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Sample records for spatial ca3 representations

  1. How informative are spatial CA3 representations established by the dentate gyrus?

    Erika Cerasti

    2010-04-01

    Full Text Available In the mammalian hippocampus, the dentate gyrus (DG is characterized by sparse and powerful unidirectional projections to CA3 pyramidal cells, the so-called mossy fibers. Mossy fiber synapses appear to duplicate, in terms of the information they convey, what CA3 cells already receive from entorhinal cortex layer II cells, which project both to the dentate gyrus and to CA3. Computational models of episodic memory have hypothesized that the function of the mossy fibers is to enforce a new, well-separated pattern of activity onto CA3 cells, to represent a new memory, prevailing over the interference produced by the traces of older memories already stored on CA3 recurrent collateral connections. Can this hypothesis apply also to spatial representations, as described by recent neurophysiological recordings in rats? To address this issue quantitatively, we estimate the amount of information DG can impart on a new CA3 pattern of spatial activity, using both mathematical analysis and computer simulations of a simplified model. We confirm that, also in the spatial case, the observed sparse connectivity and level of activity are most appropriate for driving memory storage-and not to initiate retrieval. Surprisingly, the model also indicates that even when DG codes just for space, much of the information it passes on to CA3 acquires a non-spatial and episodic character, akin to that of a random number generator. It is suggested that further hippocampal processing is required to make full spatial use of DG inputs.

  2. Characterization, scaling, and partial representation of diffuse and discrete input junctions to CA3 hippocampus.

    Ascarrunz, F G; Kisley, M A; Flach, K A; Hamilton, R W; MacGregor, R J

    1995-07-01

    This paper applies a general mathematical system for characterizing and scaling functional connectivity and information flow across the diffuse (EC) and discrete (DG) input junctions to the CA3 hippocampus. Both gross connectivity and coordinated multiunit informational firing patterns are quantitatively characterized in terms of 32 defining parameters interrelated by 17 equations, and then scaled down according to rules for uniformly proportional scaling and for partial representation. The diffuse EC-CA3 junction is shown to be uniformly scalable with realistic representation of both essential spatiotemporal cooperativity and coordinated firing patterns down to populations of a few hundred neurons. Scaling of the discrete DG-CA3 junction can be effected with a two-step process, which necessarily deviates from uniform proportionality but nonetheless produces a valuable and readily interpretable reduced model, also utilizing a few hundred neurons in the receiving population. Partial representation produces a reduced model of only a portion of the full network where each model neuron corresponds directly to a biological neuron. The mathematical analysis illustrated here shows that although omissions and distortions are inescapable in such an application, satisfactorily complete and accurate models the size of pattern modules are possible. Finally, the mathematical characterization of these junctions generates a theory which sees the DG as a definer of the fine structure of embedded traces in the hippocampus and entire coordinated patterns of sequences of 14-cell links in CA3 as triggered by the firing of sequences of individual neurons in DG.

  3. Spatial information is preferentially processed by the distal part of CA3: implication for memory retrieval.

    Flasbeck, Vera; Atucha, Erika; Nakamura, Nozomu H; Yoshida, Motoharu; Sauvage, Magdalena M

    2018-07-16

    For the past decades, CA3 was considered as a single functional entity. However, strong differences between the proximal (close to the dentate gyrus) and the distal (close to CA2) parts of CA3 in terms of connectivity patterns, gene expression and electrophysiological properties suggest that it is not the case. We recently showed that proximal CA3 (together with distal CA1) preferentially deals with non-spatial information [1]. In contrast to proximal CA3, distal CA3 mainly receives and predominantly projects to spatially tuned areas. Here, we tested if distal CA3 preferentially processes spatial information, which would suggest a segregation of the spatial information along the proximodistal axis of CA3. We used a high-resolution imaging technique based on the detection of the expression of the immediate-early gene Arc, commonly used to map activity in the medial temporal lobe. We showed that distal CA3 is strongly recruited in a newly designed delayed nonmatching-to-location task with high memory demands in rats, while proximal CA3 is not. These results indicate a functional segregation of CA3 that mirrors the one reported in CA1, and suggest the existence of a distal CA3- proximal CA1 spatial subnetwork. These findings bring further evidence for the existence of 'specialized' spatial and non-spatial subnetworks segregated along the proximodistal axis of the hippocampus and put forward the 'segregated' view of information processing in the hippocampus as a reasonable alternative to the well-accepted 'integrated' view, according to which spatial and non-spatial information are systematically integrated in the hippocampus to form episodic memory. Copyright © 2018. Published by Elsevier B.V.

  4. Dentate network activity is necessary for spatial working memory by supporting CA3 sharp-wave ripple generation and prospective firing of CA3 neurons.

    Sasaki, Takuya; Piatti, Verónica C; Hwaun, Ernie; Ahmadi, Siavash; Lisman, John E; Leutgeb, Stefan; Leutgeb, Jill K

    2018-02-01

    Complex spatial working memory tasks have been shown to require both hippocampal sharp-wave ripple (SWR) activity and dentate gyrus (DG) neuronal activity. We therefore asked whether DG inputs to CA3 contribute to spatial working memory by promoting SWR generation. Recordings from DG and CA3 while rats performed a dentate-dependent working memory task on an eight-arm radial maze revealed that the activity of dentate neurons and the incidence rate of SWRs both increased during reward consumption. We then found reduced reward-related CA3 SWR generation without direct input from dentate granule neurons. Furthermore, CA3 cells with place fields in not-yet-visited arms preferentially fired during SWRs at reward locations, and these prospective CA3 firing patterns were more pronounced for correct trials and were dentate-dependent. These results indicate that coordination of CA3 neuronal activity patterns by DG is necessary for the generation of neuronal firing patterns that support goal-directed behavior and memory.

  5. The Spatial Politics of Spatial Representation

    Olesen, Kristian; Richardson, Tim

    2011-01-01

    spatial planning in Denmark reveals how fuzzy spatial representations and relational spatial concepts are being used to depoliticise strategic spatial planning processes and to camouflage spatial politics. The paper concludes that, while relational geography might play an important role in building......This paper explores the interplay between the spatial politics of new governance landscapes and innovations in the use of spatial representations in planning. The central premise is that planning experiments with new relational approaches become enmeshed in spatial politics. The case of strategic...

  6. Representation Elements of Spatial Thinking

    Fiantika, F. R.

    2017-04-01

    This paper aims to add a reference in revealing spatial thinking. There several definitions of spatial thinking but it is not easy to defining it. We can start to discuss the concept, its basic a forming representation. Initially, the five sense catch the natural phenomenon and forward it to memory for processing. Abstraction plays a role in processing information into a concept. There are two types of representation, namely internal representation and external representation. The internal representation is also known as mental representation; this representation is in the human mind. The external representation may include images, auditory and kinesthetic which can be used to describe, explain and communicate the structure, operation, the function of the object as well as relationships. There are two main elements, representations properties and object relationships. These elements play a role in forming a representation.

  7. Spatial Representation of Ordinal Information

    Meng eZhang

    2016-04-01

    Full Text Available Right hand responds faster than left hand when shown larger numbers and vice-versa when shown smaller numbers (the SNARC effect. Accumulating evidence suggests that the SNARC effect may not be exclusive for numbers and can be extended to other ordinal sequences (e.g., months or letters in the alphabet as well. In this study, we tested the SNARC effect with a non-numerically ordered sequence: The Chinese notations for the color spectrum (Red, Orange, Yellow, Green, Blue, Indigo, and Violet. Chinese color word sequence reserves relatively weak ordinal information, because each element color in the sequence normally appears in non-sequential contexts, making it ideal to test the spatial organization of sequential information that was stored in the long-term memory. This study found a reliable SNARC-like effect for Chinese color words (deciding whether the presented color word was before or after the reference color word green, suggesting that, without access to any quantitative information or exposure to any previous training, ordinal representation can still activate a sense of space. The results support that weak ordinal information without quantitative magnitude encoded in the long-term memory can activate spatial representation in a comparison task.

  8. Spatial Representation of Ordinal Information.

    Zhang, Meng; Gao, Xuefei; Li, Baichen; Yu, Shuyuan; Gong, Tianwei; Jiang, Ting; Hu, Qingfen; Chen, Yinghe

    2016-01-01

    Right hand responds faster than left hand when shown larger numbers and vice-versa when shown smaller numbers (the SNARC effect). Accumulating evidence suggests that the SNARC effect may not be exclusive for numbers and can be extended to other ordinal sequences (e.g., months or letters in the alphabet) as well. In this study, we tested the SNARC effect with a non-numerically ordered sequence: the Chinese notations for the color spectrum (Red, Orange, Yellow, Green, Blue, Indigo, and Violet). Chinese color word sequence reserves relatively weak ordinal information, because each element color in the sequence normally appears in non-sequential contexts, making it ideal to test the spatial organization of sequential information that was stored in the long-term memory. This study found a reliable SNARC-like effect for Chinese color words (deciding whether the presented color word was before or after the reference color word "green"), suggesting that, without access to any quantitative information or exposure to any previous training, ordinal representation can still activate a sense of space. The results support that weak ordinal information without quantitative magnitude encoded in the long-term memory can activate spatial representation in a comparison task.

  9. Repeating Spatial-Temporal Motifs of CA3 Activity Dependent on Engineered Inputs from Dentate Gyrus Neurons in Live Hippocampal Networks.

    Bhattacharya, Aparajita; Desai, Harsh; DeMarse, Thomas B; Wheeler, Bruce C; Brewer, Gregory J

    2016-01-01

    Anatomical and behavioral studies, and in vivo and slice electrophysiology of the hippocampus suggest specific functions of the dentate gyrus (DG) and the CA3 subregions, but the underlying activity dynamics and repeatability of information processing remains poorly understood. To approach this problem, we engineered separate living networks of the DG and CA3 neurons that develop connections through 51 tunnels for axonal communication. Growing these networks on top of an electrode array enabled us to determine whether the subregion dynamics were separable and repeatable. We found spontaneous development of polarized propagation of 80% of the activity in the native direction from DG to CA3 and different spike and burst dynamics for these subregions. Spatial-temporal differences emerged when the relationships of target CA3 activity were categorized with to the number and timing of inputs from the apposing network. Compared to times of CA3 activity when there was no recorded tunnel input, DG input led to CA3 activity bursts that were 7× more frequent, increased in amplitude and extended in temporal envelope. Logistic regression indicated that a high number of tunnel inputs predict CA3 activity with 90% sensitivity and 70% specificity. Compared to no tunnel input, patterns of >80% tunnel inputs from DG specified different patterns of first-to-fire neurons in the CA3 target well. Clustering dendrograms revealed repeating motifs of three or more patterns at up to 17 sites in CA3 that were importantly associated with specific spatial-temporal patterns of tunnel activity. The number of these motifs recorded in 3 min was significantly higher than shuffled spike activity and not seen above chance in control networks in which CA3 was apposed to CA3 or DG to DG. Together, these results demonstrate spontaneous input-dependent repeatable coding of distributed activity in CA3 networks driven by engineered inputs from DG networks. These functional configurations at measured times

  10. Exploring the Structure of Spatial Representations

    Madl, Tamas; Franklin, Stan; Chen, Ke; Trappl, Robert; Montaldi, Daniela

    2016-01-01

    It has been suggested that the map-like representations that support human spatial memory are fragmented into sub-maps with local reference frames, rather than being unitary and global. However, the principles underlying the structure of these ‘cognitive maps’ are not well understood. We propose that the structure of the representations of navigation space arises from clustering within individual psychological spaces, i.e. from a process that groups together objects that are close in these spaces. Building on the ideas of representational geometry and similarity-based representations in cognitive science, we formulate methods for learning dissimilarity functions (metrics) characterizing participants’ psychological spaces. We show that these learned metrics, together with a probabilistic model of clustering based on the Bayesian cognition paradigm, allow prediction of participants’ cognitive map structures in advance. Apart from insights into spatial representation learning in human cognition, these methods could facilitate novel computational tools capable of using human-like spatial concepts. We also compare several features influencing spatial memory structure, including spatial distance, visual similarity and functional similarity, and report strong correlations between these dimensions and the grouping probability in participants’ spatial representations, providing further support for clustering in spatial memory. PMID:27347681

  11. Transformations and representations supporting spatial perspective taking

    Yu, Alfred B.; Zacks, Jeffrey M.

    2018-01-01

    Spatial perspective taking is the ability to reason about spatial relations relative to another’s viewpoint. Here, we propose a mechanistic hypothesis that relates mental representations of one’s viewpoint to the transformations used for spatial perspective taking. We test this hypothesis using a novel behavioral paradigm that assays patterns of response time and variation in those patterns across people. The results support the hypothesis that people maintain a schematic representation of the space around their body, update that representation to take another’s perspective, and thereby to reason about the space around their body. This is a powerful computational mechanism that can support imitation, coordination of behavior, and observational learning. PMID:29545731

  12. The spatial representation of market information

    DeSarbo, WS; Degeratu, AM; Wedel, M; Saxton, MK

    2001-01-01

    To be used effectively, market knowledge and information must be structured and represented in ways that are parsimonious and conducive to efficient managerial decision making. This manuscript proposes a new latent structure spatial model for the representation of market information that meets this

  13. Spatially variant morphological restoration and skeleton representation.

    Bouaynaya, Nidhal; Charif-Chefchaouni, Mohammed; Schonfeld, Dan

    2006-11-01

    The theory of spatially variant (SV) mathematical morphology is used to extend and analyze two important image processing applications: morphological image restoration and skeleton representation of binary images. For morphological image restoration, we propose the SV alternating sequential filters and SV median filters. We establish the relation of SV median filters to the basic SV morphological operators (i.e., SV erosions and SV dilations). For skeleton representation, we present a general framework for the SV morphological skeleton representation of binary images. We study the properties of the SV morphological skeleton representation and derive conditions for its invertibility. We also develop an algorithm for the implementation of the SV morphological skeleton representation of binary images. The latter algorithm is based on the optimal construction of the SV structuring element mapping designed to minimize the cardinality of the SV morphological skeleton representation. Experimental results show the dramatic improvement in the performance of the SV morphological restoration and SV morphological skeleton representation algorithms in comparison to their translation-invariant counterparts.

  14. Conceptual spatial representations for indoor mobile robots

    Zender, Henrik; Mozos, Oscar Martinez; Jensfelt, Patric; Kruijff, Geert-Jan M.; Wolfram, Burgard

    2008-01-01

    We present an approach for creating conceptual representations of human-made indoor environments using mobile robots. The concepts refer to spatial and functional properties of typical indoor environments. Following findings in cognitive psychology, our model is composed of layers representing maps at different levels of abstraction. The complete system is integrated in a mobile robot endowed with laser and vision sensors for place and object recognition. The system also incorporate...

  15. Representations and processes of human spatial competence.

    Gunzelmann, Glenn; Lyon, Don R

    2011-10-01

    This article presents an approach to understanding human spatial competence that focuses on the representations and processes of spatial cognition and how they are integrated with cognition more generally. The foundational theoretical argument for this research is that spatial information processing is central to cognition more generally, in the sense that it is brought to bear ubiquitously to improve the adaptivity and effectiveness of perception, cognitive processing, and motor action. We describe research spanning multiple levels of complexity to understand both the detailed mechanisms of spatial cognition, and how they are utilized in complex, naturalistic tasks. In the process, we discuss the critical role of cognitive architectures in developing a consistent account that spans this breadth, and we note some areas in which the current version of a popular architecture, ACT-R, may need to be augmented. Finally, we suggest a framework for understanding the representations and processes of spatial competence and their role in human cognition generally. Copyright © 2011 Cognitive Science Society, Inc.

  16. Dock Sud's environmental pollution: Spatial representations, space representation and spatial practices in peripheral neighborhoods

    Sandra Valeria Ursino

    2012-01-01

    Full Text Available In this article, we present some of the results and argumentative lines used in the analysis of the field work carried out in the neighborhoods of Porst, Danubio and Villa Inflamable, in the Dock Sud area, located in the district of Avellaneda, province de Buenos Aires, during 2010 and 2011. Within this framework, we observed and recorded the inhabitants' usual routes around the neighborhood, which is environmentally polluted but which has also been symbolically appropriated. Along these lines then, our general aim was to learn about social representations, representation spaces and the spatial practices of the inhabitants of the most affected neighborhoods of Dock Sud due to the area's environmental issues. To this end, there was a reconstruction of the subjects' practices in the neighborhood, of the hegemonic discourse about the pollution in this place and, finally, the population's conflict and struggle practices

  17. Place cell rate remapping by CA3 recurrent collaterals.

    Trygve Solstad

    2014-06-01

    Full Text Available Episodic-like memory is thought to be supported by attractor dynamics in the hippocampus. A possible neural substrate for this memory mechanism is rate remapping, in which the spatial map of place cells encodes contextual information through firing rate variability. To test whether memories are stored as multimodal attractors in populations of place cells, recent experiments morphed one familiar context into another while observing the responses of CA3 cell ensembles. Average population activity in CA3 was reported to transition gradually rather than abruptly from one familiar context to the next, suggesting a lack of attractive forces associated with the two stored representations. On the other hand, individual CA3 cells showed a mix of gradual and abrupt transitions at different points along the morph sequence, and some displayed hysteresis which is a signature of attractor dynamics. To understand whether these seemingly conflicting results are commensurate with attractor network theory, we developed a neural network model of the CA3 with attractors for both position and discrete contexts. We found that for memories stored in overlapping neural ensembles within a single spatial map, position-dependent context attractors made transitions at different points along the morph sequence. Smooth transition curves arose from averaging across the population, while a heterogeneous set of responses was observed on the single unit level. In contrast, orthogonal memories led to abrupt and coherent transitions on both population and single unit levels as experimentally observed when remapping between two independent spatial maps. Strong recurrent feedback entailed a hysteretic effect on the network which diminished with the amount of overlap in the stored memories. These results suggest that context-dependent memory can be supported by overlapping local attractors within a spatial map of CA3 place cells. Similar mechanisms for context-dependent memory may

  18. Language, Perception, and the Schematic Representation of Spatial Relations

    Amorapanth, Prin; Kranjec, Alexander; Bromberger, Bianca; Lehet, Matthew; Widick, Page; Woods, Adam J.; Kimberg, Daniel Y.; Chatterjee, Anjan

    2012-01-01

    Schemas are abstract nonverbal representations that parsimoniously depict spatial relations. Despite their ubiquitous use in maps and diagrams, little is known about their neural instantiation. We sought to determine the extent to which schematic representations are neurally distinguished from language on the one hand, and from rich perceptual…

  19. Spatial representations are specific to different domains of knowledge.

    Rowena Beecham

    Full Text Available There is evidence that many abstract concepts are represented cognitively in a spatial format. However, it is unknown whether similar spatial processes are employed in different knowledge domains, or whether individuals exhibit similar spatial profiles within and across domains. This research investigated similarities in spatial representation in two knowledge domains--mathematics and music. Sixty-one adults completed analogous number magnitude and pitch discrimination tasks: the Spatial-Numerical Association of Response Codes and Spatial-Musical Association of Response Codes tasks. Subgroups of individuals with different response patterns were identified through cluster analyses. For both the mathematical and musical tasks, approximately half of the participants showed the expected spatial judgment effect when explicitly cued to focus on the spatial properties of the stimuli. Despite this, performances on the two tasks were largely independent. Consistent with previous research, the study provides evidence for the spatial representation of number and pitch in the majority of individuals. However, there was little evidence to support the claim that the same spatial representation processes underpin mathematical and musical judgments.

  20. Pharmacological Intervention of Hippocampal CA3 NMDA Receptors Impairs Acquisition and Long-Term Memory Retrieval of Spatial Pattern Completion Task

    Fellini, Laetitia; Florian, Cedrick; Courtey, Julie; Roullet, Pascal

    2009-01-01

    Pattern completion is the ability to retrieve complete information on the basis of incomplete retrieval cues. Although it has been demonstrated that this cognitive capacity depends on the NMDA receptors (NMDA-Rs) of the hippocampal CA3 region, the role played by these glutamatergic receptors in the pattern completion process has not yet been…

  1. A Common Representation of Spatial Features Drives Action and Perception

    Christiansen, Jens H; Christensen, Jeppe Høy; Grünbaum, Thor

    2014-01-01

    Spatial features of an object can be specified using two different response types: either by use of symbols or motorically by directly acting upon the object. Is this response dichotomy reflected in a dual representation of the visual world: one for perception and one for action? Previously, symb...... of matching object-processing characteristics is also in agreement with the idea of a common representation driving both response types....

  2. Spatial representation in the hippocampal formation: a history.

    Moser, Edvard I; Moser, May-Britt; McNaughton, Bruce L

    2017-10-26

    Since the first place cell was recorded and the cognitive-map theory was subsequently formulated, investigation of spatial representation in the hippocampal formation has evolved in stages. Early studies sought to verify the spatial nature of place cell activity and determine its sensory origin. A new epoch started with the discovery of head direction cells and the realization of the importance of angular and linear movement-integration in generating spatial maps. A third epoch began when investigators turned their attention to the entorhinal cortex, which led to the discovery of grid cells and border cells. This review will show how ideas about integration of self-motion cues have shaped our understanding of spatial representation in hippocampal-entorhinal systems from the 1970s until today. It is now possible to investigate how specialized cell types of these systems work together, and spatial mapping may become one of the first cognitive functions to be understood in mechanistic detail.

  3. Algorithmic foundation of multi-scale spatial representation

    Li, Zhilin

    2006-01-01

    With the widespread use of GIS, multi-scale representation has become an important issue in the realm of spatial data handling. However, no book to date has systematically tackled the different aspects of this discipline. Emphasizing map generalization, Algorithmic Foundation of Multi-Scale Spatial Representation addresses the mathematical basis of multi-scale representation, specifically, the algorithmic foundation.Using easy-to-understand language, the author focuses on geometric transformations, with each chapter surveying a particular spatial feature. After an introduction to the essential operations required for geometric transformations as well as some mathematical and theoretical background, the book describes algorithms for a class of point features/clusters. It then examines algorithms for individual line features, such as the reduction of data points, smoothing (filtering), and scale-driven generalization, followed by a discussion of algorithms for a class of line features including contours, hydrog...

  4. Spatial representations elicit dual-coding effects in mental imagery.

    Verges, Michelle; Duffy, Sean

    2009-08-01

    Spatial aspects of words are associated with their canonical locations in the real world. Yet little research has tested whether spatial associations denoted in language comprehension generalize to their corresponding images. We directly tested the spatial aspects of mental imagery in picture and word processing (Experiment 1). We also tested whether spatial representations of motion words produce similar perceptual-interference effects as demonstrated by object words (Experiment 2). Findings revealed that words denoting an upward spatial location produced slower responses to targets appearing at the top of the display, whereas words denoting a downward spatial location produced slower responses to targets appearing at the bottom of the display. Perceptual-interference effects did not obtain for pictures or for words lacking a spatial relation. These findings provide greater empirical support for the perceptual-symbols system theory (Barsalou, 1999, 2008). Copyright © 2009 Cognitive Science Society, Inc.

  5. Linguistic and Perceptual Mapping in Spatial Representations: An Attentional Account.

    Valdés-Conroy, Berenice; Hinojosa, José A; Román, Francisco J; Romero-Ferreiro, Verónica

    2018-03-01

    Building on evidence for embodied representations, we investigated whether Spanish spatial terms map onto the NEAR/FAR perceptual division of space. Using a long horizontal display, we measured congruency effects during the processing of spatial terms presented in NEAR or FAR space. Across three experiments, we manipulated the task demands in order to investigate the role of endogenous attention in linguistic and perceptual space mapping. We predicted congruency effects only when spatial properties were relevant for the task (reaching estimation task, Experiment 1) but not when attention was allocated to other features (lexical decision, Experiment 2; and color, Experiment 3). Results showed faster responses for words presented in Near-space in all experiments. Consistent with our hypothesis, congruency effects were observed only when a reaching estimate was requested. Our results add important evidence for the role of top-down processing in congruency effects from embodied representations of spatial terms. Copyright © 2017 Cognitive Science Society, Inc.

  6. Thinking Egyptian: Active Models for Understanding Spatial Representation.

    Schiferl, Ellen

    This paper highlights how introductory textbooks on Egyptian art inhibit understanding by reinforcing student preconceptions, and demonstrates another approach to discussing space with a classroom exercise and software. The alternative approach, an active model for spatial representation, introduced here was developed by adapting classroom…

  7. Spatial, Temporal and Spectral Satellite Image Fusion via Sparse Representation

    Song, Huihui

    Remote sensing provides good measurements for monitoring and further analyzing the climate change, dynamics of ecosystem, and human activities in global or regional scales. Over the past two decades, the number of launched satellite sensors has been increasing with the development of aerospace technologies and the growing requirements on remote sensing data in a vast amount of application fields. However, a key technological challenge confronting these sensors is that they tradeoff between spatial resolution and other properties, including temporal resolution, spectral resolution, swath width, etc., due to the limitations of hardware technology and budget constraints. To increase the spatial resolution of data with other good properties, one possible cost-effective solution is to explore data integration methods that can fuse multi-resolution data from multiple sensors, thereby enhancing the application capabilities of available remote sensing data. In this thesis, we propose to fuse the spatial resolution with temporal resolution and spectral resolution, respectively, based on sparse representation theory. Taking the study case of Landsat ETM+ (with spatial resolution of 30m and temporal resolution of 16 days) and MODIS (with spatial resolution of 250m ~ 1km and daily temporal resolution) reflectance, we propose two spatial-temporal fusion methods to combine the fine spatial information of Landsat image and the daily temporal resolution of MODIS image. Motivated by that the images from these two sensors are comparable on corresponding bands, we propose to link their spatial information on available Landsat- MODIS image pair (captured on prior date) and then predict the Landsat image from the MODIS counterpart on prediction date. To well-learn the spatial details from the prior images, we use a redundant dictionary to extract the basic representation atoms for both Landsat and MODIS images based on sparse representation. Under the scenario of two prior Landsat

  8. DNA methylation regulates neurophysiological spatial representation in memory formation

    Eric D. Roth

    2015-04-01

    Full Text Available Epigenetic mechanisms including altered DNA methylation are critical for altered gene transcription subserving synaptic plasticity and the retention of learned behavior. Here, we tested the idea that one role for activity-dependent altered DNA methylation is stabilization of cognition-associated hippocampal place cell firing in response to novel place learning. We observed that a behavioral protocol (spatial exploration of a novel environment known to induce hippocampal place cell remapping resulted in alterations of hippocampal Bdnf DNA methylation. Further studies using neurophysiological in vivo single-unit recordings revealed that pharmacological manipulations of DNA methylation decreased long-term but not short-term place field stability. Together, our data highlight a role for DNA methylation in regulating neurophysiological spatial representation and memory formation.

  9. DNA methylation regulates neurophysiological spatial representation in memory formation.

    Roth, Eric D; Roth, Tania L; Money, Kelli M; SenGupta, Sonda; Eason, Dawn E; Sweatt, J David

    2015-04-01

    Epigenetic mechanisms including altered DNA methylation are critical for altered gene transcription subserving synaptic plasticity and the retention of learned behavior. Here we tested the idea that one role for activity-dependent altered DNA methylation is stabilization of cognition-associated hippocampal place cell firing in response to novel place learning. We observed that a behavioral protocol (spatial exploration of a novel environment) known to induce hippocampal place cell remapping resulted in alterations of hippocampal Bdnf DNA methylation. Further studies using neurophysiological in vivo single unit recordings revealed that pharmacological manipulations of DNA methylation decreased long-term but not short-term place field stability. Together our data highlight a role for DNA methylation in regulating neurophysiological spatial representation and memory formation.

  10. Evaluation of Deep Learning Representations of Spatial Storm Data

    Gagne, D. J., II; Haupt, S. E.; Nychka, D. W.

    2017-12-01

    The spatial structure of a severe thunderstorm and its surrounding environment provide useful information about the potential for severe weather hazards, including tornadoes, hail, and high winds. Statistics computed over the area of a storm or from the pre-storm environment can provide descriptive information but fail to capture structural information. Because the storm environment is a complex, high-dimensional space, identifying methods to encode important spatial storm information in a low-dimensional form should aid analysis and prediction of storms by statistical and machine learning models. Principal component analysis (PCA), a more traditional approach, transforms high-dimensional data into a set of linearly uncorrelated, orthogonal components ordered by the amount of variance explained by each component. The burgeoning field of deep learning offers two potential approaches to this problem. Convolutional Neural Networks are a supervised learning method for transforming spatial data into a hierarchical set of feature maps that correspond with relevant combinations of spatial structures in the data. Generative Adversarial Networks (GANs) are an unsupervised deep learning model that uses two neural networks trained against each other to produce encoded representations of spatial data. These different spatial encoding methods were evaluated on the prediction of severe hail for a large set of storm patches extracted from the NCAR convection-allowing ensemble. Each storm patch contains information about storm structure and the near-storm environment. Logistic regression and random forest models were trained using the PCA and GAN encodings of the storm data and were compared against the predictions from a convolutional neural network. All methods showed skill over climatology at predicting the probability of severe hail. However, the verification scores among the methods were very similar and the predictions were highly correlated. Further evaluations are being

  11. Analogical processes in children's understanding of spatial representations.

    Yuan, Lei; Uttal, David; Gentner, Dedre

    2017-06-01

    We propose that map reading can be construed as a form of analogical mapping. We tested 2 predictions that follow from this claim: First, young children's patterns of performance in map reading tasks should parallel those found in analogical mapping tasks; and, second, children will benefit from guided alignment instructions that help them see the relational correspondences between the map and the space. In 4 experiments, 3-year-olds completed a map reading task in which they were asked to find hidden objects in a miniature room, using a corresponding map. We manipulated the availability of guided alignment (showing children the analogical mapping between maps and spaces; Experiments 1, 2, and 3a), the format of guided alignment (gesture or relational language; Experiment 2), and the iconicity of maps (Experiments 3a and 3b). We found that (a) young children's difficulties in map reading follow from known patterns of analogical development-for example, focusing on object similarity over relational similarity; and (b) guided alignment based on analogical reasoning led to substantially better performance. Results also indicated that children's map reading performance was affected by the format of guided alignment, the iconicity of the maps, and the order of tasks. The results bear on the developmental mechanisms underlying young children's learning of spatial representations and also suggest ways to support this learning. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  12. How the cerebellum may monitor sensory information for spatial representation

    Rondi-Reig, Laure; Paradis, Anne-Lise; Lefort, Julie M.; Babayan, Benedicte M.; Tobin, Christine

    2014-01-01

    The cerebellum has already been shown to participate in the navigation function. We propose here that this structure is involved in maintaining a sense of direction and location during self-motion by monitoring sensory information and interacting with navigation circuits to update the mental representation of space. To better understand the processing performed by the cerebellum in the navigation function, we have reviewed: the anatomical pathways that convey self-motion information to the cerebellum; the computational algorithm(s) thought to be performed by the cerebellum from these multi-source inputs; the cerebellar outputs directed toward navigation circuits and the influence of self-motion information on space-modulated cells receiving cerebellar outputs. This review highlights that the cerebellum is adequately wired to combine the diversity of sensory signals to be monitored during self-motion and fuel the navigation circuits. The direct anatomical projections of the cerebellum toward the head-direction cell system and the parietal cortex make those structures possible relays of the cerebellum influence on the hippocampal spatial map. We describe computational models of the cerebellar function showing that the cerebellum can filter out the components of the sensory signals that are predictable, and provides a novelty output. We finally speculate that this novelty output is taken into account by the navigation structures, which implement an update over time of position and stabilize perception during navigation. PMID:25408638

  13. Reactivation of Rate Remapping in CA3.

    Schwindel, C Daniela; Navratilova, Zaneta; Ali, Karim; Tatsuno, Masami; McNaughton, Bruce L

    2016-09-07

    The hippocampus is thought to contribute to episodic memory by creating, storing, and reactivating patterns that are unique to each experience, including different experiences that happen at the same location. Hippocampus can combine spatial and contextual/episodic information using a dual coding scheme known as "global" and "rate" remapping. Global remapping selects which set of neurons can activate at a given location. Rate remapping readjusts the firing rates of this set depending on current experience, thus expressing experience-unique patterns at each location. But can the experience-unique component be retrieved spontaneously? Whereas reactivation of recent, spatially selective patterns in hippocampus is well established, it is never perfect, raising the issue of whether the experiential component might be absent. This question is key to the hypothesis that hippocampus can assist memory consolidation by reactivating and broadcasting experience-specific "index codes" to neocortex. In CA3, global remapping exhibits attractor-like dynamics, whereas rate remapping apparently does not, leading to the hypothesis that only the former can be retrieved associatively and casting doubt on the general consolidation hypothesis. Therefore, we studied whether the rate component is reactivated spontaneously during sleep. We conducted neural ensemble recordings from CA3 while rats ran on a circular track in different directions (in different sessions) and while they slept. It was shown previously that the two directions of running result in strong rate remapping. During sleep, the most recent rate distribution was reactivated preferentially. Therefore, CA3 can retrieve patterns spontaneously that are unique to both the location and the content of recent experience. The hippocampus is required for memory of events and their spatial contexts. The primary correlate of hippocampal activity is location in space, but multiple memories can occur in the same location. To be useful

  14. Think Spatial: The Representation in Mental Rotation Is Nonvisual

    Liesefeld, Heinrich R.; Zimmer, Hubert D.

    2013-01-01

    For mental rotation, introspection, theories, and interpretations of experimental results imply a certain type of mental representation, namely, visual mental images. Characteristics of the rotated representation can be examined by measuring the influence of stimulus characteristics on rotational speed. If the amount of a given type of information…

  15. Crowding in Visual Working Memory Reveals Its Spatial Resolution and the Nature of Its Representations.

    Tamber-Rosenau, Benjamin J; Fintzi, Anat R; Marois, René

    2015-09-01

    Spatial resolution fundamentally limits any image representation. Although this limit has been extensively investigated for perceptual representations by assessing how neighboring flankers degrade the perception of a peripheral target with visual crowding, the corresponding limit for representations held in visual working memory (VWM) is unknown. In the present study, we evoked crowding in VWM and directly compared resolution in VWM and perception. Remarkably, the spatial resolution of VWM proved to be no worse than that of perception. However, mixture modeling of errors caused by crowding revealed the qualitatively distinct nature of these representations. Perceptual crowding errors arose from both increased imprecision in target representations and substitution of flankers for targets. By contrast, VWM crowding errors arose exclusively from substitutions, which suggests that VWM transforms analog perceptual representations into discrete items. Thus, although perception and VWM share a common resolution limit, exceeding this limit reveals distinct mechanisms for perceiving images and holding them in mind. © The Author(s) 2015.

  16. Improving the spatial representation of basin hydrology and flow processes in the SWAT model

    Rathjens, Hendrik

    2014-01-01

    This dissertation aims at improving the spatial representation of basin hydrology and flow processes in the SWAT model. Die vorliegende Dissertation stellt die methodischen Grundlage zur räumlich differenzierten Modellierung mit dem Modell SWAT dar.

  17. Alpha-Band Activity Reveals Spontaneous Representations of Spatial Position in Visual Working Memory.

    Foster, Joshua J; Bsales, Emma M; Jaffe, Russell J; Awh, Edward

    2017-10-23

    An emerging view suggests that spatial position is an integral component of working memory (WM), such that non-spatial features are bound to locations regardless of whether space is relevant [1, 2]. For instance, past work has shown that stimulus position is spontaneously remembered when non-spatial features are stored. Item recognition is enhanced when memoranda appear at the same location where they were encoded [3-5], and accessing non-spatial information elicits shifts of spatial attention to the original position of the stimulus [6, 7]. However, these findings do not establish that a persistent, active representation of stimulus position is maintained in WM because similar effects have also been documented following storage in long-term memory [8, 9]. Here we show that the spatial position of the memorandum is actively coded by persistent neural activity during a non-spatial WM task. We used a spatial encoding model in conjunction with electroencephalogram (EEG) measurements of oscillatory alpha-band (8-12 Hz) activity to track active representations of spatial position. The position of the stimulus varied trial to trial but was wholly irrelevant to the tasks. We nevertheless observed active neural representations of the original stimulus position that persisted throughout the retention interval. Further experiments established that these spatial representations are dependent on the volitional storage of non-spatial features rather than being a lingering effect of sensory energy or initial encoding demands. These findings provide strong evidence that online spatial representations are spontaneously maintained in WM-regardless of task relevance-during the storage of non-spatial features. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. Vision and the representation of the surroundings in spatial memory.

    Tatler, Benjamin W; Land, Michael F

    2011-02-27

    One of the paradoxes of vision is that the world as it appears to us and the image on the retina at any moment are not much like each other. The visual world seems to be extensive and continuous across time. However, the manner in which we sample the visual environment is neither extensive nor continuous. How does the brain reconcile these differences? Here, we consider existing evidence from both static and dynamic viewing paradigms together with the logical requirements of any representational scheme that would be able to support active behaviour. While static scene viewing paradigms favour extensive, but perhaps abstracted, memory representations, dynamic settings suggest sparser and task-selective representation. We suggest that in dynamic settings where movement within extended environments is required to complete a task, the combination of visual input, egocentric and allocentric representations work together to allow efficient behaviour. The egocentric model serves as a coding scheme in which actions can be planned, but also offers a potential means of providing the perceptual stability that we experience.

  19. Vision and the representation of the surroundings in spatial memory

    Tatler, Benjamin W.; Land, Michael F.

    2011-01-01

    One of the paradoxes of vision is that the world as it appears to us and the image on the retina at any moment are not much like each other. The visual world seems to be extensive and continuous across time. However, the manner in which we sample the visual environment is neither extensive nor continuous. How does the brain reconcile these differences? Here, we consider existing evidence from both static and dynamic viewing paradigms together with the logical requirements of any representational scheme that would be able to support active behaviour. While static scene viewing paradigms favour extensive, but perhaps abstracted, memory representations, dynamic settings suggest sparser and task-selective representation. We suggest that in dynamic settings where movement within extended environments is required to complete a task, the combination of visual input, egocentric and allocentric representations work together to allow efficient behaviour. The egocentric model serves as a coding scheme in which actions can be planned, but also offers a potential means of providing the perceptual stability that we experience. PMID:21242146

  20. Probing the Mental Representation of Gesture: Is Handwaving Spatial?

    Wagner, Susan M.; Nusbaum, Howard; Goldin-Meadow, Susan

    2004-01-01

    What type of mental representation underlies the gestures that accompany speech? We used a dual-task paradigm to compare the demands gesturing makes on visuospatial and verbal working memories. Participants in one group remembered a string of letters (verbal working memory group) and those in a second group remembered a visual grid pattern…

  1. No functional role of attention-based rehearsal in maintenance of spatial working memory representations

    Belopolsky, A.V.; Theeuwes, J.

    2009-01-01

    The present study systematically examined the role of attention in maintenance of spatial representations in working memory as proposed by the attention-based rehearsal hypothesis [Awh, E., Jonides, J., & Reuter-Lorenz, P. A. (1998). Rehearsal in spatial working memory. Journal of Experimental

  2. Daytime sleep enhances consolidation of the spatial but not motoric representation of motor sequence memory.

    Geneviève Albouy

    Full Text Available Motor sequence learning is known to rely on more than a single process. As the skill develops with practice, two different representations of the sequence are formed: a goal representation built under spatial allocentric coordinates and a movement representation mediated through egocentric motor coordinates. This study aimed to explore the influence of daytime sleep (nap on consolidation of these two representations. Through the manipulation of an explicit finger sequence learning task and a transfer protocol, we show that both allocentric (spatial and egocentric (motor representations of the sequence can be isolated after initial training. Our results also demonstrate that nap favors the emergence of offline gains in performance for the allocentric, but not the egocentric representation, even after accounting for fatigue effects. Furthermore, sleep-dependent gains in performance observed for the allocentric representation are correlated with spindle density during non-rapid eye movement (NREM sleep of the post-training nap. In contrast, performance on the egocentric representation is only maintained, but not improved, regardless of the sleep/wake condition. These results suggest that motor sequence memory acquisition and consolidation involve distinct mechanisms that rely on sleep (and specifically, spindle or simple passage of time, depending respectively on whether the sequence is performed under allocentric or egocentric coordinates.

  3. A process analysis of the CA3 subregion of the hippocampus

    Raymond PIERRE Kesner

    2013-05-01

    Full Text Available AbstractFrom a behavioral perspective the CA3a,b subregion of the hippocampus plays an important role in the encoding of new spatial information within short-term memory with a duration of seconds and minutes. This can easily be observed in tasks that require rapid encoding, novelty detection, 1-trial short- term or working memory, and 1-trial cued recall primarily for spatial information. These are tasks that have been assumed to reflect the operations of episodic memory and require interactions between CA3a,b and the dentate gyrus via mossy fiber inputs into the CA3a,b. The CA3a,b is also important for encoding of spatial information requiring the acquisition of arbitrary and relational associations. All these tasks are assumed to operate within an autoassociative network function of the CA3 region. The CA3a,b also supports retrieval of short-term memory information based on a spatial pattern completion process. Based on afferent inputs into CA3a,b from the dentate gyrus (DG via mossy fibers and afferents from the entorhinal cortex into CA3a,b as well as reciprocal connections with the septum, CA3a,b can bias the process of encoding utilizing the operation of spatial pattern separation and the process of retrieval utilizing the operation of pattern completion. The CA3a,b also supports sequential processing of information in cooperation with CA1 based on the Schaffer collateral output from CA3a,b to CA1. The CA3c function is in part based on modulation of the DG in supporting pattern separation processes.

  4. 3D hierarchical spatial representation and memory of multimodal sensory data

    Khosla, Deepak; Dow, Paul A.; Huber, David J.

    2009-04-01

    This paper describes an efficient method and system for representing, processing and understanding multi-modal sensory data. More specifically, it describes a computational method and system for how to process and remember multiple locations in multimodal sensory space (e.g., visual, auditory, somatosensory, etc.). The multimodal representation and memory is based on a biologically-inspired hierarchy of spatial representations implemented with novel analogues of real representations used in the human brain. The novelty of the work is in the computationally efficient and robust spatial representation of 3D locations in multimodal sensory space as well as an associated working memory for storage and recall of these representations at the desired level for goal-oriented action. We describe (1) A simple and efficient method for human-like hierarchical spatial representations of sensory data and how to associate, integrate and convert between these representations (head-centered coordinate system, body-centered coordinate, etc.); (2) a robust method for training and learning a mapping of points in multimodal sensory space (e.g., camera-visible object positions, location of auditory sources, etc.) to the above hierarchical spatial representations; and (3) a specification and implementation of a hierarchical spatial working memory based on the above for storage and recall at the desired level for goal-oriented action(s). This work is most useful for any machine or human-machine application that requires processing of multimodal sensory inputs, making sense of it from a spatial perspective (e.g., where is the sensory information coming from with respect to the machine and its parts) and then taking some goal-oriented action based on this spatial understanding. A multi-level spatial representation hierarchy means that heterogeneous sensory inputs (e.g., visual, auditory, somatosensory, etc.) can map onto the hierarchy at different levels. When controlling various machine

  5. Analysis of students’ spatial thinking in geometry: 3D object into 2D representation

    Fiantika, F. R.; Maknun, C. L.; Budayasa, I. K.; Lukito, A.

    2018-05-01

    The aim of this study is to find out the spatial thinking process of students in transforming 3-dimensional (3D) object to 2-dimensional (2D) representation. Spatial thinking is helpful in using maps, planning routes, designing floor plans, and creating art. The student can engage geometric ideas by using concrete models and drawing. Spatial thinking in this study is identified through geometrical problems of transforming a 3-dimensional object into a 2-dimensional object image. The problem was resolved by the subject and analyzed by reference to predetermined spatial thinking indicators. Two representative subjects of elementary school were chosen based on mathematical ability and visual learning style. Explorative description through qualitative approach was used in this study. The result of this study are: 1) there are different representations of spatial thinking between a boy and a girl object, 2) the subjects has their own way to invent the fastest way to draw cube net.

  6. Behavioral and Neural Representations of Spatial Directions across Words, Schemas, and Images.

    Weisberg, Steven M; Marchette, Steven A; Chatterjee, Anjan

    2018-05-23

    Modern spatial navigation requires fluency with multiple representational formats, including visual scenes, signs, and words. These formats convey different information. Visual scenes are rich and specific but contain extraneous details. Arrows, as an example of signs, are schematic representations in which the extraneous details are eliminated, but analog spatial properties are preserved. Words eliminate all spatial information and convey spatial directions in a purely abstract form. How does the human brain compute spatial directions within and across these formats? To investigate this question, we conducted two experiments on men and women: a behavioral study that was preregistered and a neuroimaging study using multivoxel pattern analysis of fMRI data to uncover similarities and differences among representational formats. Participants in the behavioral study viewed spatial directions presented as images, schemas, or words (e.g., "left"), and responded to each trial, indicating whether the spatial direction was the same or different as the one viewed previously. They responded more quickly to schemas and words than images, despite the visual complexity of stimuli being matched. Participants in the fMRI study performed the same task but responded only to occasional catch trials. Spatial directions in images were decodable in the intraparietal sulcus bilaterally but were not in schemas and words. Spatial directions were also decodable between all three formats. These results suggest that intraparietal sulcus plays a role in calculating spatial directions in visual scenes, but this neural circuitry may be bypassed when the spatial directions are presented as schemas or words. SIGNIFICANCE STATEMENT Human navigators encounter spatial directions in various formats: words ("turn left"), schematic signs (an arrow showing a left turn), and visual scenes (a road turning left). The brain must transform these spatial directions into a plan for action. Here, we investigate

  7. Spatial Representations in Local Field Potential Activity of Primate Anterior Intraparietal Cortex (AIP.

    Sebastian J Lehmann

    Full Text Available The execution of reach-to-grasp movements in order to interact with our environment is an important subset of the human movement repertoire. To coordinate such goal-directed movements, information about the relative spatial position of target and effector (in this case the hand has to be continuously integrated and processed. Recently, we reported the existence of spatial representations in spiking-activity of the cortical fronto-parietal grasp network (Lehmann & Scherberger 2013, and in particular in the anterior intraparietal cortex (AIP. To further investigate the nature of these spatial representations, we explored in two rhesus monkeys (Macaca mulatta how different frequency bands of the local field potential (LFP in AIP are modulated by grip type, target position, and gaze position, during the planning and execution of reach-to-grasp movements. We systematically varied grasp type, spatial target, and gaze position and found that both spatial and grasp information were encoded in a variety of frequency bands (1-13Hz, 13-30Hz, 30-60Hz, and 60-100Hz, respectively. Whereas the representation of grasp type strongly increased towards and during movement execution, spatial information was represented throughout the task. Both spatial and grasp type representations could be readily decoded from all frequency bands. The fact that grasp type and spatial (reach information was found not only in spiking activity, but also in various LFP frequency bands of AIP, might significantly contribute to the development of LFP-based neural interfaces for the control of upper limb prostheses.

  8. Gender differences in the use of external landmarks versus spatial representations updated by self-motion.

    Lambrey, Simon; Berthoz, Alain

    2007-09-01

    Numerous data in the literature provide evidence for gender differences in spatial orientation. In particular, it has been suggested that spatial representations of large-scale environments are more accurate in terms of metric information in men than in women but are richer in landmark information in women than in men. One explanatory hypothesis is that men and women differ in terms of navigational processes they used in daily life. The present study investigated this hypothesis by distinguishing two navigational processes: spatial updating by self-motion and landmark-based orientation. Subjects were asked to perform a pointing task in three experimental conditions, which differed in terms of reliability of the external landmarks that could be used. Two groups of subjects were distinguished, a mobile group and an immobile group, in which spatial updating of environmental locations did not have the same degree of importance for the correct performance of the pointing task. We found that men readily relied on an internal egocentric representation of where landmarks were expected to be in order to perform the pointing task, a representation that could be updated during self-motion (spatial updating). In contrast, women seemed to take their bearings more readily on the basis of the stable landmarks of the external world. We suggest that this gender difference in spatial orientation is not due to differences in information processing abilities but rather due to the differences in higher level strategies.

  9. Directing spatial attention to locations within remembered and imagined mental representations

    Simon G Gosling

    2013-04-01

    Full Text Available Spatial attention enables us to enhance the processing of items at target locations, at the expense of items presented at irrelevant locations. Many studies have explored the neural correlates of these spatial biases using event-related potentials. More recently some studies have shown that these ERP correlates are also present when subjects search visual short-term memory. This suggests firstly that this type of mental representation retains a spatial organisation that is based upon that of the original percept, and secondly that these attentional biases are flexible and can act to modulate remembered as well as perceptual representations. We aimed to test whether it was necessary for subjects to have actually seen the memoranda at those spatial locations, or whether simply imagining the spatial layout was sufficient to elicit the spatial attention effects. On some trials subjects performed a ‘visual’ search of an array held in visual short-term memory, and upon other trials subjects imagined the items at those spatial locations. We found ERP markers of spatial attention in both the memory-search and the imagery-search conditions. However, there were differences between the conditions, the effect in the memory-search began earlier and included posterior electrode sites. By contrast the ERP effect in the imagery-search condition was apparent only over fronto-central electrode sites and emerged slightly later. Nonetheless, our data demonstrate that it is not necessary for subjects to have ever seen the items at spatial locations for neural markers of spatial attention to be elicited; searching an imaginary spatial layout also triggers spatially-specific attention effects in the ERP data.

  10. Continuous spatial representations in the olfactory bulb may reflect perceptual categories

    Benjamin eAuffarth

    2011-10-01

    Full Text Available In sensory processing of odors, the olfactory bulb is an important relay station, where odor representations are noise-filtered, sharpened, and possibly re-organized. An organization by perceptual qualities has been found previously in the piriform cortex, however several recent studies indicate that the olfactory bulb code reflects behaviorally relevant dimensions spatially as well as at the population level. We apply a statistical analysis on 2-deoxyglucose images, taken over the entire bulb of glomerular layer of the rat, in order to see how the recognition of odors in the nose is translated into a map of odor quality in the brain. We first confirm previous studies that the first principal component could be related to pleasantness, however the next higher principal components are not directly clear. We then find mostly continuous spatial representations for perceptual categories. We compare the space spanned by spatial and population codes to human reports of perceptual similarity between odors and our results suggest that perceptual categories could be already embedded in glomerular activations and that spatial representations give a better match than population codes. This suggests that human and rat perceptual dimensions of odorant coding are related and indicates that perceptual qualities could be represented as continuous spatial codes of the olfactory bulb glomerulus population.

  11. An investigation of spatial representation of pitch in individuals with congenital amusia.

    Lu, Xuejing; Sun, Yanan; Thompson, William Forde

    2017-09-01

    Spatial representation of pitch plays a central role in auditory processing. However, it is unknown whether impaired auditory processing is associated with impaired pitch-space mapping. Experiment 1 examined spatial representation of pitch in individuals with congenital amusia using a stimulus-response compatibility (SRC) task. For amusic and non-amusic participants, pitch classification was faster and more accurate when correct responses involved a physical action that was spatially congruent with the pitch height of the stimulus than when it was incongruent. However, this spatial representation of pitch was not as stable in amusic individuals, revealed by slower response times when compared with control individuals. One explanation is that the SRC effect in amusics reflects a linguistic association, requiring additional time to link pitch height and spatial location. To test this possibility, Experiment 2 employed a colour-classification task. Participants judged colour while ignoring a concurrent pitch by pressing one of two response keys positioned vertically to be congruent or incongruent with the pitch. The association between pitch and space was found in both groups, with comparable response times in the two groups, suggesting that amusic individuals are only slower to respond to tasks involving explicit judgments of pitch.

  12. Visual-Spatial Attention Aids the Maintenance of Object Representations in Visual Working Memory

    Williams, Melonie; Pouget, Pierre; Boucher, Leanne; Woodman, Geoffrey F.

    2013-01-01

    Theories have proposed that the maintenance of object representations in visual working memory is aided by a spatial rehearsal mechanism. In this study, we used two different approaches to test the hypothesis that overt and covert visual-spatial attention mechanisms contribute to the maintenance of object representations in visual working memory. First, we tracked observers’ eye movements while remembering a variable number of objects during change-detection tasks. We observed that during the blank retention interval, participants spontaneously shifted gaze to the locations that the objects had occupied in the memory array. Next, we hypothesized that if attention mechanisms contribute to the maintenance of object representations, then drawing attention away from the object locations during the retention interval would impair object memory during these change-detection tasks. Supporting this prediction, we found that attending to the fixation point in anticipation of a brief probe stimulus during the retention interval reduced change-detection accuracy even on the trials in which no probe occurred. These findings support models of working memory in which visual-spatial selection mechanisms contribute to the maintenance of object representations. PMID:23371773

  13. Exclusion of agricultural lands in spatial conservation prioritization strategies: consequences for biodiversity and ecosystem service representation.

    Durán, América P; Duffy, James P; Gaston, Kevin J

    2014-10-07

    Agroecosystems have traditionally been considered incompatible with biological conservation goals, and often been excluded from spatial conservation prioritization strategies. The consequences for the representativeness of identified priority areas have been little explored. Here, we evaluate these for biodiversity and carbon storage representation when agricultural land areas are excluded from a spatial prioritization strategy for South America. Comparing different prioritization approaches, we also assess how the spatial overlap of priority areas changes. The exclusion of agricultural lands was detrimental to biodiversity representation, indicating that priority areas for agricultural production overlap with areas of relatively high occurrence of species. By contrast, exclusion of agricultural lands benefits representation of carbon storage within priority areas, as lands of high value for agriculture and carbon storage overlap little. When agricultural lands were included and equally weighted with biodiversity and carbon storage, a balanced representation resulted. Our findings suggest that with appropriate management, South American agroecosystems can significantly contribute to biodiversity conservation. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  14. Unbounding the mental number line – New evidence on children’s spatial representation of numbers

    Tanja eLink

    2014-01-01

    Full Text Available Number line estimation (i.e., indicating the position of a given number on a physical line is a standard assessment of children’s spatial representation of number magnitude. Importantly, there is an ongoing debate on the question in how far the bounded task version with start and endpoint given (e.g., 0 and 100 might induce specific estimation strategies and thus may not allow for unbiased inferences on the underlying representation. Recently, a new unbounded version of the task was suggested with only the start point and a unit fixed (e.g., the distance from 0 to 1. In adults this task provided a less biased index of the spatial representation of number magnitude. Yet, so far there are no children data available for the unbounded number line estimation task. Therefore, we conducted a cross-sectional study on primary school children performing both, the bounded and the unbounded version of the task. We observed clear evidence for systematic strategic influences (i.e., the consideration of reference points in the bounded number line estimation task for children older than grade two whereas there were no such indications for the unbounded version for any one of the age groups. In summary, the current data corroborate the unbounded number line estimation task to be a valuable tool for assessing children's spatial representation of number magnitude in a systematic and unbiased manner. Yet, similar results for the bounded and the unbounded version of the task for first- and second-graders may indicate that both versions of the task might assess the same underlying representation for relatively younger children - at least in number ranges familiar to the children assessed. This is of particular importance for inferences about the nature and development of children's magnitude representation.

  15. Analysis of Spatial Concepts, Spatial Skills and Spatial Representations in New York State Regents Earth Science Examinations

    Kastens, Kim A.; Pistolesi, Linda; Passow, Michael J.

    2014-01-01

    Research has shown that spatial thinking is important in science in general, and in Earth Science in particular, and that performance on spatially demanding tasks can be fostered through instruction. Because spatial thinking is rarely taught explicitly in the U.S. education system, improving spatial thinking may be "low-hanging fruit" as…

  16. Spatial language processing in the blind: evidence for a supramodal representation and cortical reorganization.

    Marijn E Struiksma

    Full Text Available Neuropsychological and imaging studies have shown that the left supramarginal gyrus (SMG is specifically involved in processing spatial terms (e.g. above, left of, which locate places and objects in the world. The current fMRI study focused on the nature and specificity of representing spatial language in the left SMG by combining behavioral and neuronal activation data in blind and sighted individuals. Data from the blind provide an elegant way to test the supramodal representation hypothesis, i.e. abstract codes representing spatial relations yielding no activation differences between blind and sighted. Indeed, the left SMG was activated during spatial language processing in both blind and sighted individuals implying a supramodal representation of spatial and other dimensional relations which does not require visual experience to develop. However, in the absence of vision functional reorganization of the visual cortex is known to take place. An important consideration with respect to our finding is the amount of functional reorganization during language processing in our blind participants. Therefore, the participants also performed a verb generation task. We observed that only in the blind occipital areas were activated during covert language generation. Additionally, in the first task there was functional reorganization observed for processing language with a high linguistic load. As the visual cortex was not specifically active for spatial contents in the first task, and no reorganization was observed in the SMG, the latter finding further supports the notion that the left SMG is the main node for a supramodal representation of verbal spatial relations.

  17. Hyperspectral Image Classification Based on the Combination of Spatial-spectral Feature and Sparse Representation

    YANG Zhaoxia

    2015-07-01

    Full Text Available In order to avoid the problem of being over-dependent on high-dimensional spectral feature in the traditional hyperspectral image classification, a novel approach based on the combination of spatial-spectral feature and sparse representation is proposed in this paper. Firstly, we extract the spatial-spectral feature by reorganizing the local image patch with the first d principal components(PCs into a vector representation, followed by a sorting scheme to make the vector invariant to local image rotation. Secondly, we learn the dictionary through a supervised method, and use it to code the features from test samples afterwards. Finally, we embed the resulting sparse feature coding into the support vector machine(SVM for hyperspectral image classification. Experiments using three hyperspectral data show that the proposed method can effectively improve the classification accuracy comparing with traditional classification methods.

  18. A Lightweight AV System for Providing a Faithful and Spatially Manipulable Visual Hand Representation

    Pusch , Andreas; Martin , Olivier; Coquillart , Sabine

    2011-01-01

    Session: Developing new tools and technologies - Abstracts to be published in a regular issue of the journal Cyberpsychology, Behavior and Social Networking (indexed in MedLine and PsychInfo): http://online.liebertpub.com/loi/CYBER; International audience; This paper introduces the technical foundations of a system designed to embed a lightweight, faithful and spatially manipulable representation of the user's hand into an otherwise virtual world (aka Augmented Virtuality, AV). A highly intui...

  19. Impacts of spatial resolution and representation of flow connectivity on large-scale simulation of floods

    C. M. R. Mateo; C. M. R. Mateo; D. Yamazaki; D. Yamazaki; H. Kim; A. Champathong; J. Vaze; T. Oki; T. Oki

    2017-01-01

    Global-scale river models (GRMs) are core tools for providing consistent estimates of global flood hazard, especially in data-scarce regions. Due to former limitations in computational power and input datasets, most GRMs have been developed to use simplified representations of flow physics and run at coarse spatial resolutions. With increasing computational power and improved datasets, the application of GRMs to finer resolutions is becoming a reality. To support development...

  20. Impacts of spatial resolution and representation of flow connectivity on large-scale simulation of floods

    Mateo, Cherry May R.; Yamazaki, Dai; Kim, Hyungjun; Champathong, Adisorn; Vaze, Jai; Oki, Taikan

    2017-01-01

    Global-scale River Models (GRMs) are core tools for providing consistent estimates of global flood hazard, especially in data-scarce regions. Due to former limitations in computational power and input datasets, most GRMs have been developed to use simplified representation of flow physics and run at coarse spatial resolutions. With increasing computational power and improved datasets, the application of GRMs to finer resolutions is becoming a reality. To support development in this direction,...

  1. Deployment of spatial attention towards locations in memory representations. An EEG study.

    Leszczyński, Marcin; Wykowska, Agnieszka; Perez-Osorio, Jairo; Müller, Hermann J

    2013-01-01

    Recalling information from visual short-term memory (VSTM) involves the same neural mechanisms as attending to an actually perceived scene. In particular, retrieval from VSTM has been associated with orienting of visual attention towards a location within a spatially-organized memory representation. However, an open question concerns whether spatial attention is also recruited during VSTM retrieval even when performing the task does not require access to spatial coordinates of items in the memorized scene. The present study combined a visual search task with a modified, delayed central probe protocol, together with EEG analysis, to answer this question. We found a temporal contralateral negativity (TCN) elicited by a centrally presented go-signal which was spatially uninformative and featurally unrelated to the search target and informed participants only about a response key that they had to press to indicate a prepared target-present vs. -absent decision. This lateralization during VSTM retrieval (TCN) provides strong evidence of a shift of attention towards the target location in the memory representation, which occurred despite the fact that the present task required no spatial (or featural) information from the search to be encoded, maintained, and retrieved to produce the correct response and that the go-signal did not itself specify any information relating to the location and defining feature of the target.

  2. Deployment of spatial attention towards locations in memory representations. An EEG study.

    Marcin Leszczyński

    Full Text Available Recalling information from visual short-term memory (VSTM involves the same neural mechanisms as attending to an actually perceived scene. In particular, retrieval from VSTM has been associated with orienting of visual attention towards a location within a spatially-organized memory representation. However, an open question concerns whether spatial attention is also recruited during VSTM retrieval even when performing the task does not require access to spatial coordinates of items in the memorized scene. The present study combined a visual search task with a modified, delayed central probe protocol, together with EEG analysis, to answer this question. We found a temporal contralateral negativity (TCN elicited by a centrally presented go-signal which was spatially uninformative and featurally unrelated to the search target and informed participants only about a response key that they had to press to indicate a prepared target-present vs. -absent decision. This lateralization during VSTM retrieval (TCN provides strong evidence of a shift of attention towards the target location in the memory representation, which occurred despite the fact that the present task required no spatial (or featural information from the search to be encoded, maintained, and retrieved to produce the correct response and that the go-signal did not itself specify any information relating to the location and defining feature of the target.

