers in Hyperthyroid Cats

    OpenAIRE

    Sangster, Jodi Kirsten

    2013-01-01

    Background: Hyperthyroidism has substantial effects on the circulatory system. The cardiac biomarkers NT-proBNP and troponin I (cTNI) have proven useful in identifying cats with myocardial disease but have not been as extensively investigated in hyperthyroidism.Hypothesis: Plasma NT-proBNP and cTNI concentrations are higher in cats with primary cardiac disease than in cats with hyperthyroidism and higher in cats with hyperthyroidism than in healthy control cats.Animals: Twenty-three hyperthyr...

  11. Cardiac Biomarkers in Hyperthyroid Cats

    OpenAIRE

    Sangster, J.K.; Panciera, D L; Abbott, J.A.; Zimmerman, K.C.; Lantis, A.C.

    2013-01-01

    Background Hyperthyroidism has substantial effects on the circulatory system. The cardiac biomarkers NT‐proBNP and troponin I (cTNI) have proven useful in identifying cats with myocardial disease but have not been extensively investigated in hyperthyroidism. Hypothesis Plasma NT‐proBNP and cTNI concentrations are higher in cats with primary myocardial disease than in cats with hyperthyroidism and higher in cats with hyperthyroidism than in healthy control cats. Animals Twenty‐three hyperthyro...

  12. Gaze Behavior, Believability, Likability and the iCat

    OpenAIRE

    Van der Poel, M.; Heylen, D.; Meulemans, M.; Bremen, van, A.; Nijholt, A; Stock, O.; Nishida, T.

    2009-01-01

    The iCat is a user-interface robot with the ability to express a range of emotions through its facial features. This paper summarizes our research whether we can increase the believability and likability of the iCat for its human partners through the application of gaze behaviour. Gaze behaviour serves several functions during social interaction such as mediating conversation flow, communicating emotional information and avoiding distraction by restricting visual input. There are several type...

  13. 光学诱导散光对视觉信号传导及皮层反应的影响%Electrophysiological research on the effects of optic-induced astigmatism on transmission time and response intensity of visual signals in the visual cortex

    Institute of Scientific and Technical Information of China (English)

    解来青; 徐国旭; 赵堪兴

    2012-01-01

    Objective To evaluate the contribution of different degrees of astigmatism on the latency and amplitude of pattern visual evoked potentials (PVEPs).The effect of astigmatism on the transmission and response intensity of visual signals in the visual cortex was evaluated.Methods It was a random designed study.PVEPs were measured in subjects with normal or normal corrected visual acuity using a checkerboard pattern stimulus under varying conditions using different astigmatic trial lens powers in succession (0-5 D).Paired samples t test,analysis of variance and Pearson correlation was performed.Results When a lower spatial frequency (60' checkerboards stimulus) was used,there was little change in the latency of P100 (F=0.290,P>0.05).However,when a higher spatial frequency (15' checkerboards stimulus) was used,VEP latency increased with a greater degree of astigmatism (F=10.850,P<0.01; r=0.647,P<0.01).There was a gradual reduction of amplitudes of P100 as convex cylindrical lens power increased (when 60' checkerboards were used, F=3.947,P<0.01; r=-0.470,P<0.01; when 15' checkerboards were used,F=14.280,P<0.01; r=-0.699,P<0.01).Conclusion The transmission of visual signals depends on the quality of the visual image formed on the retina.Visual signal transmission time and response intensity in the visual cortex are affected not only by the defocus of the retinal image but also by the spatial frequency of the pattern stimulus.With a high spatial frequency,the transmission of visual signals is faster and the response intensity of the visual cortex is greater if the visual image formed on the retina is clear.%目的 研究光学诱导不同程度散光产生的视觉信号对皮层反应时间及强度的影响;研究散光是否可导致视觉信号传导时程异常,观察视觉信号传导时间及视皮层反应强度与散光程度的量化关系.方法 完全随机设计研究.对视力或矫正视力正常的被检者眼前依次放置0~5 D度数正

  14. Cats protecting birds revisited.

    Science.gov (United States)

    Fan, Meng; Kuang, Yang; Feng, Zhilan

    2005-09-01

    In this paper, we revisit the dynamical interaction among prey (bird), mesopredator (rat), and superpredator (cat) discussed in [Courchamp, F., Langlais, M., Sugihara, G., 1999. Cats protecting birds: modelling the mesopredator release effect. Journal of Animal Ecology 68, 282-292]. First, we develop a prey-mesopredator-superpredator (i.e., bird-rat-cat, briefly, BRC) model, where the predator's functional responses are derived based on the classical Holling's time budget arguments. Our BRC model overcomes several model construction problems in Courchamp et al. (1999), and admits richer, reasonable and realistic dynamics. We explore the possible control strategies to save or restore the bird by controlling or eliminating the rat or the cat when the bird is endangered. We establish the existence of two types of mesopredator release phenomena: severe mesopredator release, where once superpredators are suppressed, a burst of mesopredators follows which leads their shared prey to extinction; and mild mesopredator release, where the mesopredator release could assert more negative impact on the endemic prey but does not lead the endemic prey to extinction. A sharp sufficient criterion is established for the occurrence of severe mesopredator release. We also show that, in a prey-mesopredator-superpredator trophic food web, eradication of introduced superpredators such as feral domestic cats in the BRC model, is not always the best solution to protect endemic insular prey. The presence of a superpredator may have a beneficial effect in such systems. PMID:15998496