  3. Where to attend next: guiding refreshing of visual, spatial, and verbal representations in working memory.

    Souza, Alessandra S; Vergauwe, Evie; Oberauer, Klaus

    2018-04-23

    One of the functions that attention may serve in working memory (WM) is boosting information accessibility, a mechanism known as attentional refreshing. Refreshing is assumed to be a domain-general process operating on visual, spatial, and verbal representations alike. So far, few studies have directly manipulated refreshing of individual WM representations to measure the WM benefits of refreshing. Recently, a guided-refreshing method was developed, which consists of presenting cues during the retention interval of a WM task to instruct people to refresh (i.e., attend to) the cued items. Using a continuous-color reconstruction task, previous studies demonstrated that the error in reporting a color varies linearly with the frequency with which it was refreshed. Here, we extend this approach to assess the WM benefits of refreshing different representation types, from colors to spatial locations and words. Across six experiments, we show that refreshing frequency modulates performance in all stimulus domains in accordance with the tenet that refreshing is a domain-general process in WM. The benefits of refreshing were, however, larger for visual-spatial than verbal materials. © 2018 New York Academy of Sciences.

  4. Evidence for cue-independent spatial representation in the human auditory cortex during active listening.

    Higgins, Nathan C; McLaughlin, Susan A; Rinne, Teemu; Stecker, G Christopher

    2017-09-05

    Few auditory functions are as important or as universal as the capacity for auditory spatial awareness (e.g., sound localization). That ability relies on sensitivity to acoustical cues-particularly interaural time and level differences (ITD and ILD)-that correlate with sound-source locations. Under nonspatial listening conditions, cortical sensitivity to ITD and ILD takes the form of broad contralaterally dominated response functions. It is unknown, however, whether that sensitivity reflects representations of the specific physical cues or a higher-order representation of auditory space (i.e., integrated cue processing), nor is it known whether responses to spatial cues are modulated by active spatial listening. To investigate, sensitivity to parametrically varied ITD or ILD cues was measured using fMRI during spatial and nonspatial listening tasks. Task type varied across blocks where targets were presented in one of three dimensions: auditory location, pitch, or visual brightness. Task effects were localized primarily to lateral posterior superior temporal gyrus (pSTG) and modulated binaural-cue response functions differently in the two hemispheres. Active spatial listening (location tasks) enhanced both contralateral and ipsilateral responses in the right hemisphere but maintained or enhanced contralateral dominance in the left hemisphere. Two observations suggest integrated processing of ITD and ILD. First, overlapping regions in medial pSTG exhibited significant sensitivity to both cues. Second, successful classification of multivoxel patterns was observed for both cue types and-critically-for cross-cue classification. Together, these results suggest a higher-order representation of auditory space in the human auditory cortex that at least partly integrates the specific underlying cues.

  5. Representation

    Little, Daniel

    2006-01-01

    ...). The reason this is so is due to hierarchies that we take for granted. By hierarchies I mean that there is a layer of representation of us as individuals, as military professional, as members of a military unit and as citizens of an entire nation...

  6. Allocentric and contra-aligned spatial representations of a town environment in blind people.

    Chiesa, Silvia; Schmidt, Susanna; Tinti, Carla; Cornoldi, Cesare

    2017-10-01

    Evidence concerning the representation of space by blind individuals is still unclear, as sometimes blind people behave like sighted people do, while other times they present difficulties. A better understanding of blind people's difficulties, especially with reference to the strategies used to form the representation of the environment, may help to enhance knowledge of the consequences of the absence of vision. The present study examined the representation of the locations of landmarks of a real town by using pointing tasks that entailed either allocentric points of reference with mental rotations of different degrees, or contra-aligned representations. Results showed that, in general, people met difficulties when they had to point from a different perspective to aligned landmarks or from the original perspective to contra-aligned landmarks, but this difficulty was particularly evident for the blind. The examination of the strategies adopted to perform the tasks showed that only a small group of blind participants used a survey strategy and that this group had a better performance with respect to people who adopted route or verbal strategies. Implications for the comprehension of the consequences on spatial cognition of the absence of visual experience are discussed, focusing in particular on conceivable interventions. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Representation

    2006-09-01

    two weeks to arrive. Source: http://beergame.mit.edu/ Permission Granted – MIT Supply Chain Forum 2005 Professor Sterman –Sloan School of...Management - MITSource: http://web.mit.edu/jsterman/www/ SDG /beergame.html Rules of Engagement The MIT Beer Game Simulation 04-04 Slide Number 10 Professor...Sterman –Sloan School of Management - MITSource: http://web.mit.edu/jsterman/www/ SDG /beergame.html What is the Significance of Representation

  8. The Evolution of Spatial Representation During Complex Visual Data Analysis: Knowing When and How to be Exact

    Schunn, Christian D; Saner, Lelyn D; Trafton, J. G; Trickett, Susan B; Kirschenbaum, Susan K; Knepp, Michael; Shoup, Melanie

    2005-01-01

    ... (weather forecasting, submarine target motion analysis, and fMRI data analysis). Internal spatial representations are coded from spontaneous gestures made during cued-recall summaries of problem solving activities...

  9. Research on a Rotating Machinery Fault Prognosis Method Using Three-Dimensional Spatial Representations

    Xiaoni Dong

    2016-01-01

    Full Text Available Process models and parameters are two critical steps for fault prognosis in the operation of rotating machinery. Due to the requirement for a short and rapid response, it is important to study robust sensor data representation schemes. However, the conventional holospectrum defined by one-dimensional or two-dimensional methods does not sufficiently present this information in both the frequency and time domains. To supply a complete holospectrum model, a new three-dimensional spatial representation method is proposed. This method integrates improved three-dimensional (3D holospectra and 3D filtered orbits, leading to the integration of radial and axial vibration features in one bearing section. The results from simulation and experimental analysis on a complex compressor show that the proposed method can present the real operational status and clearly reveal early faults, thus demonstrating great potential for condition-based maintenance prediction in industrial machinery.

  10. Spatially-explicit estimation of geographical representation in large-scale species distribution datasets.

    Kalwij, Jesse M; Robertson, Mark P; Ronk, Argo; Zobel, Martin; Pärtel, Meelis

    2014-01-01

    Much ecological research relies on existing multispecies distribution datasets. Such datasets, however, can vary considerably in quality, extent, resolution or taxonomic coverage. We provide a framework for a spatially-explicit evaluation of geographical representation within large-scale species distribution datasets, using the comparison of an occurrence atlas with a range atlas dataset as a working example. Specifically, we compared occurrence maps for 3773 taxa from the widely-used Atlas Florae Europaeae (AFE) with digitised range maps for 2049 taxa of the lesser-known Atlas of North European Vascular Plants. We calculated the level of agreement at a 50-km spatial resolution using average latitudinal and longitudinal species range, and area of occupancy. Agreement in species distribution was calculated and mapped using Jaccard similarity index and a reduced major axis (RMA) regression analysis of species richness between the entire atlases (5221 taxa in total) and between co-occurring species (601 taxa). We found no difference in distribution ranges or in the area of occupancy frequency distribution, indicating that atlases were sufficiently overlapping for a valid comparison. The similarity index map showed high levels of agreement for central, western, and northern Europe. The RMA regression confirmed that geographical representation of AFE was low in areas with a sparse data recording history (e.g., Russia, Belarus and the Ukraine). For co-occurring species in south-eastern Europe, however, the Atlas of North European Vascular Plants showed remarkably higher richness estimations. Geographical representation of atlas data can be much more heterogeneous than often assumed. Level of agreement between datasets can be used to evaluate geographical representation within datasets. Merging atlases into a single dataset is worthwhile in spite of methodological differences, and helps to fill gaps in our knowledge of species distribution ranges. Species distribution

  11. Sparse orthogonal population representation of spatial context in the retrosplenial cortex.

    Mao, Dun; Kandler, Steffen; McNaughton, Bruce L; Bonin, Vincent

    2017-08-15

    Sparse orthogonal coding is a key feature of hippocampal neural activity, which is believed to increase episodic memory capacity and to assist in navigation. Some retrosplenial cortex (RSC) neurons convey distributed spatial and navigational signals, but place-field representations such as observed in the hippocampus have not been reported. Combining cellular Ca 2+ imaging in RSC of mice with a head-fixed locomotion assay, we identified a population of RSC neurons, located predominantly in superficial layers, whose ensemble activity closely resembles that of hippocampal CA1 place cells during the same task. Like CA1 place cells, these RSC neurons fire in sequences during movement, and show narrowly tuned firing fields that form a sparse, orthogonal code correlated with location. RSC 'place' cell activity is robust to environmental manipulations, showing partial remapping similar to that observed in CA1. This population code for spatial context may assist the RSC in its role in memory and/or navigation.Neurons in the retrosplenial cortex (RSC) encode spatial and navigational signals. Here the authors use calcium imaging to show that, similar to the hippocampus, RSC neurons also encode place cell-like activity in a sparse orthogonal representation, partially anchored to the allocentric cues on the linear track.

  12. The Focus of Spatial Attention Determines the Number and Precision of Face Representations in Working Memory.

    Towler, John; Kelly, Maria; Eimer, Martin

    2016-06-01

    The capacity of visual working memory for faces is extremely limited, but the reasons for these limitations remain unknown. We employed event-related brain potential measures to demonstrate that individual faces have to be focally attended in order to be maintained in working memory, and that attention is allocated to only a single face at a time. When 2 faces have to be memorized simultaneously in a face identity-matching task, the focus of spatial attention during encoding predicts which of these faces can be successfully maintained in working memory and matched to a subsequent test face. We also show that memory representations of attended faces are maintained in a position-dependent fashion. These findings demonstrate that the limited capacity of face memory is directly linked to capacity limits of spatial attention during the encoding and maintenance of individual face representations. We suggest that the capacity and distribution of selective spatial attention is a dynamic resource that constrains the capacity and fidelity of working memory for faces. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  13. No functional role of attention-based rehearsal in maintenance of spatial working memory representations.

    Belopolsky, Artem V; Theeuwes, Jan

    2009-10-01

    The present study systematically examined the role of attention in maintenance of spatial representations in working memory as proposed by the attention-based rehearsal hypothesis [Awh, E., Jonides, J., & Reuter-Lorenz, P. A. (1998). Rehearsal in spatial working memory. Journal of Experimental Psychology--Human Perception and Performance, 24(3), 780-790]. Three main issues were examined. First, Experiments 1-3 demonstrated that inhibition and not facilitation of visual processing is often observed at the memorized location during the retention interval. This inhibition was caused by keeping a location in memory and not by the exogenous nature of the memory cue. Second, Experiment 4 showed that inhibition of the memorized location does not lead to any significant impairment in memory accuracy. Finally, Experiment 5 connected current results to the previous findings and demonstrated facilitation of processing at the memorized location. Importantly, facilitation of processing did not lead to more accurate memory performance. The present results challenge the functional role of attention in maintenance of spatial working memory representations.

  14. Impacts of spatial resolution and representation of flow connectivity on large-scale simulation of floods

    C. M. R. Mateo

    2017-10-01

    Full Text Available Global-scale river models (GRMs are core tools for providing consistent estimates of global flood hazard, especially in data-scarce regions. Due to former limitations in computational power and input datasets, most GRMs have been developed to use simplified representations of flow physics and run at coarse spatial resolutions. With increasing computational power and improved datasets, the application of GRMs to finer resolutions is becoming a reality. To support development in this direction, the suitability of GRMs for application to finer resolutions needs to be assessed. This study investigates the impacts of spatial resolution and flow connectivity representation on the predictive capability of a GRM, CaMa-Flood, in simulating the 2011 extreme flood in Thailand. Analyses show that when single downstream connectivity (SDC is assumed, simulation results deteriorate with finer spatial resolution; Nash–Sutcliffe efficiency coefficients decreased by more than 50 % between simulation results at 10 km resolution and 1 km resolution. When multiple downstream connectivity (MDC is represented, simulation results slightly improve with finer spatial resolution. The SDC simulations result in excessive backflows on very flat floodplains due to the restrictive flow directions at finer resolutions. MDC channels attenuated these effects by maintaining flow connectivity and flow capacity between floodplains in varying spatial resolutions. While a regional-scale flood was chosen as a test case, these findings should be universal and may have significant impacts on large- to global-scale simulations, especially in regions where mega deltas exist.These results demonstrate that a GRM can be used for higher resolution simulations of large-scale floods, provided that MDC in rivers and floodplains is adequately represented in the model structure.

  15. Impacts of spatial resolution and representation of flow connectivity on large-scale simulation of floods

    Mateo, Cherry May R.; Yamazaki, Dai; Kim, Hyungjun; Champathong, Adisorn; Vaze, Jai; Oki, Taikan

    2017-10-01

    Global-scale river models (GRMs) are core tools for providing consistent estimates of global flood hazard, especially in data-scarce regions. Due to former limitations in computational power and input datasets, most GRMs have been developed to use simplified representations of flow physics and run at coarse spatial resolutions. With increasing computational power and improved datasets, the application of GRMs to finer resolutions is becoming a reality. To support development in this direction, the suitability of GRMs for application to finer resolutions needs to be assessed. This study investigates the impacts of spatial resolution and flow connectivity representation on the predictive capability of a GRM, CaMa-Flood, in simulating the 2011 extreme flood in Thailand. Analyses show that when single downstream connectivity (SDC) is assumed, simulation results deteriorate with finer spatial resolution; Nash-Sutcliffe efficiency coefficients decreased by more than 50 % between simulation results at 10 km resolution and 1 km resolution. When multiple downstream connectivity (MDC) is represented, simulation results slightly improve with finer spatial resolution. The SDC simulations result in excessive backflows on very flat floodplains due to the restrictive flow directions at finer resolutions. MDC channels attenuated these effects by maintaining flow connectivity and flow capacity between floodplains in varying spatial resolutions. While a regional-scale flood was chosen as a test case, these findings should be universal and may have significant impacts on large- to global-scale simulations, especially in regions where mega deltas exist.These results demonstrate that a GRM can be used for higher resolution simulations of large-scale floods, provided that MDC in rivers and floodplains is adequately represented in the model structure.

  16. Spatial and Foveal Biases, Not Perceived Mass or Heaviness, Explain the Effect of Target Size on Representational Momentum and Representational Gravity

    De Sá Teixeira, Nuno; Oliveira, Armando Mónica

    2014-01-01

    The spatial memory for the last position occupied by a moving target is usually displaced forward in the direction of motion. Interpreted as a mental analogue of physical momentum, this phenomenon was coined "representational momentum" (RM). As momentum is given by the product of an object's velocity and mass, both these factors came to…

  17. a Representation-Driven Ontology for Spatial Data Quality Elements, with Orthoimagery as Running Example

    Hangouët, J.-F.

    2015-08-01

    The many facets of what is encompassed by such an expression as "quality of spatial data" can be considered as a specific domain of reality worthy of formal description, i.e. of ontological abstraction. Various ontologies for data quality elements have already been proposed in literature. Today, the system of quality elements is most generally used and discussed according to the configuration exposed in the "data dictionary for data quality" of international standard ISO 19157. Our communication proposes an alternative view. This is founded on a perspective which focuses on the specificity of spatial data as a product: the representation perspective, where data in the computer are meant to show things of the geographic world and to be interpreted as such. The resulting ontology introduces new elements, the usefulness of which will be illustrated by orthoimagery examples.

  18. Reference frames for spatial frequency in face representation differ in the temporal visual cortex and amygdala.

    Inagaki, Mikio; Fujita, Ichiro

    2011-07-13

    Social communication in nonhuman primates and humans is strongly affected by facial information from other individuals. Many cortical and subcortical brain areas are known to be involved in processing facial information. However, how the neural representation of faces differs across different brain areas remains unclear. Here, we demonstrate that the reference frame for spatial frequency (SF) tuning of face-responsive neurons differs in the temporal visual cortex and amygdala in monkeys. Consistent with psychophysical properties for face recognition, temporal cortex neurons were tuned to image-based SFs (cycles/image) and showed viewing distance-invariant representation of face patterns. On the other hand, many amygdala neurons were influenced by retina-based SFs (cycles/degree), a characteristic that is useful for social distance computation. The two brain areas also differed in the luminance contrast sensitivity of face-responsive neurons; amygdala neurons sharply reduced their responses to low luminance contrast images, while temporal cortex neurons maintained the level of their responses. From these results, we conclude that different types of visual processing in the temporal visual cortex and the amygdala contribute to the construction of the neural representations of faces.

  19. Providing a non-deterministic representation of spatial variability of precipitation in the Everest region

    J. Eeckman

    2017-09-01

    Full Text Available This paper provides a new representation of the effect of altitude on precipitation that represents spatial and temporal variability in precipitation in the Everest region. Exclusive observation data are used to infer a piecewise linear function for the relation between altitude and precipitation and significant seasonal variations are highlighted. An original ensemble approach is applied to provide non-deterministic water budgets for middle and high-mountain catchments. Physical processes at the soil–atmosphere interface are represented through the Interactions Soil–Biosphere–Atmosphere (ISBA surface scheme. Uncertainties associated with the model parametrization are limited by the integration of in situ measurements of soils and vegetation properties. Uncertainties associated with the representation of the orographic effect are shown to account for up to 16 % of annual total precipitation. Annual evapotranspiration is shown to represent 26 % ± 1 % of annual total precipitation for the mid-altitude catchment and 34% ± 3 % for the high-altitude catchment. Snowfall contribution is shown to be neglectable for the mid-altitude catchment, and it represents up to 44 % ± 8 % of total precipitation for the high-altitude catchment. These simulations on the local scale enhance current knowledge of the spatial variability in hydroclimatic processes in high- and mid-altitude mountain environments.

  20. Fine-grained, local maps and coarse, global representations support human spatial working memory.

    Mohammad Zia Ul Haq Katshu

    Full Text Available While sensory processes are tuned to particular features, such as an object's specific location, color or orientation, visual working memory (vWM is assumed to store information using representations, which generalize over a feature dimension. Additionally, current vWM models presume that different features or objects are stored independently. On the other hand, configurational effects, when observed, are supposed to mainly reflect encoding strategies. We show that the location of the target, relative to the display center and boundaries, and overall memory load influenced recall precision, indicating that, like sensory processes, capacity limited vWM resources are spatially tuned. When recalling one of three memory items the target distance from the display center was overestimated, similar to the error when only one item was memorized, but its distance from the memory items' average position was underestimated, showing that not only individual memory items' position, but also the global configuration of the memory array may be stored. Finally, presenting the non-target items at recall, consequently providing landmarks and configurational information, improved precision and accuracy of target recall. Similarly, when the non-target items were translated at recall, relative to their position in the initial display, a parallel displacement of the recalled target was observed. These findings suggest that fine-grained spatial information in vWM is represented in local maps whose resolution varies with distance from landmarks, such as the display center, while coarse representations are used to store the memory array configuration. Both these representations are updated at the time of recall.

  1. Fine-Grained, Local Maps and Coarse, Global Representations Support Human Spatial Working Memory

    Katshu, Mohammad Zia Ul Haq; d'Avossa, Giovanni

    2014-01-01

    While sensory processes are tuned to particular features, such as an object's specific location, color or orientation, visual working memory (vWM) is assumed to store information using representations, which generalize over a feature dimension. Additionally, current vWM models presume that different features or objects are stored independently. On the other hand, configurational effects, when observed, are supposed to mainly reflect encoding strategies. We show that the location of the target, relative to the display center and boundaries, and overall memory load influenced recall precision, indicating that, like sensory processes, capacity limited vWM resources are spatially tuned. When recalling one of three memory items the target distance from the display center was overestimated, similar to the error when only one item was memorized, but its distance from the memory items' average position was underestimated, showing that not only individual memory items' position, but also the global configuration of the memory array may be stored. Finally, presenting the non-target items at recall, consequently providing landmarks and configurational information, improved precision and accuracy of target recall. Similarly, when the non-target items were translated at recall, relative to their position in the initial display, a parallel displacement of the recalled target was observed. These findings suggest that fine-grained spatial information in vWM is represented in local maps whose resolution varies with distance from landmarks, such as the display center, while coarse representations are used to store the memory array configuration. Both these representations are updated at the time of recall. PMID:25259601

  2. The role of spatial boundaries in shaping long-term event representations.

    Horner, Aidan J; Bisby, James A; Wang, Aijing; Bogus, Katrina; Burgess, Neil

    2016-09-01

    When remembering the past, we typically recall 'events' that are bounded in time and space. However, as we navigate our environment our senses receive a continuous stream of information. How do we create discrete long-term episodic memories from continuous input? Although previous research has provided evidence for a role of spatial boundaries in the online segmentation of our sensory experience within working memory, it is not known how this segmentation contributes to subsequent long-term episodic memory. Here we show that the presence of a spatial boundary at encoding (a doorway between two rooms) impairs participants' later ability to remember the order that objects were presented in. A sequence of two objects presented in the same room in a virtual reality environment is more accurately remembered than a sequence of two objects presented in adjoining rooms. The results are captured by a simple model in which items are associated to a context representation that changes gradually over time, and changes more rapidly when crossing a spatial boundary. We therefore provide the first evidence that the structure of long-term episodic memory is shaped by the presence of a spatial boundary and provide constraints on the nature of the interaction between working memory and long-term memory. Copyright © 2016 The Author(s). Published by Elsevier B.V. All rights reserved.

  3. Lucky numbers: spatial neglect affects physical, but not representational, choices in a lotto task.

    Loetscher, Tobias; Nicholls, Michael E R; Towse, John N; Bradshaw, John L; Brugger, Peter

    2010-05-01

    Spatial neglect can be characterized by a "magnetic attraction" towards the right side of a visual stimulus array and a selection of stimuli from that hemispace. This study examined whether these distinctive characteristics in visuo-motor space are also evident in representational number space. Given that numbers are thought to be represented along a left-to-right oriented mental number line, an affinity for the spontaneous selection of larger numbers was anticipated for neglect patients. Contrary to this expectation, neglect patients (n=20) picked a similar range of numbers compared to controls (n=17) when generating a number between 1000 and 10,000 and when playing an imaginary lottery game. There was, however, a positive correlation between the biases for the imaginary lottery, number generation and a number bisection task - demonstrating that exploration asymmetries along the mental number line are consistent within individuals across tasks. Some of the patients selected smaller numbers in all of these tasks, confirming reports of dissociations between physical and numerical-representational forms of neglect. Conversely, only four (20%) of the patients could reliably be classified as demonstrating a neglect in number space. When filling out a physical lottery ticket, the neglect patients showed the expected bias towards picking numbers placed on the right-hand side of the ticket. These results demonstrate that the magnetic attraction towards the right side of mental representations is rather weak and that representational forms of neglect only occasionally co-exist with neglect in physical space. Copyright 2009 Elsevier Srl. All rights reserved.

  4. Relative contributions of visual and auditory spatial representations to tactile localization.

    Noel, Jean-Paul; Wallace, Mark

    2016-02-01

    Spatial localization of touch is critically dependent upon coordinate transformation between different reference frames, which must ultimately allow for alignment between somatotopic and external representations of space. Although prior work has shown an important role for cues such as body posture in influencing the spatial localization of touch, the relative contributions of the different sensory systems to this process are unknown. In the current study, we had participants perform a tactile temporal order judgment (TOJ) under different body postures and conditions of sensory deprivation. Specifically, participants performed non-speeded judgments about the order of two tactile stimuli presented in rapid succession on their ankles during conditions in which their legs were either uncrossed or crossed (and thus bringing somatotopic and external reference frames into conflict). These judgments were made in the absence of 1) visual, 2) auditory, or 3) combined audio-visual spatial information by blindfolding and/or placing participants in an anechoic chamber. As expected, results revealed that tactile temporal acuity was poorer under crossed than uncrossed leg postures. Intriguingly, results also revealed that auditory and audio-visual deprivation exacerbated the difference in tactile temporal acuity between uncrossed to crossed leg postures, an effect not seen for visual-only deprivation. Furthermore, the effects under combined audio-visual deprivation were greater than those seen for auditory deprivation. Collectively, these results indicate that mechanisms governing the alignment between somatotopic and external reference frames extend beyond those imposed by body posture to include spatial features conveyed by the auditory and visual modalities - with a heavier weighting of auditory than visual spatial information. Thus, sensory modalities conveying exteroceptive spatial information contribute to judgments regarding the localization of touch. Copyright © 2016

  5. Recurrent synapses and circuits in the CA3 region of the hippocampus: an associative network.

    Richard eMiles

    2014-01-01

    Full Text Available In the CA3 region of the hippocampus, pyramidal cells excite other pyramidal cells and interneurons. The axons of CA3 pyramidal cells spread throughout most of the region to form an associative network. These connections were first drawn by Cajal and Lorente de No. Their physiological properties were explored to understand epileptiform discharges generated in the region. Synapses between pairs of pyramidal cells involve one or few release sites and are weaker than connections made by mossy fibres on CA3 pyramidal cells. Synapses with interneurons are rather effective, as needed to control unchecked excitation. We examine contributions of recurrent synapses to epileptiform synchrony, to the genesis of sharp waves in the CA3 region and to population oscillations at theta and gamma frequencies. Recurrent connections in CA3, as other associative cortices, have a lower connectivity spread over a larger area than in primary sensory cortices. This sparse, but wide-ranging connectivity serves the functions of an associative network, including acquisition of neuronal representations as activity in groups of CA3 cells and completion involving the recall from partial cues of these ensemble firing patterns.

  6. SNAP-25 in hippocampal CA3 region is required for long-term memory formation

    Hou Qiuling; Gao Xiang; Lu Qi; Zhang Xuehan; Tu Yanyang; Jin Meilei; Zhao Guoping; Yu Lei; Jing Naihe; Li Baoming

    2006-01-01

    SNAP-25 is a synaptosomal protein of 25 kDa, a key component of synaptic vesicle-docking/fusion machinery, and plays a critical role in exocytosis and neurotransmitter release. We previously reported that SNAP-25 in the hippocampal CA1 region is involved in consolidation of contextual fear memory and water-maze spatial memory (Hou et al. European J Neuroscience, 20: 1593-1603, 2004). SNAP-25 is expressed not only in the CA1 region, but also in the CA3 region, and the SNAP-25 mRNA level in the CA3 region is higher than in the CA1 region. Here, we provide evidence that SNAP-25 in the CA3 region is also involved in learning/memory. Intra-CA3 infusion of SNAP-25 antisense oligonucleotide impaired both long-term contextual fear memory and water-maze spatial memory, with short-term memory intact. Furthermore, the SNAP-25 antisense oligonucleotide suppressed the long-term potentiation (LTP) of field excitatory post-synaptic potential (fEPSP) in the mossy-fiber pathway (DG-CA3 pathway), with no effect on paired-pulse facilitation of the fEPSP. These results are consistent with the notion that SNAP-25 in the hippocampal CA3 region is required for long-term memory formation

  7. Lack of spatial segregation in the representation of pheromones and kairomones in the mouse medial amygdala.

    Vinicius Miessler de Andrade Carvalho

    2015-08-01

    Full Text Available The nervous system is organized to detect, internally represent and process sensory information to generate appropriate behaviors. Despite the crucial importance of odors that elicit instinctive behaviors, such as pheromones and kairomones, their neural representation remains little characterized in the mammalian brain. Here we used expression of the immediate early gene product c-Fos as a marker of neuronal activity to find that a wide range of pheromones and kairomones produces activation in the medial nucleus of the amygdala, a brain area anatomically connected with the olfactory sensory organs. We see that activity in this nucleus depends on vomeronasal organ input, and that distinct vomeronasal stimuli activate a dispersed ensemble of cells, without any apparent spatial segregation. This activity pattern does not reflect the chemical category of the stimuli, their valence or the induced behaviors. These findings will help build a complete understanding of how odor information is processed in the brain to generate instinctive behaviors.

  8. Attention-spreading based on hierarchical spatial representations for connected objects.

    Kasai, Tetsuko

    2010-01-01

    Attention selects objects or groups as the most fundamental unit, and this may be achieved through a process in which attention automatically spreads throughout their entire region. Previously, we found that a lateralized potential relative to an attended hemifield at occipito-temporal electrode sites reflects attention-spreading in response to connected bilateral stimuli [Kasai, T., & Kondo, M. Electrophysiological correlates of attention-spreading in visual grouping. NeuroReport, 18, 93-98, 2007]. The present study examined the nature of object representations by manipulating the extent of grouping through connectedness, while controlling the symmetrical structure of bilateral stimuli. The electrophysiological results of two experiments consistently indicated that attention was guided twice in association with perceptual grouping in the early phase (N1, 150-200 msec poststimulus) and with the unity of an object in the later phase (N2pc, 310/330-390 msec). This suggests that there are two processes in object-based spatial selection, and these are discussed with regard to their cognitive mechanisms and object representations.

  9. 3D shape representation with spatial probabilistic distribution of intrinsic shape keypoints

    Ghorpade, Vijaya K.; Checchin, Paul; Malaterre, Laurent; Trassoudaine, Laurent

    2017-12-01

    The accelerated advancement in modeling, digitizing, and visualizing techniques for 3D shapes has led to an increasing amount of 3D models creation and usage, thanks to the 3D sensors which are readily available and easy to utilize. As a result, determining the similarity between 3D shapes has become consequential and is a fundamental task in shape-based recognition, retrieval, clustering, and classification. Several decades of research in Content-Based Information Retrieval (CBIR) has resulted in diverse techniques for 2D and 3D shape or object classification/retrieval and many benchmark data sets. In this article, a novel technique for 3D shape representation and object classification has been proposed based on analyses of spatial, geometric distributions of 3D keypoints. These distributions capture the intrinsic geometric structure of 3D objects. The result of the approach is a probability distribution function (PDF) produced from spatial disposition of 3D keypoints, keypoints which are stable on object surface and invariant to pose changes. Each class/instance of an object can be uniquely represented by a PDF. This shape representation is robust yet with a simple idea, easy to implement but fast enough to compute. Both Euclidean and topological space on object's surface are considered to build the PDFs. Topology-based geodesic distances between keypoints exploit the non-planar surface properties of the object. The performance of the novel shape signature is tested with object classification accuracy. The classification efficacy of the new shape analysis method is evaluated on a new dataset acquired with a Time-of-Flight camera, and also, a comparative evaluation on a standard benchmark dataset with state-of-the-art methods is performed. Experimental results demonstrate superior classification performance of the new approach on RGB-D dataset and depth data.

  10. Spatial representation and cognitive modulation of response variability in the lateral intraparietal area priority map.

    Falkner, Annegret L; Goldberg, Michael E; Krishna, B Suresh

    2013-10-09

    The lateral intraparietal area (LIP) in the macaque contains a priority-based representation of the visual scene. We previously showed that the mean spike rate of LIP neurons is strongly influenced by spatially wide-ranging surround suppression in a manner that effectively sharpens the priority map. Reducing response variability can also improve the precision of LIP's priority map. We show that when a monkey plans a visually guided delayed saccade with an intervening distractor, variability (measured by the Fano factor) decreases both for neurons representing the saccade goal and for neurons representing the broad spatial surround. The reduction in Fano factor is maximal for neurons representing the saccade goal and steadily decreases for neurons representing more distant locations. LIP Fano factor changes are behaviorally significant: increasing expected reward leads to lower variability for the LIP representation of both the target and distractor locations, and trials with shorter latency saccades are associated with lower Fano factors in neurons representing the surround. Thus, the LIP Fano factor reflects both stimulus and behavioral engagement. Quantitative modeling shows that the interaction between mean spike count and target-receptive field (RF) distance in the surround during the predistractor epoch is multiplicative: the Fano factor increases more steeply with mean spike count further away from the RF. A negative-binomial model for LIP spike counts captures these findings quantitatively, suggests underlying mechanisms based on trial-by-trial variations in mean spike rate or burst-firing patterns, and potentially provides a principled framework to account simultaneously for the previously observed unsystematic relationships between spike rate and variability in different brain areas.

  11. Children’s Spatial Representations: 3- and 4-Year-Olds are Affected by Irrelevant Peripheral References

    Krüger, Markus; Jahn, Georg

    2015-01-01

    Children as young as 3 years can remember an object’s location within an arrangement and can retrieve it from a novel viewpoint (Nardini et al., 2006). However, this ability is impaired if the arrangement is rotated to compensate for the novel viewpoint, or, if the arrangement is rotated and children stand still. There are two dominant explanations for this phenomenon: self-motion induces an automatic spatial updating process which is beneficial if children move around the arrangement, but misleading if the children’s movement is matched by the arrangement and not activated if children stand still and only the arrangement is moved (see spatial updating; Simons and Wang, 1998). Another explanation concerns reference frames: spatial representations might depend on peripheral spatial relations concerning the surrounding room instead on proximal relations within the arrangement, even if these proximal relations are sufficient or more informative. To evaluate these possibilities, we rotated children (N = 120) aged between 3 and 6 years with an occluded arrangement. When the arrangement was in misalignment to the surrounding room, 3- and 4-year-olds’ spatial memory was impaired and 5-year-olds’ was lightly impaired suggesting that they relied on peripheral references of the surrounding room for retrieval. In contrast, 6-years-olds’ spatial representation seemed robust against misalignment indicating a successful integration of spatial representations. PMID:26617537

  12. Intransigent Vowel-Consonant Position in Korean Dysgraphia: Evidence of Spatial-Constructive Representation

    HyangHee Kim

    2007-01-01

    Full Text Available Dysgraphia due to a focal brain lesion can be characterized by substitution, transposition, deletion and/or addition errors of graphemes or strokes. However, those linguistic errors can be language-specific because the writing system of a given language may influence error patterns. We investigated a Korean stroke patient, a 57-year-old English teacher with dysgraphia both in Korean Han-geul (한글 and in English alphabet writings. The results of an experimental testing revealed transposition errors between a consonant and a vowel only in English but not in Korean writings. This austerity of vowel-consonant position may be attributed to a unique Korean writing system of a spatially well-formed syllabic configuration or block with consonant(s and a vowel. In light of a neuropsychological model of writing, which depicts a multi-level spelling and writing process, we suggest a spatial-constructional component of internal orthographic representations in Korean writing. This Korean graphemic configuration feature may be resistant to a focal, left cerebral damage, and thus, we also discuss our results in terms of cerebral lateralization of the writing processes.

  13. EnzyNet: enzyme classification using 3D convolutional neural networks on spatial representation.

    Amidi, Afshine; Amidi, Shervine; Vlachakis, Dimitrios; Megalooikonomou, Vasileios; Paragios, Nikos; Zacharaki, Evangelia I

    2018-01-01

    During the past decade, with the significant progress of computational power as well as ever-rising data availability, deep learning techniques became increasingly popular due to their excellent performance on computer vision problems. The size of the Protein Data Bank (PDB) has increased more than 15-fold since 1999, which enabled the expansion of models that aim at predicting enzymatic function via their amino acid composition. Amino acid sequence, however, is less conserved in nature than protein structure and therefore considered a less reliable predictor of protein function. This paper presents EnzyNet, a novel 3D convolutional neural networks classifier that predicts the Enzyme Commission number of enzymes based only on their voxel-based spatial structure. The spatial distribution of biochemical properties was also examined as complementary information. The two-layer architecture was investigated on a large dataset of 63,558 enzymes from the PDB and achieved an accuracy of 78.4% by exploiting only the binary representation of the protein shape. Code and datasets are available at https://github.com/shervinea/enzynet.

  14. Examination about the Spatial Representation of PM2.5 Obtained from Limited Stations Using a Network Observation

    Shi, X.; Zhao, C.

    2017-12-01

    Haze aerosol pollution has been a focus issue in China, and its characteristics is highly demanded. With limited observation sites, aerosol properties obtained from a single site is frequently used to represent the haze condition over a large domain, such as tens of kilometers. This could result in high uncertainties in the haze characteristics due to their spatial variation. Using a network observation from November 2015 to February 2016 over an urban city in North China with high spatial resolution, this study examines the spatial representation of ground site observations. A method is first developed to determine the representative area of measurements from limited stations. The key idea of this method is to determine the spatial variability of particulate matter with diameters less than 2.5 μm (PM2.5) concentration using a variance function in 2km x 2km grids. Based on the high spatial resolution (0.5km x 0.5km) measurements of PM2.5, the grids in which PM2.5 have high correlations and weak value differences are determined as the representation area of measurements at these grids. Note that the size representation area is not exactly a circle region. It shows that the size representation are for the study region and study period ranges from 0.25 km2 to 16.25 km2. The representation area varies with locations. For the 20 km x 20 km study region, 10 station observations would have a good representation of the PM2.5 observations obtained from current 169 stations at the four-month time scale.

  15. Retrieval of Brain Tumors by Adaptive Spatial Pooling and Fisher Vector Representation.

    Cheng, Jun; Yang, Wei; Huang, Meiyan; Huang, Wei; Jiang, Jun; Zhou, Yujia; Yang, Ru; Zhao, Jie; Feng, Yanqiu; Feng, Qianjin; Chen, Wufan

    2016-01-01

    Content-based image retrieval (CBIR) techniques have currently gained increasing popularity in the medical field because they can use numerous and valuable archived images to support clinical decisions. In this paper, we concentrate on developing a CBIR system for retrieving brain tumors in T1-weighted contrast-enhanced MRI images. Specifically, when the user roughly outlines the tumor region of a query image, brain tumor images in the database of the same pathological type are expected to be returned. We propose a novel feature extraction framework to improve the retrieval performance. The proposed framework consists of three steps. First, we augment the tumor region and use the augmented tumor region as the region of interest to incorporate informative contextual information. Second, the augmented tumor region is split into subregions by an adaptive spatial division method based on intensity orders; within each subregion, we extract raw image patches as local features. Third, we apply the Fisher kernel framework to aggregate the local features of each subregion into a respective single vector representation and concatenate these per-subregion vector representations to obtain an image-level signature. After feature extraction, a closed-form metric learning algorithm is applied to measure the similarity between the query image and database images. Extensive experiments are conducted on a large dataset of 3604 images with three types of brain tumors, namely, meningiomas, gliomas, and pituitary tumors. The mean average precision can reach 94.68%. Experimental results demonstrate the power of the proposed algorithm against some related state-of-the-art methods on the same dataset.

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

    Pratte, Michael S; Tong, Frank

    2014-03-19

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

  17. Preattentive representation of feature conjunctions for concurrent spatially distributed auditory objects.

    Takegata, Rika; Brattico, Elvira; Tervaniemi, Mari; Varyagina, Olga; Näätänen, Risto; Winkler, István

    2005-09-01

    The role of attention in conjoining features of an object has been a topic of much debate. Studies using the mismatch negativity (MMN), an index of detecting acoustic deviance, suggested that the conjunctions of auditory features are preattentively represented in the brain. These studies, however, used sequentially presented sounds and thus are not directly comparable with visual studies of feature integration. Therefore, the current study presented an array of spatially distributed sounds to determine whether the auditory features of concurrent sounds are correctly conjoined without focal attention directed to the sounds. Two types of sounds differing from each other in timbre and pitch were repeatedly presented together while subjects were engaged in a visual n-back working-memory task and ignored the sounds. Occasional reversals of the frequent pitch-timbre combinations elicited MMNs of a very similar amplitude and latency irrespective of the task load. This result suggested preattentive integration of auditory features. However, performance in a subsequent target-search task with the same stimuli indicated the occurrence of illusory conjunctions. The discrepancy between the results obtained with and without focal attention suggests that illusory conjunctions may occur during voluntary access to the preattentively encoded object representations.

  18. Computational hologram synthesis and representation on spatial light modulators for real-time 3D holographic imaging

    Reichelt, Stephan; Leister, Norbert

    2013-01-01

    In dynamic computer-generated holography that utilizes spatial light modulators, both hologram synthesis and hologram representation are essential in terms of fast computation and high reconstruction quality. For hologram synthesis, i.e. the computation step, Fresnel transform based or point-source based raytracing methods can be applied. In the encoding step, the complex wave-field has to be optimally represented by the SLM with its given modulation capability. For proper hologram reconstruction that implies a simultaneous and independent amplitude and phase modulation of the input wave-field by the SLM. In this paper, we discuss full complex hologram representation methods on SLMs by considering inherent SLM parameter such as modulation type and bit depth on their reconstruction performance such as diffraction efficiency and SNR. We review the three implementation schemes of Burckhardt amplitude-only representation, phase-only macro-pixel representation, and two-phase interference representation. Besides the optical performance we address their hardware complexity and required computational load. Finally, we experimentally demonstrate holographic reconstructions of different representation schemes as obtained by functional prototypes utilizing SeeReal's viewing-window holographic display technology. The proposed hardware implementations enable a fast encoding of complex-valued hologram data and thus will pave the way for commercial real-time holographic 3D imaging in the near future.

  19. Naloxone injections into CA3 disrupt pattern completion associated with relapse from cocaine seeking

    Kirk, Ryan A.; Clark, Jascha K.; Moore, Angela; Keefe, Kristen

    2016-01-01

    The goal of the present research was to assess the degree to which a pattern completion process operates in cue-induced relapse to cocaine-seeking behavior. Using a novel cue-preference version of the place preference task, rats were administered cocaine or saline, which resulted in a preference for the cocaine-paired cues. After 21 days of abstinence and prior to the preference test, for one group, PBS or naloxone was injected into the CA3 subregion of the hippocampus and for a second group, saline or naloxone was injected systemically. The results indicated that infusions of naloxone into CA3 or systemic injections produced a marked disruption for one and two cues, but had minimal disruptive effect for three or four cues, suggesting that naloxone injections disrupt CA3 function and trigger a deficit in a pattern completion process. Thus, it appears that cue-based activation of the dorsal CA3 might be a critical trigger via a pattern completion process. Based on additional analyses it appears that there is a disruption primarily for object touches for one cue naloxone injections into the CA3 or systemic injections, but no effect on time (spatial context). PMID:26815290

  20. Acute effects of alcohol on intrusive memory development and viewpoint dependence in spatial memory support a dual representation model.

    Bisby, James A; King, John A; Brewin, Chris R; Burgess, Neil; Curran, H Valerie

    2010-08-01

    A dual representation model of intrusive memory proposes that personally experienced events give rise to two types of representation: an image-based, egocentric representation based on sensory-perceptual features; and a more abstract, allocentric representation that incorporates spatiotemporal context. The model proposes that intrusions reflect involuntary reactivation of egocentric representations in the absence of a corresponding allocentric representation. We tested the model by investigating the effect of alcohol on intrusive memories and, concurrently, on egocentric and allocentric spatial memory. With a double-blind independent group design participants were administered alcohol (.4 or .8 g/kg) or placebo. A virtual environment was used to present objects and test recognition memory from the same viewpoint as presentation (tapping egocentric memory) or a shifted viewpoint (tapping allocentric memory). Participants were also exposed to a trauma video and required to detail intrusive memories for 7 days, after which explicit memory was assessed. There was a selective impairment of shifted-view recognition after the low dose of alcohol, whereas the high dose induced a global impairment in same-view and shifted-view conditions. Alcohol showed a dose-dependent inverted "U"-shaped effect on intrusions, with only the low dose increasing the number of intrusions, replicating previous work. When same-view recognition was intact, decrements in shifted-view recognition were associated with increases in intrusions. The differential effect of alcohol on intrusive memories and on same/shifted-view recognition support a dual representation model in which intrusions might reflect an imbalance between two types of memory representation. These findings highlight important clinical implications, given alcohol's involvement in real-life trauma. Copyright 2010 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

  1. How can mental maps, applied to the coast environment, help in collecting and analyzing spatial representations?

    Servane Gueben-Venière

    2011-09-01

    Full Text Available Après avoir été principalement utilisées en géographie urbaine, puis quelque peu mises de côté par les géographes, les cartes mentales font désormais l’objet d’un regain d’intérêt, en particulier dans le champ de la géographie de l’environnement. Appliquées à l’espace littoral et employées en complément de l’entretien, elles se révèlent être non seulement un bon outil de recueil des représentations spatiales, mais aussi une aide précieuse pour leur analyse. Cet article s’appuie sur l’exemple de l’utilisation des cartes mentales dans le poster scientifique Des ingénieurs de plus en plus « verts ». Évolution du regard des ingénieurs en charge de la gestion du littoral néerlandais, lauréat du concours organisé par le forum de l’École Doctorale de Géographie de Paris de 2011.After having been mainly used in urban geography, then cast aside by the geographers, mental maps are now the object of renewed interest, particularly in the field of environmental geography. Applied to the coast, and used as a supplement to the interview, these maps are not only of great assistance in collecting spatial representations, but also helpful in analyzing them. This article uses the example of the integration of mental maps in the scientific poster “Des ingénieurs de plus en plus “verts”. Évolution du regard des ingénieurs en charge de la gestion du littoral néerlandais”(Engineers are ‘greener and greener’. Evolution of the thinking of engineers in charge of Dutch coastal management., prize-winner of the competition organized by the Paris Doctoral School of Geography Forum in 2011.

  2. Disruption of hippocampal CA3 network: effects on episodic-like memory processing in C57BL/6J mice.

    Daumas, Stéphanie; Halley, Hélène; Lassalle, Jean-Michel

    2004-07-01

    Lesion studies have demonstrated the prominent role of the hippocampus in spatial and contextual learning. To better understand how contextual information is processed in the CA3 region during learning, we focused on the CA3 autoassociative network hypothesis. We took advantage of a particularity of the mossy fibre (MF) synapses, i.e. their high zinc concentration, to reversibly disrupt the afferent MF pathway by microinfusions of an intracellular (DEDTC) or an extracellular (CaEDTA) zinc chelator into the CA3 area of the dorsal hippocampus of mice. Disruption of the CA3 network significantly impaired the acquisition and the consolidation of contextual fear conditioning, whereas contextual retrieval was unaffected. These results also suggest a heterogeneity between the cognitive processes underlying spatial and contextual memory that might be linked to the specific involvement of free zinc in contextual information processing.

  3. Diagrammatic Representational Constraints of Spatial Scale in Earth-Moon System Astronomy Instruction

    Taylor, Roger S.; Grundstrom, Erika D.

    2011-01-01

    Given that astronomy heavily relies on visual representations it is especially likely for individuals to assume that instructional materials, such as visual representations of the Earth-Moon system (EMS), would be relatively accurate. However, in our research, we found that images in middle-school textbooks and educational webpages were commonly…

  4. How Fast Do Objects Fall in Visual Memory? Uncovering the Temporal and Spatial Features of Representational Gravity.

    De Sá Teixeira, Nuno

    2016-01-01

    Visual memory for the spatial location where a moving target vanishes has been found to be systematically displaced downward in the direction of gravity. Moreover, it was recently reported that the magnitude of the downward error increases steadily with increasing retention intervals imposed after object's offset and before observers are allowed to perform the spatial localization task, in a pattern where the remembered vanishing location drifts downward as if following a falling trajectory. This outcome was taken to reflect the dynamics of a representational model of earth's gravity. The present study aims to establish the spatial and temporal features of this downward drift by taking into account the dynamics of the motor response. The obtained results show that the memory for the last location of the target drifts downward with time, thus replicating previous results. Moreover, the time taken for completion of the behavioural localization movements seems to add to the imposed retention intervals in determining the temporal frame during which the visual memory is updated. Overall, it is reported that the representation of spatial location drifts downward by about 3 pixels for each two-fold increase of time until response. The outcomes are discussed in relation to a predictive internal model of gravity which outputs an on-line spatial update of remembered objects' location.

  5. Neuronal migration and its disorders affecting the CA3 region

    Richard eBelvindrah

    2014-03-01

    Full Text Available In this review, we focus on CA3 neuronal migration disorders in the rodent. We begin by introducing the main steps of hippocampal development, and we summarize characteristic hippocampal malformations in human. We then describe various mouse mutants showing structural hippocampal defects. Notably, genes identified in human cortical neuronal migration disorders consistently give rise to a CA3 phenotype when mutated in the mouse. We successively describe their molecular, physiological and behavioral phenotypes that together contribute to a better understanding of CA3-dependent functions. We finally discuss potential factors underlying the CA3 vulnerability revealed by these mouse mutants and that may also contribute to other human neurological and psychiatric disorders.

  6. Somal and dendritic development of human CA3 pyramidal neurons from midgestation to middle childhood: a quantitative Golgi study.

    Lu, Dahua; He, Lixin; Xiang, Wei; Ai, Wei-Min; Cao, Ye; Wang, Xiao-Sheng; Pan, Aihua; Luo, Xue-Gang; Li, Zhiyuan; Yan, Xiao-Xin

    2013-01-01

    The CA3 area serves a key relay on the tri-synaptic loop of the hippocampal formation which supports multiple forms of mnemonic processing, especially spatial learning and memory. To date, morphometric data about human CA3 pyramidal neurons are relatively rare, with little information available for their pre- and postnatal development. Herein, we report a set of developmental trajectory data, including somal growth, dendritic elongation and branching, and spine formation, of human CA3 pyramidal neurons from midgestation stage to middle childhood. Golgi-impregnated CA3 pyramidal neurons in fetuses at 19, 20, 26, 35, and 38 weeks of gestation (GW) and a child at 8 years of age (Y) were analyzed by Neurolucida morphometry. Somal size of the impregnated CA3 cells increased age-dependently among the cases. The length of the apical and basal dendrites of these neurons increased between 26 GW to 38 GW, and appeared to remain stable afterward until 8 Y. Dendritic branching points increased from 26 GW to 38 GW, with that on the apical dendrites slightly reduced at 8 Y. Spine density on the apical and basal dendrites increased progressively from 26 GW to 8 Y. These data suggest that somal growth and dendritic arborization of human CA3 pyramidal neurons occur largely during the second to third trimester. Spine development and likely synaptogenesis on CA3 pyramidal cells progress during the third prenatal trimester and may continue throughout childhood. Copyright © 2012 Wiley Periodicals, Inc.

  7. Spatial representation of organic carbon and active-layer thickness of high latitude soils in CMIP5 earth system models

    Mishra, Umakant; Drewniak, Beth; Jastrow, Julie D.; Matamala, Roser M.; Vitharana, U. W. A.

    2017-08-01

    Soil properties such as soil organic carbon (SOC) stocks and active-layer thickness are used in earth system models (F.SMs) to predict anthropogenic and climatic impacts on soil carbon dynamics, future changes in atmospheric greenhouse gas concentrations, and associated climate changes in the permafrost regions. Accurate representation of spatial and vertical distribution of these soil properties in ESMs is a prerequisite for redudng existing uncertainty in predicting carbon-climate feedbacks. We compared the spatial representation of SOC stocks and active-layer thicknesses predicted by the coupled Modellntercomparison Project Phase 5 { CMIP5) ESMs with those predicted from geospatial predictions, based on observation data for the state of Alaska, USA. For the geospatial modeling. we used soil profile observations {585 for SOC stocks and 153 for active-layer thickness) and environmental variables (climate, topography, land cover, and surficial geology types) and generated fine-resolution (50-m spatial resolution) predictions of SOC stocks (to 1-m depth) and active-layer thickness across Alaska. We found large inter-quartile range (2.5-5.5 m) in predicted active-layer thickness of CMIP5 modeled results and small inter-quartile range (11.5-22 kg m-2) in predicted SOC stocks. The spatial coefficient of variability of active-layer thickness and SOC stocks were lower in CMIP5 predictions compared to our geospatial estimates when gridded at similar spatial resolutions (24.7 compared to 30% and 29 compared to 38%, respectively). However, prediction errors. when calculated for independent validation sites, were several times larger in ESM predictions compared to geospatial predictions. Primaly factors leading to observed differences were ( 1) lack of spatial heterogeneity in ESM predictions, (2) differences in assumptions concerning environmental controls, and (3) the absence of pedogenic processes in ESM model structures. Our results suggest that efforts to incorporate

  8. Diminished Dentate Gyrus Filtering of Cortical Input Leads to Enhanced Area Ca3 Excitability after Mild Traumatic Brain Injury.

    Folweiler, Kaitlin A; Samuel, Sandy; Metheny, Hannah E; Cohen, Akiva S

    2018-04-06

    Mild traumatic brain injury (mTBI) disrupts hippocampal function and can lead to long-lasting episodic memory impairments. The encoding of episodic memories relies on spatial information processing within the hippocampus. As the primary entry point for spatial information into the hippocampus, the dentate gyrus is thought to function as a physiological gate, or filter, of afferent excitation before reaching downstream area Cornu Ammonis (CA3). Although injury has previously been shown to alter dentate gyrus network excitability, it is unknown whether mTBI affects dentate gyrus output to area CA3. In this study, we assessed hippocampal function, specifically the interaction between the dentate gyrus and CA3, using behavioral and electrophysiological techniques in ex vivo brain slices 1 week following mild lateral fluid percussion injury (LFPI). Behaviorally, LFPI mice were found to be impaired in an object-place recognition task, indicating that spatial information processing in the hippocampus is disrupted. Extracellular recordings and voltage-sensitive dye imaging demonstrated that perforant path activation leads to the aberrant spread of excitation from the dentate gyrus into area CA3 along the mossy fiber pathway. These results suggest that after mTBI, the dentate gyrus has a diminished capacity to regulate cortical input into the hippocampus, leading to increased CA3 network excitability. The loss of the dentate filtering efficacy reveals a potential mechanism by which hippocampal-dependent spatial information processing is disrupted, and may contribute to memory dysfunction after mTBI.

  9. Feature representation of RGB-D images using joint spatial-depth feature pooling

    Pan, Hong; Olsen, Søren Ingvor; Zhu, Yaping

    2016-01-01

    Recent development in depth imaging technology makes acquisition of depth information easier. With the additional depth cue, RGB-D cameras can provide effective support for many RGB-D perception tasks beyond traditional RGB information. However, current feature representation based on RGB-D image...

  10. The Influence of Cue Reliability and Cue Representation on Spatial Reorientation in Young Children

    Lyons, Ian M.; Huttenlocher, Janellen; Ratliff, Kristin R.

    2014-01-01

    Previous studies of children's reorientation have focused on cue representation (e.g., whether cues are geometric) as a predictor of performance but have not addressed cue reliability (the regularity of the relation between a given cue and an outcome) as a predictor of performance. Here we address both factors within the same series of…

  11. Online measurement of mental representations of complex spatial decision problems : comparison of CNET and hard laddering

    Horeni, O.; Arentze, T.A.; Dellaert, B.G.C.; Timmermans, H.J.P.

    2014-01-01

    This paper introduces the online Causal Network Elicitation Technique (CNET), as a technique for measuring components of mental representations of choice tasks and compares it with the more common technique of online 'hard' laddering (HL). While CNET works in basically two phases, one in open

  12. Online measurement of mental representations of complex spatial decision problems : Comparison of CNET and hard laddering

    O. Horeni (Oliver); T.A. Arentze (Theo); B.G.C. Dellaert (Benedict); H.J.P. Timmermans (Harry)

    2013-01-01

    textabstractThis paper introduces the online Causal Network Elicitation Technique (CNET), as a technique for measuring components of mental representations of choice tasks and compares it with the more common technique of online ‘hard’ laddering (HL). While CNET works in basically two phases, one in

  13. The Role of Cognitive Flexibility in the Spatial Representation of Children's Drawings

    Ebersbach, Mirjam; Hagedorn, Helena

    2011-01-01

    Representing the spatial appearance of objects and scenes in drawings is a difficult task for young children in particular. In the present study, the relationship between spatial drawing and cognitive flexibility was investigated. Seven- to 11-year-olds (N = 60) were asked to copy a three-dimensional model in a drawing. The use of depth cues as an…

  14. A representation of place attachment: A study of spatial cognition in Latvia

    Skilters, Jurgis; Zarina, Liga; Raita, Liva

    2017-04-01

    Perception of geographical space is reflected in place attachment, i.e., a multidimensional cognitive-affective link between humans and their spatial environment. Place attachment balances emotions, conception of proximity. It is both social and spatial cognitive structure. Place attachment has an impact on people's actions, which in turn reversibly affect the environment in which people live. Place attachment provides emotional regulation for humans linking local - neighborhood-scale and country and world-scale environments. In Latvia a large-scale spatial cognition study has been conducted within participatory research project „Telpas pavasaris" ("Spatial Spring") by foundation Viegli. In the study 1523 respondents reported their associations characterizing certain type of places (e.g., safe place, dangerous place, far place, close place, dear place). The answers were analyzed according to several cognitive-affective categories including modes of experience, emotional valence, geographical distance, and perceptual modality. The current results indicate that socio-cognitive and affective information are primary in respect to purely spatial information (referring to spatial objects or regions and their relations). However, different types of geographical places and spatial objects (natural or artefactual) have to be distinguished and are significant to a different degree. Our results are important for environmental and urban planning because they show the ways how socio-cognitive and affective knowledge shapes the spatial cognition of geographic environment.

  15. Getting to Know a Place: Built Environment Walkability and Children's Spatial Representation of Their Home-School (h-s) Route.

    Moran, Mika R; Eizenberg, Efrat; Plaut, Pnina

    2017-06-06

    The literature on environmental walkability to date has mainly focused on walking and related health outcomes. While previous studies suggest associations between walking and spatial knowledge, the associations between environmental walkability and spatial knowledge is yet to be explored. The current study addresses this lacuna in research by exploring children's mental representations of their home-school (h-s) route, vis.

  16. Spatial representation of magnitude in humans (Homo sapiens), Western lowland gorillas (Gorilla gorilla gorilla), and American black bears (Ursus americanus).

    Johnson-Ulrich, Zoe; Vonk, Jennifer

    2018-05-04

    The spatial-numerical association of response codes (SNARC) effect is the tendency for humans to respond faster to relatively larger numbers on the left or right (or with the left or right hand) and faster to relatively smaller numbers on the other side. This effect seems to occur due to a spatial representation of magnitude either in occurrence with a number line (wherein participants respond to relatively larger numbers faster on the right), other representations such as clock faces (responses are reversed from number lines), or culturally specific reading directions, begging the question as to whether the effect may be limited to humans. Given that a SNARC effect has emerged via a quantity judgement task in Western lowland gorillas and orangutans (Gazes et al., Cog 168:312-319, 2017), we examined patterns of response on a quantity discrimination task in American black bears, Western lowland gorillas, and humans for evidence of a SNARC effect. We found limited evidence for SNARC effect in American black bears and Western lowland gorillas. Furthermore, humans were inconsistent in direction and strength of effects, emphasizing the importance of standardizing methodology and analyses when comparing SNARC effects between species. These data reveal the importance of collecting data with humans in analogous procedures when testing nonhumans for effects assumed to bepresent in humans.

  17. Perirhinal cortical inactivation impairs object-in-place memory and disrupts task-dependent firing in hippocampal CA1, but not in CA3.

    Lee, Inah; Park, Seong-Beom

    2013-01-01

    Objects and their locations can associatively define an event and a conjoint representation of object-place can form an event memory. Remembering how to respond to a certain object in a spatial context is dependent on both hippocampus and perirhinal cortex (PER). However, the relative functional contributions of the two regions are largely unknown in object-place associative memory. We investigated the PER influence on hippocampal firing in a goal-directed object-place memory task by comparing the firing patterns of CA1 and CA3 of the dorsal hippocampus between conditions of PER muscimol inactivation and vehicle control infusions. Rats were required to choose one of the two objects in a specific spatial context (regardless of the object positions in the context), which was shown to be dependent on both hippocampus and PER. Inactivation of PER with muscimol (MUS) severely disrupted performance of well-trained rats, resulting in response bias (i.e., choosing any object on a particular side). MUS did not significantly alter the baseline firing rates of hippocampal neurons. We measured the similarity in firing patterns between two trial conditions in which the same target objects were chosen on opposite sides within the same arm [object-in-place (O-P) strategy] and compared the results with the similarity in firing between two trial conditions in which the rat chose any object encountered on a particular side [response-in-place (R-P) strategy]. We found that the similarity in firing patterns for O-P trials was significantly reduced with MUS compared to control conditions (CTs). Importantly, this was largely because MUS injections affected the O-P firing patterns in CA1 neurons, but not in CA3. The results suggest that PER is critical for goal-directed organization of object-place associative memory in the hippocampus presumably by influencing how object information is associated with spatial information in CA1 according to task demand.

  18. Perirhinal cortical inactivation impairs object-in-place memory and disrupts task-dependent firing in hippocampal CA1, but not in CA3

    Inah eLee

    2013-08-01

    Full Text Available Objects and their locations can associatively define an event and a conjoint representation of object-place can form an event memory. Remembering how to respond to a certain object in a spatial context is dependent on both hippocampus and perirhinal cortex (PER. However, the relative functional contributions of the two regions are largely unknown in object-place associative memory. We investigated the PER influence on hippocampal firing in a goal-directed object-place memory task by comparing the firing patterns of CA1 and CA3 of the dorsal hippocampus between conditions of PER muscimol inactivation and vehicle control infusions. Rats were required to choose one of the two objects in a specific spatial context (regardless of the object positions in the context, which was shown to be dependent on both hippocampus and PER. Inactivation of PER with muscimol (MUS severely disrupted performance of well-trained rats, resulting in response bias (i.e., choosing any object on a particular side. MUS did not significantly alter the baseline firing rates of hippocampal neurons. We measured the similarity in firing patterns between two trial conditions in which the same target objects were chosen on opposite sides within the same arm (object-in-place strategy and compared the results with the similarity in firing between two trial conditions in which the rat chose any object encountered on a particular side (response-in-place strategy. We found that the similarity in firing patterns for object-in-place trials was significantly reduced with MUS compared to control conditions. Importantly, this was largely because MUS injections affected the object-in-place firing patterns in CA1 neurons, but not in CA3. The results suggest that PER is critical for goal-directed organization of object-place associative memory in the hippocampus presumably by influencing how object information is associated with spatial information in CA1 according to task demand.

  19. A multivariate geostatistical approach to spatial representation of groundwater contamination using hydrochemistry and microbial community profiles.