  15. The Feline Mystique: Dispelling the Myth of the Independent Cat.

    Science.gov (United States)

    Soltow, Willow

    1984-01-01

    Describes learning activities about cats for primary and intermediate grades. Primary grade activity subjects include cat behavior, needs, breeds, storybook cats, and celestial cats. Intermediate grade activity subjects include cat history, care, language, literary cats, and cats in art. (BC)

  16. Expression of mGluR1 at primary visual cortex of monocular deprivation amblyopia rat and the observing of ultrastructure%代谢性谷氨酸受体1在单眼形觉剥夺弱视大鼠视皮质17区的表达及超微结构观察

    Institute of Scientific and Technical Information of China (English)

    王宗青; 刘向玲; 穆雅林; 刘爱琴; 李晓鹏

    2008-01-01

    Objective To explore the regulation of expression of mGluR1 and the changes of neuron ultrastructure at primary visual cortex of monocular deprivation amblyopia rat within cortical period.Methods Taking randomized concurrent controlled trail.Establishing the model of monocular deprivation amblyopia rat.After proving the model successful by PVEP,all of the rats were randomly divided into three groups:normal visual cortex,experimental visual cortex and experimental opposite visual cortex.Immunocytochemical technology,electron microscope,photography microscope,computer image analysis,SPSS 11.5 and ANOV were used to get the resuhs.Results Compared with the layer Ⅳ of normal visual cortex and experimental opposite visual cortex,the area of immunopositive neurons in layer Ⅳ of experimental visual cortex are deficiency.there is significant difference between them(P<0.01).There are no significant differences between the other four corresponding layers(P>0.05).Morphological abnormals were found in layer Ⅳ of experimental visual cortex by observing of ultrastructure.Conclusion The expression of mGluR1 in layer Ⅳ of primary visual cortex of monocular deprivation amblyopia is reduced.There are morphological abnormals happened in layer Ⅳ of primary visual cortex of monocular derivation amblyopia.Reduced afference of nerve pulse because of monocular deprivation leads to the expression difficiency of mGluR1 in layer Ⅳ of the primary visual cortex,then synaptic plasticity happened,then neurons atrophy occurred may be one of the etiopathogenesis of amblyopia.%目的 探讨视觉形成关键期内单眼形觉剥夺弱视大鼠初级视皮质17区中代谢性谷氨酸受体1(mGluR1)的表达规律及神经元超微结构变化,为临床上揭示弱视的病理机制及防治提供依据.方法 随机对照同期动物实验.方法是建立大鼠单眼形觉剥夺弱视模型,经图形视觉诱发电位检测证实造模成功后,与正常对照组大鼠一起灌注

  17. Microglia in the Cerebral Cortex in Autism

    Science.gov (United States)

    Tetreault, Nicole A.; Hakeem, Atiya Y.; Jiang, Sue; Williams, Brian A.; Allman, Elizabeth; Wold, Barbara J.; Allman, John M.

    2012-01-01

    We immunocytochemically identified microglia in fronto-insular (FI) and visual cortex (VC) in autopsy brains of well-phenotyped subjects with autism and matched controls, and stereologically quantified the microglial densities. Densities were determined blind to phenotype using an optical fractionator probe. In FI, individuals with autism had…

  18. ServCat Sensitivity Guidelines

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This guide covers sensitivity in ServCat. This document provides technical guidance on how sensitivity fields work in ServCat, and provides suggestions on what...

  19. 初级视觉皮层“简单”与“复杂”神经元动力学的计算建模%Computational modeling of the dynamics of simple and complex cells in primary visual cortex

    Institute of Scientific and Technical Information of China (English)

    陶乐天; 蔡申瓯

    2011-01-01

    本文回顾了我们在哺乳动物视觉皮层的建模工作.利用初级视觉皮层的大规模神经元网络模型,我们解释了初级视觉皮层里“简单”与“复杂”神经元现象的网络机制.所谓的“简单”细胞对视觉刺激的反应近似线性,而“复杂”细胞对视觉刺激是非线性的.我们的模型成功地再现了简单和复杂细胞分布的实验数据.%We review our work on computational modeling of the mammalian visual cortex.In particular,we explain the network mechanism of how simple and complex cells arise in a large scale neuronal network model of primary visual cortex.The simple cells are so-called because they respond approximately linearly to visual stimulus,whereas the complex cells exhibit nonlinear response to visual stimulation.Our model reproduces qualitatively the experimentally observed distributions of simple and complex cells.

  20. Hemodynamic Traveling Waves in Human Visual Cortex

    OpenAIRE

    Kevin M Aquino; Schira, Mark M.; P A Robinson; Drysdale, Peter M.; Michael Breakspear

    2012-01-01

    Functional MRI (fMRI) experiments rely on precise characterization of the blood oxygen level dependent (BOLD) signal. As the spatial resolution of fMRI reaches the sub-millimeter range, the need for quantitative modelling of spatiotemporal properties of this hemodynamic signal has become pressing. Here, we find that a detailed physiologically-based model of spatiotemporal BOLD responses predicts traveling waves with velocities and spatial ranges in empirically observable ranges. Two measurabl...