    Mouser, P.J.; Rizzo, D.M.; Roling, W.F.M.; van Breukelen, B.M.

    2005-01-01

    Managers of landfill sites are faced with enormous challenges when attempting to detect and delineate leachate plumes with a limited number of monitoring wells, assess spatial and temporal trends for hundreds of contaminants, and design long-term monitoring (LTM) strategies. Subsurface microbial

  20. Electrolytic lesions of dorsal CA3 impair episodic-like memory in rats.

    Li, Jay-Shake; Chao, Yuen-Shin

    2008-02-01

    Episodic memory is the ability to recollect one's past experiences occurring in an unique spatial and temporal context. In non-human animals, it is expressed in the ability to combine "what", "where" and "when" factors to form an integrated memory system. During the search for its neural substrates, the hippocampus has attracted a lot of attentions. Yet, it is not yet possible to induce a pure episodic-like memory deficit in animal studies without being confounded by impairments in the spatial cognition. Here, we present a lesion study evidencing direct links between the hippocampus CA3 region and the episodic-like memory in rats. In a spontaneous object exploration task, lesioned rats showed no interaction between the temporal and spatial elements in their memory associated with the objects. In separate tests carried out subsequently, the same animals still expressed abilities to process spatial, temporal, and object recognition memory. In conclusions, our results support the idea that the hippocampus CA3 has a particular status in the neural mechanism of the episodic-like memory system. It is responsible for combining information from different modules of cognitive processes.

  1. The effect of handedness on spatial and motor representation of pitch patterns in pianists.

    Eline Adrianne Smit

    Full Text Available This study investigated the effect of handedness on pianists' abilities to adjust their keyboard performance skills to new spatial and motor mappings. Left- and right-handed pianists practiced simple melodies on a regular MIDI piano keyboard (practice and were then asked to perform these with modified melodic contours (the same or reversed melodic contour causing a change of fingering and on a reversed MIDI piano keyboard (test. The difference of performance duration between the practice and the test phase as well as the amount of errors played were used as test measures. Overall, a stronger effect for modified melodic contours than for the reversed keyboard was observed. Furthermore, we observed a trend of left-handed pianists to be quicker and more accurate in playing melodies when reversing their fingering with reversed contours in their left-hand performances. This suggests that handedness may influence pianists' skill to adjust to new spatial and motor mappings.

  2. The role of spatial boundaries in shaping long-term event representations

    Horner, Aidan J.; Bisby, James A.; Wang, Aijing; Bogus, Katrina; Burgess, Neil

    2016-01-01

    When remembering the past, we typically recall ?events? that are bounded in time and space. However, as we navigate our environment our senses receive a continuous stream of information. How do we create discrete long-term episodic memories from continuous input? Although previous research has provided evidence for a role of spatial boundaries in the online segmentation of our sensory experience within working memory, it is not known how this segmentation contributes to subsequent long-term e...

  3. Increased Variability and Asymmetric Expansion of the Hippocampal Spatial Representation in a Distal Cue-Dependent Memory Task.

    Park, Seong-Beom; Lee, Inah

    2016-08-01

    Place cells in the hippocampus fire at specific positions in space, and distal cues in the environment play critical roles in determining the spatial firing patterns of place cells. Many studies have shown that place fields are influenced by distal cues in foraging animals. However, it is largely unknown whether distal-cue-dependent changes in place fields appear in different ways in a memory task if distal cues bear direct significance to achieving goals. We investigated this possibility in this study. Rats were trained to choose different spatial positions in a radial arm in association with distal cue configurations formed by visual cue sets attached to movable curtains around the apparatus. The animals were initially trained to associate readily discernible distal cue configurations (0° vs. 80° angular separation between distal cue sets) with different food-well positions and then later experienced ambiguous cue configurations (14° and 66°) intermixed with the original cue configurations. Rats showed no difficulty in transferring the associated memory formed for the original cue configurations when similar cue configurations were presented. Place field positions remained at the same locations across different cue configurations, whereas stability and coherence of spatial firing patterns were significantly disrupted when ambiguous cue configurations were introduced. Furthermore, the spatial representation was extended backward and skewed more negatively at the population level when processing ambiguous cue configurations, compared with when processing the original cue configurations only. This effect was more salient for large cue-separation conditions than for small cue-separation conditions. No significant rate remapping was observed across distal cue configurations. These findings suggest that place cells in the hippocampus dynamically change their detailed firing characteristics in response to a modified cue environment and that some of the firing

  4. A role for CA3 in social recognition memory.

    Chiang, Ming-Ching; Huang, Arthur J Y; Wintzer, Marie E; Ohshima, Toshio; McHugh, Thomas J

    2018-02-02

    Social recognition memory is crucial for survival across species, underlying the need to correctly identify conspecifics, mates and potential enemies. In humans the hippocampus is engaged in social and episodic memory, however the circuit mechanisms of social memory in rodent models has only recently come under scrutiny. Work in mice has established that the dorsal CA2 and ventral CA1 regions play critical roles, however a more comprehensive comparative analyses of the circuits and mechanisms required has not been reported. Here we employ conditional genetics to examine the differential contributions of the hippocampal subfields to social memory. We find that the deletion of NMDA receptor subunit 1 gene (NR1), which abolishes NMDA receptor synaptic plasticity, in CA3 pyramidal cells led to deficits in social memory; however, mice lacking the same gene in DG granule cells performed indistinguishable from controls. Further, we use conditional pharmacogenetic inhibition to demonstrate that activity in ventral, but not dorsal, CA3 is necessary for the encoding of a social memory. These findings demonstrated CA3 pyramidal cell plasticity and transmission contribute to the encoding of social stimuli and help further identify the distinct circuits underlying the role of the hippocampus in social memory. Copyright © 2018 Elsevier B.V. All rights reserved.

  5. Distinct representations for shifts of spatial attention and changes of reward contingencies in the human brain.

    Tosoni, Annalisa; Shulman, Gordon L; Pope, Anna L W; McAvoy, Mark P; Corbetta, Maurizio

    2013-06-01

    Success in a dynamically changing world requires both rapid shifts of attention to the location of important objects and the detection of changes in motivational contingencies that may alter future behavior. Here we addressed the relationship between these two processes by measuring the blood-oxygenation-level-dependent (BOLD) signal during a visual search task in which the location and the color of a salient cue respectively indicated where a rewarded target would appear and the monetary gain (large or small) associated with its detection. While cues that either shifted or maintained attention were presented every 4 to 8 sec, the reward magnitude indicated by the cue changed roughly every 30 sec, allowing us to distinguish a change in expected reward magnitude from a maintained state of expected reward magnitude. Posterior cingulate cortex was modulated by cues signaling an increase in expected reward magnitude, but not by cues for shifting versus maintaining spatial attention. Dorsal fronto-parietal regions in precuneus and frontal eye field (FEF) also showed increased BOLD activity for changes in expected reward magnitude from low to high, but in addition showed large independent modulations for shifting versus maintaining attention. In particular, the differential activation for shifting versus maintaining attention was not affected by expected reward magnitude. These results indicate that BOLD activations for shifts of attention and increases in expected reward magnitude are largely separate. Finally, visual cortex showed sustained spatially selective signals that were significantly enhanced when greater reward magnitude was expected, but this reward-related modulation was not observed in spatially selective regions of dorsal fronto-parietal cortex. Copyright © 2012 Elsevier Ltd. All rights reserved.

  6. Aware Computing in Spatial Language Understanding Guided by Cognitively Inspired Knowledge Representation

    Masao Yokota

    2012-01-01

    Full Text Available Mental image directed semantic theory (MIDST has proposed an omnisensory mental image model and its description language Lmd. This language is designed to represent and compute human intuitive knowledge of space and can provide multimedia expressions with intermediate semantic descriptions in predicate logic. It is hypothesized that such knowledge and semantic descriptions are controlled by human attention toward the world and therefore subjective to each human individual. This paper describes Lmd expression of human subjective knowledge of space and its application to aware computing in cross-media operation between linguistic and pictorial expressions as spatial language understanding.

  7. Islamic representation and urban space in Banda Aceh: Linking the social and spatial

    Istiqamah; Herlily

    2018-03-01

    Post conflict and tsunami; the city of Banda Aceh is experiencing a massive development as an effort to represent an Islamic city. Some strategic points have been chosen by the municipality to build architectural objects that are considered to represent Islam in the urban space. The issue of such representational practice is the development of neglecting the activities of local communities as users of urban public spaces. The purpose of this design study is to provide an alternative to the urban design of Banda Aceh to represent Islam that is not moving from physical development but by involving community activities. Establish and rediscover the relationship between Islam and urban life in Banda Aceh. This design study uses mental maps of 50 inhabitants of Banda Aceh city of various ages who live in 10 villages around the city center. We use mental maps as a tool to read the daily activities of the community and determine the familiar urban territory with the community. The results of this study will be used to form a Muslim community and present community activities to represent Islam in the urban space.

  8. The geological basis and the representation of spatial variability in sedimentary heterogeneous media

    Cliffe, K.A.; Franklin, D.J.; Jones, P.I.R.; Macleod, E.J.; Porter, J.D.

    1998-01-01

    The impact of different conceptual models was investigated of the heterogeneity of the Sherwood Sandstone Group (SSG) at Sellafield on calculations of flow and transport. Detailed models of the heterogeneity of the Undifferentiated St Bees Sandstone (USBS) of the SSG were produced. The models took into account directly the geological structures at the facies level. The software package STORM (STOchastic Reservoir Modelling), was used to construct the models. The data required by the model are those that characterise the geometry of the channel bodies and the properties of the various sub-facies within the channels. It was found that for the case in which all of the variability was within channels, the larger scale permeabilities did not exhibit any significant correlation structure. The up-scaled effective permeabilities also exhibited correlation lengths that were comparable with the channel dimensions. Flow and transport calculations were also performed on 90 realizations of a detailed facies scale three-dimensional representation of a larger block of the USBS. The results are broadly consistent with the analytical results for transport through a random permeability field. (R.P.)

  9. Spatially generalizable representations of facial expressions: Decoding across partial face samples.

    Greening, Steven G; Mitchell, Derek G V; Smith, Fraser W

    2018-04-01

    A network of cortical and sub-cortical regions is known to be important in the processing of facial expression. However, to date no study has investigated whether representations of facial expressions present in this network permit generalization across independent samples of face information (e.g., eye region vs mouth region). We presented participants with partial face samples of five expression categories in a rapid event-related fMRI experiment. We reveal a network of face-sensitive regions that contain information about facial expression categories regardless of which part of the face is presented. We further reveal that the neural information present in a subset of these regions: dorsal prefrontal cortex (dPFC), superior temporal sulcus (STS), lateral occipital and ventral temporal cortex, and even early visual cortex, enables reliable generalization across independent visual inputs (faces depicting the 'eyes only' vs 'eyes removed'). Furthermore, classification performance was correlated to behavioral performance in STS and dPFC. Our results demonstrate that both higher (e.g., STS, dPFC) and lower level cortical regions contain information useful for facial expression decoding that go beyond the visual information presented, and implicate a key role for contextual mechanisms such as cortical feedback in facial expression perception under challenging conditions of visual occlusion. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. The geological basis and the representation of spatial variability in fractured media

    Mazurek, M.; Gautschi, A.; Zuidema, P.

    1998-01-01

    Spatial variability of features and parameters relevant for contaminant transport modelling occurs on all scales of interest for the quantification of processes that govern solute migration, typically decimeters to hundreds of meters. Two types of spatial variability are distinguished, namely the internal heterogeneity of each individual water-conducting feature (e.g. the complex architecture of a fault) and the larger-scale heterogeneity that results from the groundwater flow through different types of water-conducting features along the flow-path from the repository to the discharge areas. An up-scaling procedure is required to obtain hydraulic parameters and the properties of the overall flow-path, whereas the heterogeneity of many other geologic features (geometry of flow and matrix porosity, mineralogy, etc.) can be fed directly into coupled codes that quantify radionuclide transport. The procedures needed to derive conceptual models integrating geological and hydraulic field measurements and observations at a given site are illustrated by examples from both crystalline and sedimentary rock formations. (author)

  11. Experience-Dependency of Reliance on Local Visual and Idiothetic Cues for Spatial Representations Created in the Absence of Distal Information

    Fabian Draht

    2017-06-01

    Full Text Available Spatial encoding in the hippocampus is based on a range of different input sources. To generate spatial representations, reliable sensory cues from the external environment are integrated with idiothetic cues, derived from self-movement, that enable path integration and directional perception. In this study, we examined to what extent idiothetic cues significantly contribute to spatial representations and navigation: we recorded place cells while rodents navigated towards two visually identical chambers in 180° orientation via two different paths in darkness and in the absence of reliable auditory or olfactory cues. Our goal was to generate a conflict between local visual and direction-specific information, and then to assess which strategy was prioritized in different learning phases. We observed that, in the absence of distal cues, place fields are initially controlled by local visual cues that override idiothetic cues, but that with multiple exposures to the paradigm, spaced at intervals of days, idiothetic cues become increasingly implemented in generating an accurate spatial representation. Taken together, these data support that, in the absence of distal cues, local visual cues are prioritized in the generation of context-specific spatial representations through place cells, whereby idiothetic cues are deemed unreliable. With cumulative exposures to the environments, the animal learns to attend to subtle idiothetic cues to resolve the conflict between visual and direction-specific information.

  12. Experience-Dependency of Reliance on Local Visual and Idiothetic Cues for Spatial Representations Created in the Absence of Distal Information.

    Draht, Fabian; Zhang, Sijie; Rayan, Abdelrahman; Schönfeld, Fabian; Wiskott, Laurenz; Manahan-Vaughan, Denise

    2017-01-01

    Spatial encoding in the hippocampus is based on a range of different input sources. To generate spatial representations, reliable sensory cues from the external environment are integrated with idiothetic cues, derived from self-movement, that enable path integration and directional perception. In this study, we examined to what extent idiothetic cues significantly contribute to spatial representations and navigation: we recorded place cells while rodents navigated towards two visually identical chambers in 180° orientation via two different paths in darkness and in the absence of reliable auditory or olfactory cues. Our goal was to generate a conflict between local visual and direction-specific information, and then to assess which strategy was prioritized in different learning phases. We observed that, in the absence of distal cues, place fields are initially controlled by local visual cues that override idiothetic cues, but that with multiple exposures to the paradigm, spaced at intervals of days, idiothetic cues become increasingly implemented in generating an accurate spatial representation. Taken together, these data support that, in the absence of distal cues, local visual cues are prioritized in the generation of context-specific spatial representations through place cells, whereby idiothetic cues are deemed unreliable. With cumulative exposures to the environments, the animal learns to attend to subtle idiothetic cues to resolve the conflict between visual and direction-specific information.

  13. Translating working memory into action: behavioral and neural evidence for using motor representations in encoding visuo-spatial sequences.

    Langner, Robert; Sternkopf, Melanie A; Kellermann, Tanja S; Grefkes, Christian; Kurth, Florian; Schneider, Frank; Zilles, Karl; Eickhoff, Simon B

    2014-07-01

    The neurobiological organization of action-oriented working memory is not well understood. To elucidate the neural correlates of translating visuo-spatial stimulus sequences into delayed (memory-guided) sequential actions, we measured brain activity using functional magnetic resonance imaging while participants encoded sequences of four to seven dots appearing on fingers of a left or right schematic hand. After variable delays, sequences were to be reproduced with the corresponding fingers. Recall became less accurate with longer sequences and was initiated faster after long delays. Across both hands, encoding and recall activated bilateral prefrontal, premotor, superior and inferior parietal regions as well as the basal ganglia, whereas hand-specific activity was found (albeit to a lesser degree during encoding) in contralateral premotor, sensorimotor, and superior parietal cortex. Activation differences after long versus short delays were restricted to motor-related regions, indicating that rehearsal during long delays might have facilitated the conversion of the memorandum into concrete motor programs at recall. Furthermore, basal ganglia activity during encoding selectively predicted correct recall. Taken together, the results suggest that to-be-reproduced visuo-spatial sequences are encoded as prospective action representations (motor intentions), possibly in addition to retrospective sensory codes. Overall, our study supports and extends multi-component models of working memory, highlighting the notion that sensory input can be coded in multiple ways depending on what the memorandum is to be used for. Copyright © 2013 Wiley Periodicals, Inc.

  14. Stakeholder Specific Multi-Scale Spatial Representation of Urban Building-Stocks

    Magnus Österbring

    2018-05-01

    Full Text Available Urban building-stocks use a significant amount of resources and energy. At the same time, they have a large potential for energy efficiency measures (EEM. To support decision-making and planning, spatial building-stock models are used to examine the current state and future development of urban building-stocks. While these models normally focus on specific cities, generic and broad stakeholder groups such as planners and policy makers are often targeted. Consequently, the visualization and communication of results are not tailored to these stakeholders. The aim of this paper is to explore the possibilities of mapping and representing energy use of urban building-stocks at different levels of aggregation and spatial distributions, to communicate with specific stakeholders involved in the urban development process. This paper uses a differentiated building-stock description based on building-specific data and measured energy use from energy performance certificates for multi-family buildings (MFB in the city of Gothenburg. The building-stock description treats every building as unique, allowing results to be provided at any level of aggregation to suit the needs of the specific stakeholders involved. Calculated energy use of the existing stock is within 10% of the measured energy use. The potential for EEM in the existing stock is negated by the increased energy use due to new construction until 2035, using a development scenario based on current renovation rates and planned developments. Visualizations of the current energy use of the stock as well as the impact of renovation and new construction are provided, targeting specific local stakeholders.

  15. Getting to Know a Place: Built Environment Walkability and Children’s Spatial Representation of Their Home-School (h–s Route

    Mika R. Moran

    2017-06-01

    Full Text Available The literature on environmental walkability to date has mainly focused on walking and related health outcomes. While previous studies suggest associations between walking and spatial knowledge, the associations between environmental walkability and spatial knowledge is yet to be explored. The current study addresses this lacuna in research by exploring children’s mental representations of their home-school (h–s route, vis-

  16. Deep Spatial-Temporal Joint Feature Representation for Video Object Detection

    Baojun Zhao

    2018-03-01

    Full Text Available With the development of deep neural networks, many object detection frameworks have shown great success in the fields of smart surveillance, self-driving cars, and facial recognition. However, the data sources are usually videos, and the object detection frameworks are mostly established on still images and only use the spatial information, which means that the feature consistency cannot be ensured because the training procedure loses temporal information. To address these problems, we propose a single, fully-convolutional neural network-based object detection framework that involves temporal information by using Siamese networks. In the training procedure, first, the prediction network combines the multiscale feature map to handle objects of various sizes. Second, we introduce a correlation loss by using the Siamese network, which provides neighboring frame features. This correlation loss represents object co-occurrences across time to aid the consistent feature generation. Since the correlation loss should use the information of the track ID and detection label, our video object detection network has been evaluated on the large-scale ImageNet VID dataset where it achieves a 69.5% mean average precision (mAP.

  17. Deep Spatial-Temporal Joint Feature Representation for Video Object Detection.

    Zhao, Baojun; Zhao, Boya; Tang, Linbo; Han, Yuqi; Wang, Wenzheng

    2018-03-04

    With the development of deep neural networks, many object detection frameworks have shown great success in the fields of smart surveillance, self-driving cars, and facial recognition. However, the data sources are usually videos, and the object detection frameworks are mostly established on still images and only use the spatial information, which means that the feature consistency cannot be ensured because the training procedure loses temporal information. To address these problems, we propose a single, fully-convolutional neural network-based object detection framework that involves temporal information by using Siamese networks. In the training procedure, first, the prediction network combines the multiscale feature map to handle objects of various sizes. Second, we introduce a correlation loss by using the Siamese network, which provides neighboring frame features. This correlation loss represents object co-occurrences across time to aid the consistent feature generation. Since the correlation loss should use the information of the track ID and detection label, our video object detection network has been evaluated on the large-scale ImageNet VID dataset where it achieves a 69.5% mean average precision (mAP).

  18. Impaired spatial body representation in complex regional pain syndrome type 1 (CRPS I).

    Reinersmann, Annika; Landwehrt, Julia; Krumova, Elena K; Ocklenburg, Sebastian; Güntürkün, Onur; Maier, Christoph

    2012-11-01

    Recently, a shift of the visual subjective body midline (vSM), a correlate of the egocentric reference frame, towards the affected side was reported in patients with complex regional pain syndrome (CRPS). However, the specificity of this finding is as yet unclear. This study compares 24 CRPS patients to 21 patients with upper limb pain of other origin (pain control) and to 24 healthy subjects using a comprehensive test battery, including assessment of the vSM in light and dark, line bisection, hand laterality recognition, neglect-like severity symptoms, and motor impairment (disability of the arm, shoulder, and hand). 1-way analysis of variance, t-tests, significance level: 0.05. In the dark, CRPS patients displayed a significantly larger leftward spatial bias when estimating their vSM, compared to pain controls and healthy subjects, and also reported lower motor function than pain controls. For right-affected CRPS patients only, the deviation of the vSM correlated significantly with the severity of distorted body perception. Results confirm previous findings of impaired visuospatial perception in CRPS patients, which might be the result of the involvement of supraspinal mechanisms in this pain syndrome. These mechanisms might accentuate the leftward bias that results from a right-hemispheric dominance in visuospatial processing and is known as pseudoneglect. Pseudoneglect reveals itself in the tendency to perceive the midpoint of horizontal lines or the subjective body midline left of the centre. It was observable in all 3 groups, but most pronounced in CRPS patients, which might be due to the cortical reorganisation processes associated with this syndrome. Copyright © 2012 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

  19. Object-based selection from spatially-invariant representations: evidence from a feature-report task.

    Matsukura, Michi; Vecera, Shaun P

    2011-02-01

    Attention selects objects as well as locations. When attention selects an object's features, observers identify two features from a single object more accurately than two features from two different objects (object-based effect of attention; e.g., Duncan, Journal of Experimental Psychology: General, 113, 501-517, 1984). Several studies have demonstrated that object-based attention can operate at a late visual processing stage that is independent of objects' spatial information (Awh, Dhaliwal, Christensen, & Matsukura, Psychological Science, 12, 329-334, 2001; Matsukura & Vecera, Psychonomic Bulletin & Review, 16, 529-536, 2009; Vecera, Journal of Experimental Psychology: General, 126, 14-18, 1997; Vecera & Farah, Journal of Experimental Psychology: General, 123, 146-160, 1994). In the present study, we asked two questions regarding this late object-based selection mechanism. In Part I, we investigated how observers' foreknowledge of to-be-reported features allows attention to select objects, as opposed to individual features. Using a feature-report task, a significant object-based effect was observed when to-be-reported features were known in advance but not when this advance knowledge was absent. In Part II, we examined what drives attention to select objects rather than individual features in the absence of observers' foreknowledge of to-be-reported features. Results suggested that, when there was no opportunity for observers to direct their attention to objects that possess to-be-reported features at the time of stimulus presentation, these stimuli must retain strong perceptual cues to establish themselves as separate objects.

  20. Illusions in the spatial sense of the eye: geometrical-optical illusions and the neural representation of space.

    Westheimer, Gerald

    2008-09-01

    Differences between the geometrical properties of simple configurations and their visual percept are called geometrical-optical illusions. They can be differentiated from illusions in the brightness or color domains, from ambiguous figures and impossible objects, from trompe l'oeil and perspective drawing with perfectly valid views, and from illusory contours. They were discovered independently by several scientists in a short time span in the 1850's. The clear distinction between object and visual space that they imply allows the question to be raised whether the transformation between the two spaces can be productively investigated in terms of differential geometry and metrical properties. Perceptual insight and psychophysical research prepares the ground for investigation of the neural representation of space but, because visual attributes are processed separately in parallel, one looks in vain for a neural map that is isomorphic with object space or even with individual forms it contains. Geometrical-optical illusions help reveal parsing rules for sensory signals by showing how conflicts are resolved when there is mismatch in the output of the processing modules for various primitives as a perceptual pattern's unitary structure is assembled. They point to a hierarchical ordering of spatial primitives: cardinal directions and explicit contours predominate over oblique orientation and implicit contours (Poggendorff illusion); rectilinearity yields to continuity (Hering illusion), point position and line length to contour orientation (Ponzo). Hence the geometrical-optical illusions show promise as analytical tools in unraveling neural processing in vision.

  1. Associative-memory representations emerge as shared spatial patterns of theta activity spanning the primate temporal cortex.

    Nakahara, Kiyoshi; Adachi, Ken; Kawasaki, Keisuke; Matsuo, Takeshi; Sawahata, Hirohito; Majima, Kei; Takeda, Masaki; Sugiyama, Sayaka; Nakata, Ryota; Iijima, Atsuhiko; Tanigawa, Hisashi; Suzuki, Takafumi; Kamitani, Yukiyasu; Hasegawa, Isao

    2016-06-10

    Highly localized neuronal spikes in primate temporal cortex can encode associative memory; however, whether memory formation involves area-wide reorganization of ensemble activity, which often accompanies rhythmicity, or just local microcircuit-level plasticity, remains elusive. Using high-density electrocorticography, we capture local-field potentials spanning the monkey temporal lobes, and show that the visual pair-association (PA) memory is encoded in spatial patterns of theta activity in areas TE, 36, and, partially, in the parahippocampal cortex, but not in the entorhinal cortex. The theta patterns elicited by learned paired associates are distinct between pairs, but similar within pairs. This pattern similarity, emerging through novel PA learning, allows a machine-learning decoder trained on theta patterns elicited by a particular visual item to correctly predict the identity of those elicited by its paired associate. Our results suggest that the formation and sharing of widespread cortical theta patterns via learning-induced reorganization are involved in the mechanisms of associative memory representation.

  2. Rosiglitazone attenuates inflammation and CA3 neuronal loss following traumatic brain injury in rats

    Liu, Hao; Rose, Marie E. [Geriatric Research Educational and Clinical Center, V.A. Pittsburgh Healthcare System, PA (United States); Department of Neurology, University of Pittsburgh School of Medicine, PA (United States); Culver, Sherman; Ma, Xiecheng; Dixon, C. Edward [Geriatric Research Educational and Clinical Center, V.A. Pittsburgh Healthcare System, PA (United States); Department of Neurosurgery, University of Pittsburgh, PA 15216 (United States); Department of Critical Care Medicine, University of Pittsburgh, PA 15216 (United States); Graham, Steven H., E-mail: Steven.Graham@va.gov [Geriatric Research Educational and Clinical Center, V.A. Pittsburgh Healthcare System, PA (United States); Department of Neurology, University of Pittsburgh School of Medicine, PA (United States)

    2016-04-15

    Rosiglitazone, a potent peroxisome proliferator-activated receptor (PPAR)-γ agonist, has been shown to confer neuroprotective effects in stroke and spinal cord injury, but its role in the traumatic brain injury (TBI) is still controversial. Using a controlled cortical impact model in rats, the current study was designed to determine the effects of rosiglitazone treatment (6 mg/kg at 5 min, 6 h and 24 h post injury) upon inflammation and histological outcome at 21 d after TBI. In addition, the effects of rosiglitazone upon inflammatory cytokine transcription, vestibulomotor behavior and spatial memory function were determined at earlier time points (24 h, 1–5 d, 14–20 d post injury, respectively). Compared with the vehicle-treated group, rosiglitazone treatment suppressed production of TNFα at 24 h after TBI, attenuated activation of microglia/macrophages and increased survival of CA3 neurons but had no effect on lesion volume at 21 d after TBI. Rosiglitazone-treated animals had improved performance on beam balance testing, but there was no difference in spatial memory function as determined by Morris water maze. In summary, this study indicates that rosiglitazone treatment in the first 24 h after TBI has limited anti-inflammatory and neuroprotective effects in rat traumatic injury. Further study using an alternative dosage paradigm and more sensitive behavioral testing may be warranted. - Highlights: • Effects of rosiglitazone after CCI were evaluated using a rat TBI model. • Rosiglitazone suppressed production of TNFα at 24 h after CCI. • Rosiglitazone inhibited microglial activation at 21 d after CCI. • Rosiglitazone increased survival of CA3 neurons at 21 d after CCI. • Rosiglitazone-treated animals had improved performance in beam balance testing.

  3. Rosiglitazone attenuates inflammation and CA3 neuronal loss following traumatic brain injury in rats

    Liu, Hao; Rose, Marie E.; Culver, Sherman; Ma, Xiecheng; Dixon, C. Edward; Graham, Steven H.

    2016-01-01

    Rosiglitazone, a potent peroxisome proliferator-activated receptor (PPAR)-γ agonist, has been shown to confer neuroprotective effects in stroke and spinal cord injury, but its role in the traumatic brain injury (TBI) is still controversial. Using a controlled cortical impact model in rats, the current study was designed to determine the effects of rosiglitazone treatment (6 mg/kg at 5 min, 6 h and 24 h post injury) upon inflammation and histological outcome at 21 d after TBI. In addition, the effects of rosiglitazone upon inflammatory cytokine transcription, vestibulomotor behavior and spatial memory function were determined at earlier time points (24 h, 1–5 d, 14–20 d post injury, respectively). Compared with the vehicle-treated group, rosiglitazone treatment suppressed production of TNFα at 24 h after TBI, attenuated activation of microglia/macrophages and increased survival of CA3 neurons but had no effect on lesion volume at 21 d after TBI. Rosiglitazone-treated animals had improved performance on beam balance testing, but there was no difference in spatial memory function as determined by Morris water maze. In summary, this study indicates that rosiglitazone treatment in the first 24 h after TBI has limited anti-inflammatory and neuroprotective effects in rat traumatic injury. Further study using an alternative dosage paradigm and more sensitive behavioral testing may be warranted. - Highlights: • Effects of rosiglitazone after CCI were evaluated using a rat TBI model. • Rosiglitazone suppressed production of TNFα at 24 h after CCI. • Rosiglitazone inhibited microglial activation at 21 d after CCI. • Rosiglitazone increased survival of CA3 neurons at 21 d after CCI. • Rosiglitazone-treated animals had improved performance in beam balance testing.

  4. Human neuroimaging studies on the hippocampal CA3 region – integrating evidence for pattern separation and completion

    Lorena eDeuker

    2014-03-01

    Full Text Available Human functional magnetic imaging (fMRI studies have long investigated the hippocampus without differentiating between its subfields, even though theoretical models and rodent studies suggest that subfields support different and potentially even opposite functions. The CA3 region of the hippocampus has been ascribed a pivotal role both in initially forming associations during encoding and in reconstructing a memory representation based on partial cues during retrieval. These functions have been related to pattern separation and pattern completion, respectively. In recent years, studies using high-resolution fMRI in humans have begun to separate different hippocampal subregions and identify the role of the CA3 subregion relative to the other subregions. However, some of these findings have been inconsistent with theoretical models and findings from electrophysiology. In this review, we describe selected recent studies and highlight how their results might help to define different processes and functions that are presumably carried out by the CA3 region, in particular regarding the seemingly opposing functions of pattern separation and pattern completion. We also describe how these subfield-specific processes are related to behavioral, functional and structural alterations in patients with mild cognitive impairment and Alzheimer’s disease. We conclude with discussing limitations of functional imaging and briefly outline possible future developments of the field.

  5. Ablation of NMDA receptors enhances the excitability of hippocampal CA3 neurons.

    Fumiaki Fukushima

    Full Text Available Synchronized discharges in the hippocampal CA3 recurrent network are supposed to underlie network oscillations, memory formation and seizure generation. In the hippocampal CA3 network, NMDA receptors are abundant at the recurrent synapses but scarce at the mossy fiber synapses. We generated mutant mice in which NMDA receptors were abolished in hippocampal CA3 pyramidal neurons by postnatal day 14. The histological and cytological organizations of the hippocampal CA3 region were indistinguishable between control and mutant mice. We found that mutant mice lacking NMDA receptors selectively in CA3 pyramidal neurons became more susceptible to kainate-induced seizures. Consistently, mutant mice showed characteristic large EEG spikes associated with multiple unit activities (MUA, suggesting enhanced synchronous firing of CA3 neurons. The electrophysiological balance between fast excitatory and inhibitory synaptic transmission was comparable between control and mutant pyramidal neurons in the hippocampal CA3 region, while the NMDA receptor-slow AHP coupling was diminished in the mutant neurons. In the adult brain, inducible ablation of NMDA receptors in the hippocampal CA3 region by the viral expression vector for Cre recombinase also induced similar large EEG spikes. Furthermore, pharmacological blockade of CA3 NMDA receptors enhanced the susceptibility to kainate-induced seizures. These results raise an intriguing possibility that hippocampal CA3 NMDA receptors may suppress the excitability of the recurrent network as a whole in vivo by restricting synchronous firing of CA3 neurons.

  6. Entorhinal-CA3 Dual-Input Control of Spike Timing in the Hippocampus by Theta-Gamma Coupling.

    Fernández-Ruiz, Antonio; Oliva, Azahara; Nagy, Gergő A; Maurer, Andrew P; Berényi, Antal; Buzsáki, György

    2017-03-08

    Theta-gamma phase coupling and spike timing within theta oscillations are prominent features of the hippocampus and are often related to navigation and memory. However, the mechanisms that give rise to these relationships are not well understood. Using high spatial resolution electrophysiology, we investigated the influence of CA3 and entorhinal inputs on the timing of CA1 neurons. The theta-phase preference and excitatory strength of the afferent CA3 and entorhinal inputs effectively timed the principal neuron activity, as well as regulated distinct CA1 interneuron populations in multiple tasks and behavioral states. Feedback potentiation of distal dendritic inhibition by CA1 place cells attenuated the excitatory entorhinal input at place field entry, coupled with feedback depression of proximal dendritic and perisomatic inhibition, allowing the CA3 input to gain control toward the exit. Thus, upstream inputs interact with local mechanisms to determine theta-phase timing of hippocampal neurons to support memory and spatial navigation. Copyright © 2017 Elsevier Inc. All rights reserved.

  7. Representational Machines

    Photography not only represents space. Space is produced photographically. Since its inception in the 19th century, photography has brought to light a vast array of represented subjects. Always situated in some spatial order, photographic representations have been operatively underpinned by social...... to the enterprises of the medium. This is the subject of Representational Machines: How photography enlists the workings of institutional technologies in search of establishing new iconic and social spaces. Together, the contributions to this edited volume span historical epochs, social environments, technological...... possibilities, and genre distinctions. Presenting several distinct ways of producing space photographically, this book opens a new and important field of inquiry for photography research....

  8. Developing Spatial Knowledge in the Absence of Vision: Allocentric and Egocentric Representations Generated by Blind People When Supported by Auditory Cues

    Luca Latini Corazzini

    2010-10-01

    Full Text Available The study of visuospatial representations and visuospatial memory can profit from the analysis of the performance of specific groups. in particular, the surprising skills and limitations of blind people may be an important source of information. For example, converging evidence indicates that, even though blind individuals are able to develop both egocentric and allocentric space representations, the latter tend to be much more restricted than those in blindfolded sighted individuals. however, no study has explored yet whether this conclusion also holds when people receive practice with the spatial environment and are supported by auditory stimuli. The present research examined these issues with the use of an experimental apparatus based on the morris Water maze (morris et al., 1982. in this setup, blind people and blindfolded controls were given the opportunity to develop knowledge of the environment with the support of simultaneous auditory cues. The results show that even in this favourable case blind people spontaneously maintain to rely on an egocentric spatial representation.

  9. Synaptically evoked Ca2+ release from intracellular stores is not influenced by vesicular zinc in CA3 hippocampal pyramidal neurones.

    Evstratova, Alesya; Tóth, Katalin

    2011-12-01

    The co-release of neuromodulatory substances in combination with classic neurotransmitters such as glutamate and GABA from individual presynaptic nerve terminals has the capacity to dramatically influence synaptic efficacy and plasticity. At hippocampal mossy fibre synapses vesicular zinc is suggested to serve as a cotransmitter capable of regulating calcium release from internal stores in postsynaptic CA3 pyramidal cells. Here we investigated this possibility using combined intracellular ratiometric calcium imaging and patch-clamp recording techniques. In acute hippocampal slices a brief train of mossy fibre stimulation produced a large, delayed postsynaptic Ca(2+) wave that was spatially restricted to the proximal apical dendrites of CA3 pyramidal cells within stratum lucidum. This calcium increase was sensitive to intracellularly applied heparin indicating reliance upon release from internal stores and was triggered by activation of both group I metabotropic glutamate and NMDA receptors. Importantly, treatment of slices with the membrane-impermeant zinc chelator CaEDTA did not influence the synaptically evoked postsynaptic Ca(2+) waves. Moreover, mossy fibre stimulus evoked postsynaptic Ca(2+) signals were not significantly different between wild-type and zinc transporter 3 (ZnT3) knock-out animals. Considered together our data do not support a role for vesicular zinc in regulating mossy fibre evoked Ca(2+) release from CA3 pyramidal cell internal stores.

  10. A Review of the Effects of Visual-Spatial Representations and Heuristics on Word Problem Solving in Middle School Mathematics

    Kribbs, Elizabeth E.; Rogowsky, Beth A.

    2016-01-01

    Mathematics word-problems continue to be an insurmountable challenge for many middle school students. Educators have used pictorial and schematic illustrations within the classroom to help students visualize these problems. However, the data shows that pictorial representations can be more harmful than helpful in that they only display objects or…

  11. Advanced techniques for the storage and use of very large, heterogeneous spatial databases. The representation of geographic knowledge: Toward a universal framework. [relations (mathematics)

    Peuquet, Donna J.

    1987-01-01

    A new approach to building geographic data models that is based on the fundamental characteristics of the data is presented. An overall theoretical framework for representing geographic data is proposed. An example of utilizing this framework in a Geographic Information System (GIS) context by combining artificial intelligence techniques with recent developments in spatial data processing techniques is given. Elements of data representation discussed include hierarchical structure, separation of locational and conceptual views, and the ability to store knowledge at variable levels of completeness and precision.

  12. On the instability and constraints of the interaction between number representation and spatial attention in healthy humans: A concise review of the literature and new experimental evidence.

    Fattorini, E; Pinto, M; Merola, S; D'Onofrio, M; Doricchi, F

    2016-01-01

    The relationship between number and space representation is still one of the most debated topics in studies of mathematical cognition. Here we offer a concise review of two important behavioral effects that have pointed out the use of a spatially left-to-right oriented mental number line (MNL) in healthy participants: the SNARC effect and the attentional SNARC effect (Att-SNARC). Following a brief summary of seminal investigations on the introspective properties of the MNL, we review recent empirical evidence and theories on the functional origin of the SNARC effect, where upon left/right response choices faster reaction times are found for small numbers with left-side responses and for large numbers with right-side responses. Then we offer a summary of the studies that have investigated whether the mere perception of visual Arabic numbers presented at central fixation can engender spatially congruent lateral shifts of attention, ie, leftward for small numbers and rightward for large ones, ie, the Att-SNARC effect. Finally, we summarize four experiments that tested whether the Att-SNARC depends on an active rather than passive processing of centrally presented digit cues. In line with other recent studies, these experiment do not replicate the original Att-SNARC and show that the mere perception of Arabic numerals does not trigger automatic shifts of attention. These shifts are instead found when the task requires the explicit left/right spatial coding of digit cues, ie, Spatial Att-SNARC (Fattorini et al., 2015b). Nonetheless, the reliability of the Spatial Att-SNARC effect seems not as strong as that of conventional SNARC effects where left/right codes are mapped onto responses rather than directly mapped on digit cues. Comparing the magnitude of digits to a numerical reference, ie, "5," also produced a Magnitude Comparison Att-SNARC that was weaker than the spatial one. However, the reliability of this Magnitude Comparison Att-SNARC should be considered with

  13. From the Real to the Virtual: The Re-Presentation of the Spatiality of the Museum on Its Website

    Kali Tzortzi

    2016-07-01

    Full Text Available The museum is not only a transmitter of information about objects, but also ‘a technology in its own right’: the spatial and conceptual arrangement of its display and the architectural layout of its spaces, which together constitute the spatiality of the museum, act as media that generate and structure the  way it presents knowledge. This paper explores whether museums seek to re-present their spatiality in the virtual sphere of the website, and if so, in what ways and why. Studies of the use of websites which stress interdependence with the real museum, provide the grounding for these questions. Forty-three websites of the most visited European museums are analyzed, on the basis of 16 themes that index spatiality. The paper clarifies high variability in the way they interpret spatiality, distinguishing three modes of relating real and virtual: the synergetic, the presentational and the discursive. Methodologically, a conceptual framework is developed for interpreting these strategic differences. Theoretically, website design is related to museum theory, in that the philosophy among leading museums to transmit their spatiality powerfully through the website can be theorized as reflecting a performing, rather than informing, museological approach, and a move towards a more ‘participatory’ website culture.

  14. INFLUENCE OF ELECTROACUPUNCTURE ON THE ULTRASTRUCTURE OF CA3 REGION OF THE HIPPOCAMPUS IN VD RATS

    YAN Bing; XU Neng-gui; HE Li-lei; TANG Chun-zhi; SHAO Ying

    2006-01-01

    Objective: To observe the effect of electroacupuncture (EA) on learning and memory abilities and ultrastructure of synapses in CA3 region of the hippocampus in vascular dementia (VD) rats. Methods: A total of 32 SD rats were randomized into control (sham-operation, n = 7), model (n = 7), EA (n = 9) and medication (n=9) groups. VD model was established by occlusion of the bilateral vertebral arteries (electrocoagulation) and bilateral common carotid arteries (occlusion for 5 min and reperfusion for 10 min, repeated the procedure for 3 times to induce global ischemia). EA (150 Hz, 1 mA) was applied to "Baihui"(百会GV 20), "Geshu"(膈俞 BL 17), "Pishu"(脾俞 BL 20) and "Shenshu"(肾俞 BL 23) for 20 min, once daily and continuously for 15 days. In medication group, the rats were fed with Nimotong (12 mg/kg), once daily and continuously for 15 days. Morris water maze method was used to test the animals' learning and memory abilities (latencies to find the hidden platform determined by place navigation trials, and latencies to cross on the location of the removed platform determined by spatial probe trials) after the treatment. Ultrastructural changes (numerical density, NA,surface density, Sv and volume density, Vv) of Gray type 1 synapses in CA3 region of the hippocampus were observed by using transmission electronic microscope and automatic image analysis system. Results: 1 ) Place navigation test showed that in comparison with control group, the average escape latency of VD group was significantly longer (P<0.01), while in comparison with VD group, the latencies of both EA and medication groups decreased significantly ( P<0.01 ). No significant difference was found between EA and medication groups in the escape latency (P>0.05). 2) Spatial probe-test displayed that in comparison with control group, the times which the animals crossed the target platform in VD group decreased significantly (P<0.01), while compared with VD group, those of both EA and

  15. Perforant path lesioning induces sprouting of CA3-associated fibre systems in mouse hippocampal formation

    Drøjdahl, Nina; Hegelund, Iørn V; Poulsen, Frantz R

    2002-01-01

    mice. We found that lesioning led to translaminar sprouting of Timm stained regio inferior hippocampus (CA3)-associated fibre systems into the denervated termination zones of the CA3 and dentate gyrus, from the adjacent non-denervated stratum radiatum of CA3. Differences were seen in the Timm staining...... pattern of the two strains of mice, while the response to lesioning appeared similar albeit less pronounced than that observed in the rat. We also observed an intensified acetylcholine esterase staining reflective of cholinergic sprouting in the denervated perforant path termination zones, which...... was particularly prominent in areas with sprouting of Timm stained CA3-associated fibres. Finally, we showed that some of the sprouting fibres within the CA3 were myelinated, due to an increased density of silver impregnated myelinated fibres in this region after lesioning. These results show that the basic...

  16. Observation of microstructure of hydrated Ca3SiO5

    Mori, Kazuhiro; Sato, Takashi; Fukunaga, Toshiharu; Oishi, Koji; Kimura, Katsuhiko; Iwase, Kenji; Sugiyama, Masaaki; Itoh, Keiji; Shikanai, Fumihito; Wuernisha, Tuerxun; Yonemura, Masao; Sulistyanintyas, Dyah; Tsukushi, Itaru; Takata, Shinich; Otomo, Toshiya; Kamiyma, Takashi; Kawai, Masayoshi

    2006-01-01

    Quasi-elastic neutron scattering experiments were carried out to evaluate the hydration rate of tricalcium silicate (Ca 3 SiO 5 ). Furthermore, in the early hydration period, a variation in surface roughness of Ca 3 SiO 5 was observed in nano-scale by the small-angle neutron scattering. From these results, it was found that the hydration rate of Ca 3 SiO 5 is suppressed when the surface of Ca 3 SiO 5 becomes rough through the creation of hydration products C-S-H gel and Ca(OH) 2 , and this roughness is associated with changes in the Ca 3 SiO 5 hydration rate

  17. The race to learn: spike timing and STDP can coordinate learning and recall in CA3.

    Nolan, Christopher R; Wyeth, Gordon; Milford, Michael; Wiles, Janet

    2011-06-01

    The CA3 region of the hippocampus has long been proposed as an autoassociative network performing pattern completion on known inputs. The dentate gyrus (DG) region is often proposed as a network performing the complementary function of pattern separation. Neural models of pattern completion and separation generally designate explicit learning phases to encode new information and assume an ideal fixed threshold at which to stop learning new patterns and begin recalling known patterns. Memory systems are significantly more complex in practice, with the degree of memory recall depending on context-specific goals. Here, we present our spike-timing separation and completion (STSC) model of the entorhinal cortex (EC), DG, and CA3 network, ascribing to each region a role similar to that in existing models but adding a temporal dimension by using a spiking neural network. Simulation results demonstrate that (a) spike-timing dependent plasticity in the EC-CA3 synapses provides a pattern completion ability without recurrent CA3 connections, (b) the race between activation of CA3 cells via EC-CA3 synapses and activation of the same cells via DG-CA3 synapses distinguishes novel from known inputs, and (c) modulation of the EC-CA3 synapses adjusts the learned versus test input similarity required to evoke a direct CA3 response prior to any DG activity, thereby adjusting the pattern completion threshold. These mechanisms suggest that spike timing can arbitrate between learning and recall based on the novelty of each individual input, ensuring control of the learn-recall decision resides in the same subsystem as the learned memories themselves. The proposed modulatory signal does not override this decision but biases the system toward either learning or recall. The model provides an explanation for empirical observations that a reduction in novelty produces a corresponding reduction in the latency of responses in CA3 and CA1. Copyright © 2010 Wiley-Liss, Inc.

  18. Assessing the spatial representability of charcoal and PAH-based paleofire records with integrated GIS, modelling, and empirical approaches

    Vachula, R. S.; Huang, Y.; Russell, J. M.

    2017-12-01

    Lake sediment-based fire reconstructions offer paleoenvironmental context in which to assess modern fires and predict future burning. However, despite the ubiquity, many uncertainties remain regarding the taphonomy of paleofire proxies and the spatial scales for which they record variations in fire history. Here we present down-core proxy analyses of polycyclic aromatic hydrocarbons (PAHs) and three size-fractions of charcoal (63-150, >150 and >250 μm) from Swamp Lake, California, an annually laminated lacustrine archive. Using a statewide historical GIS dataset of area burned, we assess the spatial scales for which these proxies are reliable recorders of fire history. We find that the coherence of observed and proxy-recorded fire history inherently depends upon spatial scale. Contrary to conventional thinking that charcoal mainly records local fires, our results indicate that macroscopic charcoal (>150 μm) may record spatially broader (250 μm) may be a more conservative proxy for local burning. We find that sub-macroscopic charcoal particles (63-150 μm) reliably record regional (up to 150 km) changes in fire history. These results indicate that charcoal-based fire reconstructions may represent spatially broader fire history than previously thought, which has major implications for our understanding of spatiotemporal paleofire variations. Our analyses of PAHs show that dispersal mobility is heterogeneous between compounds, but that PAH fluxes are reliable proxies of fire history within 25-50 km, which suggests PAHs may be a better spatially constrained paleofire proxy than sedimentary charcoal. Further, using a linear discriminant analysis model informed by modern emissions analyses, we show that PAH assemblages preserved in lake sediments can differentiate vegetation type burned, and are thus promising paleoecological biomarkers warranting further research and implementation. In sum, our analyses offer new insight into the spatial dimensions of paleofire

  19. Sensorimotor Representations in Cerebellar Granule Cells in Larval Zebrafish Are Dense, Spatially Organized, and Non-temporally Patterned.

    Knogler, Laura D; Markov, Daniil A; Dragomir, Elena I; Štih, Vilim; Portugues, Ruben

    2017-05-08

    A fundamental question in neurobiology is how animals integrate external sensory information from their environment with self-generated motor and sensory signals in order to guide motor behavior and adaptation. The cerebellum is a vertebrate hindbrain region where all of these signals converge and that has been implicated in the acquisition, coordination, and calibration of motor activity. Theories of cerebellar function postulate that granule cells encode a variety of sensorimotor signals in the cerebellar input layer. These models suggest that representations should be high-dimensional, sparse, and temporally patterned. However, in vivo physiological recordings addressing these points have been limited and in particular have been unable to measure the spatiotemporal dynamics of population-wide activity. In this study, we use both calcium imaging and electrophysiology in the awake larval zebrafish to investigate how cerebellar granule cells encode three types of sensory stimuli as well as stimulus-evoked motor behaviors. We find that a large fraction of all granule cells are active in response to these stimuli, such that representations are not sparse at the population level. We find instead that most responses belong to only one of a small number of distinct activity profiles, which are temporally homogeneous and anatomically clustered. We furthermore identify granule cells that are active during swimming behaviors and others that are multimodal for sensory and motor variables. When we pharmacologically change the threshold of a stimulus-evoked behavior, we observe correlated changes in these representations. Finally, electrophysiological data show no evidence for temporal patterning in the coding of different stimulus durations. Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.

  20. Thermodynamic, electronic, and magnetic properties of intrinsic vacancy defects in antiperovskite Ca3SnO

    Batool, Javaria; Alay-e-Abbas, Syed Muhammad; Amin, Nasir

    2018-04-01

    The density functional theory based total energy calculations are performed to examine the effect of charge neutral and fully charged intrinsic vacancy defects on the thermodynamic, electronic, and magnetic properties of Ca3SnO antiperovskite. The chemical stability of Ca3SnO is evaluated with respect to binary compounds CaO, CaSn, and Ca2Sn, and the limits of atomic chemical potentials of Ca, Sn, and O atoms for stable synthesis of Ca3SnO are determined within the generalized gradient approximation parametrization scheme. The electronic properties of the pristine and the non-stoichiometric forms of this compound have been explored and the influence of isolated intrinsic vacancy defects (Ca, Sn, and O) on the structural, bonding, and electronic properties of non-stoichiometric Ca3SnO are analyzed. We also predict the possibility of achieving stable ferromagnetism in non-stoichiometric Ca3SnO by means of charge neutral tin vacancies. From the calculated total energies and the valid ranges of atomic chemical potentials, the formation energetics of intrinsic vacancy defects in Ca3SnO are evaluated for various growth conditions. Our results indicate that the fully charged calcium vacancies are thermodynamically stable under the permissible Sn-rich condition of stable synthesis of Ca3SnO, while tin and oxygen vacancies are found to be stable under the extreme Ca-rich condition.

  1. Representational Thickness

    Mullins, Michael

    Contemporary communicational and informational processes contribute to the shaping of our physical environment by having a powerful influence on the process of design. Applications of virtual reality (VR) are transforming the way architecture is conceived and produced by introducing dynamic...... elements into the process of design. Through its immersive properties, virtual reality allows access to a spatial experience of a computer model very different to both screen based simulations as well as traditional forms of architectural representation. The dissertation focuses on processes of the current...... representation? How is virtual reality used in public participation and how do virtual environments affect participatory decision making? How does VR thus affect the physical world of built environment? Given the practical collaborative possibilities of immersive technology, how can they best be implemented...

  2. Assessment of habitat representation across a network of marine protected areas with implications for the spatial design of monitoring.

    Young, Mary; Carr, Mark

    2015-01-01

    Networks of marine protected areas (MPAs) are being adopted globally to protect ecosystems and supplement fisheries management. The state of California recently implemented a coast-wide network of MPAs, a statewide seafloor mapping program, and ecological characterizations of species and ecosystems targeted for protection by the network. The main goals of this study were to use these data to evaluate how well seafloor features, as proxies for habitats, are represented and replicated across an MPA network and how well ecological surveys representatively sampled fish habitats inside MPAs and adjacent reference sites. Seafloor data were classified into broad substrate categories (rock and sediment) and finer scale geomorphic classifications standard to marine classification schemes using surface analyses (slope, ruggedness, etc.) done on the digital elevation model derived from multibeam bathymetry data. These classifications were then used to evaluate the representation and replication of seafloor structure within the MPAs and across the ecological surveys. Both the broad substrate categories and the finer scale geomorphic features were proportionately represented for many of the classes with deviations of 1-6% and 0-7%, respectively. Within MPAs, however, representation of seafloor features differed markedly from original estimates, with differences ranging up to 28%. Seafloor structure in the biological monitoring design had mismatches between sampling in the MPAs and their corresponding reference sites and some seafloor structure classes were missed entirely. The geomorphic variables derived from multibeam bathymetry data for these analyses are known determinants of the distribution and abundance of marine species and for coastal marine biodiversity. Thus, analyses like those performed in this study can be a valuable initial method of evaluating and predicting the conservation value of MPAs across a regional network.

  3. Assessment of habitat representation across a network of marine protected areas with implications for the spatial design of monitoring.

    Mary Young

    Full Text Available Networks of marine protected areas (MPAs are being adopted globally to protect ecosystems and supplement fisheries management. The state of California recently implemented a coast-wide network of MPAs, a statewide seafloor mapping program, and ecological characterizations of species and ecosystems targeted for protection by the network. The main goals of this study were to use these data to evaluate how well seafloor features, as proxies for habitats, are represented and replicated across an MPA network and how well ecological surveys representatively sampled fish habitats inside MPAs and adjacent reference sites. Seafloor data were classified into broad substrate categories (rock and sediment and finer scale geomorphic classifications standard to marine classification schemes using surface analyses (slope, ruggedness, etc. done on the digital elevation model derived from multibeam bathymetry data. These classifications were then used to evaluate the representation and replication of seafloor structure within the MPAs and across the ecological surveys. Both the broad substrate categories and the finer scale geomorphic features were proportionately represented for many of the classes with deviations of 1-6% and 0-7%, respectively. Within MPAs, however, representation of seafloor features differed markedly from original estimates, with differences ranging up to 28%. Seafloor structure in the biological monitoring design had mismatches between sampling in the MPAs and their corresponding reference sites and some seafloor structure classes were missed entirely. The geomorphic variables derived from multibeam bathymetry data for these analyses are known determinants of the distribution and abundance of marine species and for coastal marine biodiversity. Thus, analyses like those performed in this study can be a valuable initial method of evaluating and predicting the conservation value of MPAs across a regional network.

  4. A signature of attractor dynamics in the CA3 region of the hippocampus.

    César Rennó-Costa

    2014-05-01

    Full Text Available The notion of attractor networks is the leading hypothesis for how associative memories are stored and recalled. A defining anatomical feature of such networks is excitatory recurrent connections. These "attract" the firing pattern of the network to a stored pattern, even when the external input is incomplete (pattern completion. The CA3 region of the hippocampus has been postulated to be such an attractor network; however, the experimental evidence has been ambiguous, leading to the suggestion that CA3 is not an attractor network. In order to resolve this controversy and to better understand how CA3 functions, we simulated CA3 and its input structures. In our simulation, we could reproduce critical experimental results and establish the criteria for identifying attractor properties. Notably, under conditions in which there is continuous input, the output should be "attracted" to a stored pattern. However, contrary to previous expectations, as a pattern is gradually "morphed" from one stored pattern to another, a sharp transition between output patterns is not expected. The observed firing patterns of CA3 meet these criteria and can be quantitatively accounted for by our model. Notably, as morphing proceeds, the activity pattern in the dentate gyrus changes; in contrast, the activity pattern in the downstream CA3 network is attracted to a stored pattern and thus undergoes little change. We furthermore show that other aspects of the observed firing patterns can be explained by learning that occurs during behavioral testing. The CA3 thus displays both the learning and recall signatures of an attractor network. These observations, taken together with existing anatomical and behavioral evidence, make the strong case that CA3 constructs associative memories based on attractor dynamics.

  5. Aging-related impairments of hippocampal mossy fibers synapses on CA3 pyramidal cells.

    Villanueva-Castillo, Cindy; Tecuatl, Carolina; Herrera-López, Gabriel; Galván, Emilio J

    2017-01-01

    The network interaction between the dentate gyrus and area CA3 of the hippocampus is responsible for pattern separation, a process that underlies the formation of new memories, and which is naturally diminished in the aged brain. At the cellular level, aging is accompanied by a progression of biochemical modifications that ultimately affects its ability to generate and consolidate long-term potentiation. Although the synapse between dentate gyrus via the mossy fibers (MFs) onto CA3 neurons has been subject of extensive studies, the question of how aging affects the MF-CA3 synapse is still unsolved. Extracellular and whole-cell recordings from acute hippocampal slices of aged Wistar rats (34 ± 2 months old) show that aging is accompanied by a reduction in the interneuron-mediated inhibitory mechanisms of area CA3. Several MF-mediated forms of short-term plasticity, MF long-term potentiation and at least one of the critical signaling cascades necessary for potentiation are also compromised in the aged brain. An analysis of the spontaneous glutamatergic and gamma-aminobutyric acid-mediated currents on CA3 cells reveal a dramatic alteration in amplitude and frequency of the nonevoked events. CA3 cells also exhibited increased intrinsic excitability. Together, these results demonstrate that aging is accompanied by a decrease in the GABAergic inhibition, reduced expression of short- and long-term forms of synaptic plasticity, and increased intrinsic excitability. Copyright © 2016 Elsevier Inc. All rights reserved.

  6. Ventral tegmental area disruption selectively affects CA1/CA2 but not CA3 place fields during a differential reward working memory task.

    Martig, Adria K; Mizumori, Sheri J Y

    2011-02-01

    Hippocampus (HPC) receives dopaminergic (DA) projections from the ventral tegmental area (VTA) and substantia nigra. These inputs appear to provide a modulatory signal that influences HPC dependent behaviors and place fields. We examined how efferent projections from VTA to HPC influence spatial working memory and place fields when the reward context changes. CA1 and CA3 process environmental context changes differently and VTA preferentially innervates CA1. Given these anatomical data and electrophysiological evidence that implicate DA in reward processing, we predicted that CA1 place fields would respond more strongly to both VTA disruption and changes in the reward context than CA3 place fields. Rats (N = 9) were implanted with infusion cannula targeting VTA and recording tetrodes aimed at HPC. Then they were tested on a differential reward, win-shift working memory task. One recording session consisted of 5 baseline and 5 manipulation trials during which place cells in CA1/CA2 (N = 167) and CA3 (N = 94) were recorded. Prior to manipulation trials rats were infused with either baclofen or saline and then subjected to control or reward conditions during which the learned locations of large and small reward quantities were reversed. VTA disruption resulted in an increase in errors, and in CA1/CA2 place field reorganization. There were no changes in any measures of CA3 place field stability during VTA disruption. Reward manipulations did not affect performance or place field stability in CA1/CA2 or CA3; however, changes in the reward locations "rescued" performance and place field stability in CA1/CA2 when VTA activity was compromised, perhaps by trigging compensatory mechanisms. These data support the hypothesis that VTA contributes to spatial working memory performance perhaps by maintaining place field stability selectively in CA1/CA2. Copyright © 2009 Wiley-Liss, Inc.

  7. Representation of spatial variability for modelling of flow and transport processes in the Culebra Dolomite at the WIPP site

    Meigs, L.C.; Beauheim, R.L.

    1997-01-01

    The Waste Isolation Pilot Plant (WIPP) is a proposed repository for transuranic wastes constructed in bedded Permian-acre halite deposits in southeastern New Mexico, USA. Site-characterization studies at the WIPP site identified groundwater flow in the Culebra Dolomite Member of the Rustler Formation as the most likely Geologic pathway for radio nuclide transport to the accessible environment in the event of a breach of the WIPP repository through inadvertent human intrusion. The Culebra is a 7-m-thick, variably fractured dolomite with massive and layers. Detailed studies at all scales demonstrated that the Culebra is a heterogeneous medium. Heterogeneity in Culebra properties was incorporated into numerical simulations used for data interpretation and PA calculations in different ways, depending on the amount of data available, the certainty with which the effects of a given approach could be evaluated, and the purpose of the study. When abundant, spatially distributed data were available, the heterogeneity was explicitly included. For example, a stochastic approach was used to generate numerous, equally likely, heterogeneous transmissivity fields conditioned on head and transmissivity data. In other cases, constant parameter values were applied over the model domain. These constant values were selected and applied in two different ways. In simple cases where a conservative bounding value could be identified that would not lead to unrealistically conservative results, that value was used for all calculations. In more complex cases, parameter distributions were developed and single values of the parameters were sampled from the distributions and applied across the entire model domain for each of the PA Monte Carlo simulations. We are currently working to refine our understanding of the multiple rates of diffusion attributable to small-scale spatial variability

  8. Behavior-driven arc expression is reduced in all ventral hippocampal subfields compared to CA1, CA3, and dentate gyrus in rat dorsal hippocampus.

    Chawla, M K; Sutherland, V L; Olson, K; McNaughton, B L; Barnes, C A

    2018-02-01

    Anatomical connectivity and lesion studies reveal distinct functional heterogeneity along the dorsal-ventral axis of the hippocampus. The immediate early gene Arc is known to be involved in neural plasticity and memory and can be used as a marker for cell activity that occurs, for example, when hippocampal place cells fire. We report here, that Arc is expressed in a greater proportion of cells in dorsal CA1, CA3, and dentate gyrus (DG), following spatial behavioral experiences compared to ventral hippocampal subregions (dorsal CA1 = 33%; ventral CA1 = 13%; dorsal CA3 = 23%; ventral CA3 = 8%; and dorsal DG = 2.5%; ventral DG = 1.2%). The technique used here to obtain estimates of numbers of behavior-driven cells across the dorsal-ventral axis, however, corresponds quite well with samples from available single unit recording studies. Several explanations for the two- to-threefold reduction in spatial behavior-driven cell activity in the ventral hippocampus can be offered. These include anatomical connectivity differences, differential gain of the self-motion signals that appear to alter the scale of place fields and the proportion of active cells, and possibly variations in the neuronal responses to non-spatial information within the hippocampus along its dorso-ventral axis. © 2017 Wiley Periodicals, Inc.

  9. Neuropeptide Y and nestin expression in the hippocampal CA3 region following restrained and inverted stress in rats

    Guogang Sun; Ailing Li; Bo Chen; Guangbi Fan; Hongwen Xiao; Yue Chen; Jie Xu; Ye Nie; Bing Zhang; Lin Gong

    2011-01-01

    Our preliminary study demonstrated that neuropeptide Y (NPY)/nestin-positive cells exhibit a consistent spatial distribution in the hippocampus of normal adult rats. However, following severe acute and chronic stress-induced impaired learning and memory, synchronous decreased expression of nestin and NPY takes place in the hippocampus, and the underlying mechanisms remain unclear. In the present study, acute and chronic stress rat models were established using combined restrained and inverted stress. Results showed that learning and memory significantly decreased in acute and chronic stress rats. In addition, hippocampal cells were damaged, in particular in the acute stress rats, and nestin and NPY expression, as well as the number of NPY/nestin-positive cells in the CA3 region, significantly decreased. Furthermore, mature neurofilament 200-positive neurons were absent in the chronic stress rats. The NPY and cytoskeletal protein system equally contributed to stress-induced early learning and memory deficits, as well as sustained cerebral injury in the adult hippocampus.

  10. Bi4Sr3Ca3Cu4O16 galss and superconducting glass ceramics

    Zheng, H.; Mackenzie, J.D.

    1988-01-01

    Bi 4 Sr 3 Ca 3 Cu 4 O 16 glass has been successfully fabricated by the melting process. Glass transition temperature, crystallization temperature, and liquid temperature of the glass are 434, 478, and 833 0 C, respectively. After the glass is heat treated at 800 0 C, a glass ceramic is formed. A comparison of the x-ray-diffraction pattern of the superconducting Bi 4 Sr 3 Ca 3 Cu 4 O/sub 16+//sub x/ ceramic to the Bi 4 Sr 3 Ca 3 Cu 4 O 16 glass ceramic revealed preferred orientation in the glass ceramic crystals. The superconducting transition temperatures T/sub c//sub (onset)/ and T/sub c//sub (zero)/ of the glass ceramics are 100 and 45 K, respectively

  11. Thermal conductivity of Ca3Co2O6 single crystals

    Che, H. L.; Shi, J.; Wu, J. C.; Rao, X.; Liu, X. G.; Zhao, X.; Sun, X. F.

    2018-05-01

    Ca3Co2O6 is a rare example of one-dimensional Ising spin-chain material with the moments preferentially aligned along the c axis. In this work, we study the c-axis thermal conductivity (κc) of Ca3Co2O6 single crystal at low temperatures down to 0.3 K and in magnetic fields up to 14 T. The zero-field κc(T) shows a large phonon peak and can be well fitted by using the classical Debye model, which indicates that the heat transport is purely phononic. Moreover, the low-T κc(H) isotherms with H || c display a field-independent behavior. These results indicate that there is no contribution of magnetic excitations to the thermal conductivity in Ca3Co2O6, neither carrying heat nor scattering phonons, which can be attributed to the Ising-like spin anisotropy.

  12. Photoluminescence and thermoluminescence characterization of Eu3+- and Dy3+ -activated Ca3(PO4)2 phosphor

    Nagpure, I.M.; Saha, Subhajit; Dhoble, S.J.

    2009-01-01

    Rare-earth-doped polycrystalline Ca 3 (PO 4 ) 2 :Eu, Ca 3 (PO 4 ) 2 :Dy and Ca 3 (PO 4 ) 2 :Eu,Dy phosphors prepared by a modified solid-state synthesis has been studied for its X-ray diffraction, thermoluminescence (TL) and photoluminescence (PL) characteristics. The PL emission spectra of the phosphor suggest the presence of Eu 3+ ion in Ca 3 (PO 4 ) 2 :Eu and Dy 3+ ion in Ca 3 (PO 4 ) 2 :Dy lattice sites. The TL glow curve of the Ca 3 (PO 4 ) 2 :Eu compounds has a simple structure with a prominent peak at 228 deg. C, while Ca 3 (PO 4 ) 2 :Dy peaking at 146 and 230 deg. C. TL sensitivity of phosphors are compared with CaSO 4 : Dy and found 1.52 and 1.20 times less in Ca 3 (PO 4 ) 2 :Eu and Ca 3 (PO 4 ) 2 :Dy phosphors, respectively. The Ca 3 (PO 4 ) 2 :Eu,Dy phosphors shows switching behavior under two different excitation wavelengths and enhancement in PL intensity of Dy 3+ ions were reported. The paper discusses the photoluminescence and thermoluminescence behavior of Eu 3+ and Dy 3+ ion in Ca 3 (PO 4 ) 2 hosts, it may be applicable to solid-state lighting as well as thermoluminescence dosimetry applications.

  13. Optogenetically Blocking Sharp Wave Ripple Events in Sleep Does Not Interfere with the Formation of Stable Spatial Representation in the CA1 Area of the Hippocampus.

    Krisztián A Kovács

    Full Text Available During hippocampal sharp wave/ripple (SWR events, previously occurring, sensory input-driven neuronal firing patterns are replayed. Such replay is thought to be important for plasticity-related processes and consolidation of memory traces. It has previously been shown that the electrical stimulation-induced disruption of SWR events interferes with learning in rodents in different experimental paradigms. On the other hand, the cognitive map theory posits that the plastic changes of the firing of hippocampal place cells constitute the electrophysiological counterpart of the spatial learning, observable at the behavioral level. Therefore, we tested whether intact SWR events occurring during the sleep/rest session after the first exploration of a novel environment are needed for the stabilization of the CA1 code, which process requires plasticity. We found that the newly-formed representation in the CA1 has the same level of stability with optogenetic SWR blockade as with a control manipulation that delivered the same amount of light into the brain. Therefore our results suggest that at least in the case of passive exploratory behavior, SWR-related plasticity is dispensable for the stability of CA1 ensembles.

  14. Insomnia severity is associated with a decreased volume of the CA3/Dentate Gyrus Hippocampal Subfield

    Neylan, Thomas C.; Mueller, Susanne G.; Wang, Zhen; Metzler, Thomas J.; Lenoci, Maryann; Truran, Diana; Marmar, Charles R.; Weiner, Michael W.; Schuff, Norbert

    2010-01-01

    Background Prolonged disruption of sleep in animal studies is associated with decreased neurogenesis in the dentate gyrus. Our objective was to determine if insomnia severity in a sample of PTSD and controls was associated with decreased volume in the CA3/dentate hippocampal subfield. Methods Volumes of hippocampal subfields in seventeen veteran males positive for PTSD (41 ±12 years) and nineteen age-matched male veterans negative for PTSD were measured using 4 Tesla MRI. Subjective sleep quality was measured by the Insomnia Severity Index (ISI) and the Pittsburgh Sleep Quality Index (PSQI). Results Higher scores on the ISI, indicating worse insomnia, were associated with smaller volumes of the CA3/dentate subfields (r= −.48, p < 0.01) in the combined sample. Adding the ISI score as a predictor for CA3/dentate volume to a hierarchical linear regression model after first controlling for age and PTSD symptoms accounted for a 13 % increase in incremental variance (t= −2.47, p= 0.02). Conclusions The findings indicate for the first time in humans that insomnia severity is associated with volume loss of the CA3/dentate subfields. This is consistent with animal studies showing that chronic sleep disruption is associated with decreased neurogenesis and dendritic branching in these structures. PMID:20598672

  15. Electronic Structure and Thermoelectric Properties of Ca3 Co4O9

    2006-01-01

    The relation among electronic structure, chemical bond and thermoelectric property of Ca3 Co4 O9 was studied using density function and discrete variation method (DFT-DVM).The gap between the highest valence band (HVB) and the lowest conduction band (LCB) shows a semiconducting property.Ca3 Co4 O9 colsists of CoO2 and Ca2 CoO3 two layers.The HVB and LCB near Fermi level are only mainly from O(2) 2p and Co(2) 3d in Ca2 CoO3 layer. Therefore, the semiconducting or thermoelectric property of Ca3 Co4 O9 should be mainly from Ca2 CoO3 layer, but it seems to have no direct relation to the CoO2 layer,which is consistent with that binary oxides hardly have a thermoelectric property, but trinary oxide compounds have quite a good thermoelectric property.The covalent and ionic bonds of Ca2 CoO3 layer are both weaker than those of CoO2 layer.Ca plays the role of connections between CoO2 and Ca2 CoO3 layers in Ca3 Co4 O9, decrease the ionic and covalent bond strength, and improve the thermoelectric property.

  16. Homeostatic maintenance in excitability of tree shrew hippocampal CA3 pyramidal neurons after chronic stress

    Kole, MHP; Czeh, B; Fuchs, E

    2004-01-01

    The experience of chronic stress induces a reversible regression of hippocampal CA3 apical neuron dendrites. Although such postsynaptic membrane reduction will obviously diminish the possibility of synaptic input, the consequences for the functional membrane properties of these cells are not well

  17. Focal CA3 hippocampal subfield atrophy following LGI1 VGKC-complex antibody limbic encephalitis.

    Miller, Thomas D; Chong, Trevor T-J; Aimola Davies, Anne M; Ng, Tammy W C; Johnson, Michael R; Irani, Sarosh R; Vincent, Angela; Husain, Masud; Jacob, Saiju; Maddison, Paul; Kennard, Christopher; Gowland, Penny A; Rosenthal, Clive R

    2017-05-01

    Magnetic resonance imaging has linked chronic voltage-gated potassium channel (VGKC) complex antibody-mediated limbic encephalitis with generalized hippocampal atrophy. However, autoantibodies bind to specific rodent hippocampal subfields. Here, human hippocampal subfield (subiculum, cornu ammonis 1-3, and dentate gyrus) targets of immunomodulation-treated LGI1 VGKC-complex antibody-mediated limbic encephalitis were investigated using in vivo ultra-high resolution (0.39 × 0.39 × 1.0 mm3) 7.0 T magnetic resonance imaging [n = 18 patients, 17 patients (94%) positive for LGI1 antibody and one patient negative for LGI1/CASPR2 but positive for VGKC-complex antibodies, mean age: 64.0 ± 2.55 years, median 4 years post-limbic encephalitis onset; n = 18 controls]. First, hippocampal subfield quantitative morphometry indicated significant volume loss confined to bilateral CA3 [F(1,34) = 16.87, P 3 months from symptom onset) were associated with CA3 atrophy. Third, whole-brain voxel-by-voxel morphometry revealed no significant grey matter loss. Fourth, CA3 subfield atrophy was associated with severe episodic but not semantic amnesia for postmorbid autobiographical events that was predicted by variability in CA3 volume. The results raise important questions about the links with histopathology, the impact of the observed focal atrophy on other CA3-mediated reconstructive and episodic mechanisms, and the role of potential antibody-mediated pathogenicity as part of the pathophysiology cascade in humans. © The Author (2017). Published by Oxford University Press on behalf of the Guarantors of Brain.

  18. Human limbic encephalitis serum enhances hippocampal mossy fiber-CA3 pyramidal cell synaptic transmission.

    Lalic, Tatjana; Pettingill, Philippa; Vincent, Angela; Capogna, Marco

    2011-01-01

    Limbic encephalitis (LE) is a central nervous system (CNS) disease characterized by subacute onset of memory loss and epileptic seizures. A well-recognized form of LE is associated with voltage-gated potassium channel complex antibodies (VGKC-Abs) in the patients' sera. We aimed to test the hypothesis that purified immunoglobulin G (IgG) from a VGKC-Ab LE serum would excite hippocampal CA3 pyramidal cells by reducing VGKC function at mossy-fiber (MF)-CA3 pyramidal cell synapses. We compared the effects of LE and healthy control IgG by whole-cell patch-clamp and extracellular recordings from CA3 pyramidal cells of rat hippocampal acute slices. We found that the LE IgG induced epileptiform activity at a population level, since synaptic stimulation elicited multiple population spikes extracellularly recorded in the CA3 area. Moreover, the LE IgG increased the rate of tonic firing and strengthened the MF-evoked synaptic responses. The synaptic failure of evoked excitatory postsynaptic currents (EPSCs) was significantly lower in the presence of the LE IgG compared to the control IgG. This suggests that the LE IgG increased the release probability on MF-CA3 pyramidal cell synapses compared to the control IgG. Interestingly, α-dendrotoxin (120 nm), a selective Kv1.1, 1.2, and 1.6 subunit antagonist of VGKC, mimicked the LE IgG-mediated effects. This is the first functional demonstration that LE IgGs reduce VGKC function at CNS synapses and increase cell excitability. Wiley Periodicals, Inc. © 2010 International League Against Epilepsy.

  19. Impacts of Spatial Climatic Representation on Hydrological Model Calibration and Prediction Uncertainty: A Mountainous Catchment of Three Gorges Reservoir Region, China

    Yan Li

    2016-02-01

    Full Text Available Sparse climatic observations represent a major challenge for hydrological modeling of mountain catchments with implications for decision-making in water resources management. Employing elevation bands in the Soil and Water Assessment Tool-Sequential Uncertainty Fitting (SWAT2012-SUFI2 model enabled representation of precipitation and temperature variation with altitude in the Daning river catchment (Three Gorges Reservoir Region, China where meteorological inputs are limited in spatial extent and are derived from observations from relatively low lying locations. Inclusion of elevation bands produced better model performance for 1987–1993 with the Nash–Sutcliffe efficiency (NSE increasing by at least 0.11 prior to calibration. During calibration prediction uncertainty was greatly reduced. With similar R-factors from the earlier calibration iterations, a further 11% of observations were included within the 95% prediction uncertainty (95PPU compared to the model without elevation bands. For behavioral simulations defined in SWAT calibration using a NSE threshold of 0.3, an additional 3.9% of observations were within the 95PPU while the uncertainty reduced by 7.6% in the model with elevation bands. The calibrated model with elevation bands reproduced observed river discharges with the performance in the calibration period changing to “very good” from “poor” without elevation bands. The output uncertainty of calibrated model with elevation bands was satisfactory, having 85% of flow observations included within the 95PPU. These results clearly demonstrate the requirement to account for orographic effects on precipitation and temperature in hydrological models of mountainous catchments.

  20. NMDA-dependent phase synchronization between septal and temporal CA3 hippocampal networks.

    Gu, Ning; Jackson, Jesse; Goutagny, Romain; Lowe, Germaine; Manseau, Frédéric; Williams, Sylvain

    2013-05-08

    Increasing evidence suggests that synchronization between brain regions is essential for information exchange and memory processes. However, it remains incompletely known which synaptic mechanisms contribute to the process of synchronization. Here, we investigated whether NMDA receptor-mediated synaptic plasticity was an important player in synchronization between septal and temporal CA3 areas of the rat hippocampus. We found that both the septal and temporal CA3 regions intrinsically generate weakly synchronized δ frequency oscillations in the complete hippocampus in vitro. Septal and temporal oscillators differed in frequency, power, and rhythmicity, but both required GABAA and AMPA receptors. NMDA receptor activation, and most particularly the NR2B subunit, contributed considerably more to rhythm generation at the temporal than the septal region. Brief activation of NMDA receptors by application of extracellular calcium dramatically potentiated the septal-temporal coherence for long durations (>40 min), an effect blocked by the NMDA antagonist AP-5. This long-lasting NMDA-receptor-dependent increase in coherence was also associated with an elevated phase locking of spikes locally and across regions. Changes in coherence between oscillators were associated with increases in phase locking between oscillators independent of oscillator amplitude. Finally, although the septal CA3 rhythm preceded the oscillations in temporal regions in control conditions, this was reversed during the NMDA-dependent enhancement in coherence, suggesting that NMDA receptor activation can change the direction of information flow along the septotemporal CA3 axis. These data demonstrate that plastic changes in communication between septal and temporal hippocampal regions can arise from the NMDA-dependent phase locking of neural oscillators.

  1. Hippocampal CA3 transcriptome signature correlates with initial precipitating injury in refractory mesial temporal lobe epilepsy.

    Silvia Y Bando

    Full Text Available BACKGROUND: Prolonged febrile seizures constitute an initial precipitating injury (IPI commonly associated with refractory mesial temporal lobe epilepsy (RMTLE. In order to investigate IPI influence on the transcriptional phenotype underlying RMTLE we comparatively analyzed the transcriptomic signatures of CA3 explants surgically obtained from RMTLE patients with (FS or without (NFS febrile seizure history. Texture analyses on MRI images of dentate gyrus were conducted in a subset of surgically removed sclerotic hippocampi for identifying IPI-associated histo-radiological alterations. METHODOLOGY/PRINCIPAL FINDINGS: DNA microarray analysis revealed that CA3 global gene expression differed significantly between FS and NFS subgroups. An integrative functional genomics methodology was used for characterizing the relations between GO biological processes themes and constructing transcriptional interaction networks defining the FS and NFS transcriptomic signatures and its major gene-gene links (hubs. Co-expression network analysis showed that: i CA3 transcriptomic profiles differ according to the IPI; ii FS distinctive hubs are mostly linked to glutamatergic signalization while NFS hubs predominantly involve GABAergic pathways and neurotransmission modulation. Both networks have relevant hubs related to nervous system development, what is consistent with cell genesis activity in the hippocampus of RMTLE patients. Moreover, two candidate genes for therapeutic targeting came out from this analysis: SSTR1, a relevant common hub in febrile and afebrile transcriptomes, and CHRM3, due to its putative role in epilepsy susceptibility development. MRI texture analysis allowed an overall accuracy of 90% for pixels correctly classified as belonging to FS or NFS groups. Histological examination revealed that granule cell loss was significantly higher in FS hippocampi. CONCLUSIONS/SIGNIFICANCE: CA3 transcriptional signatures and dentate gyrus morphology fairly

  2. Hydrothermal synthesis of Ca3Bi8O15 rods and their visible light photocatalytic properties

    Li, Wenjuan; Kong, Desheng; Cui, Xiaoli; Du, Dandan; Yan, Tingjiang; You, Jinmao

    2014-01-01

    Graphical abstract: The novel Ca 3 Bi 8 O 15 rods can utilize the sunlight efficiently with the small band-gap. Using methyl orange (MO) as a model organic pollutant, the photocatalysts exhibited good photocatalytic activity, with the photodegradation conversion ratio of MO being up to 90% after 2 h of visible light (420 nm < λ < 800 nm) irradiation. - Highlights: • Ca 3 Bi 8 O 15 rods were synthesized by a hydrothermal method. • They can utilize the sunlight efficiently with the small band-gap. • They showed good photocatalytic activities in the degradation of MO, RhB and 4-CP. • The conversion ratio of MO was up to 90% after 2 h of visible light irradiation. - Abstract: High efficient visible light Ca 3 Bi 8 O 15 photocatalysts were synthesized by a hydrothermal method. Characterized by X-ray diffractometer, transmission electron microscopy, and the UV–vis diffuse reflectance spectroscopy, the results showed that the novel Ca 3 Bi 8 O 15 rods can utilize the sunlight efficiently with the small band-gap. Using methyl orange (MO) as a model organic pollutant, the photocatalysts exhibited good photocatalytic activity, with the photodegradation conversion ratio of MO being up to 90% after 2 h of visible light (420 nm < λ < 800 nm) irradiation. Furthermore, they also showed good photocatalytic activities in the degradation of rhodamine B and p-chlorophenol. Through the investigation of the degraded mechanism, the main active species played important roles in the degradation process were holes, O 2 · − and ·OH

  3. Transport and NMR characteristics of the skutterudite-related compound Ca3Rh4Sn13

    Tseng, C. W.; Kuo, C. N.; Li, B. S.; Wang, L. M.; Gippius, A. A.; Kuo, Y. K.; Lue, C. S.

    2018-02-01

    We report the electronic properties of the Yb3Rh4Sn13-type single crystalline Ca3Rh4Sn13 by means of the electrical resistivity, Hall coefficient, Seebeck coefficient, thermal conductivity, as well as 119Sn nuclear magnetic resonance (NMR) measurements. The negative sign of the Hall coefficient and Seebeck coefficient at low temperatures suggests that the n-type carriers dominate the electrical transport in Ca3Rh4Sn13, in contrast to the observations in Sr3Rh4Sn13 which has a p-type conduction. Such a finding indicates a significant difference in the electronic features between these two stannides. Furthermore, we analyzed the temperature-dependent 119Sn NMR spin-lattice relaxation rate for Ca3Rh4Sn13, (Sr0.7Ca0.3)3Rh4Sn13, and Sr3Rh4Sn13 to examine the change of the electronic Fermi-level density of states (DOS) in (Sr1-xCax)3Rh4Sn13. It indicates that the Sn 5s partial Fermi-level DOS enhances with increasing the Ca content, being consistent with the trend of the superconducting temperature. Since the total Fermi-level DOS usually obeys the same trend of the partial Fermi-level DOS, the NMR analysis provides microscopic evidence for the correlation between the electronic DOS and superconductivity of the (Sr1-xCax)3Rh4Sn13 system.

  4. Transition Dynamics of a Dentate Gyrus-CA3 Neuronal Network during Temporal Lobe Epilepsy

    Liyuan Zhang

    2017-07-01

    Full Text Available In temporal lobe epilepsy (TLE, the variation of chemical receptor expression underlies the basis of neural network activity shifts, resulting in neuronal hyperexcitability and epileptiform discharges. However, dynamical mechanisms involved in the transitions of TLE are not fully understood, because of the neuronal diversity and the indeterminacy of network connection. Hence, based on Hodgkin–Huxley (HH type neurons and Pinsky–Rinzel (PR type neurons coupling with glutamatergic and GABAergic synaptic connections respectively, we propose a computational framework which contains dentate gyrus (DG region and CA3 region. By regulating the concentration range of N-methyl-D-aspartate-type glutamate receptor (NMDAR, we demonstrate the pyramidal neuron can generate transitions from interictal to seizure discharges. This suggests that enhanced endogenous activity of NMDAR contributes to excitability in pyramidal neuron. Moreover, we conclude that excitatory discharges in CA3 region vary considerably on account of the excitatory currents produced by the excitatory pyramidal neuron. Interestingly, by changing the backprojection connection, we find that glutamatergic type backprojection can promote the dominant frequency of firings and further motivate excitatory counterpropagation from CA3 region to DG region. However, GABAergic type backprojection can reduce firing rate and block morbid counterpropagation, which may be factored into the terminations of TLE. In addition, neuronal diversity dominated network shows weak correlation with different backprojections. Our modeling and simulation studies provide new insights into the mechanisms of seizures generation and connectionism in local hippocampus, along with the synaptic mechanisms of this disease.

  5. Heteroassociative storage of hippocampal pattern sequences in the CA3 subregion

    Raphael Y. de Camargo

    2018-01-01

    Full Text Available Background Recent research suggests that the CA3 subregion of the hippocampus has properties of both autoassociative network, due to its ability to complete partial cues, tolerate noise, and store associations between memories, and heteroassociative one, due to its ability to store and retrieve sequences of patterns. Although there are several computational models of the CA3 as an autoassociative network, more detailed evaluations of its heteroassociative properties are missing. Methods We developed a model of the CA3 subregion containing 10,000 integrate-and-fire neurons with both recurrent excitatory and inhibitory connections, and which exhibits coupled oscillations in the gamma and theta ranges. We stored thousands of pattern sequences using a heteroassociative learning rule with competitive synaptic scaling. Results We showed that a purely heteroassociative network model can (i retrieve pattern sequences from partial cues with external noise and incomplete connectivity, (ii achieve homeostasis regarding the number of connections per neuron when many patterns are stored when using synaptic scaling, (iii continuously update the set of retrievable patterns, guaranteeing that the last stored patterns can be retrieved and older ones can be forgotten. Discussion Heteroassociative networks with synaptic scaling rules seem sufficient to achieve many desirable features regarding connectivity homeostasis, pattern sequence retrieval, noise tolerance and updating of the set of retrievable patterns.

  6. Transition Dynamics of a Dentate Gyrus-CA3 Neuronal Network during Temporal Lobe Epilepsy.

    Zhang, Liyuan; Fan, Denggui; Wang, Qingyun

    2017-01-01

    In temporal lobe epilepsy (TLE), the variation of chemical receptor expression underlies the basis of neural network activity shifts, resulting in neuronal hyperexcitability and epileptiform discharges. However, dynamical mechanisms involved in the transitions of TLE are not fully understood, because of the neuronal diversity and the indeterminacy of network connection. Hence, based on Hodgkin-Huxley (HH) type neurons and Pinsky-Rinzel (PR) type neurons coupling with glutamatergic and GABAergic synaptic connections respectively, we propose a computational framework which contains dentate gyrus (DG) region and CA3 region. By regulating the concentration range of N-methyl-D-aspartate-type glutamate receptor (NMDAR), we demonstrate the pyramidal neuron can generate transitions from interictal to seizure discharges. This suggests that enhanced endogenous activity of NMDAR contributes to excitability in pyramidal neuron. Moreover, we conclude that excitatory discharges in CA3 region vary considerably on account of the excitatory currents produced by the excitatory pyramidal neuron. Interestingly, by changing the backprojection connection, we find that glutamatergic type backprojection can promote the dominant frequency of firings and further motivate excitatory counterpropagation from CA3 region to DG region. However, GABAergic type backprojection can reduce firing rate and block morbid counterpropagation, which may be factored into the terminations of TLE. In addition, neuronal diversity dominated network shows weak correlation with different backprojections. Our modeling and simulation studies provide new insights into the mechanisms of seizures generation and connectionism in local hippocampus, along with the synaptic mechanisms of this disease.

  7. The cumulative analgesic effect of repeated electroacupuncture involves synaptic remodeling in the hippocampal CA3 region☆

    Xu, Qiuling; Liu, Tao; Chen, Shuping; Gao, Yonghui; Wang, Junying; Qiao, Lina; Liu, Junling

    2012-01-01

    In the present study, we examined the analgesic effect of repeated electroacupuncture at bilateral Zusanli (ST36) and Yanglingquan (GB34) once a day for 14 consecutive days in a rat model of chronic sciatic nerve constriction injury-induced neuropathic pain. In addition, concomitant changes in calcium/calmodulin-dependent protein kinase II expression and synaptic ultrastructure of neurons in the hippocampal CA3 region were examined. The thermal pain threshold (paw withdrawal latency) was increased significantly in both groups at 2 weeks after electroacupuncture intervention compared with 2 days of electroacupuncture. In ovariectomized rats with chronic constriction injury, the analgesic effect was significantly reduced. Electroacupuncture for 2 weeks significantly diminished the injury-induced increase in synaptic cleft width and thinning of the postsynaptic density, and it significantly suppressed the down-regulation of intracellular calcium/calmodulin-dependent protein kinase II expression in the hippocampal CA3 region. Repeated electroacupuncture intervention had a cumulative analgesic effect on injury-induced neuropathic pain reactions, and it led to synaptic remodeling of hippocampal neurons and upregulated calcium/calmodulin-dependent protein kinase II expression in the hippocampal CA3 region. PMID:25657670

  8. Network state-dependent inhibition of identified hippocampal CA3 axo-axonic cells in vivo

    Tukker, John J; Klausberger, Thomas; Somogyi, Peter

    2015-01-01

    Hippocampal sharp waves are population discharges initiated by an unknown mechanism in pyramidal cell networks of CA3. Axo-axonic cells (AACs) regulate action potential generation through GABAergic synapses on the axon initial segment. We found that CA3 AACs in anesthetized rats and AACs in freely moving rats stopped firing during sharp waves, when pyramidal cells fire most. AACs fired strongly and rhythmically around the peak of theta oscillations, when pyramidal cells fire at low probability. Distinguishing AACs from other parvalbumin-expressing interneurons by their lack of detectable SATB1 transcription factor immunoreactivity, we discovered a somatic GABAergic input originating from the medial septum that preferentially targets AACs. We recorded septo-hippocampal GABAergic cells that were activated during hippocampal sharp waves and projected to CA3. We hypothesize that inhibition of AACs, and the resulting subcellular redistribution of inhibition from the axon initial segment to other pyramidal cell domains, is a necessary condition for the emergence of sharp waves promoting memory consolidation. PMID:24141313

  9. Ischemic damage in hippocampal CA1 is dependent on glutamate release and intact innervation from CA3

    Benveniste, H; Jørgensen, M B; Sandberg, M

    1989-01-01

    The removal of glutamatergic afferents to CA1 by destruction of the CA3 region is known to protect CA1 pyramidal cells against 10 min of transient global ischemia. To investigate further the pathogenetic significance of glutamate, we measured the release of glutamate in intact and CA3-lesioned CA...

  10. Emergent spatial patterns of excitatory and inhibitory synaptic strengths drive somatotopic representational discontinuities and their plasticity in a computational model of primary sensory cortical area 3b

    Kamil A. Grajski

    2016-07-01

    Full Text Available Mechanisms underlying the emergence and plasticity of representational discontinuities in the mammalian primary somatosensory cortical representation of the hand are investigated in a computational model. The model consists of an input lattice organized as a three-digit hand forward-connected to a lattice of cortical columns each of which contains a paired excitatory and inhibitory cell. Excitatory and inhibitory synaptic plasticity of feedforward and lateral connection weights is implemented as a simple covariance rule and competitive normalization. Receptive field properties are computed independently for excitatory and inhibitory cells and compared within and across columns. Within digit representational zones intracolumnar excitatory and inhibitory receptive field extents are concentric, single-digit, small, and unimodal. Exclusively in representational boundary-adjacent zones, intracolumnar excitatory and inhibitory receptive field properties diverge: excitatory cell receptive fields are single-digit, small, and unimodal; and the paired inhibitory cell receptive fields are bimodal, double-digit, and large. In simulated syndactyly (webbed fingers, boundary-adjacent intracolumnar receptive field properties reorganize to within-representation type; divergent properties are reacquired following syndactyly release. This study generates testable hypotheses for assessment of cortical laminar-dependent receptive field properties and plasticity within and between cortical representational zones. For computational studies, present results suggest that concurrent excitatory and inhibitory plasticity may underlie novel emergent properties.

  11. Interrelation between domain structures and polarization switching in hybrid improper ferroelectric Ca3(Mn,Ti)2O7

    Gao, Bin; Huang, Fei-Ting; Wang, Yazhong; Kim, Jae-Wook; Wang, Lihai; Lim, Seong-Joon; Cheong, Sang-Wook

    2017-05-01

    Ca3Mn2O7 and Ca3Ti2O7 have been proposed as the prototypical hybrid improper ferroelectrics (HIFs), and a significant magnetoelectric (ME) coupling in magnetic Ca3Mn2O7 is, in fact, reported theoretically and experimentally. Although the switchability of polarization is confirmed in Ca3Ti2O7 and other non-magnetic HIFs, there is no report of switchable polarization in the isostructural Ca3Mn2O7. We constructed the phase diagram of Ca3Mn2-xTixO7 through our systematic study of a series of single crystalline Ca3Mn2-xTixO7 (x = 0, 0.1, 1, 1.5, and 2). Using transmission electron microscopy, we have unveiled the unique domain structure of Ca3Mn2O7: the high-density 90° stacking of a- and b-domains along the c-axis due to the phase transition through an intermediate Acca phase and the in-plane irregular wavy ferroelastic twin domains. The interrelation between domain structures and physical properties is unprecedented: the stacking along the c-axis prevents the switching of polarization and causes the irregular in-plane ferroelastic domain pattern. In addition, we have determined the magnetic phase diagram and found complex magnetism of Ca3Mn2O7 with isotropic canted moments. These results lead to negligible observable ME coupling in Ca3Mn2O7 and guide us to explore multiferroics with large ME coupling.

  12. High-temperature resistivity and thermoelectric properties of coupled substituted Ca3Co2O6

    Meenakshisundaram Senthilkumar and Rajagopalan Vijayaraghavan

    2009-01-01

    Full Text Available Polycrystalline samples of Ca3−xNaxCo2−xMnxO6 (x=0.0–0.5 have been prepared by the sol-gel cum combustion method using sucrose in order to investigate the effects of the coupled substitution of Na and Mn on Ca and Co sites on the transport properties of Ca3Co2O6(Co326. The products were characterized by Fourier transform infrared spectroscopy, powder x-ray diffraction (XRD, thermogravimetry (TGA, differential thermal analysis and scanning electron microscopy. XRD patterns reveal the formation of single-phase products up to x=0.5. Coupled substitution increases the solubility of both Na and Mn on Ca and Co sites, respectively, in contrast to the limited solubility of Na and Mn (x=0.2 when separately substituted. TGA confirms the formation of the Ca3Co2O6 phase at temperatures ~720 °C. The grain size of the parent and substituted products is in the range 150–250 nm. Electrical resistivity and Seebeck coefficient were measured in the temperature range 300–800 K. Resistivity shows semiconducting behavior for all the compositions, particularly in the low-temperature regime. The Seebeck coefficient increases with temperature throughout the measured temperature range for all compositions. The maximum Seebeck coefficient (200 μV K−1 is observed for x=0.5 at 825 K, and this composition may be optimal for high-temperature thermoelectric applications.

  13. Regulation of phenylacetic acid uptake is sigma54 dependent in Pseudomonas putida CA-3.

    O' Leary, Niall D

    2011-10-13

    Abstract Background Styrene is a toxic and potentially carcinogenic alkenylbenzene used extensively in the polymer processing industry. Significant quantities of contaminated liquid waste are generated annually as a consequence. However, styrene is not a true xenobiotic and microbial pathways for its aerobic assimilation, via an intermediate, phenylacetic acid, have been identified in a diverse range of environmental isolates. The potential for microbial bioremediation of styrene waste has received considerable research attention over the last number of years. As a result the structure, organisation and encoded function of the genes responsible for styrene and phenylacetic acid sensing, uptake and catabolism have been elucidated. However, a limited understanding persists in relation to host specific regulatory molecules which may impart additional control over these pathways. In this study the styrene degrader Pseudomonas putida CA-3 was subjected to random mini-Tn5 mutagenesis and mutants screened for altered styrene\\/phenylacetic acid utilisation profiles potentially linked to non-catabolon encoded regulatory influences. Results One mutant, D7, capable of growth on styrene, but not on phenylacetic acid, harboured a Tn5 insertion in the rpoN gene encoding σ54. Complementation of the D7 mutant with the wild type rpoN gene restored the ability of this strain to utilise phenylacetic acid as a sole carbon source. Subsequent RT-PCR analyses revealed that a phenylacetate permease, PaaL, was expressed in wild type P. putida CA-3 cells utilising styrene or phenylacetic acid, but could not be detected in the disrupted D7 mutant. Expression of plasmid borne paaL in mutant D7 was found to fully restore the phenylacetic acid utilisation capacity of the strain to wild type levels. Bioinformatic analysis of the paaL promoter from P. putida CA-3 revealed two σ54 consensus binding sites in a non-archetypal configuration, with the transcriptional start site being resolved by

  14. High-pressure crystal growth and electromagnetic properties of 5d double-perovskite Ca3OsO6

    Feng, Hai Luke; Shi, Youguo; Guo, Yanfeng; Li, Jun; Sato, Akira; Sun, Ying; Wang, Xia; Yu, Shan; Sathish, Clastin I.; Yamaura, Kazunari

    2013-01-01

    Single crystals of the osmium-containing compound Ca 3 OsO 6 have been successfully grown under high-pressure conditions, for the first time. The crystal structure of Ca 3 OsO 6 were characterized as an ordered double-perovskite structure of space group P2 1 /n with the Ca and Os atoms being fully ordered at the perovskite B-site. The electromagnetic analysis shows that the crystal exhibits a semiconductor-like behavior below 300 K and undergoes an antiferromagnetic transition at 50 K. - Graphical Abstract: Schematic image of crystal structure of Ca 3 OsO 6 as determined by X-ray diffraction, where the gray and black octahedrons are occupied by Ca and Os, respectively. Top inset reveals an optic image of a typical Ca 3 OsO 6 single crystal. Highlights: ► Single crystals of Ca 3 OsO 6 have been successfully grown under high-pressure. ► Ca 3 OsO 6 crystalizes into an ordered double-perovskite structure. ► The Ca 3 OsO 6 undergoes an antiferromagnetic transition at 50 K

  15. Optimal recall from bounded metaplastic synapses: predicting functional adaptations in hippocampal area CA3.

    Cristina Savin

    2014-02-01

    Full Text Available A venerable history of classical work on autoassociative memory has significantly shaped our understanding of several features of the hippocampus, and most prominently of its CA3 area, in relation to memory storage and retrieval. However, existing theories of hippocampal memory processing ignore a key biological constraint affecting memory storage in neural circuits: the bounded dynamical range of synapses. Recent treatments based on the notion of metaplasticity provide a powerful model for individual bounded synapses; however, their implications for the ability of the hippocampus to retrieve memories well and the dynamics of neurons associated with that retrieval are both unknown. Here, we develop a theoretical framework for memory storage and recall with bounded synapses. We formulate the recall of a previously stored pattern from a noisy recall cue and limited-capacity (and therefore lossy synapses as a probabilistic inference problem, and derive neural dynamics that implement approximate inference algorithms to solve this problem efficiently. In particular, for binary synapses with metaplastic states, we demonstrate for the first time that memories can be efficiently read out with biologically plausible network dynamics that are completely constrained by the synaptic plasticity rule, and the statistics of the stored patterns and of the recall cue. Our theory organises into a coherent framework a wide range of existing data about the regulation of excitability, feedback inhibition, and network oscillations in area CA3, and makes novel and directly testable predictions that can guide future experiments.

  16. Cannabinoids disrupt memory encoding by functionally isolating hippocampal CA1 from CA3.

    Roman A Sandler

    2017-07-01

    Full Text Available Much of the research on cannabinoids (CBs has focused on their effects at the molecular and synaptic level. However, the effects of CBs on the dynamics of neural circuits remains poorly understood. This study aims to disentangle the effects of CBs on the functional dynamics of the hippocampal Schaffer collateral synapse by using data-driven nonparametric modeling. Multi-unit activity was recorded from rats doing an working memory task in control sessions and under the influence of exogenously administered tetrahydrocannabinol (THC, the primary CB found in marijuana. It was found that THC left firing rate unaltered and only slightly reduced theta oscillations. Multivariate autoregressive models, estimated from spontaneous spiking activity, were then used to describe the dynamical transformation from CA3 to CA1. They revealed that THC served to functionally isolate CA1 from CA3 by reducing feedforward excitation and theta information flow. The functional isolation was compensated by increased feedback excitation within CA1, thus leading to unaltered firing rates. Finally, both of these effects were shown to be correlated with memory impairments in the working memory task. By elucidating the circuit mechanisms of CBs, these results help close the gap in knowledge between the cellular and behavioral effects of CBs.

  17. Poetic representation

    Wulf-Andersen, Trine Østergaard

    2012-01-01

    , and dialogue, of situated participants. The article includes a lengthy example of a poetic representation of one participant’s story, and the author comments on the potentials of ‘doing’ poetic representations as an example of writing in ways that challenges what sometimes goes unasked in participative social...

  18. Enhanced electrochemical performance of the solid oxide fuel cell cathode using Ca3Co4O9+δ

    Samson, Alfred Junio; Søgaard, Martin; Van Nong, Ngo

    2011-01-01

    This paper reports on the electrochemical performance of an SOFC cathode for potential use in intermediate-temperature solid oxide fuel cells (IT-SOFCs) using the oxygen non-stoichiometric misfit-layered cobaltite Ca3Co4O9+δ or composites of Ca3Co4O9+δ with Ce0.9Gd0.1O1.95 (CGO/Ca3Co4O9+δ......). Electrochemical impedance spectroscopy revealed that symmetric cells with an electrode of pure Ca3Co4O9+δ exhibit a cathode polarization resistance (Rp) of 12.4 Ω cm2, at 600 °C in air. Strikingly, Rp of the composite CGO/Ca3Co4O9+δ with 50 vol.% CGO was reduced by a factor of 19 (i.e. Rp = 0.64 Ω cm2......), the lowest value reported so far for the Ca3Co4O9 family of compounds. These findings together with the reported thermal expansion coefficient, good compatibility with CGO and chemical durability of this material suggest that it is a promising candidate cathode for IT-SOFCs....

  19. Representation of spatial and temporal variability of daily wind speed and of intense wind events over the Mediterranean Sea using dynamical downscaling: impact of the regional climate model configuration

    M. Herrmann

    2011-07-01

    Full Text Available Atmospheric datasets coming from long term reanalyzes of low spatial resolution are used for different purposes. Wind over the sea is, for example, a major ingredient of oceanic simulations. However, the shortcomings of those datasets prevent them from being used without an adequate corrective preliminary treatment. Using a regional climate model (RCM to perform a dynamical downscaling of those large scale reanalyzes is one of the methods used in order to produce fields that realistically reproduce atmospheric chronology and where those shortcomings are corrected. Here we assess the influence of the configuration of the RCM used in this framework on the representation of wind speed spatial and temporal variability and intense wind events on a daily timescale. Our RCM is ALADIN-Climate, the reanalysis is ERA-40, and the studied area is the Mediterranean Sea.

    First, the dynamical downscaling significantly reduces the underestimation of daily wind speed, in average by 9 % over the whole Mediterranean. This underestimation has been corrected both globally and locally, and for the whole wind speed spectrum. The correction is the strongest for periods and regions of strong winds. The representation of spatial variability has also been significantly improved. On the other hand, the temporal correlation between the downscaled field and the observations decreases all the more that one moves eastwards, i.e. further from the atmospheric flux entry. Nonetheless, it remains ~0.7, the downscaled dataset reproduces therefore satisfactorily the real chronology.

    Second, the influence of the choice of the RCM configuration has an influence one order of magnitude smaller than the improvement induced by the initial downscaling. The use of spectral nudging or of a smaller domain helps to improve the realism of the temporal chronology. Increasing the resolution very locally (both spatially and temporally improves the representation of spatial

  20. Thermoelectric Properties of the Chemically Doped Ca3Co4O9 System: A Structural Perspective

    Wu, Tao; Tyson, Trevor; Wang, Hsin; Li, Qiang

    2010-03-01

    Cu doped and Y doped [Ca2CoO3][CoO2]1.61 (referred to as Ca3Co4O9) were prepared by solid state reaction. Temperature dependent thermoelectric properties, resistivity (ρ), Seeback coefficient (S) and thermal conductivity (κ), were measured. As seen before, it is found that doping by Cu and Y significantly enhances the thermoelectric properties. In order to understand the origin of these changes in properties in terms of the atomic structure, synchrotron x-ray diffraction and x-ray absorption spectroscopy were applied to probe the change in the average structure and the location of the dopants. The details of the location and coordination of Co and Y in the host lattice and the effect on the figure of merit are discussed. This work is supported by DOE Grant DE-FG02-07ER46402.

  1. Scintillation characteristics of Tm3+ in Ca3(BO3)2 crystals

    Fujimoto, Yutaka; Yanagida, Takayuki; Yokota, Yuui; Kawaguchi, Noriaki; Fukuda, Kentaro; Totsuka, Daisuke; Watanabe, Kenichi; Yamazaki, Atsushi; Yoshikawa, Akira

    2011-01-01

    Basic optical properties and radiation responses of undoped, Tm 3+ 1.0% and 2.0% activated Ca 3 (BO 3 ) 2 (CBO) crystalline scintillator prepared by the micro-pulling down (μ-PD) method are reported. Tm 3+ : CBO crystals showed three weak absorption bands around 190, 260 and 350 nm, owing to the Tm 3+ 4f–4f transition. Strong blue luminescence peaks at 360 and 460 nm which are ascribed to the 1 D 2 – 3 H 6 and 1 D 2 – 3 F 4 transitions of Tm 3+ respectively were observed under 241 Am 5.5 MeV α-ray excitation. The scintillation light yield of 2.0% Tm 3+ -doped CBO crystal was evaluated to be about 250 ph/n from the 252 Cf excited pulse height spectrum.

  2. THE QUADRUPLE PRE-MAIN-SEQUENCE SYSTEM LkCa 3: IMPLICATIONS FOR STELLAR EVOLUTION MODELS

    Torres, Guillermo; Latham, David W.; Ruíz-Rodríguez, Dary; Prato, L.; Wasserman, Lawrence H.; Badenas, Mariona; Schaefer, G. H.; Mathieu, Robert D.

    2013-01-01

    We report the discovery that the pre-main-sequence (PMS) object LkCa 3 in the Taurus-Auriga star-forming region is a hierarchical quadruple system of M stars. It was previously known to be a close (∼0.''5) visual pair, with one component being a moderately eccentric 12.94 day single-lined spectroscopic binary. A re-analysis of archival optical spectra complemented by new near-infrared (NIR) spectroscopy shows both visual components to be double lined; the second one has a period of 4.06 days and a circular orbit. In addition to the orbital elements, we determine optical and NIR flux ratios, effective temperatures, and projected rotational velocities for all four stars. Using existing photometric monitoring observations of the system that had previously revealed the rotational period of the primary in the longer-period binary, we also detect the rotational signal of the primary in the 4.06 day binary, which is synchronized with the orbital motion. With only the assumption of coevality, a comparison of all of these constraints with current stellar evolution models from the Dartmouth series points to an age of 1.4 Myr and a distance of 133 pc, consistent with previous estimates for the region and suggesting that the system is on the near side of the Taurus complex. Similar comparisons of the properties of LkCa 3 and the well-known quadruple PMS system GG Tau with the widely used models from the Lyon series for a mixing length parameter of α ML = 1.0 strongly favor the Dartmouth models

  3. Age-related Changes in Lateral Entorhinal and CA3 Neuron Allocation Predict Poor Performance on Object Discrimination

    Andrew P. Maurer

    2017-06-01

    Full Text Available Age-related memory deficits correlate with dysfunction in the CA3 subregion of the hippocampus, which includes both hyperactivity and overly rigid activity patterns. While changes in intrinsic membrane currents and interneuron alterations are involved in this process, it is not known whether alterations in afferent input to CA3 also contribute. Neurons in layer II of the lateral entorhinal cortex (LEC project directly to CA3 through the perforant path, but no data are available regarding the effects of advanced age on LEC activity and whether these activity patterns update in response to environmental change. Furthermore, it is not known the extent to which age-related deficits in sensory discrimination relate to the inability of aged CA3 neurons to update in response to new environments. Young and aged rats were pre-characterized on a LEGO© object discrimination task, comparable to behavioral tests in humans in which CA3 hyperactivity has been linked to impairments. The cellular compartment analysis of temporal activity with fluorescence in situ hybridization for the immediate-early gene Arc was then used to identify the principal cell populations that were active during two distinct epochs of random foraging in different environments. This approach enabled the extent to which rats could discriminate two similar objects to be related to the ability of CA3 neurons to update across different environments. In both young and aged rats, there were animals that performed poorly on the LEGO object discrimination task. In the aged rats only, however, the poor performers had a higher percent of CA3 neurons that were active during random foraging in a novel environment, but this is not related to the ability of CA3 neurons to remap when the environment changed. Afferent neurons to CA3 in LEC, as identified with the retrograde tracer choleratoxin B (CTB, also showed a higher percentage of cells that were positive for Arc mRNA in aged poor performing rats

  4. Ensemble place codes in hippocampus: CA1, CA3, and dentate gyrus place cells have multiple place fields in large environments.

    Eunhye Park

    Full Text Available Previously we reported that the hippocampus place code must be an ensemble code because place cells in the CA1 region of hippocampus have multiple place fields in a more natural, larger-than-standard enclosure with stairs that permitted movements in 3-D. Here, we further investigated the nature of hippocampal place codes by characterizing the spatial firing properties of place cells in the CA1, CA3, and dentate gyrus (DG hippocampal subdivisions as rats foraged in a standard 76-cm cylinder as well as a larger-than-standard box (1.8 m×1.4 m that did not have stairs or any internal structure to permit movements in 3-D. The rats were trained to forage continuously for 1 hour using computer-controlled food delivery. We confirmed that most place cells have single place fields in the standard cylinder and that the positional firing pattern remapped between the cylinder and the large enclosure. Importantly, place cells in the CA1, CA3 and DG areas all characteristically had multiple place fields that were irregularly spaced, as we had reported previously for CA1. We conclude that multiple place fields are a fundamental characteristic of hippocampal place cells that simplifies to a single field in sufficiently small spaces. An ensemble place code is compatible with these observations, which contradict any dedicated coding scheme.

  5. Phase transition and multicolor luminescence of Eu2+/Mn2+-activated Ca3(PO4)2 phosphors

    Li, Kai; Chen, Daqin; Xu, Ju; Zhang, Rui; Yu, Yunlong; Wang, Yuansheng

    2014-01-01

    Graphical abstract: We have synthesized Eu 2+ doped and Eu 2+ /Mn 2+ co-doped Ca 3 (PO 4 ) 2 phosphors. The emitting color varies from blue to green with increasing of Eu 2+ content for the Eu 2+ -doped phosphor, and the quantum yield of the 0.05Eu 2+ : Ca 2.95 (PO 4 ) 2 sample reaches 56.7%. Interestingly, Mn 2+ co-doping into Eu 2+ : Ca 3 (PO 4 ) 2 leads to its phase transition from orthorhombic to rhombohedral, and subsequently generates tunable multi-color luminescence from green to red via Eu 2+ → Mn 2+ energy transfer. - Highlights: • A series of novel Eu 2+ : Ca 3 (PO 4 ) 2 phosphors were successfully synthesized. • Phase transition of Ca 3 (PO 4 ) 2 from orthorhombic to rhombohedral occurred when Mn 2+ ions were doped. • The phosphors exhibited tunable multi-color luminescence. • The quantum yield of 0.05Eu 2+ : Ca 2.95 (PO 4 ) 2 phosphor can reach 56.7%. • The analyses of phosphors were carried out by many measurements. - Abstract: Intense blue-green-emitting Eu 2+ : Ca 3 (PO 4 ) 2 and tunable multicolor-emitting Eu 2+ /Mn 2+ : Ca 3 (PO 4 ) 2 phosphors are prepared via a solid-state reaction route. Eu 2+ -doped orthorhombic Ca 3 (PO 4 ) 2 phosphor exhibits a broad emission band in the wavelength range of 400–700 nm with a maximum quantum yield of 56.7%, and the emission peak red-shifts gradually from 479 to 520 nm with increase of Eu 2+ doping content. Broad excitation spectrum (250–420 nm) of Eu 2+ : Ca 3 (PO 4 ) 2 matches well with the near-ultraviolet LED chip, indicating its potential applications as tri-color phosphors in white LEDs. Interestingly, Mn 2+ co-doping into Eu 2+ : Ca 3 (PO 4 ) 2 leads to its phase transition from orthorhombic to rhombohedral, and subsequently generates tunable multi-color luminescence from green to red via Eu 2+ → Mn 2+ energy transfer, under 365 nm UV lamp excitation

  6. Control of CA3 output by feedforward inhibition despite developmental changes in the excitation-inhibition balance.

    Torborg, Christine L; Nakashiba, Toshiaki; Tonegawa, Susumu; McBain, Chris J

    2010-11-17

    In somatosensory cortex, the relative balance of excitation and inhibition determines how effectively feedforward inhibition enforces the temporal fidelity of action potentials. Within the CA3 region of the hippocampus, glutamatergic mossy fiber (MF) synapses onto CA3 pyramidal cells (PCs) provide strong monosynaptic excitation that exhibit prominent facilitation during repetitive activity. We demonstrate in the juvenile CA3 that MF-driven polysynaptic IPSCs facilitate to maintain a fixed EPSC-IPSC ratio during short-term plasticity. In contrast, in young adult mice this MF-driven polysynaptic inhibitory input can facilitate or depress in response to short trains of activity. Transgenic mice lacking the feedback inhibitory loop continue to exhibit both facilitating and depressing polysynaptic IPSCs, indicating that this robust inhibition is not caused by the secondary engagement of feedback inhibition. Surprisingly, eliminating MF-driven inhibition onto CA3 pyramidal cells by blockade of GABA(A) receptors did not lead to a loss of temporal precision of the first action potential observed after a stimulus but triggered in many cases a long excitatory plateau potential capable of triggering repetitive action potential firing. These observations indicate that, unlike other regions of the brain, the temporal precision of single MF-driven action potentials is dictated primarily by the kinetics of MF EPSPs, not feedforward inhibition. Instead, feedforward inhibition provides a robust regulation of CA3 PC excitability across development to prevent excessive depolarization by the monosynaptic EPSP and multiple action potential firings.

  7. A computational simulation of long-term synaptic potentiation inducing protocol processes with model of CA3 hippocampal microcircuit.

    Świetlik, D; Białowąs, J; Kusiak, A; Cichońska, D

    2018-01-01

    An experimental study of computational model of the CA3 region presents cog-nitive and behavioural functions the hippocampus. The main property of the CA3 region is plastic recurrent connectivity, where the connections allow it to behave as an auto-associative memory. The computer simulations showed that CA3 model performs efficient long-term synaptic potentiation (LTP) induction and high rate of sub-millisecond coincidence detection. Average frequency of the CA3 pyramidal cells model was substantially higher in simulations with LTP induction protocol than without the LTP. The entropy of pyramidal cells with LTP seemed to be significantly higher than without LTP induction protocol (p = 0.0001). There was depression of entropy, which was caused by an increase of forgetting coefficient in pyramidal cells simulations without LTP (R = -0.88, p = 0.0008), whereas such correlation did not appear in LTP simulation (p = 0.4458). Our model of CA3 hippocampal formation microcircuit biologically inspired lets you understand neurophysiologic data. (Folia Morphol 2018; 77, 2: 210-220).

  8. Crystal structure and magnetic properties of the solid-solution phase Ca3Co2-v Sc v O6

    Hervoches, Charles H.; Fredenborg, Vivian Miksch; Kjekshus, Arne; Fjellvag, Helmer; Hauback, Bjorn C.

    2007-01-01

    The two crystallographically non-equivalent Co atoms of the quasi-one-dimensional crystal structure of Ca 3 Co 2 O 6 form chains with alternating, face-sharing polyhedra of Co2O 6 trigonal prisms and Co1O 6 octahedra. This compound forms a substitutional solid-solution phase with Sc, in which the Sc atoms enter the Co2 sublattice exclusively. The homogeneity range of Ca 3 Co 2- v Sc v O 6 (more specifically Ca 3 Co1Co2 1- v Sc v O 6 ) extends up to v∼0.55. The crystal structure belongs to space group R3-barc with lattice parameters (in hexagonal setting): 9.0846(3)≤a≤9.1300(2) A and 10.3885(4)≤c≤10.4677(4) A. The magnetic moment decreases rapidly with increasing amount of the non-magnetic Sc solute in the lattice. - Graphical abstract: The quasi-one-dimensional Ca 3 Co 2 O 6 phase forms a substitutional solid-solution system with Sc, in which the Sc atoms enter the Co2 sublattice exclusively. The homogeneity range of Ca 3 Co 2- v Sc v O 6 extends up to v∼0.55. The magnetic moment decreases rapidly with increasing amount of the non-magnetic Sc solute in the lattice

  9. Special Theme Section--Representation and Blindness: The Effect of Extended Acoustic Training on Spatial Updating in Adults Who Are Congenitally Blind.

    Easton, Randolph D.; Bentzen, Billie Louise

    1999-01-01

    A study, including research and practice notes by various authors, investigated whether extended training in an acoustically rich environment could enhance the spatial updating ability of 12 adults with congenital blindness. After training, the adults' distance perception from a home-base location and novel locations was superior to a sighted…

  10. Quiver representations

    Schiffler, Ralf

    2014-01-01

    This book is intended to serve as a textbook for a course in Representation Theory of Algebras at the beginning graduate level. The text has two parts. In Part I, the theory is studied in an elementary way using quivers and their representations. This is a very hands-on approach and requires only basic knowledge of linear algebra. The main tool for describing the representation theory of a finite-dimensional algebra is its Auslander-Reiten quiver, and the text introduces these quivers as early as possible. Part II then uses the language of algebras and modules to build on the material developed before. The equivalence of the two approaches is proved in the text. The last chapter gives a proof of Gabriel’s Theorem. The language of category theory is developed along the way as needed.

  11. Synthesis of Ca_3CO_4O_9 via solid state reaction

    Melo, K.P.; Dutra, R.P.S.; Marques, K.A.; Junior, S.M.S.; Brasileiro, C.T.; Coutinho, S.V.C.R.; Souza, T.; Chagas, T.F.; Silva, R.M.; Macedo, D.A.

    2016-01-01

    Solid oxide fuel cells (SOFCs) stand out as the most promising today's energy conversion technologies. In the development of cathode materials for SOFC, calcium cobaltate (Ca3Co4O9, C349) appears as a potential alternative to traditional lanthanum manganites. In this work, C349 was prepared via solid state reaction of stoichiometric mixtures containing CaCO3 from mollusk shells, in natura (M1) and heat treated at 550 ° C (M2), and Co3O4 obtained by citrate method. The M1 and M2 mixtures were calcined at 800 (powder) and 900 ° C (tablets) for 12 h. The crystal structure and phase composition of the powder and the reaction products were studied by X-ray diffraction Rietveld refinement of the diffraction data. The results showed the formation of free C349 secondary stages, showing a good alternative to use waste from seafood shells as raw material for obtaining high-value ceramics.(author)

  12. Group representations

    Karpilovsky, G

    1994-01-01

    This third volume can be roughly divided into two parts. The first part is devoted to the investigation of various properties of projective characters. Special attention is drawn to spin representations and their character tables and to various correspondences for projective characters. Among other topics, projective Schur index and projective representations of abelian groups are covered. The last topic is investigated by introducing a symplectic geometry on finite abelian groups. The second part is devoted to Clifford theory for graded algebras and its application to the corresponding theory

  13. Value Representations

    Rasmussen, Majken Kirkegaard; Petersen, Marianne Graves

    2011-01-01

    Stereotypic presumptions about gender affect the design process, both in relation to how users are understood and how products are designed. As a way to decrease the influence of stereotypic presumptions in design process, we propose not to disregard the aspect of gender in the design process......, as the perspective brings valuable insights on different approaches to technology, but instead to view gender through a value lens. Contributing to this perspective, we have developed Value Representations as a design-oriented instrument for staging a reflective dialogue with users. Value Representations...

  14. Excitatory Synaptic Drive and Feedforward Inhibition in the Hippocampal CA3 Circuit Are Regulated by SynCAM 1.

    Park, Kellie A; Ribic, Adema; Laage Gaupp, Fabian M; Coman, Daniel; Huang, Yuegao; Dulla, Chris G; Hyder, Fahmeed; Biederer, Thomas

    2016-07-13

    Select adhesion proteins control the development of synapses and modulate their structural and functional properties. Despite these important roles, the extent to which different synapse-organizing mechanisms act across brain regions to establish connectivity and regulate network properties is incompletely understood. Further, their functional roles in different neuronal populations remain to be defined. Here, we applied diffusion tensor imaging (DTI), a modality of magnetic resonance imaging (MRI), to map connectivity changes in knock-out (KO) mice lacking the synaptogenic cell adhesion protein SynCAM 1. This identified reduced fractional anisotropy in the hippocampal CA3 area in absence of SynCAM 1. In agreement, mossy fiber refinement in CA3 was impaired in SynCAM 1 KO mice. Mossy fibers make excitatory inputs onto postsynaptic specializations of CA3 pyramidal neurons termed thorny excrescences and these structures were smaller in the absence of SynCAM 1. However, the most prevalent targets of mossy fibers are GABAergic interneurons and SynCAM 1 loss unexpectedly reduced the number of excitatory terminals onto parvalbumin (PV)-positive interneurons in CA3. SynCAM 1 KO mice additionally exhibited lower postsynaptic GluA1 expression in these PV-positive interneurons. These synaptic imbalances in SynCAM 1 KO mice resulted in CA3 disinhibition, in agreement with reduced feedforward inhibition in this network in the absence of SynCAM 1-dependent excitatory drive onto interneurons. In turn, mice lacking SynCAM 1 were impaired in memory tasks involving CA3. Our results support that SynCAM 1 modulates excitatory mossy fiber inputs onto both interneurons and principal neurons in the hippocampal CA3 area to balance network excitability. This study advances our understanding of synapse-organizing mechanisms on two levels. First, the data support that synaptogenic proteins guide connectivity and can function in distinct brain regions even if they are expressed broadly

  15. Effects of Synthesis and Spark Plasma Sintering Conditions on the Thermoelectric Properties of Ca3Co4O9+δ

    Wu, NingYu; Holgate, Tim; Van Nong, Ngo

    2013-01-01

    Ca3Co4O9+δ samples were synthesized by solid-state (SS) and sol–gel (SG) reactions, followed by spark plasma sintering under different processing conditions. The synthesis process was optimized and the resulting materials characterized with respect to their microstructure, bulk density, and therm......Ca3Co4O9+δ samples were synthesized by solid-state (SS) and sol–gel (SG) reactions, followed by spark plasma sintering under different processing conditions. The synthesis process was optimized and the resulting materials characterized with respect to their microstructure, bulk density...

  16. High-pressure crystal growth and electromagnetic properties of 5d double-perovskite Ca3OsO6

    Feng, Hai Luke; Shi, Youguo; Guo, Yanfeng; Li, Jun; Sato, Akira; Sun, Ying; Wang, Xia; Yu, Shan; Sathish, Clastin I.; Yamaura, Kazunari

    2013-05-01

    Single crystals of the osmium-containing compound Ca3OsO6 have been successfully grown under high-pressure conditions, for the first time. The crystal structure of Ca3OsO6 were characterized as an ordered double-perovskite structure of space group P21/n with the Ca and Os atoms being fully ordered at the perovskite B-site. The electromagnetic analysis shows that the crystal exhibits a semiconductor-like behavior below 300 K and undergoes an antiferromagnetic transition at 50 K.

  17. Encoding, Consolidation, and Retrieval of Contextual Memory: Differential Involvement of Dorsal CA3 and CA1 Hippocampal Subregions

    Daumas, Stephanie; Halley, Helene; Frances, Bernard; Lassalle, Jean-Michel

    2005-01-01

    Studies on human and animals shed light on the unique hippocampus contributions to relational memory. However, the particular role of each hippocampal subregion in memory processing is still not clear. Hippocampal computational models and theories have emphasized a unique function in memory for each hippocampal subregion, with the CA3 area acting…

  18. Evidence of the Current Collector Effect: Study of the SOFC Cathode Material Ca3Co4O9+d

    Rolle, A.; Thoréton, V.; Rozier, P.; Capoen, E.; Mentré, O.; Boukamp, Bernard A.; Daviero-Minaud, S.

    2012-01-01

    In the study of the performance of solid oxide fuel cell (SOFC) electrodes, the possible influence of the applied current collector is often not mentioned or recognized. In this article, as part of an optimization study of the potentially attractive Ca3Co4O9+δ cathode material (Ca349), special

  19. Mechanical and thermal-expansion characteristics of Ca10(PO46(OH2-Ca3(PO42 composites

    Ruseska G.

    2006-01-01

    Full Text Available Three types of composites consisting of Ca10(PO46(OH2 and Ca3(PO42 with composition: 75% (wt Ca10(PO46(OH2: 25%(wt Ca3(PO42; 50%(wt Ca10(PO46(OH2: 50%(wtCa3(PO42 and 25 %(wt Ca10(PO46(OH2: 75%(wt Ca3(PO42 were the subject of our investigation. Sintered compacts were in thermal equilibrium, which was proved by the absence of hysteresis effect of the dependence ΔL/L=f(T during heating /cooling in the temperature interval 20-1000-200C. Sintered compacts with the previously mentioned composition possess 26-50% higher values of the E-modulus, G-modulus and K-modulus indicating the presence of a synergism effect. Several proposed model equations for predicting the thermal expansion coefficient in dependence of the thermal and elastic properties of the constitutive phases and their volume fractions, given by: Turner, Kerner, Tummala and Friedberg, Thomas and Taya, were used for making correlations between mechanical and thermal-expansion characteristics of the Ca10(PO46(OH2 - Ca3(PO42 composites. Application of the previously mentioned model equations to all kinds of composites leads to the conclusion that the experimentally obtained results for the thermal expansion coefficient are in an excellent agreement with the theoretical calculated values on account of the volume fraction of each constitutive phase and with all applied model equations, with a coefficient of correlation from 98.16-99.86 %.

  20. Dentate gyrus supports slope recognition memory, shades of grey-context pattern separation and recognition memory, and CA3 supports pattern completion for object memory.

    Kesner, Raymond P; Kirk, Ryan A; Yu, Zhenghui; Polansky, Caitlin; Musso, Nick D

    2016-03-01

    In order to examine the role of the dorsal dentate gyrus (dDG) in slope (vertical space) recognition and possible pattern separation, various slope (vertical space) degrees were used in a novel exploratory paradigm to measure novelty detection for changes in slope (vertical space) recognition memory and slope memory pattern separation in Experiment 1. The results of the experiment indicate that control rats displayed a slope recognition memory function with a pattern separation process for slope memory that is dependent upon the magnitude of change in slope between study and test phases. In contrast, the dDG lesioned rats displayed an impairment in slope recognition memory, though because there was no significant interaction between the two groups and slope memory, a reliable pattern separation impairment for slope could not be firmly established in the DG lesioned rats. In Experiment 2, in order to determine whether, the dDG plays a role in shades of grey spatial context recognition and possible pattern separation, shades of grey were used in a novel exploratory paradigm to measure novelty detection for changes in the shades of grey context environment. The results of the experiment indicate that control rats displayed a shades of grey-context pattern separation effect across levels of separation of context (shades of grey). In contrast, the DG lesioned rats displayed a significant interaction between the two groups and levels of shades of grey suggesting impairment in a pattern separation function for levels of shades of grey. In Experiment 3 in order to determine whether the dorsal CA3 (dCA3) plays a role in object pattern completion, a new task requiring less training and using a choice that was based on choosing the correct set of objects on a two-choice discrimination task was used. The results indicated that control rats displayed a pattern completion function based on the availability of one, two, three or four cues. In contrast, the dCA3 lesioned rats

  1. A Change in Igneous Activity of the Jack Hills Zircon Sources ca. 3.9 Ga

    Bell, E. A.; Harrison, T. M.

    2010-12-01

    New Ti-in-zircon crystallization temperature (Txlln) data for Jack Hills zircons reveal that the tight clustering of Hadean grains around a Txlln of 680°C, possibly indicative of felsic-to-intermediate minimum melting conditions, continues to ~3.92 Ga. Between 3.92-3.82 Ga the 680°C clustering ceases and most concordant grains cluster around an apparent Txlln of 610°C. A small group of zircons with higher Txlln (~750°C), present during the Hadean, is also observed during this period. After 3.82 Ga a Hadean-like distribution resumes for ~100 Ma. This large, concordant, low-Ti group at ~3.9 Ga is statistically distinct from the Hadean distribution and appears to be unique in the Jack Hills zircon record. The existence of coeval high- and low-Ti groups suggests that two distinct zircon-forming processes are distinguishable ~3.9 Ga, unlike during the Hadean. The significant numbers of zircons with apparent Txlln below 600°C may be suggestive of subsolidus formation, since igneous units with solidii below 600°C are relatively rare. The higher-Ti group is more consistent with an intermediate to mafic igneous origin but metamorphic overprinting or subsolidus formation at granulite grade cannot be ruled out by Txlln alone. A substantial proportion of the high-Ti group display oscillatory and disrupted oscillatory zoning in cathodoluminescence images, usually indicative of igneous origins and later metamorphism, respectively; most low-Ti grains are homogeneous. Several of each group display patchy zonation indicative of metamorphic overprinting. Although several grains with apparent Txlln >600°C display oscillatory zonation, the majority of the low-Ti group do not show textural evidence for igneous origins. We interpret these results to indicate the transition from a mechanism(s) that produced dominantly 680°C apparent zircon temperatures at ca. 3.9 Ga to include a new zircon-forming process in the sediment source(s), likely a protracted period of metamorphism

  2. Biomedical image representation approach using visualness and spatial information in a concept feature space for interactive region-of-interest-based retrieval.

    Rahman, Md Mahmudur; Antani, Sameer K; Demner-Fushman, Dina; Thoma, George R

    2015-10-01

    This article presents an approach to biomedical image retrieval by mapping image regions to local concepts where images are represented in a weighted entropy-based concept feature space. The term "concept" refers to perceptually distinguishable visual patches that are identified locally in image regions and can be mapped to a glossary of imaging terms. Further, the visual significance (e.g., visualness) of concepts is measured as the Shannon entropy of pixel values in image patches and is used to refine the feature vector. Moreover, the system can assist the user in interactively selecting a region-of-interest (ROI) and searching for similar image ROIs. Further, a spatial verification step is used as a postprocessing step to improve retrieval results based on location information. The hypothesis that such approaches would improve biomedical image retrieval is validated through experiments on two different data sets, which are collected from open access biomedical literature.

  3. Differentiating Spatial Memory from Spatial Transformations

    Street, Whitney N.; Wang, Ranxiao Frances

    2014-01-01

    The perspective-taking task is one of the most common paradigms used to study the nature of spatial memory, and better performance for certain orientations is generally interpreted as evidence of spatial representations using these reference directions. However, performance advantages can also result from the relative ease in certain…

  4. Spin texture of the surface state of three-dimensional Dirac material Ca3PbO

    Kariyado, Toshikaze

    2015-04-01

    The bulk and surface electronic structures of a candidate three-dimensional Dirac material Ca3PbO and its family are discussed especially focusing on the spin texture on the surface states. We first explain the basic features of the bulk band structure of Ca3PbO, such as emergence of Dirac fermions near the Fermi energy, and compare it with the other known three-dimensional Dirac semimetals. Then, the surface bands and spin-texture on them are investigated in detail. It is shown that the surface bands exhibit strong momentum-spin locking, which may be useful in some application for spin manipulation, induced by a combination of the inversion symmetry breaking at the surface and the strong spin-orbit coupling of Pb atoms. The surface band structure and the spin-textures are sensitive to the surface types.

  5. Spin texture of the surface state of three-dimensional Dirac material Ca3PbO

    Kariyado, Toshikaze

    2015-01-01

    The bulk and surface electronic structures of a candidate three-dimensional Dirac material Ca 3 PbO and its family are discussed especially focusing on the spin texture on the surface states. We first explain the basic features of the bulk band structure of Ca 3 PbO, such as emergence of Dirac fermions near the Fermi energy, and compare it with the other known three-dimensional Dirac semimetals. Then, the surface bands and spin-texture on them are investigated in detail. It is shown that the surface bands exhibit strong momentum-spin locking, which may be useful in some application for spin manipulation, induced by a combination of the inversion symmetry breaking at the surface and the strong spin-orbit coupling of Pb atoms. The surface band structure and the spin-textures are sensitive to the surface types. (paper)

  6. Complex Visual Data Analysis, Uncertainty, and Representation

    Schunn, Christian D; Saner, Lelyn D; Kirschenbaum, Susan K; Trafton, J. G; Littleton, Eliza B

    2007-01-01

    ... (weather forecasting, submarine target motion analysis, and fMRI data analysis). Internal spatial representations are coded from spontaneous gestures made during cued-recall summaries of problem solving activities...

  7. Estrogen induces rapid decrease in dendritic thorns of CA3 pyramidal neurons in adult male rat hippocampus

    Tsurugizawa, Tomokazu; Mukai, Hideo

    2005-01-01

    Modulation of hippocampal synaptic plasticity by estrogen has been attracting much attention. Thorns of thorny excrescences of CA3 hippocampal neurons are post-synaptic regions whose presynaptic partners are mossy fiber terminals. Here we demonstrated the rapid effect of estradiol on the density of thorns of thorny excrescences, by imaging Lucifer Yellow-injected CA3 neurons in adult male rat hippocampal slices. The application of 1 nM estradiol induced rapid decrease in the density of thorns on pyramidal neurons within 2 h. The estradiol-mediated decrease in the density of thorns was blocked by CNQX (AMPA receptor antagonist) and PD98059 (MAP kinase inhibitor), but not by MK-801 (NMDA receptor antagonist). ERα agonist PPT induced the same suppressive effect as that induced by estradiol on the density of thorns, but ERβ agonist DPN did not affect the density of thorns. Note that a 1 nM estradiol treatment did not affect the density of spines in the stratum radiatum and stratum oriens. A search for synaptic ERα was performed using purified RC-19 antibody. The localization of ERα (67 kDa) in the CA3 mossy fiber terminals and thorns was demonstrated using immunogold electron microscopy. These results imply that estradiol drives the signaling pathway including ERα and MAP kinase

  8. Corticosterone rapidly increases thorns of CA3 neurons via synaptic/extranuclear glucocorticoid receptor in rat hippocampus

    Miyuki eYoshiya

    2013-11-01

    Full Text Available Modulation of synapses under acute stress is attracting much attention. Exposure to acute stress induces corticosterone (CORT secretion from the adrenal cortex, resulting in rapid increase of CORT levels in plasma and the hippocampus. We tried to test whether rapid CORT effects involve activation of essential kinases as non-genomic processes.We demonstrated rapid effects (~ 1 h of CORT on the density of thorns, by imaging Lucifer Yellow-injected neurons in adult male rat hippocampal slices. Thorns of thorny excrescences of CA3 hippocampal neurons are post-synaptic regions whose presynaptic partners are mossy fiber terminals. The application of CORT at 100, 500 and 1000 nM induced a rapid increase in the density of thorns in the stratum lucidum of CA3 pyramidal neurons. Co-administration of RU486, an antagonist of glucocorticoid receptor (GR, abolished the effect of CORT. Blocking a single kinase, including MAPK, PKA or PKC, suppressed CORT-induced enhancement of thorn-genesis. On the other hand, GSK-3β was not involved in the signaling of thorn-genesis. Blocking AMPA receptors suppressed the CORT effect. Expression of CA3 synaptic/extranuclear GR was demonstrated by immunogold electron microscopic analysis. From these results, stress levels of CORT (100-1000 nM might drive the rapid thorn-genesis via synaptic/extranuclear GR and multiple kinase pathways, although a role of nuclear GRs cannot be completely excluded.

  9. Hippocampal CA3-dentate gyrus volume uniquely linked to improvement in associative memory from childhood to adulthood.

    Daugherty, Ana M; Flinn, Robert; Ofen, Noa

    2017-06-01

    Associative memory develops into adulthood and critically depends on the hippocampus. The hippocampus is a complex structure composed of subfields that are functionally-distinct, and anterior-posterior divisions along the length of the hippocampal horizontal axis that may also differ by cognitive correlates. Although each of these aspects has been considered independently, here we evaluate their relative contributions as correlates of age-related improvement in memory. Volumes of hippocampal subfields (subiculum, CA1-2, CA3-dentate gyrus) and anterior-posterior divisions (hippocampal head, body, tail) were manually segmented from high-resolution images in a sample of healthy participants (age 8-25 years). Adults had smaller CA3-dentate gyrus volume as compared to children, which accounted for 67% of the indirect effect of age predicting better associative memory via hippocampal volumes. Whereas hippocampal body volume demonstrated non-linear age differences, larger hippocampal body volume was weakly related to better associative memory only when accounting for the mutual correlation with subfields measured within that region. Thus, typical development of associative memory was largely explained by age-related differences in CA3-dentate gyrus. Copyright © 2017 Elsevier Inc. All rights reserved.

  10. Hippocampal CA3-dentate gyrus volume uniquely linked to improvement in associative memory from childhood to adulthood

    Daugherty, Ana M.; Flinn, Robert; Ofen, Noa

    2017-01-01

    Associative memory develops into adulthood and critically depends on the hippocampus. The hippocampus is a complex structure composed of subfields that are functionally-distinct, and anterior-posterior divisions along the length of the hippocampal horizontal axis that may also differ by cognitive correlates. Although each of these aspects has been considered independently, here we evaluate their relative contributions as correlates of age-related improvement in memory. Volumes of hippocampal subfields (subiculum, CA1-2, CA3-dentate gyrus) and anterior-posterior divisions (hippocampal head, body, tail) were manually segmented from high-resolution proton density-weighted images in a sample of healthy participants (age 8–25 years). Adults had smaller CA3-dentate gyrus volume as compared to children, which accounted for 67% of the indirect effect of age predicting better associative memory via hippocampal volumes. Whereas hippocampal body volume demonstrated non-linear age differences, larger hippocampal body volume was weakly related to better associative memory only when accounting for the mutual correlation with subfields measured within that region. Thus, typical development of associative memory was largely explained by age-related differences in CA3-dentate gyrus. PMID:28342999

  11. Behavior-Dependent Activity and Synaptic Organization of Septo-hippocampal GABAergic Neurons Selectively Targeting the Hippocampal CA3 Area.

    Joshi, Abhilasha; Salib, Minas; Viney, Tim James; Dupret, David; Somogyi, Peter

    2017-12-20

    Rhythmic medial septal (MS) GABAergic input coordinates cortical theta oscillations. However, the rules of innervation of cortical cells and regions by diverse septal neurons are unknown. We report a specialized population of septal GABAergic neurons, the Teevra cells, selectively innervating the hippocampal CA3 area bypassing CA1, CA2, and the dentate gyrus. Parvalbumin-immunopositive Teevra cells show the highest rhythmicity among MS neurons and fire with short burst duration (median, 38 ms) preferentially at the trough of both CA1 theta and slow irregular oscillations, coincident with highest hippocampal excitability. Teevra cells synaptically target GABAergic axo-axonic and some CCK interneurons in restricted septo-temporal CA3 segments. The rhythmicity of their firing decreases from septal to temporal termination of individual axons. We hypothesize that Teevra neurons coordinate oscillatory activity across the septo-temporal axis, phasing the firing of specific CA3 interneurons, thereby contributing to the selection of pyramidal cell assemblies at the theta trough via disinhibition. VIDEO ABSTRACT. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  12. Effects of inhaled anesthetic isoflurane on long-term potentiation of CA3 pyramidal cell afferents in vivo

    Ballesteros KA

    2012-11-01

    Full Text Available Kristen A Ballesteros,1 Angela Sikorski,2 James E Orfila,3 Joe L Martinez Jr41Department of Biology, The University of Texas at San Antonio, San Antonio, TX, USA; 2Texas A&M University Texarkana, Texarkana, TX, USA; 3University of Colorado in Denver, Denver, CO, USA; 4University of Illinois in Chicago, Chicago, IL, USAAbstract: Isoflurane is a preferred anesthetic, due to its properties that allow a precise concentration to be delivered continually during in vivo experimentation. The major mechanism of action of isoflurane is modulation of the γ-amino butyric acid (GABAA receptor-chloride channel, mediating inhibitory synaptic transmission. Animal studies have shown that isoflurane does not cause cell death, but it does inhibit cell growth and causes long-term hippocampal learning deficits. As there are no studies characterizing the effects of isoflurane on electrophysiological aspects of long-term potentiation (LTP in the hippocampus, it is important to determine whether isoflurane alters the characteristic responses of hippocampal afferents to cornu ammonis region 3 (CA3. We investigated the effects of isoflurane on adult male rats during in vivo induction of LTP, using the mossy fiber pathway, the lateral perforant pathway, the medial perforant pathway, and the commissural CA3 (cCA3 to CA3, with intracranial administration of Ringer’s solution, naloxone, RS-aminoindan-1, 5-dicarboxylic acid (AIDA, or 3-[(R-2-carboxypiperazin-4-yl]-propo-2-enyl-1-phosphonic acid (CPP. Then, we compared these responses to published electrophysiological data, using sodium pentobarbital as an anesthetic, under similar experimental conditions. Our results showed that LTP was exhibited in animals anesthetized with isoflurane under vehicle conditions. With the exception of AIDA in the lateral perforant pathway, the defining characteristics of the four pathways appeared to remain intact, except for the observation that LTP was markedly reduced in animals

  13. Attention and Representational Momentum

    Hayes, Amy; Freyd, Jennifer J

    1995-01-01

    Representational momentum, the tendency for memory to be distorted in the direction of an implied transformation, suggests that dynamics are an intrinsic part of perceptual representations. We examined the effect of attention on dynamic representation by testing for representational momentum under conditions of distraction. Forward memory shifts increase when attention is divided. Attention may be involved in halting but not in maintaining dynamic representations.

  14. Dietary Supplementation of Hericium erinaceus Increases Mossy Fiber-CA3 Hippocampal Neurotransmission and Recognition Memory in Wild-Type Mice

    Federico Brandalise

    2017-01-01

    Full Text Available Hericium erinaceus (Bull. Pers. is a medicinal mushroom capable of inducing a large number of modulatory effects on human physiology ranging from the strengthening of the immune system to the improvement of cognitive functions. In mice, dietary supplementation with H. erinaceus prevents the impairment of spatial short-term and visual recognition memory in an Alzheimer model. Intriguingly other neurobiological effects have recently been reported like the effect on neurite outgrowth and differentiation in PC12 cells. Until now no investigations have been conducted to assess the impact of this dietary supplementation on brain function in healthy subjects. Therefore, we have faced the problem by considering the effect on cognitive skills and on hippocampal neurotransmission in wild-type mice. In wild-type mice the oral supplementation with H. erinaceus induces, in behaviour test, a significant improvement in the recognition memory and, in hippocampal slices, an increase in spontaneous and evoked excitatory synaptic current in mossy fiber-CA3 synapse. In conclusion, we have produced a series of findings in support of the concept that H. erinaceus induces a boost effect onto neuronal functions also in nonpathological conditions.

  15. Dietary Supplementation of Hericium erinaceus Increases Mossy Fiber-CA3 Hippocampal Neurotransmission and Recognition Memory in Wild-Type Mice.

    Brandalise, Federico; Cesaroni, Valentina; Gregori, Andrej; Repetti, Margherita; Romano, Chiara; Orrù, Germano; Botta, Laura; Girometta, Carolina; Guglielminetti, Maria Lidia; Savino, Elena; Rossi, Paola

    2017-01-01

    Hericium erinaceus (Bull.) Pers. is a medicinal mushroom capable of inducing a large number of modulatory effects on human physiology ranging from the strengthening of the immune system to the improvement of cognitive functions. In mice, dietary supplementation with H. erinaceus prevents the impairment of spatial short-term and visual recognition memory in an Alzheimer model. Intriguingly other neurobiological effects have recently been reported like the effect on neurite outgrowth and differentiation in PC12 cells. Until now no investigations have been conducted to assess the impact of this dietary supplementation on brain function in healthy subjects. Therefore, we have faced the problem by considering the effect on cognitive skills and on hippocampal neurotransmission in wild-type mice. In wild-type mice the oral supplementation with H. erinaceus induces, in behaviour test, a significant improvement in the recognition memory and, in hippocampal slices, an increase in spontaneous and evoked excitatory synaptic current in mossy fiber-CA3 synapse. In conclusion, we have produced a series of findings in support of the concept that H. erinaceus induces a boost effect onto neuronal functions also in nonpathological conditions.

  16. The functional genome of CA1 and CA3 neurons under native conditions and in response to ischemia

    Rossner Moritz

    2007-10-01

    Full Text Available Abstract Background The different physiological repertoire of CA3 and CA1 neurons in the hippocampus, as well as their differing behaviour after noxious stimuli are ultimately based upon differences in the expressed genome. We have compared CA3 and CA1 gene expression in the uninjured brain, and after cerebral ischemia using laser microdissection (LMD, RNA amplification, and array hybridization. Results Profiling in CA1 vs. CA3 under normoxic conditions detected more than 1000 differentially expressed genes that belong to different, physiologically relevant gene ontology groups in both cell types. The comparison of each region under normoxic and ischemic conditions revealed more than 5000 ischemia-regulated genes for each individual cell type. Surprisingly, there was a high co-regulation in both regions. In the ischemic state, only about 100 genes were found to be differentially expressed in CA3 and CA1. The majority of these genes were also different in the native state. A minority of interesting genes (e.g. inhibinbetaA displayed divergent expression preference under native and ischemic conditions with partially opposing directions of regulation in both cell types. Conclusion The differences found in two morphologically very similar cell types situated next to each other in the CNS are large providing a rational basis for physiological differences. Unexpectedly, the genomic response to ischemia is highly similar in these two neuron types, leading to a substantial attenuation of functional genomic differences in these two cell types. Also, the majority of changes that exist in the ischemic state are not generated de novo by the ischemic stimulus, but are preexistant from the genomic repertoire in the native situation. This unexpected influence of a strong noxious stimulus on cell-specific gene expression differences can be explained by the activation of a cell-type independent conserved gene-expression program. Our data generate both novel

  17. Npas4 Is a Critical Regulator of Learning-Induced Plasticity at Mossy Fiber-CA3 Synapses during Contextual Memory Formation.

    Weng, Feng-Ju; Garcia, Rodrigo I; Lutzu, Stefano; Alviña, Karina; Zhang, Yuxiang; Dushko, Margaret; Ku, Taeyun; Zemoura, Khaled; Rich, David; Garcia-Dominguez, Dario; Hung, Matthew; Yelhekar, Tushar D; Sørensen, Andreas Toft; Xu, Weifeng; Chung, Kwanghun; Castillo, Pablo E; Lin, Yingxi

    2018-03-07

    Synaptic connections between hippocampal mossy fibers (MFs) and CA3 pyramidal neurons are essential for contextual memory encoding, but the molecular mechanisms regulating MF-CA3 synapses during memory formation and the exact nature of this regulation are poorly understood. Here we report that the activity-dependent transcription factor Npas4 selectively regulates the structure and strength of MF-CA3 synapses by restricting the number of their functional synaptic contacts without affecting the other synaptic inputs onto CA3 pyramidal neurons. Using an activity-dependent reporter, we identified CA3 pyramidal cells that were activated by contextual learning and found that MF inputs on these cells were selectively strengthened. Deletion of Npas4 prevented both contextual memory formation and this learning-induced synaptic modification. We further show that Npas4 regulates MF-CA3 synapses by controlling the expression of the polo-like kinase Plk2. Thus, Npas4 is a critical regulator of experience-dependent, structural, and functional plasticity at MF-CA3 synapses during contextual memory formation. Copyright © 2018 Elsevier Inc. All rights reserved.

  18. Luminescent properties of Mg3Ca3(PO4)4: Eu2+ blue-emitting phosphor for white light emitting diodes

    Li Yinqun; Deng Degang; Wang Qian; Li Gaofeng; Hua Youjie; Jia Guohua; Huang Lihui; Zhao Shilong; Wang Huanping; Li Chenxia; Xu Shiqing

    2012-01-01

    A blue-emitting phosphor, Eu 2+ -activated Mg 3 Ca 3 (PO 4 ) 4 phosphor was synthesized by conventional solid-state reaction. X-ray powder diffraction (XRD) analysis confirmed the phase formation. Photoluminescence (PL) results showed that Mg 3 Ca 3 (PO 4 ) 4 : Eu 2+ could be efficiently excited by UV–visible light from 250 to 430 nm, which matched well with the emission wavelengths of near-UV and UV LED chips. The effects of the doped-Eu 2+ concentration in Mg 3 Ca 3 (PO 4 ) 4 : Eu 2+ on the PL were also investigated. The result reveals that Mg 3 Ca 3 (PO 4 ) 4 : Eu 2+ is a potential blue-emitting phosphor for white LEDs. - Graphical Abstract: The excitation spectra show a broad peak from 250 to 430 nm, which means Mg 3 Ca 3 (PO 4 ) 4 : Eu 2+ phosphor can be suitable for application in white LEDs excited by the near-UV and UV LEDs. The emission spectrum peaked at 456 nm with the full-width half-maximum (FWHM) of 102 nm is attributed to the 4f 6 5d 1 –4f 7 transition of the Eu 2+ ion. The asymmetric emission spectra show that Eu 2+ has more one emission center in Mg 3 Ca 3 (PO 4 ) 4 , which can be deconvoluted into at least four Gaussian components peaked at 423, 446, 483 and 510 nm. Highlights: ► Mg 3 Ca 3 (PO 4 ) 4 : Eu 2+ phosphor could be effectively excited by UV chips (360–430 nm). ► Mg 3 Ca 3 (PO 4 ) 4 : Eu 2+ phosphor is a potential blue-emitting phosphor for white LEDs. ► Mg 3 Ca 3 (PO 4 ) 4 : Eu 2+ phosphor shows a broadband emission.

  19. Safety of the Transcranial Focal Electrical Stimulation via Tripolar Concentric Ring Electrodes for Hippocampal CA3 Subregion Neurons in Rats.

    Mucio-Ramírez, Samuel; Makeyev, Oleksandr

    2017-01-01

    Epilepsy is a neurological disorder that affects approximately one percent of the world population. Noninvasive electrical brain stimulation via tripolar concentric ring electrodes has been proposed as an alternative/complementary therapy for seizure control. Previous results suggest its efficacy attenuating acute seizures in penicillin, pilocarpine-induced status epilepticus, and pentylenetetrazole-induced rat seizure models and its safety for the rat scalp, cortical integrity, and memory formation. In this study, neuronal counting was used to assess possible tissue damage in rats ( n = 36) due to the single dose or five doses (given every 24 hours) of stimulation on hippocampal CA3 subregion neurons 24 hours, one week, and one month after the last stimulation dose. Full factorial analysis of variance showed no statistically significant difference in the number of neurons between control and stimulation-treated animals ( p  = 0.71). Moreover, it showed no statistically significant differences due to the number of stimulation doses ( p  = 0.71) nor due to the delay after the last stimulation dose ( p  = 0.96). Obtained results suggest that stimulation at current parameters (50 mA, 200  μ s, 300 Hz, biphasic, charge-balanced pulses for 2 minutes) does not induce neuronal damage in the hippocampal CA3 subregion of the brain.

  20. Safety of the Transcranial Focal Electrical Stimulation via Tripolar Concentric Ring Electrodes for Hippocampal CA3 Subregion Neurons in Rats

    Samuel Mucio-Ramírez

    2017-01-01

    Full Text Available Epilepsy is a neurological disorder that affects approximately one percent of the world population. Noninvasive electrical brain stimulation via tripolar concentric ring electrodes has been proposed as an alternative/complementary therapy for seizure control. Previous results suggest its efficacy attenuating acute seizures in penicillin, pilocarpine-induced status epilepticus, and pentylenetetrazole-induced rat seizure models and its safety for the rat scalp, cortical integrity, and memory formation. In this study, neuronal counting was used to assess possible tissue damage in rats (n=36 due to the single dose or five doses (given every 24 hours of stimulation on hippocampal CA3 subregion neurons 24 hours, one week, and one month after the last stimulation dose. Full factorial analysis of variance showed no statistically significant difference in the number of neurons between control and stimulation-treated animals (p = 0.71. Moreover, it showed no statistically significant differences due to the number of stimulation doses (p = 0.71 nor due to the delay after the last stimulation dose (p = 0.96. Obtained results suggest that stimulation at current parameters (50 mA, 200 μs, 300 Hz, biphasic, charge-balanced pulses for 2 minutes does not induce neuronal damage in the hippocampal CA3 subregion of the brain.

  1. Effects of Synthesis and Processing on the Thermoelectric Properties of Ca3Co4O9+δ

    Wu, NingYu; Holgate, Tim; Van Nong, Ngo

    In the present study, Ca3Co4O9+δ was synthesized by solid-state and sol-gel reactions followed by spark plasma sintering (SPS) under different conditions such as sintering temperatures, applied pressures and ramping rates. The materials were then characterized with respect to their microstructure......, phase purity and thermoelectric properties. With the identical optimal SPS process, the power factor of about 400 µW/m•K2 and 465 µW/m•K2 (at 800 °C) is measured from samples produced by solid-state and sol-gel reactions respectively, both of these values are higher than the value reported so far....... The thermoelectric performance improvement observed for the solid-state and sol-gel reactions suggests that the particle sizes may be a predominant key parameter of the Ca3Co4O9+δ thermoelectric properties. Smaller particle size (500 nm) as produced in this study by sol-gel synthesis method with optimal SPS process...

  2. Identification of Potentially Neuroprotective Genes Upregulated by Neurotrophin Treatment of CA3 Neurons in the Injured Brain

    Malik, Saafan Z.; Motamedi, Shahab; Royo, Nicolas C.; LeBold, David

    2011-01-01

    Abstract Specific neurotrophic factors mediate histological and/or functional improvement in animal models of traumatic brain injury (TBI). In previous work, several lines of evidence indicated that the mammalian neurotrophin NT-4/5 is neuroprotective for hippocampal CA3 pyramidal neurons after experimental TBI. We hypothesized that NT-4/5 neuroprotection is mediated by changes in the expression of specific sets of genes, and that NT-4/5-regulated genes are potential therapeutic targets for blocking delayed neuronal death after TBI. In this study, we performed transcription profiling analysis of CA3 neurons to identify genes regulated by lateral fluid percussion injury, or by treatment with the trkB ligands NT-4/5 or brain-derived neurotrophic factor (BDNF). The results indicate extensive overlap between genes upregulated by neurotrophins and genes upregulated by injury, suggesting that the mechanism behind neurotrophin neuroprotection may mimic the brain's endogenous protective response. A subset of genes selected for further study in vitro exhibited neuroprotection against glutamate excitotoxicity. The neuroprotective genes identified in this study were upregulated at 30 h post-injury, and are thus expected to act during a clinically useful time frame of hours to days after injury. Modulation of these factors and pathways by genetic manipulation or small molecules may confer hippocampal neuroprotection in vivo in preclinical models of TBI. PMID:21083427

  3. Housing under the pyramid reduces susceptibility of hippocampal CA3 pyramidal neurons to prenatal stress in the developing rat offspring.

    Murthy, Krishna Dilip; George, Mitchel Constance; Ramasamy, Perumal; Mustapha, Zainal Arifin

    2013-12-01

    Mother-offspring interaction begins before birth. The foetus is particularly vulnerable to environmental insults and stress. The body responds by releasing excess of the stress hormone cortisol, which acts on glucocorticoid receptors. Hippocampus in the brain is rich in glucocorticoid receptors and therefore susceptible to stress. The stress effects are reduced when the animals are placed under a model wooden pyramid. The present study was to first explore the effects of prenatal restraint-stress on the plasma corticosterone levels and the dendritic arborisation of CA3 pyramidal neurons in the hippocampus of the offspring. Further, to test whether the pyramid environment would alter these effects, as housing under a pyramid is known to reduce the stress effects, pregnant Sprague Dawley rats were restrained for 9 h per day from gestation day 7 until parturition in a wire-mesh restrainer. Plasma corticosterone levels were found to be significantly increased. In addition, there was a significant reduction in the apical and the basal total dendritic branching points and intersections of the CA3 hippocampal pyramidal neurons. The results thus suggest that, housing in the pyramid dramatically reduces prenatal stress effects in rats.

  4. Npas4 Is a Critical Regulator of Learning-Induced Plasticity at Mossy Fiber-CA3 Synapses during Contextual Memory Formation

    Weng, Feng-Ju; Garcia, Rodrigo I; Lutzu, Stefano

    2018-01-01

    Synaptic connections between hippocampal mossy fibers (MFs) and CA3 pyramidal neurons are essential for contextual memory encoding, but the molecular mechanisms regulating MF-CA3 synapses during memory formation and the exact nature of this regulation are poorly understood. Here we report...... pyramidal cells that were activated by contextual learning and found that MF inputs on these cells were selectively strengthened. Deletion of Npas4 prevented both contextual memory formation and this learning-induced synaptic modification. We further show that Npas4 regulates MF-CA3 synapses by controlling...... the expression of the polo-like kinase Plk2. Thus, Npas4 is a critical regulator of experience-dependent, structural, and functional plasticity at MF-CA3 synapses during contextual memory formation....

  5. Factorizations and physical representations

    Revzen, M; Khanna, F C; Mann, A; Zak, J

    2006-01-01

    A Hilbert space in M dimensions is shown explicitly to accommodate representations that reflect the decomposition of M into prime numbers. Representations that exhibit the factorization of M into two relatively prime numbers: the kq representation (Zak J 1970 Phys. Today 23 51), and related representations termed q 1 q 2 representations (together with their conjugates) are analysed, as well as a representation that exhibits the complete factorization of M. In this latter representation each quantum number varies in a subspace that is associated with one of the prime numbers that make up M

  6. Size and receptor density of glutamatergic synapses: a viewpoint from left-right asymmetry of CA3-CA1 connections

    Yoshiaki Shinohara

    2009-07-01

    Full Text Available Synaptic plasticity is considered to be the main mechanism for learning and memory. Excitatory synapses in the cerebral cortex and hippocampus undergo plastic changes during development and in response to electric stimulation. It is widely accepted that this process is mediated by insertion and elimination of various glutamate receptors. In a series of recent investigations on left-right asymmetry of hippocampal CA3-CA1 synapses, glutamate receptor subunits have been found to have distinctive expression patterns that depend on the postsynaptic density (PSD area. Particularly notable are the GluR1 AMPA receptor subunit and NR2B NMDA receptor subunit, where receptor density has either a supra-linear (GluR1 AMPA or inverse (NR2B NMDAR relationship to the PSD area. We review current understanding of structural and physiological synaptic plasticity and propose a scheme to classify receptor subtypes by their expression pattern with respect to PSD area.

  7. X-ray spectra and electronic structure of the Ca3Ga2Ge3О12 compound

    Shcherba, I. D.; Kostyk, L. V.; Noga, H.; Bekenov, L. V.; Uskokovich, D.; Jatsyk, B. M.

    2017-09-01

    The band structure of Ca3Ga2Ge3О12 with the garnet structure has been determined for the first time by X-ray emission and photoelectron spectroscopy. It has been established that the bottom of the valence band is formed by Ge d states, which are not dominant in the chemical bonding. Strong hybridization of oxygen 2s states with 4p states of Ga and Ge revealed by the presence of an extra structure in the X-ray emission spectra has been found. The middle of the valence band has been demonstrated to be occupied by d states of Ga, while Ga and Ge 4рstates with a considerable admixture of oxygen 2p states form the top of the valence band.

  8. Ih tunes theta/gamma oscillations and cross-frequency coupling in an in silico CA3 model.

    Samuel A Neymotin

    Full Text Available Ih channels are uniquely positioned to act as neuromodulatory control points for tuning hippocampal theta (4-12 Hz and gamma (25 Hz oscillations, oscillations which are thought to have importance for organization of information flow. contributes to neuronal membrane resonance and resting membrane potential, and is modulated by second messengers. We investigated oscillatory control using a multiscale computer model of hippocampal CA3, where each cell class (pyramidal, basket, and oriens-lacunosum moleculare cells, contained type-appropriate isoforms of . Our model demonstrated that modulation of pyramidal and basket allows tuning theta and gamma oscillation frequency and amplitude. Pyramidal also controlled cross-frequency coupling (CFC and allowed shifting gamma generation towards particular phases of the theta cycle, effected via 's ability to set pyramidal excitability. Our model predicts that in vivo neuromodulatory control of allows flexibly controlling CFC and the timing of gamma discharges at particular theta phases.

  9. Exercise reduces diet-induced cognitive decline and increases hippocampal brain-derived neurotrophic factor in CA3 neurons.

    Noble, Emily E; Mavanji, Vijayakumar; Little, Morgan R; Billington, Charles J; Kotz, Catherine M; Wang, ChuanFeng

    2014-10-01

    Previous studies have shown that a western diet impairs, whereas physical exercise enhances hippocampus-dependent learning and memory. Both diet and exercise influence expression of hippocampal brain-derived neurotrophic factor (BDNF), which is associated with improved cognition. We hypothesized that exercise reverses diet-induced cognitive decline while increasing hippocampal BDNF. To test the effects of exercise on hippocampal-dependent memory, we compared cognitive scores of Sprague-Dawley rats exercised by voluntary running wheel (RW) access or forced treadmill (TM) to sedentary (Sed) animals. Memory was tested by two-way active avoidance test (TWAA), in which animals are exposed to a brief shock in a specific chamber area. When an animal avoids, escapes or has reduced latency to do either, this is considered a measure of memory. In a second experiment, rats were fed either a high-fat diet or control diet for 16 weeks, then randomly assigned to running wheel access or sedentary condition, and TWAA memory was tested once a week for 7 weeks of exercise intervention. Both groups of exercised animals had improved memory as indicated by reduced latency to avoid and escape shock, and increased avoid and escape episodes (pdiet resulted in poor performance during both the acquisition and retrieval phases of the memory test as compared to controls. Exercise reversed high-fat diet-induced memory impairment, and increased brain-derived neurotrophic factor (BDNF) in neurons of the hippocampal CA3 region. These data suggest that exercise improves memory retrieval, particularly with respect to avoiding aversive stimuli, and may be beneficial in protecting against diet induced cognitive decline, likely via elevated BDNF in neurons of the CA3 region. Published by Elsevier Inc.

  10. Microarray profile of seizure damage-refractory hippocampal CA3 in a mouse model of epileptic preconditioning.

    Hatazaki, S; Bellver-Estelles, C; Jimenez-Mateos, E M; Meller, R; Bonner, C; Murphy, N; Matsushima, S; Taki, W; Prehn, J H M; Simon, R P; Henshall, D C

    2007-12-05

    A neuroprotected state can be acquired by preconditioning brain with a stimulus that is subthreshold for damage (tolerance). Acquisition of tolerance involves coordinate, bi-directional changes to gene expression levels and the re-programmed phenotype is determined by the preconditioning stimulus. While best studied in ischemic brain there is evidence brief seizures can confer tolerance against prolonged seizures (status epilepticus). Presently, we developed a model of epileptic preconditioning in mice and used microarrays to gain insight into the transcriptional phenotype within the target hippocampus at the time tolerance had been acquired. Epileptic tolerance was induced by an episode of non-damaging seizures in adult C57Bl/6 mice using a systemic injection of kainic acid. Neuron and DNA damage-positive cell counts 24 h after status epilepticus induced by intraamygdala microinjection of kainic acid revealed preconditioning given 24 h prior reduced CA3 neuronal death by approximately 45% compared with non-tolerant seizure mice. Microarray analysis of over 39,000 transcripts (Affymetrix 430 2.0 chip) from microdissected CA3 subfields was undertaken at the point at which tolerance was acquired. Results revealed a unique profile of small numbers of equivalently up- and down-regulated genes with biological functions that included transport and localization, ubiquitin metabolism, apoptosis and cell cycle control. Select microarray findings were validated post hoc by real-time polymerase chain reaction and Western blotting. The present study defines a paradigm for inducing epileptic preconditioning in mice and first insight into the global transcriptome of the seizure-damage refractory brain.

  11. Effect of acetylcholine receptors on the pain-related electrical activities in the hippocampal CA3 region of morphine-addicted rats

    Guan Zeng Li

    2015-07-01

    Full Text Available Objective(s:To determine the effect of acetylcholine (ACh, pilocarpine, and atropine on pain evoked responses of pain excited neurons (PEN and pain inhibited neurons (PIN in hippocampal CA3 region of morphine addicted rats. Materials and Methods:Female Wistar rats, weighing between 230-260 g were used in this study. Morphine addicted rats were generated by subcutaneous injection of increasing concentrations of morphine hydrochloride for six days. Trains of electrical impulses applied to the sciatic nerve were used as noxious stimulation and the evoked electrical activities of PEN or PIN in hippocampal CA3 area were recorded using extracellular electrophysiological recording techniques in hippocampal slices. The effect of acetylcholine receptor stimulation byACh, the muscarinic agonist pilocarpine, and the muscarinic antagonist atropine on the pain evoked responses of pain related electrical activities was analyzed in hippocampal CA3 area of morphine addicted rats. Results:Intra-CA3 microinjection of ACh (2 μg/1 μl or pilocarpine (2 μg/1 μl decreased the discharge frequency and prolonged the firing latency of PEN, but increased the discharge frequency and shortened the firing inhibitory duration (ID of PIN. The intra-CA3 administration of atropine (0.5 μg/1 μl produced opposite effect. The peak activity of cholinergic modulators was 2 to 4 min later in morphine addicted rats compared to peak activity previously observed in normal rats. Conclusion: ACh dependent modulation of noxious stimulation exists in hippocampal CA3 area of morphine addicted rats. Morphine treatment may shift the sensitivity of pain related neurons towards a delayed response to muscarinergic neurotransmission in hippocampal CA3 region.

  12. Effect of acetylcholine receptors on the pain-related electrical activities in the hippocampal CA3 region of morphine-addicted rats.

    Li, Guan Zeng; Liu, Zhe Hui; Wei, XinYa; Zhao, Pan; Yang, Chun Xiao; Xu, Man Ying

    2015-07-01

    To determine the effect of acetylcholine (ACh), pilocarpine, and atropine on pain evoked responses of pain excited neurons (PEN) and pain inhibited neurons (PIN) in hippocampal CA3 region of morphine addicted rats. Female Wistar rats, weighing between 230-260 g were used in this study. Morphine addicted rats were generated by subcutaneous injection of increasing concentrations of morphine hydrochloride for six days. Trains of electrical impulses applied to the sciatic nerve were used as noxious stimulation and the evoked electrical activities of PEN or PIN in hippocampal CA3 area were recorded using extracellular electrophysiological recording techniques in hippocampal slices. The effect of acetylcholine receptor stimulation by ACh, the muscarinic agonist pilocarpine, and the muscarinic antagonist atropine on the pain evoked responses of pain related electrical activities was analyzed in hippocampal CA3 area of morphine addicted rats. Intra-CA3 microinjection of ACh (2 μg/1 μl) or pilocarpine (2 μg/1 μl) decreased the discharge frequency and prolonged the firing latency of PEN, but increased the discharge frequency and shortened the firing inhibitory duration (ID) of PIN. The intra-CA3 administration of atropine (0.5 μg/1 μl) produced opposite effect. The peak activity of cholinergic modulators was 2 to 4 min later in morphine addicted rats compared to peak activity previously observed in normal rats. ACh dependent modulation of noxious stimulation exists in hippocampal CA3 area of morphine addicted rats. Morphine treatment may shift the sensitivity of pain related neurons towards a delayed response to muscarinergic neurotransmission in hippocampal CA3 region.

  13. Visual representation of spatiotemporal structure

    Schill, Kerstin; Zetzsche, Christoph; Brauer, Wilfried; Eisenkolb, A.; Musto, A.

    1998-07-01

    The processing and representation of motion information is addressed from an integrated perspective comprising low- level signal processing properties as well as higher-level cognitive aspects. For the low-level processing of motion information we argue that a fundamental requirement is the existence of a spatio-temporal memory. Its key feature, the provision of an orthogonal relation between external time and its internal representation, is achieved by a mapping of temporal structure into a locally distributed activity distribution accessible in parallel by higher-level processing stages. This leads to a reinterpretation of the classical concept of `iconic memory' and resolves inconsistencies on ultra-short-time processing and visual masking. The spatial-temporal memory is further investigated by experiments on the perception of spatio-temporal patterns. Results on the direction discrimination of motion paths provide evidence that information about direction and location are not processed and represented independent of each other. This suggests a unified representation on an early level, in the sense that motion information is internally available in form of a spatio-temporal compound. For the higher-level representation we have developed a formal framework for the qualitative description of courses of motion that may occur with moving objects.

  14. Evaluation of Ca3(Co,M2O6 (M=Co, Fe, Mn, Ni as new cathode materials for solid-oxide fuel cells

    Fushao Li

    2015-10-01

    Full Text Available Series compounds Ca3(Co0.9M0.12O6 (M=Co, Fe, Mn, Ni with hexagonal crystal structure were prepared by sol–gel route as the cathode materials for solid oxide fuel cells (SOFCs. Effects of the varied atomic compositions on the structure, electrical conductivity, thermal expansion and electrochemical performance were systematically evaluated. Experimental results showed that the lattice parameters of Ca3(Co0.9Fe0.12O6 and Ca3(Co0.9Mn0.12O6 were both expanded to certain degree. Electron-doping and hole-doping effects were expected in Ca3(Co0.9Mn0.12O6 and Ca3(Co0.9Ni0.12O6 respectively according to the chemical states of constituent elements and thermal-activated behavior of electrical conductivity. Thermal expansion coefficients (TEC of Ca3(Co0.9M0.12O6 were measured to be distributed around 16×10−6 K−1, and compositional elements of Fe, Mn, and Ni were especially beneficial for alleviation of the thermal expansion problem of cathode materials. By using Ca3(Co0.9M0.12O6 as the cathodes operated at 800 °C, the interfacial area-specific resistance varied in the order of M=CoCa3(Co0.9Fe0.12O6 showed the best electrochemical performance and the power density as high as ca. 500 mW cm−2 at 800 °C achieved in the single cell with La0.8Sr0.2Ga0.83Mg0.17O2.815 as electrolyte and Ni–Ce0.8Sm0.2O1.9 as anode. Ca3(Co0.9M0.12O6 (M=Co, Fe, Mn, Ni can be used as the cost-effective cathode materials for SOFCs.

  15. Adolescent mice show anxiety- and aggressive-like behavior and the reduction of long-term potentiation in mossy fiber-CA3 synapses after neonatal maternal separation.

    Shin, S Y; Han, S H; Woo, R-S; Jang, S H; Min, S S

    2016-03-01

    Exposure to maternal separation (MS) during early life is an identified risk factor for emotional disorders such as anxiety and depression later in life. This study investigated the effects of neonatal MS on the behavior and long-term potentiation (LTP) as well as basic synaptic transmission at hippocampal CA3-CA1 and mossy fiber (MF)-CA3 synapses in adolescent mice for 19days. When mice were adolescents, we measured depression, learning, memory, anxious and aggressive behavior using the forced swimming test (FST), Y-maze, Morris water maze (MWM), elevated plus maze (EPM), three consecutive days of the open field test, the social interaction test, the tube-dominance test and the resident-intruder test. The results showed that there was no difference in FST, Y-maze, and MWM performance. However, MS mice showed more anxiety-like behavior in the EPM test and aggressive-like behavior in the tube-dominance and resident-intruder tests. In addition, the magnitude of LTP and release probability in the MF-CA3 synapses was reduced in the MS group but not in the CA3-CA1 synapse. Our results indicate that early life stress due to MS may induce anxiety- and aggressive-like behavior during adolescence, and these effects are associated with synaptic plasticity at the hippocampal MF-CA3 synapses. Copyright © 2015 IBRO. Published by Elsevier Ltd. All rights reserved.

  16. Spatiality of environmental law

    Baaner, Lasse; Hvingel, Line

    2015-01-01

    , examines legal regulation as spatial information. It aims to deepen the understanding of spatiality as a core element of environmental law, and to connect it to the basic concept of representation used in giscience. It concludes that the future path for e-Government demands a shift in legal paradigm, from...... maps showing representations of applied legal norms, to maps build on datasets that have legal authority. That will integrate legal and geographic information systems, and improve the legal accountability of decision support systems used in e-Government services based on spatio-legal data....

  17. Representation in Memory.

    Rumelhart, David E.; Norman, Donald A.

    This paper reviews work on the representation of knowledge from within psychology and artificial intelligence. The work covers the nature of representation, the distinction between the represented world and the representing world, and significant issues concerned with propositional, analogical, and superpositional representations. Specific topics…

  18. Growth and characterization of Nd-doped disordered Ca3Gd2(BO3)4 crystal

    Pan, Z. B.; Zhang, H. J.; Yu, H. H.; Xu, M.; Zhang, Y. Y.; Sun, S. Q.; Wang, J. Y.; Wang, Q.; Wei, Z. Y.; Zhang, Z. G.

    2012-01-01

    A high-quality disordered Nd3+:Ca3Gd2(BO3)4 (Nd3+:CGB) laser crystal was grown by the Czochralski method. The space group and effective segregation coefficient of Nd3+ were determined to be Pnma and 1.06, respectively. The thermal properties, including the average linear thermal expansion coefficient, thermal diffusivity, specific heat, and thermal conductivity were systematically measured for the first time. It was found that the thermal conductivity increases with increasing temperature, indicating glasslike behavior. The polarized spectral properties of the crystal were investigated, including the polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay. The spectroscopic parameters of Nd3+ ions in Nd3+:CGB crystal have been obtained based on Judd-Ofelt theory. The anisotropy of the spectral properties for different polarized directions was discussed. Additionally, the continuous-wave (CW) laser performance at 1.06 μm was demonstrated for the first time. The maximum output power of 603 mW was achieved with corresponding optical conversion efficiency of 8.33% and slope efficiency of 9.95%.

  19. HERC 1 ubiquitin ligase mutation affects neocortical, CA3 hippocampal and spinal cord projection neurons. An ultrastructural study

    Rocío eRuiz

    2016-04-01

    Full Text Available The spontaneous mutation tambaleante is caused by the Gly483Glu substitution in the highly conserved N terminal RCC1-like domain of the HERC1 protein, which leads to the increase of mutated protein levels responsible for cerebellar Purkinje cell death by autophagy. Until now, Purkinje cells have been the only central nervous neurons reported as being targeted by the mutation, and their degeneration elicits an ataxic syndrome in adult mutant mice. However, the ultrastructural analysis performed here demonstrates that signs of autophagy, such as autophagosomes, lysosomes, and altered mitochondria, are present in neocortical pyramidal, CA3 hippocampal pyramidal, and spinal cord motor neurons. The main difference is that the reduction in the number of neurons affected in the tambaleante mutation in the neocortex, the hippocampus, and the spinal cord is not so evident as the dramatic loss of cerebellar Purkinje cells. Interestingly, signs of autophagy are absent in both interneurons and neuroglia cells. Affected neurons have in common that they are projection neurons which receive strong and varied synaptic inputs, and possess the highest degree of neuronal activity. Therefore, because the integrity of the ubiquitin-proteasome system is essential for protein degradation and, hence, for normal protein turnover, it could be hypothesized that the deleterious effects of the misrouting of these pathways would depend directly on the neuronal activity.

  20. Zinc-mediated transactivation of TrkB potentiates the hippocampal mossy fiber-CA3 pyramid synapse.

    Huang, Yang Z; Pan, Enhui; Xiong, Zhi-Qi; McNamara, James O

    2008-02-28

    The receptor tyrosine kinase, TrkB, is critical to diverse functions of the mammalian nervous system in health and disease. Evidence of TrkB activation during epileptogenesis in vivo despite genetic deletion of its prototypic neurotrophin ligands led us to hypothesize that a non-neurotrophin, the divalent cation zinc, can transactivate TrkB. We found that zinc activates TrkB through increasing Src family kinase activity by an activity-regulated mechanism independent of neurotrophins. One subcellular locale at which zinc activates TrkB is the postsynaptic density of excitatory synapses. Exogenous zinc potentiates the efficacy of the hippocampal mossy fiber (mf)-CA3 pyramid synapse by a TrkB-requiring mechanism. Long-term potentiation of this synapse is impaired by deletion of TrkB, inhibition of TrkB kinase activity, and by CaEDTA, a selective chelator of zinc. The activity-dependent activation of synaptic TrkB in a neurotrophin-independent manner provides a mechanism by which this receptor can regulate synaptic plasticity.

  1. Polarized spectra calculation and continuous wave laser operation of Yb-doped disordered Ca3La2(BO3)4 crystal

    Wang, Yeqing; Chen, Aixi; You, Zhenyu; Tu, Chaoyang

    2015-12-01

    A notable disorder crystal Yb:Ca3La2(BO3)4 crystal with Yb3+ ion doping concentration of 10 at.% was grown by the Czochralski method. The polarized absorption, polarized emission, and polarized gain cross sections were systematically calculated. The laser operations were investigated with Yb:Ca3La2(BO3)4 crystals cut along the a, b, and c crystallographic axes. The highest output power of 3.88 W was obtained by using the b-cut Yb:Ca3La2(BO3)4 crystal, with a slope efficiency of 62%. Additionally, it was confirmed that the output laser spectra were largely dependent on the output coupler.

  2. Polarized spectra calculation and continuous wave laser operation of Yb-doped disordered Ca3La2(BO3)4 crystal

    Wang, Yeqing; Chen, Aixi; You, Zhenyu; Tu, Chaoyang

    2015-01-01

    A notable disorder crystal Yb:Ca 3 La 2 (BO 3 ) 4 crystal with Yb 3+ ion doping concentration of 10 at.% was grown by the Czochralski method. The polarized absorption, polarized emission, and polarized gain cross sections were systematically calculated. The laser operations were investigated with Yb:Ca 3 La 2 (BO 3 ) 4 crystals cut along the a, b, and c crystallographic axes. The highest output power of 3.88 W was obtained by using the b-cut Yb:Ca 3 La 2 (BO 3 ) 4 crystal, with a slope efficiency of 62%. Additionally, it was confirmed that the output laser spectra were largely dependent on the output coupler. (paper)

  3. Structure determinations for Ca3Ti2O7, Ca4Ti3O10, Ca3.6Sr0.4Ti3O10 and a refinement of Sr3Ti2O7

    Elcombe, M.M.; Kisi, E.H.; Hawkins, K.D.; White, T.J.; Goodman, P.; Matheson, S.

    1991-01-01

    The structures of the orthorhombic Ruddlesden-Popper (A n+1 B n X 3n+1 ) phases Ca 3 Ti 2 O 7 (n=2) refined from neutron powder diffraction data at λ=1.893 A. They consist of coherent intergrowths of perovskite (CaTiO 3 ) blocks, n TiO 6 octahedra thick, with single layers of CaO having a distorted NaCl configuration. TiO 6 octahedra are tilted and distorted in a very similar fashion to those in CaTiO 3 (n=∞). This fact was used to determine the space groups of the layered structures. Convergent-beam electron diffraction patterns are best matched by calculations in the above space groups which are thus confirmed. Octahedral tilt angles increase slightly in the sequence n=2, 3, ∞. Strontium addition reduces the octahedral tilt angles because of preferential substitution of Sr on the Ca sites within the perovskite blocks of Ca 4 Ti 3 O 10 . The algorithm used to produce starting models for structure refinements is thought to be generally applicable to Ruddlesden-Popper and possibly other layered perovskite structures. It furnishes the predictions: (a) all n-even compounds in the Ca n+1 Ti n O 3n+1 series will have space group Ccm2 1 , (b) all n-odd compounds in this series will have space group Pcab, (c) all A n+1 B n X 3n+1 series for which the n=∞ end member (ABX 3 ) is isostructural with CaTiO 3 will be isostructural with the compounds reported above (e.g. Ca n+1 Zr n O 3n+1 ). (orig./WL)

  4. Ternary phosphates in Ca3(PO4)2-Na3Ln(PO4)2 (Ln-Nd, Eu, Er) systems

    Lazoryak, B.I.; Ivanov, L.N.; Strunenkova, T.V.; Golubev, V.N.; Viting, B.N.

    1990-01-01

    Ternary phosphates, formed in Ca 3 (PO 4 ) 2 -Na 3 Ln(PO 4 ) 2 (Ln-Nd, Eu, Er) systems were investigated by the methods of X-ray phase, luminescent analyses and IR spectroscopy. 5 regions of homogeneity were found. Two of them (I and II) were distinguished for all systems. Samples in the region of up to 14.285 mol.% Na 3 Ln(PO 4 ) 2 crystallize on the basis of β-Ca 3 (PO 4 ) 2 structure, and in other homogeneity regions - on the basis of β-K 2 SO 4 structure

  5. Improvement of the mechanical properties and corrosion resistance of biodegradable β-Ca3(PO4)2/Mg-Zn composites prepared by powder metallurgy: the adding β-Ca3(PO4)2, hot extrusion and aging treatment.

    Yan, Yang; Kang, Yijun; Li, Ding; Yu, Kun; Xiao, Tao; Deng, Youwen; Dai, Han; Dai, Yilong; Xiong, Hanqing; Fang, Hongjie

    2017-05-01

    In this study, 10%β-Ca 3 (PO 4 ) 2 /Mg-6%Zn (wt.%) composites with Mg-6%Zn alloy as control were prepared by powder metallurgy. After hot extrusion, the as-extruded composites were aged for 72h at 150°C. The effects of the adding β-Ca 3 (PO 4 ) 2 , hot extrusion and aging treatment on their microstructure, mechanical properties and corrosion resistance were investigated. The XRD results identified α-Mg, MgZn phase and β-Ca 3 (PO 4 ) 2 phase in these composites. After hot extrusion, grains were significantly refined, and the larger-sized β-Ca 3 (PO 4 ) 2 particles and coarse MgZn phases were broken into linear-distributed β-Ca 3 (PO 4 ) 2 and MgZn phases along the extrusion direction. After aging treatment, the elements of Zn, Ca, P and O presented a more homogeneous distribution. The compressive strengths of the β-Ca 3 (PO 4 ) 2 /Mg-Zn composites were approximately double those of natural bone, and their densities and elastic moduli matched those of natural bone. The immersion tests and electrochemical tests revealed that the adding β-Ca 3 (PO 4 ) 2 , hot extrusion and aging treatment could promote the formation of protective corrosion product layer on the sample surface in Ringer's solution, which improved corrosion resistance of the β-Ca 3 (PO 4 ) 2 /Mg-Zn composites. The XRD results indicated that the corrosion product layer contained Mg(OH) 2 , β-Ca 3 (PO 4 ) 2 and hydroxyapatite (HA). The cytotoxicity assessments showed the as-extruded β-Ca 3 (PO 4 ) 2 /Mg-Zn composite aged for 72h was harmless to L-929 cells. These results suggested that the β-Ca 3 (PO 4 ) 2 /Mg-Zn composites prepared by powder metallurgy were promising to be used for bone tissue engineering. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Snake representation of a superprocess in random environment

    Mytnik, Leonid; Xiong, Jie; Zeitouni, Ofer

    2011-01-01

    We consider (discrete time) branching particles in a random environment which is i.i.d. in time and possibly spatially correlated. We prove a representation of the limit process by means of a Brownian snake in random environment.

  7. Representation of Numerical and Non-Numerical Order in Children

    Berteletti, Ilaria; Lucangeli, Daniela; Zorzi, Marco

    2012-01-01

    The representation of numerical and non-numerical ordered sequences was investigated in children from preschool to grade 3. The child's conception of how sequence items map onto a spatial scale was tested using the Number-to-Position task (Siegler & Opfer, 2003) and new variants of the task designed to probe the representation of the alphabet…

  8. Anisomycin Injection in Area CA3 of the Hippocampus Impairs Both Short-Term and Long-Term Memories of Contextual Fear

    Remaud, Jessica; Ceccom, Johnatan; Carponcy, Julien; Dugué, Laura; Menchon, Gregory; Pech, Stéphane; Halley, Helene; Francés, Bernard; Dahan, Lionel

    2014-01-01

    Protein synthesis is involved in the consolidation of short-term memory into long-term memory. Previous electrophysiological data concerning LTP in CA3 suggest that protein synthesis in that region might also be necessary for short-term memory. We tested this hypothesis by locally injecting the protein synthesis inhibitor anisomycin in hippocampal…

  9. Effects of unpredictable chronic stress on behavior and brain-derived neurotrophic factor expression in CA3 subfield and dentate gyrus of the hippocampus in different aged rats.

    Li, Ying; Ji, Yong-juan; Jiang, Hong; Liu, De-xiang; Zhang, Qian; Fan, Shu-jian; Pan, Fang

    2009-07-05

    Brain-derived neurotrophic factor (BDNF) is a stress-responsive intercellular messenger modifying hypothalamic-pituitary-adrenal (HPA) axis activity. The interaction between stress and age in BDNF expression is currently not fully understood. This study was conducted to observe unpredictable stress effect on behavior and BDNF expression in CA3 subfield (CA3) and dentate gyrus of hippocampus in different aged rats. Forty-eight Wistar rats of two different ages (2 months and 15 months) were randomly assigned to six groups: two control groups and four stress groups. The rats in the stress group received three weeks of unpredictable mild stress. The depression state and the stress level of the animals were determined by sucrose preference test and observation of exploratory behavior in an open field (OF) test. The expressions of BDNF in CA3 and dentate gyrus of the hippocampus were measured using immunohistochemistry. Age and stress had different effects on the behavior of different aged animals (age: F = 6.173, P BDNF expression in the CA3 and dentate gyrus regions of the hippocampus following stress in both age groups (P BDNF (F = 9.408, P BDNF expression compared to the young stressed group at every testing time point. Stress has age-dependent effects on behavioral responses and hippocampal BDNF expression in rats.

  10. Photoluminescence Properties of Red-Emitting Ca3Sr3-x(PO4)4:xEu3+ Phosphors for White Light-Emitting Diodes.

    Hakeem, D A; Park, K

    2015-07-01

    The photoluminescent properties of the Eu(3+)-activated Ca3Sr3(PO4)4 phosphors prepared by a solution combustion method were investigated. The excitation spectra of Ca3Sr3-x(PO4)4:xEu3+ (0.05 ≤ x ≤ 0.6) phosphors under 614 nm wavelength showed a broad band centered at 266 nm along with other peaks at 320, 362, 381, 394, 414, 464, and 534 nm. The emission spectra observed in the range of 450 to 750 nm under excitation at 394 nm were ascribed to the 5D0-7F1-4 transitions of Eu3+ ions. The Ca3Sr3-x(PO4)4:xEu3+ phosphors showed the strongest red emission at 614 nm due to the electric dipole 5DO -->7F2 transition of Eu3+. The strongest emission intensity was obtained for the Eu3+ ions of x = 0.5. The prepared Ca3Sr3-x(PO4)4:xEu3+ can be used as an efficient red phosphor for UV-based white LEDs.

  11. Understanding representations in design

    Bødker, Susanne

    1998-01-01

    Representing computer applications and their use is an important aspect of design. In various ways, designers need to externalize design proposals and present them to other designers, users, or managers. This article deals with understanding design representations and the work they do in design....... The article is based on a series of theoretical concepts coming out of studies of scientific and other work practices and on practical experiences from design of computer applications. The article presents alternatives to the ideas that design representations are mappings of present or future work situations...... and computer applications. It suggests that representations are primarily containers of ideas and that representation is situated at the same time as representations are crossing boundaries between various design and use activities. As such, representations should be carriers of their own contexts regarding...

  12. Prenatal nicotine and maternal deprivation stress de-regulate the development of CA1, CA3, and dentate gyrus neurons in hippocampus of infant rats.

    Hong Wang

    Full Text Available Adverse experiences by the developing fetus and in early childhood are associated with profound effects on learning, emotional behavior, and cognition as a whole. In this study we investigated the effects of prenatal nicotine exposure (NIC, postnatal maternal deprivation (MD or the combination of the two (NIC+MD to determine if hippocampal neuron development is modulated by exposure to drugs of abuse and/or stress. Growth of rat offspring exposed to MD alone or NIC+MD was repressed until after weaning. In CA1 but not CA3 of postnatal day 14 (P14 pups, MD increased pyramidal neurons, however, in dentate gyrus (DG, decreased granule neurons. NIC had no effect on neuron number in CA1, CA3 or DG. Unexpectedly, NIC plus MD combined caused a synergistic increase in the number of CA1 or CA3 neurons. Neuron density in CA regions was unaffected by treatment, but in the DG, granule neurons had a looser packing density after NIC, MD or NIC+MD exposure. When septotemporal axes were analyzed, the synergism of stress and drug exposure in CA1 and CA3 was associated with rostral, whereas MD effects were predominantly associated with caudal neurons. TUNEL labeling suggests no active apoptosis at P14, and doublecortin positive neurons and mossy fibers were diminished in NIC+MD relative to controls. The laterality of the effect of nicotine and/or maternal deprivation in right versus left hippocampus was also analyzed and found to be insiginificant. We report for the first time that early life stressors such as postnatal MD and prenatal NIC exposure, when combined, may exhibit synergistic consequences for CA1 and CA3 pyramidal neuron development, and a potential antagonistic influence on developing DG neurons. These results suggest that early stressors may modulate neurogenesis, apoptosis, or maturation of glutamatergic neurons in the hippocampus in a region-specific manner during critical periods of neurodevelopment.

  13. Tricolor emission Ca3Si2O7:Ln (Ln=Ce, Tb, Eu) phosphors for near-UV white light-emitting-diode

    Mao, Zhi-yong; Zhu, Ying-chun; Gan, Lin; Zeng, Yi; Xu, Fang-fang; Wang, Yang; Tian, Hua; Li, Jian; Wang, Da-jian

    2013-01-01

    Tricolor emission in a same Ca 3 Si 2 O 7 host with independent Ln (Ln=Ce 3+ , Eu 2+ , Tb 3+ ) dopants is demonstrated to construct a near-UV white light emitting diode (LED). The luminescence properties and thermal quenching properties, as well as the applications in near-UV white LED are investigated. These phosphors show typical blue, red, and green, three-basal-color, luminescence in the CIE chromaticity diagram for Ce 3+ , Eu 2+ and Tb 3+ dopants, respectively. Thermal quenching properties show that the luminescence thermal stability strongly depends on the different dopant types; better thermal quenching property of Ce 3+ and Tb 3+ is recorded in comparison with that of Eu 2+ . The white LED prototype fabricated with near-UV chip and as-prepared tricolor phosphors exhibits acceptable CIE chromaticity coordinates (0.32, 0.30) with a CCT of 6000 K and a CRI of 87, indicating the potential application of Ca 3 Si 2 O 7 :Ln phosphors in near-UV white LED. - Highlights: ► Tricolor Ca 3 Si 2 O 7 : Ln phosphors were demonstrated to construct near-UV white LED. ► Eu 2+ doped Ca 3 Si 2 O 7 red-emitting phosphor was confirmed by this work once again. ► Thermal quenching properties for Ca 3 Si 2 O 7 :Ln phosphors were reported for the first time. ► Performances of fabricated white LED indicated the potential application of phosphors.

  14. Sustained increase of spontaneous input and spike transfer in the CA3-CA1 pathway following long term potentiation in vivo

    Oscar eHerreras

    2012-10-01

    Full Text Available Long term potentiation (LTP is commonly used to study synaptic plasticity but the associated changes in the spontaneous activity of individual neurons or the computational properties of neural networks in vivo remain largely unclear. The multisynaptic origin of spontaneous spikes makes difficult estimating the impact of a particular potentiated input. Accordingly, we adopted an approach that isolates pathway-specific postsynaptic activity from raw local field potentials (LFPs in the rat hippocampus in order to study the effects of LTP on ongoing spike transfer between cell pairs in the CA3-CA1 pathway. CA1 Schaffer-specific LFPs elicited by spontaneous clustered firing of CA3 pyramidal cells involved a regular succession of elementary micro-field-EPSPs (gamma-frequency that fired spikes in CA1 units. LTP increased the amplitude but not the frequency of these ongoing excitatory quanta. Also, the proportion of Schaffer-driven spikes in both CA1 pyramidal cells and interneurons increased in a cell-specific manner only in previously connected CA3-CA1 cell pairs, i.e., when the CA3 pyramidal cell had shown pre-LTP significant correlation with firing of a CA1 unit and potentiated spike-triggered average of Schaffer LFPs following LTP. Moreover, LTP produced subtle reorganization of presynaptic CA3 cell assemblies. These findings show effective enhancement of pathway specific ongoing activity which leads to increased spike transfer in potentiated segments of a network. These indicate that plastic phenomena induced by external protocols may intensify spontaneous information flow across specific channels as proposed in transsynaptic propagation of plasticity and synfire chain hypotheses that may be the substrate for different types of memory involving multiple brain structures.

  15. Embedded data representations

    Willett, Wesley; Jansen, Yvonne; Dragicevic, Pierre

    2017-01-01

    We introduce embedded data representations, the use of visual and physical representations of data that are deeply integrated with the physical spaces, objects, and entities to which the data refers. Technologies like lightweight wireless displays, mixed reality hardware, and autonomous vehicles...

  16. Spatiotemporal representation of cardiac vectorcardiogram (VCG signals

    Yang Hui

    2012-03-01

    Full Text Available Abstract Background Vectorcardiogram (VCG signals monitor both spatial and temporal cardiac electrical activities along three orthogonal planes of the body. However, the absence of spatiotemporal resolution in conventional VCG representations is a major impediment for medical interpretation and clinical usage of VCG. This is especially so because time-domain features of 12-lead ECG, instead of both spatial and temporal characteristics of VCG, are widely used for the automatic assessment of cardiac pathological patterns. Materials and methods We present a novel representation approach that captures critical spatiotemporal heart dynamics by displaying the real time motion of VCG cardiac vectors in a 3D space. Such a dynamic display can also be realized with only one lead ECG signal (e.g., ambulatory ECG through an alternative lag-reconstructed ECG representation from nonlinear dynamics principles. Furthermore, the trajectories are color coded with additional dynamical properties of space-time VCG signals, e.g., the curvature, speed, octant and phase angles to enhance the information visibility. Results In this investigation, spatiotemporal VCG signal representation is used to characterize various spatiotemporal pathological patterns for healthy control (HC, myocardial infarction (MI, atrial fibrillation (AF and bundle branch block (BBB. The proposed color coding scheme revealed that the spatial locations of the peak of T waves are in the Octant 6 for the majority (i.e., 74 out of 80 of healthy recordings in the PhysioNet PTB database. In contrast, the peak of T waves from 31.79% (117/368 of MI subjects are found to remain in Octant 6 and the rest (68.21% spread over all other octants. The spatiotemporal VCG signal representation is shown to capture the same important heart characteristics as the 12-lead ECG plots and more. Conclusions Spatiotemporal VCG signal representation is shown to facilitate the characterization of space-time cardiac

  17. Group and representation theory

    Vergados, J D

    2017-01-01

    This volume goes beyond the understanding of symmetries and exploits them in the study of the behavior of both classical and quantum physical systems. Thus it is important to study the symmetries described by continuous (Lie) groups of transformations. We then discuss how we get operators that form a Lie algebra. Of particular interest to physics is the representation of the elements of the algebra and the group in terms of matrices and, in particular, the irreducible representations. These representations can be identified with physical observables. This leads to the study of the classical Lie algebras, associated with unitary, unimodular, orthogonal and symplectic transformations. We also discuss some special algebras in some detail. The discussion proceeds along the lines of the Cartan-Weyl theory via the root vectors and root diagrams and, in particular, the Dynkin representation of the roots. Thus the representations are expressed in terms of weights, which are generated by the application of the elemen...

  18. Introduction to representation theory

    Etingof, Pavel; Hensel, Sebastian; Liu, Tiankai; Schwendner, Alex

    2011-01-01

    Very roughly speaking, representation theory studies symmetry in linear spaces. It is a beautiful mathematical subject which has many applications, ranging from number theory and combinatorics to geometry, probability theory, quantum mechanics, and quantum field theory. The goal of this book is to give a "holistic" introduction to representation theory, presenting it as a unified subject which studies representations of associative algebras and treating the representation theories of groups, Lie algebras, and quivers as special cases. Using this approach, the book covers a number of standard topics in the representation theories of these structures. Theoretical material in the book is supplemented by many problems and exercises which touch upon a lot of additional topics; the more difficult exercises are provided with hints. The book is designed as a textbook for advanced undergraduate and beginning graduate students. It should be accessible to students with a strong background in linear algebra and a basic k...

  19. Covariant representations of nuclear *-algebras

    Moore, S.M.

    1978-01-01

    Extensions of the Csup(*)-algebra theory for covariant representations to nuclear *-algebra are considered. Irreducible covariant representations are essentially unique, an invariant state produces a covariant representation with stable vacuum, and the usual relation between ergodic states and covariant representations holds. There exist construction and decomposition theorems and a possible relation between derivations and covariant representations

  20. Profile of biology prospective teachers’ representation on plant anatomy learning

    Ermayanti; Susanti, R.; Anwar, Y.

    2018-04-01

    This study aims to obtaining students’ representation ability in understanding the structure and function of plant tissues in plant anatomy course. Thirty students of The Biology Education Department of Sriwijaya University were involved in this study. Data on representation ability were collected using test and observation. The instruments had been validated by expert judgment. Test scores were used to represent students’ ability in 4 categories: 2D-image, 3D-image, spatial, and verbal representations. The results show that students’ representation ability is still low: 2D-image (40.0), 3D-image (25.0), spatial (20.0), and verbal representation (45.0). Based on the results of this study, it is suggested that instructional strategies be developed for plant anatomy course.

  1. Synaptic Remodeling in the Dentate Gyrus, CA3, CA1, Subiculum, and Entorhinal Cortex of Mice: Effects of Deprived Rearing and Voluntary Running

    Andrea T. U. Schaefers

    2010-01-01

    Full Text Available Hippocampal cell proliferation is strongly increased and synaptic turnover decreased after rearing under social and physical deprivation in gerbils (Meriones unguiculatus. We examined if a similar epigenetic effect of rearing environment on adult neuroplastic responses can be found in mice (Mus musculus. We examined synaptic turnover rates in the dentate gyrus, CA3, CA1, subiculum, and entorhinal cortex. No direct effects of deprived rearing on rates of synaptic turnover were found in any of the studied regions. However, adult wheel running had the effect of leveling layer-specific differences in synaptic remodeling in the dentate gyrus, CA3, and CA1, but not in the entorhinal cortex and subiculum of animals of both rearing treatments. Epigenetic effects during juvenile development affected adult neural plasticity in mice, but seemed to be less pronounced than in gerbils.

  2. Characterization of the interface between an Fe–Cr alloy and the p-type thermoelectric oxide Ca3Co4O9

    Holgate, Tim; Han, Li; Wu, NingYu

    2014-01-01

    A customized Fe–Cr alloy that has been optimized for high temperature applications in oxidizing atmospheres has been interfaced via spark plasma sintering (SPS) with a p-type thermoelectric oxide material: calcium cobaltate (Ca3Co4O9). The properties of the alloy have been analyzed for its...... calcium and chromium in the interface that is highly resistive at room temperature, but conducting at the intended thermoelectric device hot-side operating temperature of 800 °C. As the alloy is well matched in terms of its thermal expansion and highly conducting compared to the Ca3Co4O9, it may...... be further considered as an interconnect material candidate at least with application on the hot-side of an oxide thermoelectric power generation module....

  3. Growth, thermal properties and laser operation of a novel disordered Yb:Ca3La2(BO3)4 laser crystal

    Pan, Zhongben; Cai, Huaqiang; Huang, Hui; Yu, Haohai; Zhang, Huaijin; Wang, Jiyang

    2014-10-01

    A high quality disordered Yb:Ca3La2(BO3)4 laser crystal has been successfully grown by the Czochralski method. The complete set of anisotropic thermal properties were systematically measured for the first time. In addition, continuous-wave laser along the three crystallographic axis were obtained. Passively Q-switched by a Cr4+:YAG saturable absorber, the laser yielded an average output power of 0.47 W with a slope efficiency of 7.6% for the first time. The generated pulse energy, duration, and peak power were 94 μJ, 33 ns, and 2.85 KW, respectively. We believe that the reliability and stability of these lasers makes the disordered Yb:Ca3La2(BO3)4 crystal of considerable interest for future applications.

  4. Stability of the geometrically frustrated magnetic state of Ca3CoRhO6 to applications of positive and negative pressure

    Mohapatra, Niharika; Iyer, Kartik K; Jammalamadaka, S Narayana; Sampathkumaran, E V; Rayaprol, Sudhindra

    2008-01-01

    The influence of negative chemical pressure induced by gradual replacement of Ca by Sr as well as of external pressure (up to 10 kbar) on the magnetism of Ca 3 CoRhO 6 has been investigated by magnetization studies. It is found that the solid solution, Ca 3-x Sr x CoRhO 6 , exists at least until about x = 1.0 without any change in the crystal structure. Apart from insensitivity of the spin-chain feature to volume expansion, the characteristic features of geometrical frustration interestingly appear at the same temperatures for all compositions, in sharp contrast to the response to Y substitution for Ca (reported previously). Interestingly, the huge frequency dependence of ac susceptibility known for the parent compound persists for all compositions. We do not find a change in the properties under external pressure. The stability of the magnetic anomalies of this compound to volume change (about 4%) is puzzling

  5. Ca3Co4O9+δ, a growing potential SOFC cathode material: impact of the layer composition and thickness on the electrochemical properties

    Rolle, A.; Abbas, H.A.A.; Huo, D.; Capoen, E.; Mentré, O.; Vannier, R.N.; Daviero-Minaud, S.; Boukamp, Bernard A.

    2016-01-01

    The thermoelectric material Ca3Co4O9 + δ (CCO), with an electronic conductivity of σe = 240 S·cm− 1 at 650 °C and a good chemical and mechanical compatibility with the standard Ce0.9Gd0.1O1.95 electrolyte (CGO, TEC: 9–10 · 10− 6 K− 1), was recently identified as a potential cathode material for

  6. Crystal and magnetic structure of the Ca3Mn2O7 Ruddlesden-Popper phase: neutron and synchrotron x-ray diffraction study

    Lobanov, Maxim V; Greenblatt, Martha; Caspi, El'ad N; Jorgensen, James D; Sheptyakov, Denis V; Toby, Brian H; Botez, Cristian E; Stephens, Peter W

    2004-01-01

    The crystallographic and magnetic structures of Ca 3 Mn 2 O 7 Ruddlesden-Popper phase have been determined by a combination of neutron and synchrotron x-ray diffraction. Two-phase behaviour observed at room temperature is attributed to an incomplete structural phase transition. The magnetic structure was solved in the Cm'c2 1 ' Shubnikov group with dominant G-type antiferromagnetic order in the perovskite bilayers. The temperature evolution of the structural and magnetic parameters is presented

  7. Effect of acetylcholine receptors on the pain-related electrical activities in the hippocampal CA3 region of morphine-addicted rats

    Li, Guan Zeng; Liu, Zhe Hui; Wei, XinYa; Zhao, Pan; Yang, Chun Xiao; Xu, Man Ying

    2015-01-01

    Objective(s): To determine the effect of acetylcholine (ACh), pilocarpine, and atropine on pain evoked responses of pain excited neurons (PEN) and pain inhibited neurons (PIN) in hippocampal CA3 region of morphine addicted rats. Materials and Methods: Female Wistar rats, weighing between 230-260 g were used in this study. Morphine addicted rats were generated by subcutaneous injection of increasing concentrations of morphine hydrochloride for six days. Trains of electrical impulses applied to...

  8. Evidence for a Specific Integrative Mechanism for Episodic Memory Mediated by AMPA/kainate Receptors in a Circuit Involving Medial Prefrontal Cortex and Hippocampal CA3 Region.

    de Souza Silva, Maria A; Huston, Joseph P; Wang, An-Li; Petri, David; Chao, Owen Yuan-Hsin

    2016-07-01

    We asked whether episodic-like memory requires neural mechanisms independent of those that mediate its component memories for "what," "when," and "where," and if neuronal connectivity between the medial prefrontal cortex (mPFC) and the hippocampus (HPC) CA3 subregion is essential for episodic-like memory. Unilateral lesion of the mPFC was combined with unilateral lesion of the CA3 in the ipsi- or contralateral hemispheres in rats. Episodic-like memory was tested using a task, which assesses the integration of memories for "what, where, and when" concomitantly. Tests for novel object recognition (what), object place (where), and temporal order memory (when) were also applied. Bilateral disconnection of the mPFC-CA3 circuit by N-methyl-d-aspartate (NMDA) lesions disrupted episodic-like memory, but left the component memories for object, place, and temporal order, per se, intact. Furthermore, unilateral NMDA lesion of the CA3 plus injection of (6-cyano-7-nitroquinoxaline-2,3-dione) (CNQX) (AMPA/kainate receptor antagonist), but not AP-5 (NMDA receptor antagonist), into the contralateral mPFC also disrupted episodic-like memory, indicating the mPFC AMPA/kainate receptors as critical for this circuit. These results argue for a selective neural system that specifically subserves episodic memory, as it is not critically involved in the control of its component memories for object, place, and time. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  9. The GLP-1 Receptor Agonist Exendin-4 and Diazepam Differentially Regulate GABAA Receptor-Mediated Tonic Currents in Rat Hippocampal CA3 Pyramidal Neurons.

    Sergiy V Korol

    Full Text Available Glucagon-like peptide-1 (GLP-1 is a metabolic hormone that is secreted in a glucose-dependent manner and enhances insulin secretion. GLP-1 receptors are also found in the brain where their signalling affects neuronal activity. We have previously shown that the GLP-1 receptor agonists, GLP-1 and exendin-4 enhanced GABA-activated synaptic and tonic currents in rat hippocampal CA3 pyramidal neurons. The hippocampus is the centre for memory and learning and is important for cognition. Here we examined if exendin-4 similarly enhanced the GABA-activated currents in the presence of the benzodiazepine diazepam. In whole-cell recordings in rat brain slices, diazepam (1 μM, an allosteric positive modulator of GABAA receptors, alone enhanced the spontaneous inhibitory postsynaptic current (sIPSC amplitude and frequency by a factor of 1.3 and 1.6, respectively, and doubled the tonic GABAA current normally recorded in the CA3 pyramidal cells. Importantly, in the presence of exendin-4 (10 nM plus diazepam (1 μM, only the tonic but not the sIPSC currents transiently increased as compared to currents recorded in the presence of diazepam alone. The results suggest that exendin-4 potentiates a subpopulation of extrasynaptic GABAA receptors in the CA3 pyramidal neurons.

  10. XAFS Analysis of Local Structure around Ce in Ca3Sc2Si3O12:Ce Phosphor for White LEDs

    Akai, Toshio; Shigeiwa, Motoyuki; Okamoto, Kaoru; Shimomura, Yasuo; Kijima, Naoto; Honma, Tetsuo

    2007-01-01

    We have studied the local structure around Ce atom in Ca3Sc2Si3O12 host crystal, which has been developed as a new green phosphor for white light emitting diodes (LEDs). As the local structure and chemical environment of the dopant atom are very important to improve the performance of the phosphor, we have used XAFS to get chemical and structural information around the Ce dopant. The XANES spectrum of the Ce LIII-edge reveals that the Ce atom is trivalent in Ca3Sc2Si3O12. There are two kinds of possible Ce substitution sites, Ca site and Sc site, in garnet type Ca3Sc2Si3O12 crystal structure. The Ce atom is found to be at the Ca site in the host crystal by the comparison of the Fourier transform of Ce K-edge EXAFS spectrum with those of Ca and Sc K-edge EXAFS spectra. The theoretical analysis with FEFF also clarified the Ce substitution at the Ca site. Furthermore, the result of the analysis indicates the structural disorder around Ca and Si atoms at 3.75 A. It is possible that there are some defects around the Ca and Si atoms at 3.75 A to compensate the excess positive charge by introduced Ce3+ at the Ca2+ site

  11. Imaging a memory trace over half a life-time in the medial temporal lobe reveals a time-limited role of CA3 neurons in retrieval

    Lux, Vanessa; Atucha, Erika; Kitsukawa, Takashi; Sauvage, Magdalena M

    2016-01-01

    Whether retrieval still depends on the hippocampus as memories age or relies then on cortical areas remains a major controversy. Despite evidence for a functional segregation between CA1, CA3 and parahippocampal areas, their specific role within this frame is unclear. Especially, the contribution of CA3 is questionable as very remote memories might be too degraded to be used for pattern completion. To identify the specific role of these areas, we imaged brain activity in mice during retrieval of recent, early remote and very remote fear memories by detecting the immediate-early gene Arc. Investigating correlates of the memory trace over an extended period allowed us to report that, in contrast to CA1, CA3 is no longer recruited in very remote retrieval. Conversely, we showed that parahippocampal areas are then maximally engaged. These results suggest a shift from a greater contribution of the trisynaptic loop to the temporoammonic pathway for retrieval. DOI: http://dx.doi.org/10.7554/eLife.11862.001 PMID:26880561

  12. Revising the Subsystem Nurse’s A-Phase-Silicocarnotite within the System Ca3(PO42–Ca2SiO4

    Patricia Ros-Tárraga

    2016-04-01

    Full Text Available The subsystem Nurse’s A-phase-silicocarnotite within the system Ca3(PO42–Ca2SiO4 was conducted as a preliminary step toward obtaining new biomaterials with controlled microstructures. Phase composition of the resulting ceramics was studied by X-ray diffraction, differential thermal analysis, and scanning electron microscopy with attached wavelength dispersive spectroscopy. The results showed that the sub-system presents an invariant eutectoid point at 1366 ± 4 °C with a composition of 59.5 wt % Ca3(PO42 and 40.5 wt % Ca2SiO4, and typical eutectoid microstructure of lamellae morphology. These results are in disagreement with the previous reported data, which locate the invariant eutectoid point at 1250 ± 20 °C with a composition of 55 wt % Ca3(PO42 and 45 wt % Ca2SiO4. In addition, cell attachment testing showed that the new eutectoid material supported the mesenchymal stem cell adhesion and spreading, and the cells established close contact with the ceramic after 28 days of culture. These findings indicate that the new ceramic material with eutectoid microstructure of lamellae morphology possesses good bioactivity and biocompatibility and might be a promising bone implant material.

  13. NMDA Signaling in CA1 Mediates Selectively the Spatial Component of Episodic Memory

    Place, Ryan; Lykken, Christy; Beer, Zachery; Suh, Junghyup; McHugh, Thomas J.; Tonegawa, Susumu; Eichenbaum, Howard; Sauvage, Magdalena M.

    2012-01-01

    Recent studies focusing on the memory for temporal order have reported that CA1 plays a critical role in the memory for the sequences of events, in addition to its well-described role in spatial navigation. In contrast, CA3 was found to principally contribute to the memory for the association of items with spatial or contextual information in…

  14. Representations and Relations

    Koťátko, Petr

    2014-01-01

    Roč. 21, č. 3 (2014), s. 282-302 ISSN 1335-0668 Institutional support: RVO:67985955 Keywords : representation * proposition * truth-conditions * belief-ascriptions * reference * externalism * fiction Subject RIV: AA - Philosophy ; Religion

  15. Wigner's Symmetry Representation Theorem

    Home; Journals; Resonance – Journal of Science Education; Volume 19; Issue 10. Wigner's Symmetry Representation Theorem: At the Heart of Quantum Field Theory! Aritra Kr Mukhopadhyay. General Article Volume 19 Issue 10 October 2014 pp 900-916 ...

  16. Boundary representation modelling techniques

    2006-01-01

    Provides the most complete presentation of boundary representation solid modelling yet publishedOffers basic reference information for software developers, application developers and users Includes a historical perspective as well as giving a background for modern research.

  17. Polynomial representations of GLn

    Green, James A; Erdmann, Karin

    2007-01-01

    The first half of this book contains the text of the first edition of LNM volume 830, Polynomial Representations of GLn. This classic account of matrix representations, the Schur algebra, the modular representations of GLn, and connections with symmetric groups, has been the basis of much research in representation theory. The second half is an Appendix, and can be read independently of the first. It is an account of the Littelmann path model for the case gln. In this case, Littelmann's 'paths' become 'words', and so the Appendix works with the combinatorics on words. This leads to the repesentation theory of the 'Littelmann algebra', which is a close analogue of the Schur algebra. The treatment is self- contained; in particular complete proofs are given of classical theorems of Schensted and Knuth.

  18. Polynomial representations of GLN

    Green, James A

    1980-01-01

    The first half of this book contains the text of the first edition of LNM volume 830, Polynomial Representations of GLn. This classic account of matrix representations, the Schur algebra, the modular representations of GLn, and connections with symmetric groups, has been the basis of much research in representation theory. The second half is an Appendix, and can be read independently of the first. It is an account of the Littelmann path model for the case gln. In this case, Littelmann's 'paths' become 'words', and so the Appendix works with the combinatorics on words. This leads to the repesentation theory of the 'Littelmann algebra', which is a close analogue of the Schur algebra. The treatment is self- contained; in particular complete proofs are given of classical theorems of Schensted and Knuth.

  19. Loss of protohaem IX farnesyltransferase in mature dentate granule cells impairs short-term facilitation at mossy fibre to CA3 pyramidal cell synapses.

    Booker, Sam A; Campbell, Graham R; Mysiak, Karolina S; Brophy, Peter J; Kind, Peter C; Mahad, Don J; Wyllie, David J A

    2017-03-15

    Neurodegenerative disorders can exhibit dysfunctional mitochondrial respiratory chain complex IV activity. Conditional deletion of cytochrome c oxidase, the terminal enzyme in the respiratory electron transport chain of mitochondria, from hippocampal dentate granule cells in mice does not affect low-frequency dentate to CA3 glutamatergic synaptic transmission. High-frequency dentate to CA3 glutamatergic synaptic transmission and feedforward inhibition are significantly attenuated in cytochrome c oxidase-deficient mice. Intact presynaptic mitochondrial function is critical for the short-term dynamics of mossy fibre to CA3 synaptic function. Neurodegenerative disorders are characterized by peripheral and central symptoms including cognitive impairments which have been associated with reduced mitochondrial function, in particular mitochondrial respiratory chain complex IV or cytochrome c oxidase activity. In the present study we conditionally removed a key component of complex IV, protohaem IX farnesyltransferase encoded by the COX10 gene, in granule cells of the adult dentate gyrus. Utilizing whole-cell patch-clamp recordings from morphologically identified CA3 pyramidal cells from control and complex IV-deficient mice, we found that reduced mitochondrial function did not result in overt deficits in basal glutamatergic synaptic transmission at the mossy-fibre synapse because the amplitude, input-output relationship and 50 ms paired-pulse facilitation were unchanged following COX10 removal from dentate granule cells. However, trains of stimuli given at high frequency (> 20 Hz) resulted in dramatic reductions in short-term facilitation and, at the highest frequencies (> 50 Hz), also reduced paired-pulse facilitation, suggesting a requirement for adequate mitochondrial function to maintain glutamate release during physiologically relevant activity patterns. Interestingly, local inhibition was reduced, suggesting the effect observed was not restricted to synapses

  20. Procedural Media Representation

    Henrysson, Anders

    2002-01-01

    We present a concept for using procedural techniques to represent media. Procedural methods allow us to represent digital media (2D images, 3D environments etc.) with very little information and to render it photo realistically. Since not all kind of content can be created procedurally, traditional media representations (bitmaps, polygons etc.) must be used as well. We have adopted an object-based media representation where an object can be represented either with a procedure or with its trad...

  1. Sparse Representations of Hyperspectral Images

    Swanson, Robin J.

    2015-01-01

    Hyperspectral image data has long been an important tool for many areas of sci- ence. The addition of spectral data yields significant improvements in areas such as object and image classification, chemical and mineral composition detection, and astronomy. Traditional capture methods for hyperspectral data often require each wavelength to be captured individually, or by sacrificing spatial resolution. Recently there have been significant improvements in snapshot hyperspectral captures using, in particular, compressed sensing methods. As we move to a compressed sensing image formation model the need for strong image priors to shape our reconstruction, as well as sparse basis become more important. Here we compare several several methods for representing hyperspectral images including learned three dimensional dictionaries, sparse convolutional coding, and decomposable nonlocal tensor dictionaries. Addi- tionally, we further explore their parameter space to identify which parameters provide the most faithful and sparse representations.

  2. Sparse Representations of Hyperspectral Images

    Swanson, Robin J.

    2015-11-23

    Hyperspectral image data has long been an important tool for many areas of sci- ence. The addition of spectral data yields significant improvements in areas such as object and image classification, chemical and mineral composition detection, and astronomy. Traditional capture methods for hyperspectral data often require each wavelength to be captured individually, or by sacrificing spatial resolution. Recently there have been significant improvements in snapshot hyperspectral captures using, in particular, compressed sensing methods. As we move to a compressed sensing image formation model the need for strong image priors to shape our reconstruction, as well as sparse basis become more important. Here we compare several several methods for representing hyperspectral images including learned three dimensional dictionaries, sparse convolutional coding, and decomposable nonlocal tensor dictionaries. Addi- tionally, we further explore their parameter space to identify which parameters provide the most faithful and sparse representations.

  3. Knowledge representation and use. II. Representations

    Lauriere, J L

    1982-03-01

    The use of computers is less and less restricted to numerical and data processing. On the other hand, current software mostly contains algorithms on universes with complete information. The paper discusses a different family of programs: expert systems are designed as aids in human reasoning in various specific areas. Symbolic knowledge manipulation, uncertain and incomplete deduction capabilities, natural communication with humans in non-procedural ways are their essential features. This part is mainly a reflection and a debate about the various modes of acquisition and representation of human knowledge. 32 references.

  4. Spatially Resolved Artificial Chemistry

    Fellermann, Harold

    2009-01-01

    Although spatial structures can play a crucial role in chemical systems and can drastically alter the outcome of reactions, the traditional framework of artificial chemistry is a well-stirred tank reactor with no spatial representation in mind. Advanced method development in physical chemistry has...... made a class of models accessible to the realms of artificial chemistry that represent reacting molecules in a coarse-grained fashion in continuous space. This chapter introduces the mathematical models of Brownian dynamics (BD) and dissipative particle dynamics (DPD) for molecular motion and reaction...

  5. Spatially Resolved Artificial Chemistry

    Fellermann, Harold

    2009-01-01

    made a class of models accessible to the realms of artificial chemistry that represent reacting molecules in a coarse-grained fashion in continuous space. This chapter introduces the mathematical models of Brownian dynamics (BD) and dissipative particle dynamics (DPD) for molecular motion and reaction......Although spatial structures can play a crucial role in chemical systems and can drastically alter the outcome of reactions, the traditional framework of artificial chemistry is a well-stirred tank reactor with no spatial representation in mind. Advanced method development in physical chemistry has...

  6. Operator representations of frames

    Christensen, Ole; Hasannasab, Marzieh

    2017-01-01

    of the properties of the operator T requires more work. For example it is a delicate issue to obtain a representation with a bounded operator, and the availability of such a representation not only depends on the frame considered as a set, but also on the chosen indexing. Using results from operator theory we show......The purpose of this paper is to consider representations of frames {fk}k∈I in a Hilbert space ℋ of the form {fk}k∈I = {Tkf0}k∈I for a linear operator T; here the index set I is either ℤ or ℒ0. While a representation of this form is available under weak conditions on the frame, the analysis...... that by embedding the Hilbert space ℋ into a larger Hilbert space, we can always represent a frame via iterations of a bounded operator, composed with the orthogonal projection onto ℋ. The paper closes with a discussion of an open problem concerning representations of Gabor frames via iterations of a bounded...

  7. Effect of pertussis and cholera toxins administered supraspinally on CA3 hippocampal neuronal cell death and the blood glucose level induced by kainic acid in mice.

    Kim, Chea-Ha; Park, Soo-Hyun; Sim, Yun-Beom; Sharma, Naveen; Kim, Sung-Su; Lim, Su-Min; Jung, Jun-Sub; Suh, Hong-Won

    2014-12-01

    The effect of cholera toxin (CTX) or pertussis toxin (PTX) administered supraspinally on hippocampal neuronal cell death in CA3 region induced by kainic acid (KA) was examined in mice. After the pretreatment with either PTX or CTX intracerebroventricularly (i.c.v.), mice were administered i.c.v. with KA. The i.c.v. treatment with KA caused a neuronal cell death in CA3 region and PTX, but not CTX, attenuated the KA-induced neuronal cell death. In addition, i.c.v. treatment with KA caused an elevation of the blood glucose level. The i.c.v. PTX pretreatment alone caused a hypoglycemia and inhibited KA-induced hyperglycemic effect. However, i.c.v. pretreatment with CTX did not affect the basal blood glucose level and KA-induced hyperglycemic effect. Moreover, KA administered i.c.v. caused an elevation of corticosterone level and reduction of the blood insulin level. Whereas, i.c.v. pretreatment with PTX further enhanced KA-induced up-regulation of corticosterone level. Furthermore, i.c.v. administration of PTX alone increased the insulin level and KA-induced hypoinsulinemic effect was reversed. In addition, PTX pretreatment reduces the KA-induced seizure activity. Our results suggest that supraspinally administered PTX, exerts neuroprotective effect against KA-induced neuronal cells death in CA3 region and neuroprotective effect of PTX is mediated by the reduction of KA-induced blood glucose level. Copyright © 2014 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.

  8. Spontaneous release from mossy fiber terminals inhibits Ni2+-sensitive T-type Ca2+ channels of CA3 pyramidal neurons in the rat organotypic hippocampal slice.

    Reid, Christopher A; Xu, Shenghong; Williams, David A

    2008-01-01

    Mossy fibers (axons arising from dentate granule cells) form large synaptic contacts exclusively onto the proximal apical dendrites of CA3 pyramidal neurons. They can generate large synaptic currents that occur in close proximity to the soma. These properties mean that active conductance in the proximal apical dendrite could have a disproportionate influence on CA3 pyramidal neuron excitability. Ni(2+)-sensitive T-type Ca(2+) channels are important modulators of dendritic excitability. Here, we use an optical approach to determine the contribution of Ni(2+) (100 microM)-sensitive Ca(2+) channels to action potential (AP) elicited Ca(2+) flux in the soma, proximal apical and distal apical dendrites. At resting membrane potentials Ni(2+)-sensitive Ca(2+) channels do not contribute to the Ca(2+) signal in the proximal apical dendrite, but do contribute in the other cell regions. Spontaneous release from mossy fiber terminals acting on 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX)-sensitive postsynaptic channels underlies a tonic inhibition of Ni(2+)-sensitive channels. Chelating Zn(2+) with CaEDTA blocks CNQX-sensitive changes in Ca(2+) flux implicating a mechanistic role of this ion in T-type Ca(2+) channel block. To test if this inhibition influenced excitability, progressively larger depolarizing pulses were delivered to CA3 pyramidal neurons. CNQX significantly reduced the size of the depolarizing step required to generate APs and increased the absolute number of APs per depolarizing step. This change in AP firing was completely reversed by the addition of Ni(2+). This mechanism may reduce the impact of T-type Ca(2+) channels in a region where large synaptic events are common.

  9. Mobilities and Representations

    Thelle, Mikkel

    2017-01-01

    to consider how they and their peers are currently confronting representations of mobility. This is particularly timely given the growing academic focus on practices, material mediation, and nonrepresentational theories, as well as on bodily reactions, emotions, and feelings that, according to those theories......As the centerpiece of the eighth T2M yearbook, the following interview about representations of mobility signals a new and exciting focus area for Mobility in History. In future issues we hope to include reviews that grapple more with how mobilities have been imagined and represented in the arts......, literature, and film. Moreover, we hope the authors of future reviews will reflect on the ways they approached those representations. Such commentaries would provide valuable methodological insights, and we hope to begin that effort with this interview. We have asked four prominent mobility scholars...

  10. Memetics of representation

    Roberto De Rubertis

    2012-06-01

    Full Text Available This article will discuss about the physiological genesis of representation and then it will illustrate the developments, especially in evolutionary perspective, and it will show how these are mainly a result of accidental circumstances, rather than of deliberate intention of improvement. In particular, it will be argue that the representation has behaved like a meme that has arrived to its own progressive evolution coming into symbiosis with the different cultures in which it has spread, and using in this activity human work “unconsciously”. Finally it will be shown how in this action the geometry is an element key, linked to representation both to construct images using graphics operations and to erect buildings using concrete operations.

  11. Post-representational cartography

    Rob Kitchin

    2010-03-01

    Full Text Available Over the past decade there has been a move amongst critical cartographers to rethink maps from a post-representational perspective – that is, a vantage point that does not privilege representational modes of thinking (wherein maps are assumed to be mirrors of the world and automatically presumes the ontological security of a map as a map, but rather rethinks and destabilises such notions. This new theorisation extends beyond the earlier critiques of Brian Harley (1989 that argued maps were social constructions. For Harley a map still conveyed the truth of a landscape, albeit its message was bound within the ideological frame of its creator. He thus advocated a strategy of identifying the politics of representation within maps in order to circumnavigate them (to reveal the truth lurking underneath, with the ontology of cartographic practice remaining unquestioned.

  12. Introduction to computer data representation

    Fenwick, Peter

    2014-01-01

    Introduction to Computer Data Representation introduces readers to the representation of data within computers. Starting from basic principles of number representation in computers, the book covers the representation of both integer and floating point numbers, and characters or text. It comprehensively explains the main techniques of computer arithmetic and logical manipulation. The book also features chapters covering the less usual topics of basic checksums and 'universal' or variable length representations for integers, with additional coverage of Gray Codes, BCD codes and logarithmic repre

  13. Representation Discovery using Harmonic Analysis

    Mahadevan, Sridhar

    2008-01-01

    Representations are at the heart of artificial intelligence (AI). This book is devoted to the problem of representation discovery: how can an intelligent system construct representations from its experience? Representation discovery re-parameterizes the state space - prior to the application of information retrieval, machine learning, or optimization techniques - facilitating later inference processes by constructing new task-specific bases adapted to the state space geometry. This book presents a general approach to representation discovery using the framework of harmonic analysis, in particu

  14. Effects of conducting oxide barrier layers on the stability of Crofer® 22 APU/Ca3Co4O9 interfaces

    Holgate, Tim C.; Han, Li; Wu, NingYu

    2014-01-01

    Practical implementation of oxide thermoelectrics on an industrial or commercial scale for waste heat energy conversion requires the development of chemically stable interfaces between metal interconnects and oxide thermoelements that exhibit low electrical contact resistances. A commercially...... available high-chrome iron alloy (i.e., Crofer® 22 APU) serving as the interconnect metal was spray coated with LaNi0.6Fe0.4O3 (LNFO) or (Mn,Co)3O4 spinel and then interfaced with a p-type thermoelectric material—calcium cobaltate (Ca3Co4O9)—using spark plasma sintering. The interfaces have been...

  15. Rapamycin inhibits mTOR/p70S6K activation in CA3 region of the hippocampus of the rat and impairs long term memory.

    Lana, D; Di Russo, J; Mello, T; Wenk, G L; Giovannini, M G

    2017-01-01

    The present study was aimed at establishing whether the mTOR pathway and its downstream effector p70S6K in CA3 pyramidal neurons are under the modulation of the cholinergic input to trigger the formation of long term memories, similar to what we demonstrated in CA1 hippocampus. We performed in vivo behavioral experiments using the step down inhibitory avoidance test in adult Wistar rats to evaluate memory formation under different conditions. We examined the effects of rapamycin, an inhibitor of mTORC1 formation, scopolamine, a muscarinic receptor antagonist or mecamylamine, a nicotinic receptor antagonist, on short and long term memory formation and on the functionality of the mTOR pathway. Acquisition was conducted 30min after i.c.v. injection of rapamycin. Recall testing was performed 1h, 4h or 24h after acquisition. We found that (1) mTOR and p70S6K activation in CA3 pyramidal neurons were involved in long term memory formation; (2) rapamycin significantly inhibited mTOR and of p70S6K activation at 4h, and long term memory impairment 24h after acquisition; (3) scopolamine impaired short but not long term memory, with an early increase of mTOR/p70S6K activation at 1h followed by stabilization at longer times; (4) mecamylamine and scopolamine co-administration impaired short term memory at 1h and 4h and reduced the scopolamine-induced increase of mTOR/p70S6K activation at 1h and 4h; (5) mecamylamine and scopolamine treatment did not impair long term memory formation; (6) unexpectedly, rapamycin increased mTORC2 activation in microglial cells. Our results demonstrate that in CA3 pyramidal neurons the mTOR/p70S6K pathway is under the modulation of the cholinergic system and is involved in long-term memory encoding, and are consistent with the hypothesis that the CA3 region of the hippocampus is involved in memory mechanisms based on rapid, one-trial object-place learning and recall. Furthermore, our results are in accordance with previous reports that selective

  16. Analyses of stable isotopes in camelids collagen bones from Tulan Ravine, Atacama Puna, early formative period (CA 3,1000-2,400BP)

    Lopez, Patricio; Cartajena, Isabel; Nunez, Lautaro

    2013-01-01

    This paper presents the results of isotope analysis (δ 13 C y δ 15 N) conducted on bone collagen found in Lama guanicoe and Lama glama remains from Tulan-85 and Tulan-54 archaeological sites. Both sites have been dated to the Early Formative Period (ca. 3,100-2,400 ap) and are located southeast of the Atacama Puna basin. Faunal samples were selected using anatomical and morphometric criteria. The results indicate divergences in the diets of both species, reflecting vegetation variation in the Tulan Quebrada caused by altitude differences and linked to hunting and herding areas [es

  17. Oriented thin films of Na0.6CoO2 and Ca3Co4O9 deposited by spin-coating method on polycrystalline substrate

    Buršík, Josef; Soroka, Miroslav; Knížek, Karel; Hirschner, Jan; Levinský, Petr; Hejtmánek, Jiří

    2016-01-01

    Roč. 603, MAR (2016), s. 400-403 ISSN 0040-6090 R&D Projects: GA ČR(CZ) GA14-18392S; GA ČR(CZ) GA13-03708S Institutional support: RVO:61388980 ; RVO:68378271 Keywords : Cobaltates * Thermoelectrics * NaxCoO2 * Ca3Co4O9 * Thin film s * ZrO2 Subject RIV: CA - Inorganic Chemistry; BM - Solid Matter Physics ; Magnetism (FZU-D) Impact factor: 1.879, year: 2016

  18. Additive and polynomial representations

    Krantz, David H; Suppes, Patrick

    1971-01-01

    Additive and Polynomial Representations deals with major representation theorems in which the qualitative structure is reflected as some polynomial function of one or more numerical functions defined on the basic entities. Examples are additive expressions of a single measure (such as the probability of disjoint events being the sum of their probabilities), and additive expressions of two measures (such as the logarithm of momentum being the sum of log mass and log velocity terms). The book describes the three basic procedures of fundamental measurement as the mathematical pivot, as the utiliz

  19. On the spinor representation

    Hoff da Silva, J.M.; Rogerio, R.J.B. [Universidade Estadual Paulista, Departamento de Fisica e Quimica, Guaratingueta, SP (Brazil); Villalobos, C.H.C. [Universidade Estadual Paulista, Departamento de Fisica e Quimica, Guaratingueta, SP (Brazil); Universidade Federal Fluminense, Instituto de Fisica, Niteroi, RJ (Brazil); Rocha, Roldao da [Universidade Federal do ABC-UFABC, Centro de Matematica, Computacao e Cognicao, Santo Andre (Brazil)

    2017-07-15

    A systematic study of the spinor representation by means of the fermionic physical space is accomplished and implemented. The spinor representation space is shown to be constrained by the Fierz-Pauli-Kofink identities among the spinor bilinear covariants. A robust geometric and topological structure can be manifested from the spinor space, wherein the first and second homotopy groups play prominent roles on the underlying physical properties, associated to fermionic fields. The mapping that changes spinor fields classes is then exemplified, in an Einstein-Dirac system that provides the spacetime generated by a fermion. (orig.)

  20. Differential engagement of attention and visual working memory in the representation and evaluation of the number of relevant targets and their spatial relations: Evidence from the N2pc and SPCN.

    Maheux, Manon; Jolicœur, Pierre

    2017-04-01

    We examined the role of attention and visual working memory in the evaluation of the number of target stimuli as well as their relative spatial position using the N2pc and the SPCN. Participants performed two tasks: a simple counting task in which they had to determine if a visual display contained one or two coloured items among grey fillers and one in which they had to identify a specific relation between two coloured items. The same stimuli were used for both tasks. Each task was designed to permit an easier evaluation of either the same-coloured or differently-coloured stimuli. We predicted a greater involvement of attention and visual working memory for more difficult stimulus-task pairings. The results confirmed these predictions and suggest that visuospatial configurations that require more time to evaluate induce a greater (and presumably longer) involvement of attention and visual working memory. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Orienting attention to locations in mental representations

    Astle, Duncan Edward; Summerfield, Jennifer; Griffin, Ivan; Nobre, Anna Christina

    2014-01-01

    Many cognitive processes depend on our ability to hold information in mind, often well beyond the offset of the original sensory input. The capacity of this ‘visual short-term memory’ (VSTM) is limited to around three to four items. Recent research has demonstrated that the content of VSTM can be modulated by top-down attentional biases. This has been demonstrated using retrodictive spatial cues, termed ‘retro-cues’, which orient participants’ attention to spatial locations within VSTM. In the current paper, we tested whether the use of these cues is modulated by memory load and cue delay. There are a number of important conclusions: i) top-down biases can operate upon very brief iconic traces as well as older VSTM representations (Experiment 1); ii) when operating within capacity, subjects use the cue to prioritize where they initiate their memory search, rather than to discard un-cued items (Experiments 2 and 3); iii) when capacity is exceeded there is little benefit to top-down biasing relative to a neutral condition, however, unattended items are lost, with there being a substantial cost of invalid spatial cueing (Experiment 3); iv) these costs and benefits of orienting spatial attention differ across iconic memory and VSTM representations when VSTM capacity is exceeded (Experiment 4). PMID:21972046

  2. Going beyond representational anthropology

    Winther, Ida Wentzel

    Going beyond representational anthropology: Re-presenting bodily, emotional and virtual practices in everyday life. Separated youngsters and families in Greenland Greenland is a huge island, with a total of four high-schools. Many youngsters (age 16-18) move far away from home in order to get...

  3. Reflection on Political Representation

    Kusche, Isabel

    2017-01-01

    This article compares how Members of Parliament in the United Kingdom and Ireland reflect on constituency service as an aspect of political representation. It differs from existing research on the constituency role of MPs in two regards. First, it approaches the question from a sociological viewp...

  4. Social representations about cancer

    Andreja Cirila Škufca

    2003-09-01

    Full Text Available In this article we are presenting the results of the comparison study on social representations and causal attributions about cancer. We compared a breast cancer survivors group and control group without own experience of cancer of their own. Although social representations about cancer differ in each group, they are closely related to the concept of suffering, dying and death. We found differences in causal attribution of cancer. In both groups we found a category of risky behavior, which attributes a responsibility for a disease to an individual. Besides these factors we found predominate stress and psychological influences in cancer survivors group. On the other hand control group indicated factors outside the ones control e.g. heredity and environmental factors. Representations about a disease inside person's social space are important in co-shaping the individual process of coping with own disease. Since these representations are not always coherent with the knowledge of modern medicine their knowledge and appreciation in the course of treatment is of great value. We find the findingss of applied social psychology important as starting points in the therapeutic work with patients.

  5. The Problem of Representation

    Tervo, Juuso

    2012-01-01

    In "Postphysical Vision: Art Education's Challenge in an Age of Globalized Aesthetics (AMondofesto)" (2008) and "Beyond Aesthetics: Returning Force and Truth to Art and Its Education" (2009), jan jagodzinski argued for politics that go "beyond" representation--a project that radically questions visual culture…

  6. Women and political representation.

    Rathod, P B

    1999-01-01

    A remarkable progress in women's participation in politics throughout the world was witnessed in the final decade of the 20th century. According to the Inter-Parliamentary Union report, there were only eight countries with no women in their legislatures in 1998. The number of women ministers at the cabinet level worldwide doubled in a decade, and the number of countries without any women ministers dropped from 93 to 48 during 1987-96. However, this progress is far from satisfactory. Political representation of women, minorities, and other social groups is still inadequate. This may be due to a complex combination of socioeconomic, cultural, and institutional factors. The view that women's political participation increases with social and economic development is supported by data from the Nordic countries, where there are higher proportions of women legislators than in less developed countries. While better levels of socioeconomic development, having a women-friendly political culture, and higher literacy are considered favorable factors for women's increased political representation, adopting one of the proportional representation systems (such as a party-list system, a single transferable vote system, or a mixed proportional system with multi-member constituencies) is the single factor most responsible for the higher representation of women.

  7. Discovery of novel solid solution Ca3Si3-x O3+x N4-2x : Eu2+ phosphors: structural evolution and photoluminescence tuning.

    Wang, Baochen; Liu, Yan-Gai; Huang, Zhaohui; Fang, Minghao; Wu, Xiaowen

    2017-12-22

    Discovery of novel phosphors is one of the main issues for improving the color rendering index (CRI) and correlated color temperature (CCT) of white light-emitting diodes (w-LEDs). This study mainly presents a systematic research on the synthesis, crystal structure variation and photoluminescence tuning of novel (oxy)nitride solid solution Ca 3 Si 3-x O 3+x N 4-2x : Eu 2+ phosphors. XRD refinements show that lattice distortion occurs when x value diverges the optimum one (x = 1). The lattice distortion causes a widening of emission spectrum and an increase of Stokes shift (ΔSS), which leads to a bigger thermal quenching. With decrease of x value, the emission spectrum shows an obvious red-shift from 505.2 to 540.8 nm, which is attributed to the crystal field splitting. The enhanced crystal field splitting also broadens the excitation spectrum, making it possible to serve as the phosphor for near ultraviolet (n-UV) LEDs. A 3-phosphor-conversion w-LED lamp was fabricated with the as-prepared phosphor, which exhibits high CRI (Ra = 85.29) and suitable CCT (4903.35 K). All these results indicate that the Ca 3 Si 3-x O 3+x N 4-2x : Eu 2+ phosphor can serve as the green phosphor for n-UV w-LEDs, with a tunable spectrum by controlling the crystal structure and morphology.

  8. Critical current density of four-CuO2-layer T1Ba2Ca3Cu4O11-δ

    Zhang, L.; Liu, J.Z.; Shelton, R.N.

    1998-01-01

    Full text: A key requirement for technological application is to have superconductors with high critical current density at practical operating temperatures and magnetic fields. The critical current density is strongly related to underlying properties of high T c superconductors, such as layering, anisotropy and other intrinsic material structures. The thallium-based superconductors attracted much attention at early stage mainly due to their high superconducting transitions. Recent studies show that these materials appear to be a better choice for achieving higher critical current density because of a stronger interlayer coupling between superconducting layers. Single crystals of TlBa 2 Ca 3 Cu 4 O 11-δ were grown by a self-flux method. This material is a strong-layered superconductor with four-CuO 2 -planes in a unit cell and a superconducting transition temperature of 128K. Our experimental results show that TlBa 2 Ca 3 Cu 4 O 11-δ crystals have high irreversibility line, large critical current density and high upper critical field. The impact of layering and the number of Cu-O layers on flux pinning, critical current density and other magnetic properties will also be discussed

  9. Crystal growth and piezoelectric properties of Ca3Ta(Ga0.9Sc0.1)3Si2O14 bulk single crystal

    Igarashi, Yu; Yokota, Yuui; Ohashi, Yuji; Inoue, Kenji; Yamaji, Akihiro; Shoji, Yasuhiro; Kamada, Kei; Kurosawa, Shunsuke; Yoshikawa, Akira

    2018-03-01

    Ca3Ta(Ga0.9Sc0.1)3Si2O14 langasite-type single crystal with a diameter of 1 in. was grown by Czochralski (Cz) method. Obtained crystal had good crystallinity and its lattice constants exceeded those of Ca3TaGa3Si2O14 (CTGS) according to the X-ray analysis. A crack-free specimen cut from the grown crystal was used for the measurements of dielectric constant ε11T/ε0, electromechanical coupling factor k12, and piezoelectric constant d11. The accuracies of these measurements were better than those for the crystal grown by micro-pulling-down (μ-PD) method. Substitution of Ga with Sc resulted modification of these constants in the directions opposite to those observed after partial substitution of Ga (of CTGS) with Al. This suggests that increase of |d14| was most probably associated with enlargement of average size of the Ga sites. The crystal reported here had greater dimensions as compared to analogous crystals grown by the μ-PD method. As a result, accuracy of determination of acoustic constants of this material may be improved.

  10. Luminescent Enhancement of Na+ and Sm3+ Co-doping Reddish Orange SrCa3Si2O8 Phosphors

    Chun, Fengjun; Zhang, Binbin; Li, Wen; Liu, Honggang; Deng, Wen; Chu, Xiang; Osman, Hanan; Zhang, Haitao; Yang, Weiqing

    2018-04-01

    Reddish orange SrCa3Si2O8 phosphors, prepared by the facile solid state reaction method, are a luminescent enhancement of Na+ and Sm3+ co-doping luminescent material. Na+ was designed to compensate the charge imbalance of Sm3+ ion substituting for the Sr2+ ion of orthorhombic SrCa3Si2O8 crystals. The results suggest that Na+ can effectively enhance the luminescent intensity of the reddish orange light peaked at about 562 nm (4 G 5/2 → 6 H 5/2), 600 nm (4 G 5/2 → 6 H 7/2) and 645 nm (4 G 5/2 → 6 H 9/2) excited by the near ultraviolet excited light 404 nm (4 L 13/2 → 6 H 5/2). The energy transfer has been further verified by the florescence lifetime. Additionally, the luminescent lifetime τ of as-grown phosphors was separated into two parts, a rapid lifetime and a slow lifetime. The average lifetime results ranged from 2.098 to 1.329 ms which were influenced by the concentration of Sm3+ doping. The systematic researches of as-grown phosphors have clearly suggested a potential application for white-light-emitting diodes ( w-LEDs).

  11. Structural and optical properties of Tb and Na-Tb co-doped Ca3V2O8 phosphors prepared by sol-gel process

    Parab, Shambhu S.; Salker, A. V.

    2018-01-01

    A malic acid assisted sol-gel route was successfully employed to prepare two distinct series of green emitting Ca3V2O8 phosphors. In the first series, Tb was solely doped whereas in the second series Na and Tb were doped simultaneously in the Ca3V2O8 crystal lattice. X-ray diffraction studies proved the utility of adopted preparative method by confirming the monophasic formation of all compounds from both the series. Spectral analysis like Raman spectroscopy, UV-DRS were undertaken to analyse the local structure, crystallinity and absorptive characteristics. XPS validated the presence of desired oxidation states of all the elements present. Finally, photoluminescence studies were done to elucidate the scope of prepared compounds as green emitting phosphors and also to understand the effect of both doping schemes on the luminescence. Intense green emission was observed in both the cases. Tb concentration of 0.08 was found to be optimum in case of Tb singly doped compounds whereas Tb = 0.12 showed highest intensity among the Na-Tb co-doped samples. Moreover, a red shift in the excitation wavelength was observed after Na doping signifying a change in the local electronic environment which in turn has affected the luminescence pattern. Local crystallinity and vacancy concentrations were found to have a major say on the emission intensities.

  12. Bluish-White Luminescence in Rare-Earth-Free Vanadate Garnet Phosphors: Structural Characterization of LiCa3MV3O12 (M = Zn and Mg).

    Hasegawa, Takuya; Abe, Yusuke; Koizumi, Atsuya; Ueda, Tadaharu; Toda, Kenji; Sato, Mineo

    2018-01-16

    Extensive attention has been focused toward studies on inexpensive and rare-earth-free garnet-structure vanadate phosphors, which do not have a low optical absorption due to the luminescence color being easily controlled by its high composition flexibility. However, bluish emission phosphors with a high quantum efficiency have not been found until now. In this study, we successfully discovered bluish-white emitting, garnet structure-based LiCa 3 MV 3 O 12 (M = Zn and Mg) phosphors with a high quantum efficiency, and the detailed crystal structure was refined by the Rietveld analysis technique. These phosphors exhibit a broad-band emission spectra peak at 481 nm under near UV-light excitation at 341 nm, indicating no clear difference in the emission and excitation spectra. A very compact tetrahedral [VO 4 ] unit is observed in the LiCa 3 MV 3 O 12 (M = Zn and Mg) phosphors, which is not seen in other conventional garnet compounds, and generates a bluish-white emission. In addition, these phosphors exhibit high quantum efficiencies of 40.1% (M = Zn) and 44.0% (M = Mg), respectively. Therefore, these vanadate garnet phosphors can provide a new blue color source for LED devices.

  13. Diffeomorphism Group Representations in Relativistic Quantum Field Theory

    Goldin, Gerald A. [Rutgers Univ., Piscataway, NJ (United States); Sharp, David H. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-12-20

    We explore the role played by the di eomorphism group and its unitary representations in relativistic quantum eld theory. From the quantum kinematics of particles described by representations of the di eomorphism group of a space-like surface in an inertial reference frame, we reconstruct the local relativistic neutral scalar eld in the Fock representation. An explicit expression for the free Hamiltonian is obtained in terms of the Lie algebra generators (mass and momentum densities). We suggest that this approach can be generalized to elds whose quanta are spatially extended objects.

  14. A high-level product representation for automatic design reasoning

    Kroll, E.; Qamar, Z.; Mohammad, R. [Texas A and M Univ., College Station, TX (United States). Mechanical Engineering Dept.

    1994-12-31

    A high-level product representation has been developed and implemented, using features for part description and mating conditions between features for the relationships among parts. The underlying ideas are that features are necessary for effective design representation; that spatial and functional relationships among parts of an assembly are best expressed through mating conditions; that assembly features of a part may, at times, be different from its manufacturing features; and that a good representation should be natural, intelligent, comprehensive, and integrated with a visual display. Some new mating conditions have been defined and classified. Several problems concerning the use of features with mating conditions are discussed.

  15. Utilização de métodos de representação espacial para cálculo do fator topográfico na equação universal de perda de solo revisada em bacias hidrográficas Use of spatial representation to calculate the topographic factor in the revised universal soil loss equation in watersheds

    Jean Paolo Gomes Minella

    2010-08-01

    Full Text Available Métodos de representação espacial para o cálculo do fator topográfico (LS da Equação Universal de Perda de Solo Revisada (RUSLE têm sido utilizados para estimar a erosão do solo e a produção de sedimentos em bacias hidrográficas. Esses procedimentos baseiam-se nas equações tradicionalmente empregadas para determinação do fator LS e em informações que caracterizam a forma das vertentes derivadas do modelo numérico de elevação (MNE. Neste estudo foram analisados dois métodos de representação espacial utilizados no cálculo do fator LS em modelos matemáticos de erosão e produção de sedimentos em bacias hidrográficas. A análise foi realizada em quatro bacias rurais de relevo movimentado. Os valores de LS obtidos pelos métodos de representação espacial foram comparados entre si e com valores de LS determinados pelo método tradicional com levantamento em campo. Resultados mostraram que os valores de LS gerados pelos métodos de representação espacial apresentam diferenças significativas entre si, sendo dependentes do procedimento de cálculo e do método utilizado para determinar a direção de fluxo no MNE. Também foi verificado que os valores numéricos do fator LS determinados pelos métodos de representação espacial apresentam diferenças em relação àqueles estimados pelo método tradicional.Methods of spatial representation to calculate the topographic factor (LS of the Revised Universal Soil Loss Equation (USLE have been used to estimate soil erosion and sediment yield of watersheds. These procedures are based on equations traditionally used to determine the LS factor and information that characterize the hillslope forms and processes, derived from the Digital Elevation Model (DEM. Two computational methods commonly used to calculate LS factor in soil erosion and sediment yield models were analyzed in this study. The analysis was performed in four small rural watersheds with hilly terrain. The LS values

  16. Standard model of knowledge representation

    Yin, Wensheng

    2016-09-01

    Knowledge representation is the core of artificial intelligence research. Knowledge representation methods include predicate logic, semantic network, computer programming language, database, mathematical model, graphics language, natural language, etc. To establish the intrinsic link between various knowledge representation methods, a unified knowledge representation model is necessary. According to ontology, system theory, and control theory, a standard model of knowledge representation that reflects the change of the objective world is proposed. The model is composed of input, processing, and output. This knowledge representation method is not a contradiction to the traditional knowledge representation method. It can express knowledge in terms of multivariate and multidimensional. It can also express process knowledge, and at the same time, it has a strong ability to solve problems. In addition, the standard model of knowledge representation provides a way to solve problems of non-precision and inconsistent knowledge.

  17. Focusing on Presentation Instead of Representation: Perspectives on Representational and Non-Representational Language-Games for Educational History and Theory

    Fendler, Lynn; Smeyers, Paul

    2015-01-01

    Debates in science seem to depend on referential language-games, but in other senses they do not. This article addresses non-representational theory. It is a branch of newer approaches to cultural geography that strive to get a handle on spatial relationships not by representing them, but rather by presenting them. In this case, present connotes…

  18. Constructing visual representations

    Huron, Samuel; Jansen, Yvonne; Carpendale, Sheelagh

    2014-01-01

    tangible building blocks. We learned that all participants, most of whom had little experience in visualization authoring, were readily able to create and talk about their own visualizations. Based on our observations, we discuss participants’ actions during the development of their visual representations......The accessibility of infovis authoring tools to a wide audience has been identified as a major research challenge. A key task in the authoring process is the development of visual mappings. While the infovis community has long been deeply interested in finding effective visual mappings......, comparatively little attention has been placed on how people construct visual mappings. In this paper, we present the results of a study designed to shed light on how people transform data into visual representations. We asked people to create, update and explain their own information visualizations using only...

  19. Naturalising Representational Content

    Shea, Nicholas

    2014-01-01

    This paper sets out a view about the explanatory role of representational content and advocates one approach to naturalising content – to giving a naturalistic account of what makes an entity a representation and in virtue of what it has the content it does. It argues for pluralism about the metaphysics of content and suggests that a good strategy is to ask the content question with respect to a variety of predictively successful information processing models in experimental psychology and cognitive neuroscience; and hence that data from psychology and cognitive neuroscience should play a greater role in theorising about the nature of content. Finally, the contours of the view are illustrated by drawing out and defending a surprising consequence: that individuation of vehicles of content is partly externalist. PMID:24563661

  20. Knowledge Representation and Ontologies

    Grimm, Stephan

    Knowledge representation and reasoning aims at designing computer systems that reason about a machine-interpretable representation of the world. Knowledge-based systems have a computational model of some domain of interest in which symbols serve as surrogates for real world domain artefacts, such as physical objects, events, relationships, etc. [1]. The domain of interest can cover any part of the real world or any hypothetical system about which one desires to represent knowledge for com-putational purposes. A knowledge-based system maintains a knowledge base, which stores the symbols of the computational model in the form of statements about the domain, and it performs reasoning by manipulating these symbols. Applications can base their decisions on answers to domain-relevant questions posed to a knowledge base.

  1. P2X7 receptor activation ameliorates CA3 neuronal damage via a tumor necrosis factor-α-mediated pathway in the rat hippocampus following status epilepticus

    Ryu Hea Jin

    2011-06-01

    Full Text Available Abstract Background The release of tumor necrosis factor-α (TNF-α appears depend on the P2X7 receptor, a purinergic receptor. In the present study, we addressed the question of whether P2X7 receptor-mediated TNF-α regulation is involved in pathogenesis and outcome of status epilepticus (SE. Methods SE was induced by pilocarpine in rats that were intracerebroventricularly infused with saline-, 2',3'-O-(4-benzoylbenzoyl-adenosine 5'-triphosphate (BzATP, adenosine 5'-triphosphate-2',3'-dialdehyde (OxATP, A-438079, or A-740003 prior to SE induction. Thereafter, we performed Fluoro-Jade B staining and immunohistochemical studies for TNF-α and NF-κB subunit phosphorylations. Results Following SE, P2X7 receptor agonist (BzATP infusion increased TNF-α immunoreactivity in dentate granule cells as compared with that in saline-infused animals. In addition, TNF-α immunoreactivity was readily apparent in the mossy fibers, while TNF-α immunoreactivity in CA1-3 pyramidal cells was unaltered. However, P2X7 receptor antagonist (OxATP-, A-438079, and A-740003 infusion reduced SE-induced TNF-α expression in dentate granule cells. In the CA3 region, BzATP infusion attenuated SE-induced neuronal damage, accompanied by enhancement of p65-Ser276 and p65-Ser311 NF-κB subunit phosphorylations. In contrast, OxATP-, A-438079, and A-740003 infusions increased SE-induced neuronal death. Soluble TNF p55 receptor (sTNFp55R, and cotreatment with BzATP and sTNFp55R infusion also increased SE-induced neuronal damage in CA3 region. However, OxATP-, sTNFp55R or BzATP+sTNFp55R infusions could not exacerbate SE-induced neuronal damages in the dentate gyrus and the CA1 region, as compared to BzATP infusion. Conclusions These findings suggest that TNF-α induction by P2X7 receptor activation may ameliorate SE-induced CA3 neuronal damage via enhancing NF-κB p65-Ser276 and p65-Ser311 phosphorylations.

  2. Europe representations in textbooks

    Brennetot , Arnaud

    2011-01-01

    This EuroBroadMap working paper presents an analysis of textbooks dealing with the representations of Europe and European Union. In most of these textbooks from secondary school, the teaching of the geography of Europe precedes the evocation of the EU. Europe is often depicted as a given object, reduced to a number of structural aspects (relief, climate, demography, traditional cultures, economic activities, etc.) whose only common point is their location within conventional boundaries. Such ...

  3. Non-Representational Theory

    Jensen, Ole B.

    2016-01-01

    Dette kapitel gennemgår den såkaldte ”Non-Representational Theory” (NRT), der primært er kendt fra den Angelsaksiske humangeografi, og som særligt er blevet fremført af den engelske geograf Nigel Thrift siden midten af 2000 årtiet. Da positionen ikke kan siges at være specielt homogen vil kapitlet...

  4. Harmonic Analysis and Group Representation

    Figa-Talamanca, Alessandro

    2011-01-01

    This title includes: Lectures - A. Auslander, R. Tolimeri - Nilpotent groups and abelian varieties, M Cowling - Unitary and uniformly bounded representations of some simple Lie groups, M. Duflo - Construction de representations unitaires d'un groupe de Lie, R. Howe - On a notion of rank for unitary representations of the classical groups, V.S. Varadarajan - Eigenfunction expansions of semisimple Lie groups, and R. Zimmer - Ergodic theory, group representations and rigidity; and, Seminars - A. Koranyi - Some applications of Gelfand pairs in classical analysis.

  5. Functional representations for quantized fields

    Jackiw, R.

    1988-01-01

    This paper provides information on Representing transformations in quantum theory bosonic quantum field theories: Schrodinger Picture; Represnting Transformations in Bosonic Quantum Field Theory; Two-Dimensional Conformal Transformations, Schrodinger picture representation, Fock space representation, Inequivalent Schrodinger picture representations; Discussion, Self-Dual and Other Models; Field Theory in de Sitter Space. Fermionic Quantum Field Theories: Schroedinger Picture; Schrodinger Picture Representation for Two-Dimensional; Conformal Transformations; Fock Space Dynamics in the Schrodinger Picture; Fock Space Evaluation of Anomalous Current and Conformal Commutators

  6. An evaluation of space time cube representation of spatiotemporal patterns.

    Kristensson, Per Ola; Dahlbäck, Nils; Anundi, Daniel; Björnstad, Marius; Gillberg, Hanna; Haraldsson, Jonas; Mårtensson, Ingrid; Nordvall, Mathias; Ståhl, Josefine

    2009-01-01

    Space time cube representation is an information visualization technique where spatiotemporal data points are mapped into a cube. Information visualization researchers have previously argued that space time cube representation is beneficial in revealing complex spatiotemporal patterns in a data set to users. The argument is based on the fact that both time and spatial information are displayed simultaneously to users, an effect difficult to achieve in other representations. However, to our knowledge the actual usefulness of space time cube representation in conveying complex spatiotemporal patterns to users has not been empirically validated. To fill this gap, we report on a between-subjects experiment comparing novice users' error rates and response times when answering a set of questions using either space time cube or a baseline 2D representation. For some simple questions, the error rates were lower when using the baseline representation. For complex questions where the participants needed an overall understanding of the spatiotemporal structure of the data set, the space time cube representation resulted in on average twice as fast response times with no difference in error rates compared to the baseline. These results provide an empirical foundation for the hypothesis that space time cube representation benefits users analyzing complex spatiotemporal patterns.

  7. Self-organizing representations

    Kohonen, T.

    1983-01-01

    A property which is commonplace in the brain but which has always been ignored in learning machines is the spatial order of the processing units. This order is clearly highly significant and in nature it develops gradually during the lifetime of the organism. It then serves as the basis for perceptual and cognitive processes, and memory, too. The spatial order in biological organisms is often believed to be genetically determined. It is therefore intriguing to learn that a meaningful and optimal spatial order is formed in an extremely simple self-organizing process whereby certain feature maps are formed automatically. 8 references.

  8. The impact of spatial resolution on resolving spatial precipitation patterns in the Himalayas

    Bonekamp, P.N.J.; Collier, S.E.; Immerzeel, W.W.

    2017-01-01

    Frequently used gridded meteorological datasets poorly represent precipitation in the Himalaya due to their relatively low spatial resolution and the associated coarse representation of the complex topography. Dynamical downscaling using high-resolution atmospheric models may improve the accuracy

  9. Pioneers of representation theory

    Curtis, Charles W

    1999-01-01

    The year 1897 was marked by two important mathematical events: the publication of the first paper on representations of finite groups by Ferdinand Georg Frobenius (1849-1917) and the appearance of the first treatise in English on the theory of finite groups by William Burnside (1852-1927). Burnside soon developed his own approach to representations of finite groups. In the next few years, working independently, Frobenius and Burnside explored the new subject and its applications to finite group theory. They were soon joined in this enterprise by Issai Schur (1875-1941) and some years later, by Richard Brauer (1901-1977). These mathematicians' pioneering research is the subject of this book. It presents an account of the early history of representation theory through an analysis of the published work of the principals and others with whom the principals' work was interwoven. Also included are biographical sketches and enough mathematics to enable readers to follow the development of the subject. An introductor...

  10. Cohen-Macaulay representations

    Leuschke, Graham J

    2012-01-01

    This book is a comprehensive treatment of the representation theory of maximal Cohen-Macaulay (MCM) modules over local rings. This topic is at the intersection of commutative algebra, singularity theory, and representations of groups and algebras. Two introductory chapters treat the Krull-Remak-Schmidt Theorem on uniqueness of direct-sum decompositions and its failure for modules over local rings. Chapters 3-10 study the central problem of classifying the rings with only finitely many indecomposable MCM modules up to isomorphism, i.e., rings of finite CM type. The fundamental material--ADE/simple singularities, the double branched cover, Auslander-Reiten theory, and the Brauer-Thrall conjectures--is covered clearly and completely. Much of the content has never before appeared in book form. Examples include the representation theory of Artinian pairs and Burban-Drozd's related construction in dimension two, an introduction to the McKay correspondence from the point of view of maximal Cohen-Macaulay modules, Au...

  11. High-pressure synthesis of CuBa2Ca3Cu4O10+δ superconductor from precursors prepared by a polymerized complex method

    Aoba, Tomoya; Bizen, Takeshi; Suzuki, Tsuneo; Nakayama, Tadachika; Suematsu, Hisayuki; Niihara, Koichi; Katsumata, Tetsuhiro; Inaguma, Yoshiyuki

    2011-01-01

    Samples of a CuBa 2 Ca 3 Cu 4 O 10+ δ superconductor were synthesized under a high pressure of 5 GPa at 1100-1200degC for 30 min using precursors produced by solid-state reaction and polymerized complex methods. Compared with the precursors prepared by the solid-state reaction method, the precursors produced by the polymerized complex method have low grain sizes. The superconductive transition temperature of the samples prepared using precursors made by the polymerized complex method was found to be 113 K. The volume fractions of the superconducting phase in the samples prepared using precursors made by the solid-state reaction and polymerized complex methods were 49 and 36%, respectively. From these results, precursors made by the polymerized complex method can be used in the high-pressure synthesis of superconductors similarly to those made by the solid-state reaction method. (author)

  12. Spectroscopic evidence of two-dimensional character of the 90 K Bi2(Sr,La,Ca)3Cu2O8 superconductors

    Lindberg, P.A.P.; Shen, Z.; Wells, B.O.; Dessau, D.S.; Borg, A.; Lindau, I.; Spicer, W.E.; Mitzi, D.B.; Kapitulnik, A.

    1989-01-01

    Polarization-dependent angle-resolved photoemission experiments in the constant final state mode (absorption measurements) were performed on single crystals of the Bi-based 2212 material using synchrotron radiation in the photon energy range 10--40 eV. Evidence of polarization-dependent transitions due to Bi 5d→6p, Sr 4p→4d, and Ca 3p→3d excitations is observed. The data show that the electronic charge is highly localized to the layers of the crystal structure, thus providing a direct spectroscopic confirmation of the two-dimensional nature of these types of materials. Polarization-sensitive absorption signals at 14--15 eV attributed to Bi 6s→6p transitions show that the density of states (DOS) of the Bi 6p z holes peaks at about 0.7 eV higher energy than the DOS of the Bi 6p x,y holes

  13. Preparation and luminescence properties of Ca3(VO4)2: Eu3+, Sm3+ phosphor for light-emitting diodes

    Huang Jiaping; Li Qiuxia; Chen Donghua

    2010-01-01

    Rare-earth ions co-activated red phosphors Ca 3 (VO 4 ) 2 : Eu 3+ , Sm 3+ were synthesized by modified solid-state reactions. The samples were characterized by X-ray powder diffractometer (XRD), energy-dispersive X-ray spectrometer (EDS), transmission electron microscopy (TEM) and luminescence spectrometer (LS). The results showed that the Eu-Sm system exhibits higher emission intensity than those of the Eu single-doped system and Sm separate-doped system under blue light. Samarium (III) ions are effective in broadening and strengthening absorptions around 467 nm. Furthermore, they exhibit enhanced luminescence emission. Luminescent measurements showed that the phosphors can be efficiently excited by ultraviolet (UV) to visible region, emitting a red light with a peak wavelength of 616 nm. The material has potential application as a phosphor for light-emitting diodes (LEDs).

  14. Crystal Growth of Ca3Nb(Ga1−xAlx3Si2O14 Piezoelectric Single Crystals with Various Al Concentrations

    Yuui Yokota

    2015-08-01

    Full Text Available Ca3Nb(Ga1−xAlx3Si2O14 (CNGAS single crystals with various Al concentrations were grown by a micro-pulling-down (µ-PD method and their crystal structures, chemical compositions, crystallinities were investigated. CNGAS crystals with x = 0.2, 0.4 and 0.6 indicated a single phase of langasite-type structure without any secondary phases. In contrast, the crystals with x = 0.8 and 1 included some secondary phases in addition to the langasite-type phase. Lattice parameters, a- and c-axes lengths, of the langasite-type phase systematically decreased with an increase of Al concentration. The results of chemical composition analysis revealed that the actual Al concentrations in as-grown crystals were almost consistent with the nominal compositions. In addition, there was no large segregation of each cation along the growth direction.

  15. Teacher spatial skills are linked to differences in geometry instruction.

    Otumfuor, Beryl Ann; Carr, Martha

    2017-12-01

    Spatial skills have been linked to better performance in mathematics. The purpose of this study was to examine the relationship between teacher spatial skills and their instruction, including teacher content and pedagogical knowledge, use of pictorial representations, and use of gestures during geometry instruction. Fifty-six middle school teachers participated in the study. The teachers were administered spatial measures of mental rotations and spatial visualization. Next, a single geometry class was videotaped. Correlational analyses revealed that spatial skills significantly correlate with teacher's use of representational gestures and content and pedagogical knowledge during instruction of geometry. Spatial skills did not independently correlate with the use of pointing gestures or the use of pictorial representations. However, an interaction term between spatial skills and content and pedagogical knowledge did correlate significantly with the use of pictorial representations. Teacher experience as measured by the number of years of teaching and highest degree did not appear to affect the relationships among the variables with the exception of the relationship between spatial skills and teacher content and pedagogical knowledge. Teachers with better spatial skills are also likely to use representational gestures and to show better content and pedagogical knowledge during instruction. Spatial skills predict pictorial representation use only as a function of content and pedagogical knowledge. © 2017 The British Psychological Society.

  16. Ceramic Materials in a Ti–C–Co–Ca3(PO42–Ag–Mg System Obtained by MA SHS for the Deposition of Biomedical Coatings

    Artem Potanin

    2017-09-01

    Full Text Available This study aimed to obtain biocompatible ceramic materials in a Ti–C–Co–Ca3(PO42–Ag–Mg system by the combustion mode of mechanically activated (MA reaction mixtures. The influence of the MA time on the reaction ability capability of the mixtures, on their structural and chemical homogeneity, on the combustion parameters and structural-phase conversions in the combustion wave, as well as on the structure and phase composition of the electrode materials has been researched. It was found that the intense treatment of powder mixtures causes plastic deformation of components, the formation of lamellar composite granules, a reduction in the sizes of coherent scattering regions, and also the formation of minor amounts of products. The influence of the activation duration of the ignition temperature and heat release during the combustion of the reaction mixtures was studied. By the method of quenching the combustion front, it was demonstrated that in a combustion wave, chemical transformations occur within the lamellar structures formed during the process of mechanoactivation. It was shown that in the combustion wave, parallel chemical reactions of Ti with C as well as Ti with Co and Ca3(PO42 occur, with a Ti–Co-based melt forming the reaction surface. Ceramic electrodes with different contents of Ag and Mg were synthesized by force self-propagating high-temperature synthesis (SHS-pressing technology using the MA mixtures. The microstructure of the materials consisted of round-shaped grains of nonstoichiometric titanium carbide TiCx grains, intermetallic matrix (TiCo, TiCo2, CoTiP, inclusions of Ca and Mg oxides, and grains of the Ag-based solid solution. An increased content of Ag and Mg in the composition of the electrodes, as well as an increased MA duration, leads to an enlargement of the inclusions of the Ag-containing phase size and deterioration in the uniformity of their distribution.

  17. Removal of area CA3 from hippocampal slices induces postsynaptic plasticity at Schaffer collateral synapses that normalizes CA1 pyramidal cell discharge.

    Dumas, Theodore C; Uttaro, Michael R; Barriga, Carolina; Brinkley, Tiffany; Halavi, Maryam; Wright, Susan N; Ferrante, Michele; Evans, Rebekah C; Hawes, Sarah L; Sanders, Erin M

    2018-05-05

    Neural networks that undergo acute insults display remarkable reorganization. This injury related plasticity is thought to permit recovery of function in the face of damage that cannot be reversed. Previously, an increase in the transmission strength at Schaffer collateral to CA1 pyramidal cell synapses was observed after long-term activity reduction in organotypic hippocampal slices. Here we report that, following acute preparation of adult rat hippocampal slices and surgical removal of area CA3, input to area CA1 was reduced and Schaffer collateral synapses underwent functional strengthening. This increase in synaptic strength was limited to Schaffer collateral inputs (no alteration to temporoammonic synapses) and acted to normalize postsynaptic discharge, supporting a homeostatic or compensatory response. Short-term plasticity was not altered, but an increase in immunohistochemical labeling of GluA1 subunits was observed in the stratum radiatum (but not stratum moleculare), suggesting increased numbers of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors and a postsynaptic locus of expression. Combined, these data support the idea that, in response to the reduction in presynaptic activity caused by removal of area CA3, Schaffer collateral synapses undergo a relatively rapid increase in functional efficacy likely supported by insertion of more AMPARs, which maintains postsynaptic excitability in CA1 pyramidal neurons. This novel fast compensatory plasticity exhibits properties that would allow it to maintain optimal network activity levels in the hippocampus, a brain structure lauded for its ongoing experience-dependent malleability. Copyright © 2018 Elsevier B.V. All rights reserved.

  18. Spatial allocation of forest recreation value

    Kenneth A. Baerenklau; Armando Gonzalez-Caban; Catrina Paez; Edgard Chavez

    2009-01-01

    Non-market valuation methods and geographic information systems are useful planning and management tools for public land managers. Recent attention has been given to investigation and demonstration of methods for combining these tools to provide spatially-explicit representations of non-market value. Most of these efforts have focused on spatial allocation of...

  19. MPEG DASH SRD : Spatial Relationship Description

    Niamut, O.A.; Thomas, E.D.R.; D'Acunto, L.; Concolato, C.; Denoual, F.; Yong Lim, S.

    2016-01-01

    This paper presents the Spatial Representation Description (SRD)feature of the second amendment of MPEG DASH standard part 1, 23009-1:2014 [1]. SRD is an approach for streaming only spatial sub-parts of a video to display devices, in combination with the form of adaptive multi-rate streaming that is

  20. A influência do método de musicoterapia de John Bean e da musicoterapia em geral na representação espacial do corpo de pessoas com paralisia cerebral (2004 -2010 The influence of John Bean's music therapy method and of music therapy in general in body spatial representation in people with cerebral palsy (2004-2010

    Jose M.ª Fernández Batanero

    2010-12-01

    Full Text Available Acreditar no princípio da normalização, pressupõem acreditar que todas as pessoas merecem uma sociedade que atenda aos direitos humanos. Uma sociedade que vá ao encontro das características e das particularidades de cada pessoa, atendendo de modo diferenciado às necessidades dos seus elementos, sejam eles ditos "normais", ou com problemáticas. Assim, este artigo, tendo por base um método de investigação quantitativo/qualitativo, aborda a influência do método de musicoterapia de John Bean e da musicoterapia em geral na representação espacial do corpo de pessoas com paralisia cerebral.Believing in the principle of normalization implies believing that all people deserve a society that defends human rights. A society that respects each person's characteristics and particularities, must respond differently to the needs of its constituents, whether or not they are "normal" or have problems. Thus, this article, based on a quantitative/qualitative research approach, discusses the influence of John Bean's music therapy method and of music therapy in general on the spatial representation of the body in people with cerebral palsy.

  1. Categorification and higher representation theory

    Beliakova, Anna

    2017-01-01

    The emergent mathematical philosophy of categorification is reshaping our view of modern mathematics by uncovering a hidden layer of structure in mathematics, revealing richer and more robust structures capable of describing more complex phenomena. Categorified representation theory, or higher representation theory, aims to understand a new level of structure present in representation theory. Rather than studying actions of algebras on vector spaces where algebra elements act by linear endomorphisms of the vector space, higher representation theory describes the structure present when algebras act on categories, with algebra elements acting by functors. The new level of structure in higher representation theory arises by studying the natural transformations between functors. This enhanced perspective brings into play a powerful new set of tools that deepens our understanding of traditional representation theory. This volume exhibits some of the current trends in higher representation theory and the diverse te...

  2. The Koslowski-Sahlmann representation: quantum configuration space

    Campiglia, Miguel; Varadarajan, Madhavan

    2014-09-01

    The Koslowski-Sahlmann (KS) representation is a generalization of the representation underlying the discrete spatial geometry of loop quantum gravity (LQG), to accommodate states labelled by smooth spatial geometries. As shown recently, the KS representation supports, in addition to the action of the holonomy and flux operators, the action of operators which are the quantum counterparts of certain connection dependent functions known as ‘background exponentials’. Here we show that the KS representation displays the following properties which are the exact counterparts of LQG ones: (i) the abelian * algebra of SU(2) holonomies and ‘U(1)’ background exponentials can be completed to a C* algebra, (ii) the space of semianalytic SU(2) connections is topologically dense in the spectrum of this algebra, (iii) there exists a measure on this spectrum for which the KS Hilbert space is realized as the space of square integrable functions on the spectrum, (iv) the spectrum admits a characterization as a projective limit of finite numbers of copies of SU(2) and U(1), (v) the algebra underlying the KS representation is constructed from cylindrical functions and their derivations in exactly the same way as the LQG (holonomy-flux) algebra except that the KS cylindrical functions depend on the holonomies and the background exponentials, this extra dependence being responsible for the differences between the KS and LQG algebras. While these results are obtained for compact spaces, they are expected to be of use for the construction of the KS representation in the asymptotically flat case.

  3. Representations built from a true geographic database

    Bodum, Lars

    2005-01-01

    the whole world in 3d and with a spatial reference given by geographic coordinates. Built on top of this is a customised viewer, based on the Xith(Java) scenegraph. The viewer reads the objects directly from the database and solves the question about Level-Of-Detail on buildings, orientation in relation...... a representation based on geographic and geospatial principles. The system GRIFINOR, developed at 3DGI, Aalborg University, DK, is capable of creating this object-orientation and furthermore does this on top of a true Geographic database. A true Geographic database can be characterized as a database that can cover...

  4. The Roles of Representations in Building Design

    Harty, Chris; Tryggestad, Kjell

    2012-01-01

    minimum) spatial requirements should be to allow effective care of patients. The first representation is a three dimensional augmented reality model of a single room for a new hospital in the UK, using a CAVE (Cave Automatic Virtual Environment) where the room is reproduced virtually at one-to-one scale......, and which can be explored or navigated using head-tracker technology and a joystick controller. The second is a physical mock up of a single room for a Danish hospital where actual medical procedures are simulated using real equipment and real people. Drawing on Latour’s concepts of matters of concern...

  5. Representation of the Divine

    Loddegaard, Anne

    2012-01-01

    out of place in a novel belonging to the serious combat literature of the Catholic Revival, and the direct representation of the supernatural is also surprising because previous Catholic Revival novelists, such as Léon Bloy and Karl-Joris Huysmans, maintain a realistic, non-magical world and deal...... Satan episode in Under Satan’s Sun is neither a break with the seriousness nor with the realism of the Catholic novel. On the basis of Tvetan Todorov’s definition of the traditional fantastic tale, the analysis shows that only the beginning of the fantastic episode follows Todorov’s definition...

  6. Representation of the Divine

    Loddegaard, Anne

    2009-01-01

    out of place in a novel belonging to the serious combat literature of the Catholic Revival, and the direct representation of the supernatural is also surprising because previous Catholic Revival novelists, such as Léon Bloy and Karl-Joris Huysmans, maintain a realistic, non-magical world and deal...... Satan episode in Under Satan’s Sun is neither a break with the seriousness nor with the realism of the Catholic novel. On the basis of Tvetan Todorov’s definition of the traditional fantastic tale, the analysis shows that only the beginning of the fantastic episode follows Todorov’s definition...

  7. Representations of commonsense knowledge

    Davis, Ernest

    1990-01-01

    Representations of Commonsense Knowledge provides a rich language for expressing commonsense knowledge and inference techniques for carrying out commonsense knowledge. This book provides a survey of the research on commonsense knowledge.Organized into 10 chapters, this book begins with an overview of the basic ideas on artificial intelligence commonsense reasoning. This text then examines the structure of logic, which is roughly analogous to that of a programming language. Other chapters describe how rules of universal validity can be applied to facts known with absolute certainty to deduce ot

  8. Between Representation and Eternity

    Atzbach, Rainer

    2016-01-01

    This paper seeks to explore how prayer and praying practice are reflected in archaeological sources. Apart from objects directly involved in the personal act of praying, such as rosaries and praying books, churches and religious foundations played a major role in the medieval system of intercession....... At death, an indi- vidual’s corpse and burial primarily reflect the social act of representation during the funeral. The position of the arms, which have incorrectly been used as a chronological tool in Scandinavia, may indicate an evolution from a more collective act of prayer up to the eleventh century...

  9. Parametric time-frequency domain spatial audio

    Delikaris-Manias, Symeon; Politis, Archontis

    2018-01-01

    This book provides readers with the principles and best practices in spatial audio signal processing. It describes how sound fields and their perceptual attributes are captured and analyzed within the time-frequency domain, how essential representation parameters are coded, and how such signals are efficiently reproduced for practical applications. The book is split into four parts starting with an overview of the fundamentals. It then goes on to explain the reproduction of spatial sound before offering an examination of signal-dependent spatial filtering. The book finishes with coverage of both current and future applications and the direction that spatial audio research is heading in. Parametric Time-frequency Domain Spatial Audio focuses on applications in entertainment audio, including music, home cinema, and gaming--covering the capturing and reproduction of spatial sound as well as its generation, transduction, representation, transmission, and perception. This book will teach readers the tools needed...

  10. Cultural Shifts, Multimodal Representations, and Assessment Practices: A Case Study

    Curwood, Jen Scott

    2012-01-01

    Multimodal texts involve the presence, absence, and co-occurrence of alphabetic text with visual, audio, tactile, gestural, and spatial representations. This article explores how teachers' evaluation of students' multimodal work can be understood in terms of cognition and culture. When teachers apply a paradigm of assessment rooted in print-based…

  11. Social Representations of Intelligence

    Elena Zubieta

    2016-02-01

    Full Text Available The article stresses the relationship between Explicit and Implicit theories of Intelligence. Following the line of common sense epistemology and the theory of Social Representations, a study was carried out in order to analyze naive’s explanations about Intelligence Definitions. Based on Mugny & Carugati (1989 research, a self-administered questionnaire was designed and filled in by 286 subjects. Results are congruent with the main hyphotesis postulated: A general overlap between explicit and implicit theories showed up. According to the results Intelligence appears as both, a social attribute related to social adaptation and as a concept defined in relation with contextual variables similar to expert’s current discourses. Nevertheless, conceptions based on “gifted ideology” still are present stressing the main axes of Intelligence debate: biological and sociological determinism. In the same sense, unfamiliarity and social identity are reaffirmed as organizing principles of social representation. The distance with the object -measured as the belief in intelligence differences as a solve/non solve problem- and the level of implication with the topic -teachers/no teachers- appear as discriminating elements at the moment of supporting specific dimensions. 

  12. Spatial navigation by congenitally blind individuals

    Schinazi, Victor R.; Thrash, Tyler; Chebat, Daniel?Robert

    2015-01-01

    Spatial navigation in the absence of vision has been investigated from a variety of perspectives and disciplines. These different approaches have progressed our understanding of spatial knowledge acquisition by blind individuals, including their abilities, strategies, and corresponding mental representations. In this review, we propose a framework for investigating differences in spatial knowledge acquisition by blind and sighted people consisting of three longitudinal models (i.e., convergen...

  13. Mechanisms for Human Spatial Competence

    Gunzelmann, Glenn; Lyon, Don R.

    Research spanning decades has generated a long list of phenomena associated with human spatial information processing. Additionally, a number of theories have been proposed about the representation, organization and processing of spatial information by humans. This paper presents a broad account of human spatial competence, integrated with the ACT-R cognitive architecture. Using a cognitive architecture grounds the research in a validated theory of human cognition, enhancing the plausibility of the overall account. This work posits a close link of aspects of spatial information processing to vision and motor planning, and integrates theoretical perspectives that have been proposed over the history of research in this area. In addition, the account is supported by evidence from neuropsychological investigations of human spatial ability. The mechanisms provide a means of accounting for a broad range of phenomena described in the experimental literature.

  14. Mental map and spatial thinking

    Vanzella Castellar, Sonia Maria; Cristiane Strina Juliasz, Paula

    2018-05-01

    The spatial thinking is a central concept in our researches at the Faculty of Education of University of São Paulo (FE-USP). The cartography is fundamental to this kind of thinking, because it contributes to the development of the representation of space. The spatial representations are the drawings - mental maps - maps, chart, aerial photos, satellite images, graphics and diagrams. To think spatially - including the contents and concepts geographical and their representations - also corresponds to reason, defined by the skills the individual develops to understand the structure, function of a space, and describe your organization and relation to other spaces. The aim of this paper is to analyze the role of mental maps in the development of concepts of city and landscape - structuring concepts for school geography. The purpose is to analyze how students in Geography and Pedagogy - future teachers - and young children in Early Childhood Education think, feel, and appropriate these concepts. The analys is indicates the importance of developing mental map in activities with pedagogy and geography graduate student to know that students at school can be producers of maps. Cartography is a language and allows the student to develop the spatial and temporal relationships and notions such as orientation, distance and location, learning the concepts of geographical science. Mental maps present the basic features of the location such as the conditions - the features verified in one place - and the connections that is to understand how this place connects to other places.

  15. Selection of spatial reference frames depends on task's demands

    Greeshma Sharma

    2016-12-01

    Full Text Available Spatial reference frames (SRF are the means of representing spatial relations or locations either in an egocentric coordinate system (centred on navigator or in an allocentric coordinate system (Centred on object. It is necessary to understand when and how spatial representation switches between allocentric and egocentric reference frames in context to spatial tasks. The objective of this study was to explore if the elementary spatial representation does exist, whether it would remain consistent or change under the influence of a task's demand. Also, we explored how the SRF would assist if the environment is enriched with landmarks, having multiple routes for wayfinding. The results showed that the switching of SRF depends not only on the default representation but also on a task's demand. They also demonstrated that participants who were using allocentric representation performed better in the presence of landmarks.

  16. Vision and the representation of the surroundings in spatial memory

    Tatler, Benjamin W.; Land, Michael F.

    2011-01-01

    One of the paradoxes of vision is that the world as it appears to us and the image on the retina at any moment are not much like each other. The visual world seems to be extensive and continuous across time. However, the manner in which we sample the visual environment is neither extensive nor continuous. How does the brain reconcile these differences? Here, we consider existing evidence from both static and dynamic viewing paradigms together with the logical requirements of any representatio...

  17. Dualgrid : a closed representation space for consistent spatial databases

    Cotelo Lema, José Antonio

    2013-01-01

    [Resumen] En las últimas décadas se ha dedicado un significativo esfuerzo a la integración de las tecnologías de Sistemas de Información Geográfica (SIG) con sistemas de información más tradicionales. Para dar soporte a esa integración la tecnología de representación de datos espaciales ha sido mejorada en múltiples aspectos, desde los modelos (conceptuales y discretos) de representación de datos y lenguajes de consulta a las tecnologías de indexación y visualización y a los estándares de int...

  18. Parental representations of transsexuals.

    Parker, G; Barr, R

    1982-06-01

    The parental representations of 30 male-to-female transsexuals were rated using a measure of fundamental parental dimensions and shown to be of acceptable validity as a measure both of perceived and actual parental characteristics. Scores on that measure were compared separately against scores returned by matched male and female controls. The transsexuals did not differ from the male controls in their scoring of their mothers but did score their fathers as less caring and more overprotective. These differences were weaker for the comparisons made against the female controls. Item analyses suggested that the greater paternal "overprotection" experienced by transsexuals was due to their fathers being perceived as offering less encouragement to their sons' independence and autonomy. Several interpretations of the findings are considered.

  19. Computer aided surface representation

    Barnhill, R.E.

    1990-02-19

    The central research problem of this project is the effective representation, computation, and display of surfaces interpolating to information in three or more dimensions. If the given information is located on another surface, then the problem is to construct a surface defined on a surface''. Sometimes properties of an already defined surface are desired, which is geometry processing''. Visualization of multivariate surfaces is possible by means of contouring higher dimensional surfaces. These problems and more are discussed below. The broad sweep from constructive mathematics through computational algorithms to computer graphics illustrations is utilized in this research. The breadth and depth of this research activity makes this research project unique.

  20. The representation of neutron polarization

    Byrne, J.

    1979-01-01

    Neutron beam polarization representation is discussed under the headings; transfer matrices, coherent parity violation for neutrons, neutron spin rotation in helical magnetic fields, polarization and interference. (UK)

  1. Sinusoidal Representation of Acoustic Signals

    Honda, Masaaki

    Sinusoidal representation of acoustic signals has been an important tool in speech and music processing like signal analysis, synthesis and time scale or pitch modifications. It can be applicable to arbitrary signals, which is an important advantage over other signal representations like physical modeling of acoustic signals. In sinusoidal representation, acoustic signals are composed as sums of sinusoid (sine wave) with different amplitudes, frequencies and phases, which is based on the timedependent short-time Fourier transform (STFT). This article describes the principles of acoustic signal analysis/synthesis based on a sinusoid representation with focus on sine waves with rapidly varying frequency.

  2. Spin-on Bi4Sr3Ca3Cu4O16μ/sub x/ superconducting thin films from citrate precursors

    Furcone, S.L.; Chiang, Y.

    1988-01-01

    Thin films in the Bi-Sr-Ca-Cu-O system have been synthesized from homogeneous liquid citrate precursors by a spin-coating and pyrolysis method. Films prepared on SrTiO 3 substrates of [100] orientation show strongly textured orientations with the c axis of the predominant Bi 4 Sr 3 Ca 3 Cu 4 O 16 μ/sub x/ phase normal to the film plane. In a single coating and firing, crack-free films of 0.2--0.5 μm thickness are obtained. For films fired to peak temperatures of 850--875 0 C, linearly decreasing resistance with temperature is observed, with rho (300 K)∼460 μΩ cm and rho (300 K)rho (100 K)∼2.4. Clear onsets of superconductivity are observed at 90--100 K, with occasional films showing smaller resistant drops at 110--120 K. For all films, T/sub c/ (R = 0) occurs in the range 70--75 K. High critical current densities at 4.2 K of 5--8 x 10 5 Acm 2 are measured by direct transport

  3. Dual role of an ac driving force and the underlying two distinct order–disorder transitions in the vortex phase diagram of Ca3Ir4Sn13

    Kumar, Santosh; Singh, Ravi P.; Thamizhavel, A.; Tomy, C.V.; Grover, A.K.

    2014-01-01

    Highlights: • This work pertains to new findings related to a broad SMP anomaly. • Broad SMP prima facie encompasses two phase transformations in vortex matter. • We demarcated two phase boundaries pertaining to order–disorder transitions which have quasi first-order nature. - Abstract: We present distinct demarcation of the Bragg glass (BG) to multi-domain vortex glass (VG) transition line and the eventual amorphization of the VG phase in a weakly pinned single crystal of the superconducting compound Ca 3 Ir 4 Sn 13 on the basis of comprehension of the different yields about the second magnetization peak (SMP) anomaly in the dc magnetization and the corresponding anomalous feature in the ac susceptibility measurements. The shaking by a small ac magnetic field, inevitably present in the ac susceptibility measurements, is seen to result in contrasting responses in two different portions of the field-temperature (H, T) phase space of the multi-domain VG. In one of the portions, embracing the BG to VG transition across the onset of the SMP anomaly, the ac drive is surprisingly seen to assist the transformation of the well ordered BG phase to a lesser ordered VG phase. The BG phase exists as a superheated state over a small portion of the VG space and this attests to the first order nature of the BG to VG transition

  4. A neuronal lactate uptake inhibitor slows recovery of extracellular ion concentration changes in the hippocampal CA3 region by affecting energy metabolism.

    Angamo, Eskedar Ayele; Rösner, Joerg; Liotta, Agustin; Kovács, Richard; Heinemann, Uwe

    2016-11-01

    Astrocyte-derived lactate supports pathologically enhanced neuronal metabolism, but its role under physiological conditions is still a matter of debate. Here, we determined the contribution of astrocytic neuronal lactate shuttle for maintenance of ion homeostasis and energy metabolism. We tested for the effects of α-cyano-4-hydroxycinnamic acid (4-CIN), which could interfere with energy metabolism by blocking monocarboxylate-transporter 2 (MCT2)-mediated neuronal lactate uptake, on evoked potentials, stimulus-induced changes in K + , Na + , Ca 2+ , and oxygen concentrations as well as on changes in flavin adenine dinucleotide (FAD) autofluorescence in the hippocampal area CA3. MCT2 blockade by 4-CIN reduced synaptically evoked but not antidromic population spikes. This effect was dependent on the activation of K ATP channels indicating reduced neuronal ATP synthesis. By contrast, lactate receptor activation by 3,5-dihydroxybenzoic acid (3,5-DHBA) resulted in increased antidromic and orthodromic population spikes suggesting that 4-CIN effects are not mediated by lactate accumulation and subsequent activation of lactate receptors. Recovery kinetics of all ion transients were prolonged and baseline K + concentration became elevated by blockade of lactate uptake. Lactate contributed to oxidative metabolism as both baseline respiration and stimulus-induced changes in Po 2 were decreased, while FAD fluorescence increased likely due to a reduced conversion of FAD into FADH 2 These data suggest that lactate shuttle contributes to regulation of ion homeostatsis and synaptic signaling even in the presence of ample glucose. Copyright © 2016 the American Physiological Society.

  5. Soft antiphase tilt of oxygen octahedra in the hybrid improper multiferroic Ca3Mn1.9Ti0.1O7

    Ye, Feng; Wang, Jinchen; Sheng, Jieming; Hoffmann, C.; Gu, T.; Xiang, H. J.; Tian, Wei; Molaison, J. J.; dos Santos, A. M.; Matsuda, M.; Chakoumakos, B. C.; Fernandez-Baca, J. A.; Tong, X.; Gao, Bin; Kim, Jae Wook; Cheong, S.-W.

    2018-01-01

    We report a single crystal neutron and x-ray diffraction study of the hybrid improper multiferroic Ca3Mn1.9Ti0.1O7 (CMTO), a prototypical system where the electric polarization arises from the condensation of two lattice distortion modes. With increasing temperature (T ), the out-of-plane, antiphase tilt of MnO6 decreases in amplitude while the in-plane, in-phase rotation remains robust and experiences abrupt changes across the first-order structural transition. Application of hydrostatic pressure (P ) to CMTO at room temperature shows a similar effect. The consistent behavior under both T and P reveals the softness of antiphase tilt and highlights the role of the partially occupied d orbital of the transition-metal ions in determining the stability of the octahedral distortion. Polarized neutron analysis indicates the symmetry-allowed canted ferromagnetic moment is less than the 0.04 μB/Mn site, despite a substantial out-of-plane tilt of the MnO6 octahedra.

  6. The role of memory representation in the vigilance decrement.

    Caggiano, Daniel M; Parasuraman, Raja

    2004-10-01

    Working memory load is critically important for the overall level of performance on vigilance tasks. However, its role in a key aspect of vigilance-sensitivity decrement over time-is unclear. We used a dual-task procedure in which either a spatial or a nonspatial working memory task was performed simultaneously with a spatial vigilance task for 20 min. Sensitivity in the vigilance task declined over time when the concurrent task involved spatial working memory. In contrast, there was no sensitivity decrement with a nonspatial working memory task. The results provide the first evidence of a specific role for working memory representation in vigilance decrement. The findings are also consistent with a multiple resource theory in which separate resources for memory representation and cognitive control operations are differentially susceptible to depletion over time, depending on the demands of the task at hand.

  7. Representation of critical natural capital in China.

    Lü, Yihe; Zhang, Liwei; Zeng, Yuan; Fu, Bojie; Whitham, Charlotte; Liu, Shuguang; Wu, Bingfang

    2017-08-01

    Traditional means of assessing representativeness of conservation value in protected areas depend on measures of structural biodiversity. The effectiveness of priority conservation areas at representing critical natural capital (CNC) (i.e., an essential and renewable subset of natural capital) remains largely unknown. We analyzed the representativeness of CNC-conservation priority areas in national nature reserves (i.e., nature reserves under jurisdiction of the central government with large spatial distribution across the provinces) in China with a new biophysical-based composite indicator approach. With this approach, we integrated the net primary production of vegetation, topography, soil, and climate variables to map and rank terrestrial ecosystems capacities to generate CNC. National nature reserves accounted for 6.7% of CNC-conservation priority areas across China. Considerable gaps (35.2%) existed between overall (or potential) CNC representativeness nationally and CNC representation in national reserves, and there was significant spatial heterogeneity of representativeness in CNC-conservation priority areas at the regional and provincial levels. For example, the best and worst representations were, respectively, 13.0% and 1.6% regionally and 28.9% and 0.0% provincially. Policy in China is transitioning toward the goal of an ecologically sustainable civilization. We identified CNC-conservation priority areas and conservation gaps and thus contribute to the policy goals of optimization of the national nature reserve network and the demarcation of areas critical to improving the representativeness and conservation of highly functioning areas of natural capital. Moreover, our method for assessing representation of CNC can be easily adapted to other large-scale networks of conservation areas because few data are needed, and our model is relatively simple. © 2017 Society for Conservation Biology.

  8. The Spatial and the Visual in Mental Spatial Reasoning: An Ill-Posed Distinction

    Schultheis, Holger; Bertel, Sven; Barkowsky, Thomas; Seifert, Inessa

    It is an ongoing and controversial debate in cognitive science which aspects of knowledge humans process visually and which ones they process spatially. Similarly, artificial intelligence (AI) and cognitive science research, in building computational cognitive systems, tended to use strictly spatial or strictly visual representations. The resulting systems, however, were suboptimal both with respect to computational efficiency and cognitive plau sibility. In this paper, we propose that the problems in both research strands stem from a mis conception of the visual and the spatial in mental spatial knowl edge pro cessing. Instead of viewing the visual and the spatial as two clearly separable categories, they should be conceptualized as the extremes of a con tinuous dimension of representation. Regarding psychology, a continuous di mension avoids the need to exclusively assign processes and representations to either one of the cate gories and, thus, facilitates a more unambiguous rating of processes and rep resentations. Regarding AI and cognitive science, the con cept of a continuous spatial / visual dimension provides the possibility of rep re sentation structures which can vary continuously along the spatial / visual di mension. As a first step in exploiting these potential advantages of the pro posed conception we (a) introduce criteria allowing for a non-dichotomic judgment of processes and representations and (b) present an approach towards rep re sentation structures that can flexibly vary along the spatial / visual dimension.

  9. Hacked Landscapes: Tensions, Borders, and Positionality in Spatial Literacy

    Schmidt, Sandra J.

    2017-01-01

    By focusing on critical geographies, landscape, and spatial literacy, this article evaluates a semester-long spatial justice project conducted in a preservice teacher education program. The analysis recognizes the limitations of reading the products literally as a means of comprehending spatial representation. It expands the analysis by hacking…

  10. Language and Spatial Reorientation: Evidence from Severe Aphasia

    Bek, Judith; Blades, Mark; Siegal, Michael; Varley, Rosemary

    2010-01-01

    Investigating spatial cognition in individuals with acquired language impairments can inform our understanding of how components of language are involved in spatial representation. Using the reorientation paradigm of Hermer-Vazquez, Spelke, and Katsnelson (1999), we examined spatial cue integration (landmark-geometry conjunctions) in individuals…

  11. Cognitive maps, spatial abilities and human wayfinding.

    Golledge, Reginald G.; Jacobson, R. Daniel; Kitchin, Rob; Blades, Mark

    2000-01-01

    In this paper we discuss the relations between cognitive maps, spatial abilities and human wayfinding, particularly in the context of traveling without the use of sight. Initially we discuss the nature of cognitive maps and the process of cognitive mapping as mechanisms for developing person to object (egocentric) and object to object (allocentric) internal representations. Imperfections in encoding either relations can introduce imperfections in representations of environments in memory. Thi...

  12. Congruence properties of induced representations

    Mayer, Dieter; Momeni, Arash; Venkov, Alexei

    In this paper we study representations of the projective modular group induced from the Hecke congruence group of level 4 with Selberg's character. We show that the well known congruence properties of Selberg's character are equivalent to the congruence properties of the induced representations...

  13. Factorial representations of path groups

    Albeverio, S.; Hoegh-Krohn, R.; Testard, D.; Vershik, A.

    1983-11-01

    We give the reduction of the energy representation of the group of mappings from I = [ 0,1 ], S 1 , IRsub(+) or IR into a compact semi simple Lie group G. For G = SU(2) we prove the factoriality of the representation, which is of type III in the case I = IR

  14. Using Integer Manipulatives: Representational Determinism

    Bossé, Michael J.; Lynch-Davis, Kathleen; Adu-Gyamfi, Kwaku; Chandler, Kayla

    2016-01-01

    Teachers and students commonly use various concrete representations during mathematical instruction. These representations can be utilized to help students understand mathematical concepts and processes, increase flexibility of thinking, facilitate problem solving, and reduce anxiety while doing mathematics. Unfortunately, the manner in which some…

  15. Knowledge Representation: A Brief Review.

    Vickery, B. C.

    1986-01-01

    Reviews different structures and techniques of knowledge representation: structure of database records and files, data structures in computer programming, syntatic and semantic structure of natural language, knowledge representation in artificial intelligence, and models of human memory. A prototype expert system that makes use of some of these…

  16. International agreements on commercial representation

    Slanař, Jan

    2014-01-01

    The purpose of the thesis is to describe the possibilities for fixing the position of a company in the market through contracts for commercial representation with a focus to finding legal and economic impact on the company that contracted for exclusive representation.

  17. Scientific Representation and Science Learning

    Matta, Corrado

    2014-01-01

    In this article I examine three examples of philosophical theories of scientific representation with the aim of assessing which of these is a good candidate for a philosophical theory of scientific representation in science learning. The three candidate theories are Giere's intentional approach, Suárez's inferential approach and Lynch and…

  18. A generalized wavelet extrema representation

    Lu, Jian; Lades, M.

    1995-10-01

    The wavelet extrema representation originated by Stephane Mallat is a unique framework for low-level and intermediate-level (feature) processing. In this paper, we present a new form of wavelet extrema representation generalizing Mallat`s original work. The generalized wavelet extrema representation is a feature-based multiscale representation. For a particular choice of wavelet, our scheme can be interpreted as representing a signal or image by its edges, and peaks and valleys at multiple scales. Such a representation is shown to be stable -- the original signal or image can be reconstructed with very good quality. It is further shown that a signal or image can be modeled as piecewise monotonic, with all turning points between monotonic segments given by the wavelet extrema. A new projection operator is introduced to enforce piecewise inonotonicity of a signal in its reconstruction. This leads to an enhancement to previously developed algorithms in preventing artifacts in reconstructed signal.

  19. Multiple representations in physics education

    Duit, Reinders; Fischer, Hans E

    2017-01-01

    This volume is important because despite various external representations, such as analogies, metaphors, and visualizations being commonly used by physics teachers, educators and researchers, the notion of using the pedagogical functions of multiple representations to support teaching and learning is still a gap in physics education. The research presented in the three sections of the book is introduced by descriptions of various psychological theories that are applied in different ways for designing physics teaching and learning in classroom settings. The following chapters of the book illustrate teaching and learning with respect to applying specific physics multiple representations in different levels of the education system and in different physics topics using analogies and models, different modes, and in reasoning and representational competence. When multiple representations are used in physics for teaching, the expectation is that they should be successful. To ensure this is the case, the implementati...

  20. Islam and Media Representations

    Mohamed Bensalah

    2006-04-01

    Full Text Available For the author of this article, the media’s treatment of Islam has raised numerous polymorphous questions and debates. Reactivated by the great scares of current events, the issue, though an ancient one, calls many things into question. By way of introduction, the author tries to analyse the complex processes of elaboration and perception of the representations that have prevailed during the past century. In referring to the semantic decoding of the abundant colonial literature and iconography, the author strives to translate the extreme xenophobic tensions and the identity crystallisations associated with the current media orchestration of Islam, both in theWest and the East. He then evokes the excesses of the media that are found at the origin of many amalgams wisely maintained between Islam, Islamism and Islamic terrorism, underscoring their duplicity and their willingness to put themselves, consciously, in service to deceivers and directors of awareness, who are very active at the heart of the politico-media sphere. After levelling a severe accusation against the harmful drifts of the media, especially in times of crisis and war, the author concludes by asserting that these tools of communication, once they are freed of their masks and invective apparatuses, can be re-appropriated by new words and bya true communication between peoples and cultures.

  1. Chemical thermodynamic representation of

    Lindemer, T.B.; Besmann, T.M.

    1984-01-01

    The entire data base for the dependence of the nonstoichiometry, x, on temperature and chemical potential of oxygen (oxygen potential) was retrieved from the literature and represented. This data base was interpreted by least-squares analysis using equations derived from the classical thermodynamic theory for the solid solution of a solute in a solvent. For hyperstoichiometric oxide at oxygen potentials more positive than -266700 + 16.5T kJ/mol, the data were best represented by a [UO 2 ]-[U 3 O 7 ] solution. For O/U ratios above 2 and oxygen potentials below this boundary, a [UO 2 ]-[U 2 O 4 . 5 ] solution represented the data. The data were represented by a [UO 2 ]-[U 1 / 3 ] solution. The resulting equations represent the experimental ln(PO 2 ) - ln(x) behavior and can be used in thermodynamic calculations to predict phase boundary compositions consistent with the literature. Collectively, the present analysis permits a mathematical representation of the behavior of the total data base

  2. Changes in the content of fatty acids in CA1 and CA3 areas of the hippocampus of Krushinsky-Molodkina rats after single and fivefold audiogenic seizures.

    Savina, Tatyana; Aripovsky, Alexander; Kulagina, Tatyana

    2017-09-01

    Audiogenic seizures (AS) are generalized seizures evoked by high frequency sounds. Since the hippocampus is involved in the generation and maintenance of seizures, the effect of AS on the composition and content of fatty acids in the CA1 and CA3 hippocampal areas of AS-susceptible Krushinsky-Molodkina (KM) rats on days 1, 3, and 14 after single and fivefold seizures were examined. The total content of all fatty acids in field СА1 was found to be lower compared with the control at all times of observation after both a single seizure or fivefold seizures. The total content of fatty acids in field СА3 decreased at all times of examination after a single seizure, whereas it remained unchanged on days 3 and 14 following five AS. The content of omega-3 fatty acids in both fields at all times of observation after a single seizure and fivefold AS did not significantly differ from that in intact animals. The absence of significant changes in the content of stearic and α-linolenic acids and a considerable decrease in the levels of palmitic, oleic, and eicosapentaenoic acids were common to both fields at all times after both a single seizure or fivefold AS. The changes in the content of fatty acids in the СА3 and СА1 fields of the brain of AS-susceptible rats indicate that fatty acids are involved in both the development of seizure activity and neuroprotective anticonvulsive processes. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Structural and photoluminescence properties of stannate based displaced pyrochlore-type red phosphors: Ca(3-x)Sn₃Nb₂O₁₄:xEu³⁺.

    Sreena, T S; Prabhakar Rao, P; Francis, T Linda; Raj, Athira K V; Babu, Parvathi S

    2015-05-14

    New stannate based displaced pyrochlore-type red phosphors, Ca(3-x)Sn3Nb2O14:xEu(3+), were prepared via a conventional solid state method. The influence of partial occupancy of Sn in both A and B sites of the pyrochlore-type oxides on the photoluminescence properties was studied using powder X-ray diffraction, FT-Raman, transmission electron microscopy, scanning electron microscopy with energy dispersive spectrometry, UV-visible absorption spectroscopy, and photoluminescence excitation and emission spectra with lifetime measurements. The structural analysis establishes that these oxides belong to a cubic displaced pyrochlore type structure with a space group Fd3̄m. These phosphors exhibit strong absorptions at near UV and blue wavelength regions and emit intense multiband emissions due to Eu(3+ 5)D0-(7)F(0, 1, 2) transitions. The absence of characteristic MD transition splitting points out that local cation disorder exists in this type of displaced pyrochlores, reducing the D(3d) inversion symmetry, which is not evidenced by such disorder in the X-ray diffraction analysis. The unusual forbidden intense sharp (5)D0-(7)F0 transition indicates single site occupancy of Eu(3+) with a narrower range of bonding environment, preventing the cluster formation. This is supported by the stable (5)D0 lifetime with Eu(3+) concentration. The Judd-Ofelt intensity parameter assessment corroborates these results. The CIE color coordinates of these phosphors were found to be (0.60, 0.40), which are close to the NTSC standard values (0.67, 0.33) for a potential red phosphor.

  4. 3D-Printed Bioactive Ca3SiO5 Bone Cement Scaffolds with Nano Surface Structure for Bone Regeneration.

    Yang, Chen; Wang, Xiaoya; Ma, Bing; Zhu, Haibo; Huan, Zhiguang; Ma, Nan; Wu, Chengtie; Chang, Jiang

    2017-02-22

    Silicate bioactive materials have been widely studied for bone regeneration because of their eminent physicochemical properties and outstanding osteogenic bioactivity, and different methods have been developed to prepare porous silicate bioactive ceramics scaffolds for bone-tissue engineering applications. Among all of these methods, the 3D-printing technique is obviously the most efficient way to control the porous structure. However, 3D-printed bioceramic porous scaffolds need high-temperature sintering, which will cause volume shrinkage and reduce the controllability of the pore structure accuracy. Unlike silicate bioceramic, bioactive silicate cements such as tricalcium silicate (Ca 3 SiO 5 and C 3 S) can be self-set in water to obtain high mechanical strength under mild conditions. Another advantage of using C 3 S to prepare 3D scaffolds is the possibility of simultaneous drug loading. Herein, we, for the first time, demonstrated successful preparation of uniform 3D-printed C 3 S bone cement scaffolds with controllable 3D structure at room temperature. The scaffolds were loaded with two model drugs and showed a loading location controllable drug-release profile. In addition, we developed a surface modification process to create controllable nanotopography on the surface of pore wall of the scaffolds, which showed activity to enhance rat bone-marrow stem cells (rBMSCs) attachment, spreading, and ALP activities. The in vivo experiments revealed that the 3D-printed C 3 S bone cement scaffolds with nanoneedle-structured surfaces significantly improved bone regeneration, as compared to pure C 3 S bone cement scaffolds, suggesting that 3D-printed C 3 S bone cement scaffolds with controllable nanotopography surface are bioactive implantable biomaterials for bone repair.

  5. Transport properties of Pb-doped Bi4Sr3Ca3Cu4Ox semiconducting glasses and glass-ceramic superconductors

    Chatterjee, S.; Banerjee, S.; Mollah, S.; Chaudhuri, B.K.

    1996-01-01

    Electrical conductivity and thermoelectric power (TEP) of the as-quenched and annealed (at 500 degree C for 10 h and 840 degree C for 24 h) Bi 4-n Pb n Sr 3 Ca 3 Cu 4 O x (x = 0 endash 1.0) glasses have been measured. The dc conductivity data of the as-quenched and the partially annealed (at 500 degree C) glasses can be explained by considering the small-polaron hopping conduction mechanism which is found to change from the nonadiabatic to the adiabatic regime with annealing the glasses at 500 degree C. This change over is due to the presence of microcrystals in the partially annealed glasses as observed from x-ray-diffraction and scanning electron microscopic studies. This adiabatic behavior is also visualized even for some as-quenched glasses having a very small amount of the more conducting microcrystalline phase. All the 840 degree C annealed glasses are superconductors with T c between 110 and 115 K. The Seebeck coefficient (S) of the partially annealed glass system is found to be positive and increases linearly with temperature. The S values of the corresponding glass-ceramic superconductors showing broad peaks around T c . A change over in the values of S from positive (below ∼290 K) to negative (above ∼290 K) indicates the coexistence of both electrons and holes in these superconductors. The TEP data can be fitted with both the two-band model of Forro et al. [Solid State Commun. 73, 501 (1990)] and the Nagaosa-Lee model [Phys. Rev. Lett. 64, 2450 (1990)]. Therefore, the bosonic contribution in the transport properties of these superconductors, as suggested by the Nagaosa-Lee model, is supported. copyright 1996 The American Physical Society

  6. (Cu,C)Ba2Ca3Cu4Ox (LiF)y: addition of LiF—an effective way to synthesize overdoped superconductor

    Badica, P.; Iyo, A.; Aldica, G.; Kito, H.; Crisan, A.; Tanaka, Y.

    2004-03-01

    (Cu,C)Ba2Ca3Cu4Ox superconductor with addition of y mol LiF has been synthesized by a high-pressure method. For the same synthesis conditions it was found that (almost) single-phase Cu, C-1234 samples can be synthesized for yLiF = 0-0.1 if the amount of z mol AgO oxidizer is increased linearly from zAgO = 0.45 to 0.73 and for yLiF = 0.1-0.2 if zAgO = 0.73 = constant. Transport measurements (rgr(T) and room-temperature Seebeck coefficient) have shown that these samples are overdoped: LiF is an effective addition for synthesis of overdoped Cu, C-1234 with a controlled level of carriers. LiF addition continuously decreases Tc. The critical point at yLiF = 0.1 is discussed as the solubility limit of LiF and/or the point where the doping mechanism changes. It is proposed that the reason is the reaction of extra Li with C and O to form Li2CO3, inducing a lower concentration of C in Cu, C-1234/LiF crystals, and at the same time a possible substitution of Li not only for the Cu site but also for the Ca site, resulting in formation of a higher amount of residual Ca0.828CuO2 (for yLiF>0.1). LiF induces the formation of a liquid phase and acts as a flux promoting the formation of Cu,C-12 (n-1)n with n \\ge 4 . LiF modifies to some degree the grain growth from a 3D to a 2D type (thinner platelike grains have been observed in the LiF added samples).

  7. X-ray photo-emission studies of Cu1-xTlxBa2Ca3Cu4O12-y superconductor thin films

    Khan, Nawazish A.; Mumtaz, M.; Ahadian, M.M.; Iraji-zad, Azam

    2006-01-01

    X-ray photo-emission spectroscopy (XPS) studies of Cu 1-x Tl x Ba 2 Ca 3 Cu 4 O 12-y superconductor thin films have been carried out for understanding the mechanism of superconductivity and to find out the reasons for the increase of zero resistivity critical temperature T c (R = 0) with post-annealing in a nitrogen atmosphere. It is observed from these studies that reduction of charge state of thallium is a source of doping of carriers to the CuO 2 planes. The reduced charge state of thallium (i.e. Tl 1+ ) promotes lower oxygen concentration in the charge reservoir layer, which possibly results in movement of electrons to the conducting CuO 2 planes. The higher density of electrons in the CuO 2 planes optimizes the hole concentration 'n p ' in these planes. The reduced charge state of thallium in the Cu 1-x Tl x Ba 2 O 4-δ charge reservoir layer is also supported by a shift of the Ba 3d 5/2 and Ba 3d 3/2 XPS lines to lower binding energies with post-annealing in nitrogen atmosphere. Moreover, the movement of the valance band spectrum to lower binding energies suggested that the electronic density of states changes in the valance band with the post-annealing in nitrogen, which possibly becomes a source of doping of carriers to the CuO 2 planes. The increased doping of electrons to the CuO 2 planes optimizes the Fermi-vector K F and Fermi-velocity V F of the carriers and increases the T c (R = 0) of final compound

  8. (Cu,C)Ba2Ca3Cu4Ox-(LiF)y: addition of LiF-an effective way to synthesize overdoped superconductor

    Badica, P; Iyo, A; Aldica, G; Kito, H; Crisan, A; Tanaka, Y

    2004-01-01

    (Cu,C)Ba 2 Ca 3 Cu 4 O x superconductor with addition of y mol LiF has been synthesized by a high-pressure method. For the same synthesis conditions it was found that (almost) single-phase Cu, C-1234 samples can be synthesized for y LiF = 0-0.1 if the amount of z mol AgO oxidizer is increased linearly from z AgO = 0.45 to 0.73 and for y LiF 0.1-0.2 if z AgO = 0.73 constant. Transport measurements (ρ(T) and room-temperature Seebeck coefficient) have shown that these samples are overdoped: LiF is an effective addition for synthesis of overdoped Cu, C-1234 with a controlled level of carriers. LiF addition continuously decreases T c . The critical point at y LiF = 0.1 is discussed as the solubility limit of LiF and/or the point where the doping mechanism changes. It is proposed that the reason is the reaction of extra Li with C and O to form Li 2 CO 3 , inducing a lower concentration of C in Cu, C-1234/LiF crystals, and at the same time a possible substitution of Li not only for the Cu site but also for the Ca site, resulting in formation of a higher amount of residual Ca 0.828 CuO 2 (for y LiF >0.1). LiF induces the formation of a liquid phase and acts as a flux promoting the formation of Cu,C-12 (n-1)n with n ≥ 4. LiF modifies to some degree the grain growth from a 3D to a 2D type (thinner platelike grains have been observed in the LiF added samples)

  9. The oxidation of alkylaryl sulfides and benzo[b]thiophenes by Escherichia coli cells expressing wild-type and engineered styrene monooxygenase from Pseudomonas putida CA-3.

    Nikodinovic-Runic, Jasmina; Coulombel, Lydie; Francuski, Djordje; Sharma, Narain D; Boyd, Derek R; Ferrall, Rory Moore O; O'Connor, Kevin E

    2013-06-01

    Nine different sulfur-containing compounds were biotransformed to the corresponding sulfoxides by Escherichia coli Bl21(DE3) cells expressing styrene monooxygenase (SMO) from Pseudomonas putida CA-3. Thioanisole was consumed at 83.3 μmoles min(-1) g cell dry weight(-1) resulting mainly in the formation of R-thioanisole sulfoxide with an enantiomeric excess (ee) value of 45 %. The rate of 2-methyl-, 2-chloro- and 2-bromo-thioanisole consumption was 2-fold lower than that of thioanisole. Surprisingly, the 2-methylthioanisole sulfoxide product had the opposite (S) configuration to that of the other 2-substituted thioanisole derivatives and had a higher ee value (84 %). The rate of oxidation of 4-substituted thioanisoles was higher than the corresponding 2-substituted substrates but the ee values of the products were consistently lower (10-23 %). The rate of benzo[b]thiophene and 2-methylbenzo[b]thiophene sulfoxidation was approximately 10-fold lower than that of thioanisole. The ee value of the benzo[b]thiophene sulfoxide could not be determined as the product racemized rapidly. E. coli cells expressing an engineered SMO (SMOeng R3-11) oxidised 2-substituted thioanisoles between 1.8- and 2.8-fold faster compared to cells expressing the wild-type enzyme. SMOeng R3-11 oxidised benzo[b]thiophene and 2-methylbenzo[b]thiophene 10.1 and 5.6 times faster that the wild-type enzyme. The stereospecificity of the reaction catalysed by SMOeng was unchanged from that of the wild type. Using the X-ray crystal structure of the P. putida S12 SMO, it was evident that the entrance of substrates into the SMO active site is limited by the binding pocket bottleneck formed by the side chains of Val-211 and Asn-46 carboxyamide group.

  10. Spatial Operations

    Anda VELICANU

    2010-09-01

    Full Text Available This paper contains a brief description of the most important operations that can be performed on spatial data such as spatial queries, create, update, insert, delete operations, conversions, operations on the map or analysis on grid cells. Each operation has a graphical example and some of them have code examples in Oracle and PostgreSQL.

  11. Spatializing Time

    Thomsen, Bodil Marie Stavning

    2011-01-01

    The article analyses some of artist Søren Lose's photographic installations in which time, history and narration is reflected in the creation of allegoric, spatial relations.......The article analyses some of artist Søren Lose's photographic installations in which time, history and narration is reflected in the creation of allegoric, spatial relations....

  12. Spatial Computation

    2003-12-01

    Computation and today’s microprocessors with the approach to operating system architecture, and the controversy between microkernels and monolithic kernels...Both Spatial Computation and microkernels break away a relatively monolithic architecture into in- dividual lightweight pieces, well specialized...for their particular functionality. Spatial Computation removes global signals and control, in the same way microkernels remove the global address

  13. Possible cause for altered spatial cognition of prepubescent rats exposed to chronic radiofrequency electromagnetic radiation.

    Narayanan, Sareesh Naduvil; Kumar, Raju Suresh; Karun, Kalesh M; Nayak, Satheesha B; Bhat, P Gopalakrishna

    2015-10-01

    The effects of chronic and repeated radiofrequency electromagnetic radiation (RFEMR) exposure on spatial cognition and hippocampal architecture were investigated in prepubescent rats. Four weeks old male Wistar rats were exposed to RF-EMR (900 MHz; SAR-1.15 W/kg with peak power density of 146.60 μW/cm(2)) for 1 h/day, for 28 days. Followed by this, spatial cognition was evaluated by Morris water maze test. To evaluate the hippocampal morphology; H&E staining, cresyl violet staining, and Golgi-Cox staining were performed on hippocampal sections. CA3 pyramidal neuron morphology and surviving neuron count (in CA3 region) were studied using H&E and cresyl violet stained sections. Dendritic arborization pattern of CA3 pyramidal neuron was investigated by concentric circle method. Progressive learning abilities were found to be decreased in RF-EMR exposed rats. Memory retention test performed 24 h after the last training revealed minor spatial memory deficit in RF-EMR exposed group. However, RF-EMR exposed rats exhibited poor spatial memory retention when tested 48 h after the final trial. Hirano bodies and Granulovacuolar bodies were absent in the CA3 pyramidal neurons of different groups studied. Nevertheless, RF-EMR exposure affected the viable cell count in dorsal hippocampal CA3 region. RF-EMR exposure influenced dendritic arborization pattern of both apical and basal dendritic trees in RF-EMR exposed rats. Structural changes found in the hippocampus of RF-EMR exposed rats could be one of the possible reasons for altered cognition.

  14. Coarse-to-Fine Encoding of Spatial Frequency Information into Visual Short-Term Memory for Faces but Impartial Decay

    Gao, Zaifeng; Bentin, Shlomo

    2011-01-01

    Face perception studies investigated how spatial frequencies (SF) are extracted from retinal display while forming a perceptual representation, or their selective use during task-imposed categorization. Here we focused on the order of encoding low-spatial frequencies (LSF) and high-spatial frequencies (HSF) from perceptual representations into…

  15. Ca 3d unoccupied states in Bi2Sr2CaCu2O8 investigated by Ca L2,3 x-ray-absorption near-edge structure

    Borg, A.; King, P.L.; Pianetta, P.; Lindau, I.; Mitzi, D.B.; Kapitulnik, A.; Soldatov, A.V.; Della Longa, S.; Bianconi, A.

    1992-01-01

    The high-resolution Ca L 2,3 x-ray-absorption near-edge-structure (XANES) spectrum of a Bi 2 Sr 2 CaCu 2 O 8 single crystal has been measured by use of a magnetic-projection x-ray microscope probing a surface area of 200x200 μm 2 . The Ca L 2,3 XANES spectrum is analyzed by performing a multiple-scattering XANES calculation in real space and comparing the results with the spectrum of CaF 2 . Good agreement between the calculated and experimental crystal-field splitting Δ f of the Ca 3d final states is found and the splitting is shown to be smaller by 0.5 eV than in the initial state. The Ca 3d partial density of states is found to be close to the Fermi level in the initial state. The Ca-O(in plane) distance is shown to be a critical parameter associated with the shift of the Ca 3d states relative to the Fermi level; in particular, we have studied the effect of the out-of-plane dimpling mode of the in-plane oxygen atoms O(in plane) that will move the Ca 3d states on or off the Fermi level. This mode can therefore play a role in modulating the charge transfer between the two CuO 2 planes separated by the Ca ions

  16. Ca 3d unoccupied states in Bi2Sr2CaCu2O8 investigated by Ca L2,3 x-ray-absorption near-edge structure

    Borg, A; King, P L; Pianetta, P; Lindau, I; Mitzi, D B

    1992-01-01

    The high-resolution Ca L(2,3) x-ray-absorption near-edge-structure (XANES) spectrum of a Bi2Sr2CaCu2O8 single crystal has been measured by use of a magnetic-projection x-ray microscope probing a surface area of 200x200 micrometers square. The Ca L(2,3) XANES spectrum is analyzed by performing a multiple-scattering XANES calculation in real space and comparing the results with the spectrum of CaF2. Good agreement between the calculated and experimental crystal-field splitting Delta f of the Ca 3d final states is found and the splitting is shown to be smaller by 0.5 eV than in the initial state. The Ca 3d partial density of states is found to be close to the Fermi level in the initial state. The Ca-O (in plane) distance is shown to be a critical parameter associated with the shift of the Ca 3d states relative to the Fermi level; in particular, the authors have studied the effect of the out-of-plane dimpling mode of the in-plane oxygen atoms O(in plane) that will move the Ca 3d states on or off the Fermi level. This mode can therefore play a role in modulating the charge transfer between the two CuO2 planes separated by the Ca ions.

  17. Towards a general theory of multi-representation data capture in GIS ...

    Normally, spatial databases were built by digitizing existing different scale maps. When there was a requirement for capturing new datasets in order to update databases or build new databases, the process usually follows a similar methodology, whereby different spatial databases were created with representations of each ...

  18. Tunable white light of a Ce3+,Tb3+,Mn2+ triply doped Na2Ca3Si2O8 phosphor for high colour-rendering white LED applications: tunable luminescence and energy transfer.

    Lü, Wei; Xu, Huawei; Huo, Jiansheng; Shao, Baiqi; Feng, Yang; Zhao, Shuang; You, Hongpeng

    2017-07-18

    A tunable white light emitting Na 2 Ca 3 Si 2 O 8 :Ce 3+ ,Tb 3+ ,Mn 2+ phosphor with a high color rendering index (CRI) has been prepared. Under UV excitation, Na 2 Ca 3 Si 2 O 8 :Ce 3+ phosphors present blue luminescence and exhibit a broad excitation ranging from 250 to 400 nm. When codoping Tb 3+ /Mn 2+ ions into Na 2 Ca 3 Si 2 O 8 , energy transfer from Ce 3+ to Tb 3+ and Ce 3+ to Mn 2+ ions is observed from the spectral overlap between Ce 3+ emission and Tb 3+ /Mn 2+ excitation spectra. The energy-transfer efficiencies and corresponding mechanisms are discussed in detail. The mechanism of energy transfer from Ce 3+ to Tb 3+ is demonstrated to be a dipole-quadrupole mechanism by the Inokuti-Hirayama model. The wavelength-tunable white light can be realized by coupling the emission bands centered at 440, 550 and 590 nm ascribed to the contribution from Ce 3+ , Tb 3+ and Mn 2+ , respectively. The commission on illumination value of color tunable emission can be tuned by controlling the content of Ce 3+ , Tb 3+ and Mn 2+ . Temperature-dependent luminescence spectra proved the good thermal stability of the as-prepared phosphor. White LEDs with CRI = 93.5 are finally fabricated using a 365 nm UV chip and the as-prepared Na 2 Ca 3 Si 2 O 8 :Ce 3+ ,Tb 3+ ,Mn 2+ phosphor. All the results suggest that Na 2 Ca 3 Si 2 O 8 :Ce 3+ ,Tb 3+ ,Mn 2+ can act as potential color-tunable and single-phase white emission phosphors for possible applications in UV based white LEDs.

  19. Tunable blue-green emission and energy transfer properties in β-Ca3(PO4)2:Eu(2+), Tb(3+) phosphors with high quantum efficiencies for UV-LEDs.

    Li, Kai; Zhang, Yang; Li, Xuejiao; Shang, Mengmeng; Lian, Hongzhou; Lin, Jun

    2015-03-14

    A series of Eu(2+) and Tb(3+) singly-doped and co-doped β-Ca3(PO4)2 phosphors have been synthesized via the high-temperature solid-state reaction method. Thermogravimetric (TG) analysis, fourier transform infrared (FT-IR) spectra, X-ray diffraction (XRD) patterns and Rietveld refinements, photoluminescence (PL) spectra including temperature-dependent PL and quantum efficiency, and fluorescence decay lifetimes have been used to characterise the as-prepared samples. Under UV excitation, β-Ca3(PO4)2:Eu(2+) presents a broad emission band centered at 415 nm, which can be decomposed into five symmetrical bands peaking at 390, 408, 421, 435 and 511 nm based on the substitution of five kinds of Ca(2+) sites by Eu(2+) ions. β-Ca3(PO4)2:Tb(3+) shows characteristic emission lines under Tb(3+) 4f-5d transition excitation around 223 nm. In β-Ca3(PO4)2:Eu(2+), Tb(3+) phosphors, similar excitation spectra monitored at 415 and 547 nm have been observed, which illustrates the possibility of energy transfer from Eu(2+) to Tb(3+) ions. The variations in the emission spectra and decay lifetimes further demonstrate the existence of energy transfer from Eu(2+) to Tb(3+) ions under UV excitation. The energy transfer mechanism has been confirmed to be dipole-quadrupole, which can be validated via the agreement of critical distances obtained from the concentration quenching (12.11 Å) and spectrum overlap methods (9.9-13.2 Å). The best quantum efficiency can reach 90% for the β-Ca3(PO4)2:0.01Eu(2+), 0.15Tb(3+) sample under 280 nm excitation. These results show that the developed phosphors may possess potential applications in UV-pumped white light-emitting diodes.

  20. Unimodal and crossmodal gradients of spatial attention

    Föcker, J.; Hötting, K.; Gondan, Matthias

    2010-01-01

    Behavioral and event-related potential (ERP) studies have shown that spatial attention is gradually distributed around the center of the attentional focus. The present study compared uni- and crossmodal gradients of spatial attention to investigate whether the orienting of auditory and visual...... spatial attention is based on modality specific or supramodal representations of space. Auditory and visual stimuli were presented from five speaker locations positioned in the right hemifield. Participants had to attend to the innermost or outmost right position in order to detect either visual...... or auditory deviant stimuli. Detection rates and event-related potentials (ERPs) indicated that spatial attention is distributed as a gradient. Unimodal spatial ERP gradients correlated with the spatial resolution of the modality. Crossmodal spatial gradients were always broader than the corresponding...

  1. Vietnamese Document Representation and Classification

    Nguyen, Giang-Son; Gao, Xiaoying; Andreae, Peter

    Vietnamese is very different from English and little research has been done on Vietnamese document classification, or indeed, on any kind of Vietnamese language processing, and only a few small corpora are available for research. We created a large Vietnamese text corpus with about 18000 documents, and manually classified them based on different criteria such as topics and styles, giving several classification tasks of different difficulty levels. This paper introduces a new syllable-based document representation at the morphological level of the language for efficient classification. We tested the representation on our corpus with different classification tasks using six classification algorithms and two feature selection techniques. Our experiments show that the new representation is effective for Vietnamese categorization, and suggest that best performance can be achieved using syllable-pair document representation, an SVM with a polynomial kernel as the learning algorithm, and using Information gain and an external dictionary for feature selection.

  2. Number theory via Representation theory

    2014-11-09

    Number theory via Representation theory. Eknath Ghate. November 9, 2014. Eightieth Annual Meeting, Chennai. Indian Academy of Sciences1. 1. This is a non-technical 20 minute talk intended for a general Academy audience.

  3. (Self)-representations on youtube

    Simonsen, Thomas Mosebo

    This paper examines forms of self-representation on YouTube with specific focus on Vlogs (Video blogs). The analytical scope of the paper is on how User-generated Content on YouTube initiates a certain kind of audiovisual representation and a particular interpretation of reality that can...... be distinguished within Vlogs. This will be analysed through selected case studies taken from a representative sample of empirically based observations of YouTube videos. The analysis includes a focus on how certain forms of representation can be identified as representations of the self (Turkle 1995, Scannell...... 1996, Walker 2005) and further how these forms must be comprehended within a context of technological constrains, institutional structures and social as well as economical practices on YouTube (Burgess and Green 2009, Van Dijck 2009). It is argued that these different contexts play a vital part...

  4. Semantic Knowledge Representation (SKR) API

    U.S. Department of Health & Human Services — The SKR Project was initiated at NLM in order to develop programs to provide usable semantic representation of biomedical free text by building on resources...

  5. Solitons and theory of representations

    Kulish, P.P.

    1985-01-01

    Problems on the theory of group representations finding application in constructing the quantum variant of the inverse scattering problem are discussed. The multicomponent nonlinear Shroedinger equation is considered as a main example of nonlinear evolution equations (NEE)

  6. Computer representation of molecular surfaces

    Max, N.L.

    1981-01-01

    This review article surveys recent work on computer representation of molecular surfaces. Several different algorithms are discussed for producing vector or raster drawings of space-filling models formed as the union of spheres. Other smoother surfaces are also considered

  7. Paired structures in knowledge representation

    Montero, J.; Bustince, H.; Franco de los Ríos, Camilo

    2016-01-01

    In this position paper we propose a consistent and unifying view to all those basic knowledge representation models that are based on the existence of two somehow opposite fuzzy concepts. A number of these basic models can be found in fuzzy logic and multi-valued logic literature. Here...... of the relationships between several existing knowledge representation formalisms, providing a basis from which more expressive models can be later developed....

  8. Functional representations of integrable hierarchies

    Dimakis, Aristophanes; Mueller-Hoissen, Folkert

    2006-01-01

    We consider a general framework for integrable hierarchies in Lax form and derive certain universal equations from which 'functional representations' of particular hierarchies (such as KP, discrete KP, mKP, AKNS), i.e. formulations in terms of functional equations, are systematically and quite easily obtained. The formalism genuinely applies to hierarchies where the dependent variables live in a noncommutative (typically matrix) algebra. The obtained functional representations can be understood as 'noncommutative' analogues of 'Fay identities' for the KP hierarchy

  9. Spatial Theography

    van Noppen, Jean Pierre

    1995-01-01

    Descriptive theology («theography») frequently resorts to metaphorical modes of meaning. Among these metaphors, the spatial language of localization and orientation plays an important role to delineate tentative insights into the relationship between the human and the divine. These spatial metaphors are presumably based on the universal human experience of interaction between the body and its environment. It is dangerous, however, to postulate universal agreement on meanings associated with s...

  10. Spatial Displays and Spatial Instruments

    1989-01-01

    assistance and to Evi Fricke, Werner Haustein , Werner Mohren, Stephen R. Ellis, and Heiner Deubel for their valuable contributions to...by Harris et al. (1979) at the Mayo Clinic and Herman et al. (1984) at the University of Pennsylvania in the area of medical imaging. In 1983, Jaffey...graphics techniques for interactive visualization of data based on surface representations. The groundwork for this was done by Herman et al. Work

  11. Factors affecting the representation of objects in distributed attention

    Maxwell, Tricia Lesley

    2011-01-01

    Our phenomenological experience of what we see around us is of an accurate representation. However, such information is widely distributed in the brain so necessitates that some form of co-ordination of this information takes place to enable a coherent view of the world. The most prominently researched theory is Feature Integration Theory (Treisman, 1993). This proposes that accurate binding is dependent on the current spatial distribution of attention. Individual objects compete for attentio...

  12. Bridging the Gap: Possible Roles and Contributions of Representational Momentum

    Timothy L. Hubbard

    2006-01-01

    Full Text Available Memory for the position of a moving target is often displaced in the direction of anticipated motion, and this has been referred to as representational momentum. Such displacement might aid spatial localization by bridging the gap between perception and action, and might reflect a second-order isomorphism between subjective consequences of environmentally invariant physical principles and the functional architecture of mental representation that can be modulated by an observer’s expectations (e.g., that a moving target will change its heading or by the presence of nontarget stimuli (e.g., landmarks. Representational momentum and related types of displacement reflect properties of the world and properties of mental representation, and so a consideration of representational momentum and related types of displacement contribute an important component of contemporary psychophysics, and also broaden the reach of psychophysics to include numerous topics not usually considered within psychophysics (e.g., naive physics, boundary extension, flash-lag effect, aesthetics, mental imagery.

  13. Magnetorresistência colossal em La5/8-yPr yCa3/8MnO3 Magnetoresistance in La5/8-yPr yCa3/8MnO3

    S. H. Masunaga

    2007-09-01

    Full Text Available Amostras policristalinas de La5/8-yPr yCa3/8MnO3, 0 0,35 também mostram uma transição para o estado de ordenamento de carga/orbital T OC. Uma análise das medidas de ro(T, H sugere a coexistência de pelo menos duas fases distintas nesses materiais: uma ferromagnética-metálica FMM e uma segunda, com ordenamento de carga/orbital e comportamento isolante OCI. Os resultados também permitem concluir que as frações volumétricas dessas fases podem ser manipuladas, alterando-se parâmetros termodinâmicos como T e H. A magnetorresistência MR(T, determinada através das medidas de ro(T, H, foi observada ocorrer em uma larga faixa de temperatura e em todas as amostras pertencentes à série. Amostras ricas em Pr (y > 0,35 revelam um efeito de magnetorresistência colossal amplificado devido à coexistência e competição das FMM e OCI cujas frações volumétricas podem ser alteradas via mudança da temperatura e aplicação de um campo magnético externo.Polycrystalline samples of La5/8-yPr yCa3/8MnO3; 0 0.35 a transition to a charge and orbital-ordered state was also observed. The rho(T, H data analyses suggest the coexistence of at least two ordered phases in these samples: a ferromagnetic metallic phase FMM and a charge and orbital-ordered insulating COI phase.The data also indicate that the volume fraction of these phases can be changed by the variation of thermodynamic parameters like temperature T and magnetic field H. The magnetoresistance MR(T determined from rho(T, H data were observed in a large temperature range for all samples. In addition, samples with y > 0.35 were found to display a pronounced colossal magnetoresistance effect due to a severe competition between FMM and COI coexisting phases.

  14. A Method of Vector Map Multi-scale Representation Considering User Interest on Subdivision Gird

    YU Tong

    2016-12-01

    Full Text Available Compared with the traditional spatial data model and method, global subdivision grid show a great advantage in the organization and expression of massive spatial data. In view of this, a method of vector map multi-scale representation considering user interest on subdivision gird is proposed. First, the spatial interest field is built using a large number POI data to describe the spatial distribution of the user interest in geographic information. Second, spatial factor is classified and graded, and its representation scale range can be determined. Finally, different levels of subdivision surfaces are divided based on GeoSOT subdivision theory, and the corresponding relation of subdivision level and scale is established. According to the user interest of subdivision surfaces, the spatial feature can be expressed in different degree of detail. It can realize multi-scale representation of spatial data based on user interest. The experimental results show that this method can not only satisfy general-to-detail and important-to-secondary space cognitive demands of users, but also achieve better multi-scale representation effect.

  15. Evolved Representation and Computational Creativity

    Ashraf Fouad Hafez Ismail

    2001-01-01

    Full Text Available Advances in science and technology have influenced designing activity in architecture throughout its history. Observing the fundamental changes to architectural designing due to the substantial influences of the advent of the computing era, we now witness our design environment gradually changing from conventional pencil and paper to digital multi-media. Although designing is considered to be a unique human activity, there has always been a great dependency on design aid tools. One of the greatest aids to architectural design, amongst the many conventional and widely accepted computational tools, is the computer-aided object modeling and rendering tool, commonly known as a CAD package. But even though conventional modeling tools have provided designers with fast and precise object handling capabilities that were not available in the pencil-and-paper age, they normally show weaknesses and limitations in covering the whole design process.In any kind of design activity, the design worked on has to be represented in some way. For a human designer, designs are for example represented using models, drawings, or verbal descriptions. If a computer is used for design work, designs are usually represented by groups of pixels (paintbrush programs, lines and shapes (general-purpose CAD programs or higher-level objects like ‘walls’ and ‘rooms’ (purpose-specific CAD programs.A human designer usually has a large number of representations available, and can use the representation most suitable for what he or she is working on. Humans can also introduce new representations and thereby represent objects that are not part of the world they experience with their sensory organs, for example vector representations of four and five dimensional objects. In design computing on the other hand, the representation or representations used have to be explicitly defined. Many different representations have been suggested, often optimized for specific design domains

  16. Roles for the subiculum in spatial information processing, memory, motivation and the temporal control of behaviour.

    O'Mara, Shane M; Sanchez-Vives, Maria V; Brotons-Mas, Jorge R; O'Hare, Eugene

    2009-08-01

    The subiculum is in a pivotal position governing the output of the hippocampal formation. Despite this, it is a rather under-explored and sometimes ignored structure. Here, we discuss recent data indicating that the subiculum participates in a wide range of neurocognitive functions and processes. Some of the functions of subiculum are relatively well-known-these include providing a relatively coarse representation of space and participating in, and supporting certain aspects of, memory (particularly in the dynamic bridging of temporal intervals). The subiculum also participates in a wide variety of other neurocognitive functions too, however. Much less well-known are roles for the subiculum, and particularly the ventral subiculum, in the response to fear, stress and anxiety, and in the generation of motivated behaviour (particularly the behaviour that underlies drug addiction and the response to reward). There is an emerging suggestion that the subiculum participates in the temporal control of behaviour. It is notable that these latter findings have emerged from a consideration of instrumental behaviour using operant techniques; it may well be the case that the use of the watermaze or similar spatial tasks to assess subicular function (on the presumption that its functions are very similar to the hippocampus proper) has obscured rather than revealed neurocognitive functions of subiculum. The anatomy of subiculum suggests it participates in a rather subtle fashion in a very broad range of functions, rather than in a relatively more isolated fashion in a narrower range of functions, as might be the case for "earlier" components of hippocampal circuitry, such as the CA1 and CA3 subfields. Overall, there appears to a strong dorso-ventral segregation of function within subiculum, with the dorsal subiculum relatively more concerned with space and memory, and the ventral hippocampus concerned with stress, anxiety and reward. Finally, it may be the case that the whole

  17. Attikaite, Ca3Cu2Al2(AsO4)4(OH)4 · 2H2O, a new mineral species

    Chukanov, N. V.; Pekov, I. V.; Zadov, A. E.

    2007-12-01

    Attikaite, a new mineral species, has been found together with arsenocrandalite, arsenogoyazite, conichalcite, olivenite, philipsbornite, azurite, malachite, carminite, beudantite, goethite, quartz, and allophane at the Christina Mine No. 132, Kamareza, Lavrion District, Attiki Prefecture (Attika), Greece. The mineral is named after the type locality. It forms spheroidal segregations (up to 0.3 mm in diameter) consisting of thin flexible crystals up to 3 × 20 × 80 μm in size. Its color is light blue to greenish blue, with a pale blue streak. The Mohs’ hardness is 2 to 2.5. The cleavage is eminent mica-like parallel to {001}. The density is 3.2(2) g/cm3 (measured in heavy liquids) and 3.356 g/cm3 (calculated). The wave numbers of the absorption bands in the infrared spectrum of attikaite are (cm-1; sh is shoulder; w is a weak band): 3525 sh, 3425, 3180, 1642, 1120 w, 1070 w, 1035 w, 900 sh, 874, 833, 820, 690 w, 645 w, 600 sh, 555, 486, 458, and 397. Attikaite is optically biaxial, negative, α = 1.642(2), β = γ = 1.644(2) ( X = c) 2 V means = 10(8)°, and 2 V calc = 0°. The new mineral is microscopically colorless and nonpleochroic. The chemical composition (electron microprobe, average over 4 point analyses, wt %) is: 0.17 MgO, 17.48 CaO, 0.12 FeO, 16.28 CuO, 10.61 Al2O3, 0.89 P2O5, 45.45 As2O5, 1.39 SO3, and H2O (by difference) 7.61, where the total is 100.00. The empirical formula calculated on the basis of (O,OH,H2O)22 is: Ca2.94Cu{1.93/2+} Al1.97Mg0.04Fe{0.02/2+} [(As3.74S0.16P0.12)Σ4.02O16.08](OH)3.87 · 2.05H2 O. The simplified formula is Ca3Cu2Al2(AsO4)4(OH)4 · 2H2O. Attikaite is orthorhombic, space group Pban, Pbam or Pba2; the unit-cell dimensions are a = 10.01(1), b = 8.199(5), c = 22.78(1) Å, V = 1870(3) Å3, and Z = 4. In the result of the ignition of attikaite for 30 to 35 min at 128 140°, the H2O bands in the IR spectrum disappear, while the OH-group band is not modified; the weight loss is 4.3%, which approximately corresponds to two H2O

  18. On Behavioral Equivalence of Rational Representations

    Trentelman, Harry L.; Willems, JC; Hara, S; Ohta, Y; Fujioka, H

    2010-01-01

    This article deals with the equivalence of representations of behaviors of linear differential systems In general. the behavior of a given linear differential system has many different representations. In this paper we restrict ourselves to kernel representations and image representations Two kernel

  19. Spatial resolution in visual memory.

    Ben-Shalom, Asaf; Ganel, Tzvi

    2015-04-01

    Representations in visual short-term memory are considered to contain relatively elaborated information on object structure. Conversely, representations in earlier stages of the visual hierarchy are thought to be dominated by a sensory-based, feed-forward buildup of information. In four experiments, we compared the spatial resolution of different object properties between two points in time along the processing hierarchy in visual short-term memory. Subjects were asked either to estimate the distance between objects or to estimate the size of one of the objects' features under two experimental conditions, of either a short or a long delay period between the presentation of the target stimulus and the probe. When different objects were referred to, similar spatial resolution was found for the two delay periods, suggesting that initial processing stages are sensitive to object-based properties. Conversely, superior resolution was found for the short, as compared with the long, delay when features were referred to. These findings suggest that initial representations in visual memory are hybrid in that they allow fine-grained resolution for object features alongside normal visual sensitivity to the segregation between objects. The findings are also discussed in reference to the distinction made in earlier studies between visual short-term memory and iconic memory.

  20. On Representation in Information Theory

    Joseph E. Brenner

    2011-09-01

    Full Text Available Semiotics is widely applied in theories of information. Following the original triadic characterization of reality by Peirce, the linguistic processes involved in information—production, transmission, reception, and understanding—would all appear to be interpretable in terms of signs and their relations to their objects. Perhaps the most important of these relations is that of the representation-one, entity, standing for or representing some other. For example, an index—one of the three major kinds of signs—is said to represent something by being directly related to its object. My position, however, is that the concept of symbolic representations having such roles in information, as intermediaries, is fraught with the same difficulties as in representational theories of mind. I have proposed an extension of logic to complex real phenomena, including mind and information (Logic in Reality; LIR, most recently at the 4th International Conference on the Foundations of Information Science (Beijing, August, 2010. LIR provides explanations for the evolution of complex processes, including information, that do not require any entities other than the processes themselves. In this paper, I discuss the limitations of the standard relation of representation. I argue that more realistic pictures of informational systems can be provided by reference to information as an energetic process, following the categorial ontology of LIR. This approach enables naïve, anti-realist conceptions of anti-representationalism to be avoided, and enables an approach to both information and meaning in the same novel logical framework.

  1. The medial prefrontal cortex is involved in spatial memory retrieval under partial-cue conditions.

    Jo, Yong Sang; Park, Eun Hye; Kim, Il Hwan; Park, Soon Kwon; Kim, Hyun; Kim, Hyun Taek; Choi, June-Seek

    2007-12-05

    Brain circuits involved in pattern completion, or retrieval of memory from fragmented cues, were investigated. Using different versions of the Morris water maze, we explored the roles of the CA3 subregion of the hippocampus and the medial prefrontal cortex (mPFC) in spatial memory retrieval under various conditions. In a hidden platform task, both CA3 and mPFC lesions disrupted memory retrieval under partial-cue, but not under full-cue, conditions. For a delayed matching-to-place task, CA3 lesions produced a deficit in both forming and recalling spatial working memory regardless of extramaze cue conditions. In contrast, damage to mPFC impaired memory retrieval only when a fraction of cues was available. To corroborate the lesion study, we examined the expression of the immediate early gene c-fos in mPFC and the hippocampus. After training of spatial reference memory in full-cue conditions for 6 d, the same training procedure in the absence of all cues except one increased the number of Fos-immunoreactive cells in mPFC and CA3. Furthermore, mPFC inactivation with muscimol, a GABA agonist, blocked memory retrieval in the degraded-cue environment. However, mPFC-lesioned animals initially trained in a single-cue environment had no difficulty in retrieving spatial memory when the number of cues was increased, demonstrating that contextual change per se did not impair the behavioral performance of the mPFC-lesioned animals. Together, these findings strongly suggest that pattern completion requires interactions between mPFC and the hippocampus, in which mPFC plays significant roles in retrieving spatial information maintained in the hippocampus for efficient navigation.

  2. Social representations of female orgasm.

    Lavie-Ajayi, Maya; Joffe, Hélène

    2009-01-01

    This study examines women's social representations of female orgasm. Fifty semi-structured interviews were conducted with British women. The data were thematically analysed and compared with the content of female orgasm-related writing in two women's magazines over a 30-year period. The results indicate that orgasm is deemed the goal of sex with emphasis on its physiological dimension. However, the women and the magazines graft onto this scientifically driven representation the importance of relational and emotive aspects of orgasm. For the women, particularly those who experience themselves as having problems with orgasm, the scientifically driven representations induce feelings of failure, but are also resisted. The findings highlight the role played by the social context in women's subjective experience of their sexual health.

  3. An introduction to quiver representations

    Derksen, Harm

    2017-01-01

    This book is an introduction to the representation theory of quivers and finite dimensional algebras. It gives a thorough and modern treatment of the algebraic approach based on Auslander-Reiten theory as well as the approach based on geometric invariant theory. The material in the opening chapters is developed starting slowly with topics such as homological algebra, Morita equivalence, and Gabriel's theorem. Next, the book presents Auslander-Reiten theory, including almost split sequences and the Auslander-Reiten transform, and gives a proof of Kac's generalization of Gabriel's theorem. Once this basic material is established, the book goes on with developing the geometric invariant theory of quiver representations. The book features the exposition of the saturation theorem for semi-invariants of quiver representations and its application to Littlewood-Richardson coefficients. In the final chapters, the book exposes tilting modules, exceptional sequences and a connection to cluster categories. The book is su...

  4. Preon representations and composite models

    Kang, Kyungsik

    1982-01-01

    This is a brief report on the preon models which are investigated by In-Gyu Koh, A. N. Schellekens and myself and based on complex, anomaly-free and asymptotically free representations of SU(3) to SU(8), SO(4N+2) and E 6 with no more than two different preons. Complete list of the representations that are complex anomaly-free and asymptotically free has been given by E. Eichten, I.-G. Koh and myself. The assumptions made about the ground state composites and the role of Fermi statistics to determine the metaflavor wave functions are discussed in some detail. We explain the method of decompositions of tensor products with definite permutation properties which has been developed for this purpose by I.-G. Koh, A.N. Schellekens and myself. An example based on an anomaly-free representation of the confining metacolor group SU(5) is discussed

  5. Representational constraints on children's suggestibility.

    Ceci, Stephen J; Papierno, Paul B; Kulkofsky, Sarah

    2007-06-01

    In a multistage experiment, twelve 4- and 9-year-old children participated in a triad rating task. Their ratings were mapped with multidimensional scaling, from which euclidean distances were computed to operationalize semantic distance between items in target pairs. These children and age-mates then participated in an experiment that employed these target pairs in a story, which was followed by a misinformation manipulation. Analyses linked individual and developmental differences in suggestibility to children's representations of the target items. Semantic proximity was a strong predictor of differences in suggestibility: The closer a suggested distractor was to the original item's representation, the greater was the distractor's suggestive influence. The triad participants' semantic proximity subsequently served as the basis for correctly predicting memory performance in the larger group. Semantic proximity enabled a priori counterintuitive predictions of reverse age-related trends to be confirmed whenever the distance between representations of items in a target pair was greater for younger than for older children.

  6. Digital models for architectonical representation

    Stefano Brusaporci

    2011-12-01

    Full Text Available Digital instruments and technologies enrich architectonical representation and communication opportunities. Computer graphics is organized according the two phases of visualization and construction, that is modeling and rendering, structuring dichotomy of software technologies. Visualization modalities give different kinds of representations of the same 3D model and instruments produce a separation between drawing and image’s creation. Reverse modeling can be related to a synthesis process, ‘direct modeling’ follows an analytic procedure. The difference between interactive and not interactive applications is connected to the possibilities offered by informatics instruments, and relates to modeling and rendering. At the same time the word ‘model’ describes different phenomenon (i.e. files: mathematical model of the building and of the scene; raster representation and post-processing model. All these correlated different models constitute the architectonical interpretative model, that is a simulation of reality made by the model for improving the knowledge.

  7. Asymptotical representation of discrete groups

    Mishchenko, A.S.; Mohammad, N.

    1995-08-01

    If one has a unitary representation ρ: π → U(H) of the fundamental group π 1 (M) of the manifold M then one can do may useful things: 1. To construct a natural vector bundle over M; 2. To construct the cohomology groups with respect to the local system of coefficients; 3. To construct the signature of manifold M with respect to the local system of coefficients; and others. In particular, one can write the Hirzebruch formula which compares the signature with the characteristic classes of the manifold M, further based on this, find the homotopy invariant characteristic classes (i.e. the Novikov conjecture). Taking into account that the family of known representations is not sufficiently large, it would be interesting to extend this family to some larger one. Using the ideas of A.Connes, M.Gromov and H.Moscovici a proper notion of asymptotical representation is defined. (author). 7 refs

  8. Vivid Representations and Their Effects

    Kengo Miyazono

    2018-04-01

    Full Text Available Sinhababu’s Humean Nature contains many interesting and important ideas, but in this short commentary I focus on the idea of vivid representations. Sinhababu inherits his idea of vivid representations from Hume’s discussions, in particular his discussion of calm and violent passions. I am sympathetic to the idea of developing Hume’s insight that has been largely neglected by philosophers. I believe that Sinhababu and Hume are on the right track. What I do in this short commentary is to raise some questions about the details. The aim of asking these questions is not to challenge Sinhababu’s proposal (at least his main ideas, but rather to point at some interesting issues arising out of his proposal. The questions are about (1 the nature of vividness, (2 the effects of vivid representations, and (3 Sinhababu’s account of alief cases.

  9. Room-temperature picosecond high-order stimulated Raman scattering in laser garnet crystal hosts Gd3Ga5O12, Gd3Sc2Ga3O12, and Ca3(Nb,Ga)2Ga3O12

    Kaminskii, Alexandr A; Eichler, H J; Findeisen, J; Ueda, Ken-ichi; Fernandez, J; Balda, R

    1998-01-01

    High-order Stokes and anti-Stokes generation in the visible and near-infrared in cubic laser crystal hosts Gd 3 Ga 5 O 12 , Gd 3 Sc 2 Ga 3 O 12 , and Ca 3 (Nb,Ga) 2 Ga 3 O 12 was observed for the first time. All scattering-laser components were identified and attributed to the SRS-active vibration modes of these garnet crystals. (letters to the editor)

  10. Spatial networks

    Barthélemy, Marc

    2011-02-01

    Complex systems are very often organized under the form of networks where nodes and edges are embedded in space. Transportation and mobility networks, Internet, mobile phone networks, power grids, social and contact networks, and neural networks, are all examples where space is relevant and where topology alone does not contain all the information. Characterizing and understanding the structure and the evolution of spatial networks is thus crucial for many different fields, ranging from urbanism to epidemiology. An important consequence of space on networks is that there is a cost associated with the length of edges which in turn has dramatic effects on the topological structure of these networks. We will thoroughly explain the current state of our understanding of how the spatial constraints affect the structure and properties of these networks. We will review the most recent empirical observations and the most important models of spatial networks. We will also discuss various processes which take place on these spatial networks, such as phase transitions, random walks, synchronization, navigation, resilience, and disease spread.

  11. Spatial interpolation

    Stein, A.

    1991-01-01

    The theory and practical application of techniques of statistical interpolation are studied in this thesis, and new developments in multivariate spatial interpolation and the design of sampling plans are discussed. Several applications to studies in soil science are

  12. (Self)-representations on youtube

    Simonsen, Thomas Mosebo

    2011-01-01

    This paper examines forms of self-representation on YouTube with specific focus on Vlogs (Video blogs). The analytical scope of the paper is on how User-generated Content on YouTube initiates a certain kind of audiovisual representation and a particular interpretation of reality that can be distinguished within Vlogs. This will be analysed through selected case studies taken from a representative sample of empirically based observations of YouTube videos. The analysis includes a focus on how ...

  13. Concepts, ontologies, and knowledge representation

    Jakus, Grega; Omerovic, Sanida; Tomažic, Sašo

    2013-01-01

    Recording knowledge in a common framework that would make it possible to seamlessly share global knowledge remains an important challenge for researchers. This brief examines several ideas about the representation of knowledge addressing this challenge. A widespread general agreement is followed that states uniform knowledge representation should be achievable by using ontologies populated with concepts. A separate chapter is dedicated to each of the three introduced topics, following a uniform outline: definition, organization, and use. This brief is intended for those who want to get to know

  14. Thinking together with material representations

    Stege Bjørndahl, Johanne; Fusaroli, Riccardo; Østergaard, Svend

    2014-01-01

    of an experiment. Qualitative micro-analyses of the group interactions motivate a taxonomy of different roles that the material representations play in the joint epistemic processes: illustration, elaboration and exploration. Firstly, the LEGO blocks were used to illustrate already well-formed ideas in support......-down and bottom-up cognitive processes and division of cognitive labor.......How do material representations such as models, diagrams and drawings come to shape and aid collective, epistemic processes? This study investigated how groups of participants spontaneously recruited material objects (in this case LEGO blocks) to support collective creative processes in the context...

  15. Determining the mechanism of dehydration of primary, secondary, and tertiary alcohols by means of deuterium uptake on deuterated catalysts (BPO4, Ca3(PO4)2 and Sm2O3)

    Thomke, K.

    1977-01-01

    In order to gain insight into the mechanisms of dehydration (E1, E2, E1cB) of α- and β-substituted ethanols, the uptake of deuterium on deuterated catalysts [BPO 4 , Ca 3 (PO 4 ) 2 , Sm 2 O 3 ] into the alcohols and the thus formed olefines was measured. For that purpose microcatalytic and mass-spectrometric techniques were used. Most of the examined alcohols showed E1 on BPO 4 , E2 (sometimes mingled with E1) on Ca 3 (PO 4 ) 2 , and E1cB on Sm 2 O 3 . The common mechanism for ethanol on BPO 4 , for 2-propanol on Ca 3 (PO 4 ) 2 , and for 2-ethyl-2-propanol on Sm 2 O 3 was E2, i.e. that the OH-group and the β-proton were split off simultaneously. This can be explained by a decrease of the strength of the α-C-OH-bound caused by α-methyl-substitution on the one hand and by an increase of basicity of the catalyst on the other hand. (orig.) 891 HK [de

  16. Towards a computational spatial knowledge acquisition model in architectural space

    Lyu, J.; Vries, de B.; Sun, C.; Sun, C.; Zhang, J.

    2013-01-01

    Abstract. Existing research which is related to spatial knowledge acquisition often shows a limited scope because of the complexity in the cognition process. Research in spatial representation such as space syntax presumes that vision drives movement. This assumption is only true under certain

  17. A Principal Components Analysis of Dynamic Spatial Memory Biases

    Motes, Michael A.; Hubbard, Timothy L.; Courtney, Jon R.; Rypma, Bart

    2008-01-01

    Research has shown that spatial memory for moving targets is often biased in the direction of implied momentum and implied gravity, suggesting that representations of the subjective experiences of these physical principles contribute to such biases. The present study examined the association between these spatial memory biases. Observers viewed…

  18. Tackling the 2nd V: Big Data, Variety and the Need for Representation Consistency

    Clune, T.; Kuo, K. S.

    2016-12-01

    While Big Data technologies are transforming our ability to analyze ever larger volumes of Earth science data, practical constraints continue to limit our ability to compare data across datasets from different sources in an efficient and robust manner. Within a single data collection, invariants such as file format, grid type, and spatial resolution greatly simplify many types of analysis (often implicitly). However, when analysis combines data across multiple data collections, researchers are generally required to implement data transformations (i.e., "data preparation") to provide appropriate invariants. These transformation include changing of file formats, ingesting into a database, and/or regridding to a common spatial representation, and they can either be performed once, statically, or each time the data is accessed. At the very least, this process is inefficient from the perspective of the community as each team selects its own representation and privately implements the appropriate transformations. No doubt there are disadvantages to any "universal" representation, but we posit that major benefits would be obtained if a suitably flexible spatial representation could be standardized along with tools for transforming to/from that representation. We regard this as part of the historic trend in data publishing. Early datasets used ad hoc formats and lacked metadata. As better tools evolved, published data began to use standardized formats (e.g., HDF and netCDF) with attached metadata. We propose that the modern need to perform analysis across data sets should drive a new generation of tools that support a standardized spatial representation. More specifically, we propose the hierarchical triangular mesh (HTM) as a suitable "generic" resolution that permits standard transformations to/from native representations in use today, as well as tools to convert/regrid existing datasets onto that representation.

  19. Representations of quantum bicrossproduct algebras

    Arratia, Oscar; Olmo, Mariano A del

    2002-01-01

    We present a method to construct induced representations of quantum algebras which have a bicrossproduct structure. We apply this procedure to some quantum kinematical algebras in (1+1) dimensions with this kind of structure: null-plane quantum Poincare algebra, non-standard quantum Galilei algebra and quantum κ-Galilei algebra

  20. Reusable Lexical Representations for Idioms

    Odijk, J.E.J.M.

    2004-01-01

    In this paper I introduce (1) a technically simple and highly theory-independent way for lexically representing flexible idiomatic expressions, and (2) a procedure to incorporate these lexical representations in a wide variety of NLP systems. The method is based on Structural EQuivalence Classes

  1. Symmetric group representations and Z

    Adve, Anshul; Yong, Alexander

    2017-01-01

    We discuss implications of the following statement about the representation theory of symmetric groups: every integer appears infinitely often as an irreducible character evaluation, and every nonnegative integer appears infinitely often as a Littlewood-Richardson coefficient and as a Kronecker coefficient.

  2. Guideline Knowledge Representation Model (GLIKREM)

    Buchtela, David; Peleška, Jan; Veselý, Arnošt; Zvárová, Jana; Zvolský, Miroslav

    2008-01-01

    Roč. 4, č. 1 (2008), s. 17-23 ISSN 1801-5603 R&D Projects: GA MŠk(CZ) 1M06014 Institutional research plan: CEZ:AV0Z10300504 Keywords : knowledge representation * GLIF model * guidelines Subject RIV: IN - Informatics, Computer Science http://www.ejbi.org/articles/200812/34/1.html

  3. Conceptual Knowledge Representation and Reasoning

    Oldager, Steen Nikolaj

    2003-01-01

    One of the main areas in knowledge representation and logic-based artificial intelligence concerns logical formalisms that can be used for representing and reasoning with concepts. For almost 30 years, since research in this area began, the issue of intensionality has had a special status...

  4. Octonionic matrix representation and electromagnetism

    Chanyal, B. C. [Kumaun University, S. S. J. Campus, Almora (India)

    2014-12-15

    Keeping in mind the important role of octonion algebra, we have obtained the electromagnetic field equations of dyons with an octonionic 8 x 8 matrix representation. In this paper, we consider the eight - dimensional octonionic space as a combination of two (external and internal) four-dimensional spaces for the existence of magnetic monopoles (dyons) in a higher-dimensional formalism. As such, we describe the octonion wave equations in terms of eight components from the 8 x 8 matrix representation. The octonion forms of the generalized potential, fields and current source of dyons in terms of 8 x 8 matrix are discussed in a consistent manner. Thus, we have obtained the generalized Dirac-Maxwell equations of dyons from an 8x8 matrix representation of the octonion wave equations in a compact and consistent manner. The generalized Dirac-Maxwell equations are fully symmetric Maxwell equations and allow for the possibility of magnetic charges and currents, analogous to electric charges and currents. Accordingly, we have obtained the octonionic Dirac wave equations in an external field from the matrix representation of the octonion-valued potentials of dyons.

  5. Realizations of the canonical representation

    Traditionally, the canonical representation is realized on the Hilbert space ... Fix a decomposition R2n = Rn × Rn ..... to an orthonormal basis {ψ1,ψ2,. ..... [7] Vemuri M K, A non-commutative Sobolev inequality and its application to spectral.

  6. Non-Hermitian Heisenberg representation

    Znojil, Miloslav

    2015-01-01

    Roč. 379, č. 36 (2015), s. 2013-2017 ISSN 0375-9601 Institutional support: RVO:61389005 Keywords : quantum mechanics * Non-Hermitian representation of observables * Generalized Heisenberg equations Subject RIV: BE - Theoretical Physics Impact factor: 1.677, year: 2015

  7. Adaptive representations for reinforcement learning

    Whiteson, S.

    2010-01-01

    This book presents new algorithms for reinforcement learning, a form of machine learning in which an autonomous agent seeks a control policy for a sequential decision task. Since current methods typically rely on manually designed solution representations, agents that automatically adapt their own

  8. Representational Momentum in Older Adults

    Piotrowski, Andrea S.; Jakobson, Lorna S.

    2011-01-01

    Humans have a tendency to perceive motion even in static images that simply "imply" movement. This tendency is so strong that our memory for actions depicted in static images is distorted in the direction of implied motion--a phenomenon known as representational momentum (RM). In the present study, we created an RM display depicting a pattern of…

  9. The representation of inherent properties.

    Prasada, Sandeep

    2014-10-01

    Research on the representation of generic knowledge suggests that inherent properties can have either a principled or a causal connection to a kind. The type of connection determines whether the outcome of the storytelling process will include intuitions of inevitability and a normative dimension and whether it will ground causal explanations.

  10. Representation and redistribution in federations.

    Dragu, Tiberiu; Rodden, Jonathan

    2011-05-24

    Many of the world's most populous democracies are political unions composed of states or provinces that are unequally represented in the national legislature. Scattered empirical studies, most of them focusing on the United States, have discovered that overrepresented states appear to receive larger shares of the national budget. Although this relationship is typically attributed to bargaining advantages associated with greater legislative representation, an important threat to empirical identification stems from the fact that the representation scheme was chosen by the provinces. Thus, it is possible that representation and fiscal transfers are both determined by other characteristics of the provinces in a specific country. To obtain an improved estimate of the relationship between representation and redistribution, we collect and analyze provincial-level data from nine federations over several decades, taking advantage of the historical process through which federations formed and expanded. Controlling for a variety of country- and province-level factors and using a variety of estimation techniques, we show that overrepresented provinces in political unions around the world are rather dramatically favored in the distribution of resources.

  11. Spatial distribution

    Borregaard, Michael Krabbe; Hendrichsen, Ditte Katrine; Nachman, Gøsta Støger

    2008-01-01

    , depending on the nature of intraspecific interactions between them: while the individuals of some species repel each other and partition the available area, others form groups of varying size, determined by the fitness of each group member. The spatial distribution pattern of individuals again strongly......Living organisms are distributed over the entire surface of the planet. The distribution of the individuals of each species is not random; on the contrary, they are strongly dependent on the biology and ecology of the species, and vary over different spatial scale. The structure of whole...... populations reflects the location and fragmentation pattern of the habitat types preferred by the species, and the complex dynamics of migration, colonization, and population growth taking place over the landscape. Within these, individuals are distributed among each other in regular or clumped patterns...

  12. Spatial Culture

    Reeh, Henrik

    2012-01-01

    Spatial Culture – A Humanities Perspective Abstract of introductory essay by Henrik Reeh Secured by alliances between socio-political development and cultural practices, a new field of humanistic studies in spatial culture has developed since the 1990s. To focus on links between urban culture...... and modern society is, however, an intellectual practice which has a much longer history. Already in the 1980s, the debate on the modern and the postmodern cited Paris and Los Angeles as spatio-cultural illustrations of these major philosophical concepts. Earlier, in the history of critical studies, the work...... Foucault considered a constitutive feature of 20th-century thinking and one that continues to occupy intellectual and cultural debates in the third millennium. A conceptual framework is, nevertheless, necessary, if the humanities are to adequa-tely address city and space – themes that have long been...

  13. SEVERAL REPRESENTATIONS OF THE FOREIGNER IN ROMANIAN POPULAR EPICS NOTES FOR A FOLKLORIC IMAGOLOGY

    Corina Daniela POPESCU

    2015-05-01

    Full Text Available From the perspective of the anthropology of space, the problem of perception and representation of the alien remains a fertile subject of research, nevertheless inevitably interfering with imagology, in the sense assigned to the concept of image as any representation of a cultural r eality through which the individual or the group translate the cultural, social, ideological space in which they are located Identity does not justify an existence in itself, but only in relation to alterity The imagological perspective of the foreigner in Romanian traditional culture proves rich in categories of representation dictated inevitably by reference to spatiality

  14. The impact of spatial resolution on resolving spatial precipitation patterns in the Himalayas

    Bonekamp, P.N.J.; Collier, S.E.; Immerzeel, W.W.

    2017-01-01

    Frequently used gridded meteorological datasets poorly represent precipitation in the Himalaya due to their relatively low spatial resolution and the associated coarse representation of the complex topography. Dynamical downscaling using high-resolution atmospheric models may improve the accuracy and quality of the precipitation fields, as simulations at higher spatial resolution are more capable of resolving the interaction between the topography and the atmosphere. However, most physics par...

  15. The protection of warranties and representations

    Spence, C.D.; Thusoo, N.

    1999-01-01

    Most acquisition contracts within the oil and gas industry consist of representations and warranties. The legal distinction between representations and warranties was explained as follows: a representation is a statement of fact made by the representor before making the contract, but a warranty is a statement of fact which forms part of the terms of the contract. The paper outlines the nature of a representation or warranty and explains why certain warranties are not given. The protection offered by representations and warranties in breach of contract cases is also explained. Suggestions are offered for increasing protection by representations and warranties. 22 refs

  16. Reasoning with inaccurate spatial knowledge. [for Planetary Rover

    Doshi, Rajkumar S.; White, James E.; Lam, Raymond; Atkinson, David J.

    1988-01-01

    This paper describes work in progress on spatial planning for a semiautonomous mobile robot vehicle. The overall objective is to design a semiautonomous rover to plan routes in unknown, natural terrains. The approach to spatial planning involves deduction of common-sense spatial knowledge using geographical information, natural terrain representations, and assimilation of new and possibly conflicting terrain information. This report describes the ongoing research and implementation.

  17. Human action recognition using trajectory-based representation

    Haiam A. Abdul-Azim

    2015-07-01

    Full Text Available Recognizing human actions in video sequences has been a challenging problem in the last few years due to its real-world applications. A lot of action representation approaches have been proposed to improve the action recognition performance. Despite the popularity of local features-based approaches together with “Bag-of-Words” model for action representation, it fails to capture adequate spatial or temporal relationships. In an attempt to overcome this problem, a trajectory-based local representation approaches have been proposed to capture the temporal information. This paper introduces an improvement of trajectory-based human action recognition approaches to capture discriminative temporal relationships. In our approach, we extract trajectories by tracking the detected spatio-temporal interest points named “cuboid features” with matching its SIFT descriptors over the consecutive frames. We, also, propose a linking and exploring method to obtain efficient trajectories for motion representation in realistic conditions. Then the volumes around the trajectories’ points are described to represent human actions based on the Bag-of-Words (BOW model. Finally, a support vector machine is used to classify human actions. The effectiveness of the proposed approach was evaluated on three popular datasets (KTH, Weizmann and UCF sports. Experimental results showed that the proposed approach yields considerable performance improvement over the state-of-the-art approaches.

  18. Spatial displacement of numbers on a vertical number line in spatial neglect

    Urszula eMihulowicz

    2015-04-01

    Full Text Available Previous studies that investigated the association of numbers and space in humans came to contradictory conclusions about the spatial character of the mental number magnitude representation and about how it may be influenced by unilateral spatial neglect. The present study aimed to disentangle the debated influence of perceptual versus representational aspects via explicit mapping of numbers onto space by applying the number line estimation paradigm with vertical orientation of stimulus lines. Thirty-five acute right-brain damaged stroke patients (6 with neglect were asked to place two-digit numbers on vertically oriented lines with 0 marked at the bottom and 100 at the top. In contrast to the expected, nearly linear mapping in the control patient group, patients with spatial neglect overestimated the position of numbers in the lower middle range. The results corroborate spatial characteristics of the number magnitude representation. In neglect patients, this representation seems to be biased towards the ipsilesional side, independent of the physical orientation of the task stimuli.

  19. 48 CFR 2009.570-4 - Representation.

    2010-10-01

    ... type required by the organizational conflicts of interest representation provisions has previously been... ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Organizational Conflicts of Interest 2009.570-4 Representation... whether situations or relationships exist which may constitute organizational conflicts of interest with...

  20. Democracy and Representation in Paraguay

    Liliana Rocío Duarte-Recalde

    2017-05-01

    Full Text Available This article reviews the electoral accountability dimension as a constitutive mechanism of Paraguayan democracy since 1989, analyzing the factors that limit the representation contained in the administration of the Paraguayan government as a result of the electoral process. We provide an analytic contrast between the democratic principles that guide the Paraguayan electoral institutions and the way their designs are enforced, identifying the gap between formal and informal rules as determinants of political representation. We also describe the barriers that prevent effective access of the population to political participation and competition, the advantages possessed by traditional political parties and interest groups, as well as their implications for democracy. We also review the degree to which elected officials are representative of historically excluded social groups as a result, emphasizing the way women, indigenous and peasant communities have potentially limited power to exercise political influence due to limitations to participation by structural and institutional factors.

  1. Time representations in social science.

    Schulz, Yvan

    2012-12-01

    Time has long been a major topic of study in social science, as in other sciences or in philosophy. Social scientists have tended to focus on collective representations of time, and on the ways in which these representations shape our everyday experiences. This contribution addresses work from such disciplines as anthropology, sociology and history. It focuses on several of the main theories that have preoccupied specialists in social science, such as the alleged "acceleration" of life and overgrowth of the present in contemporary Western societies, or the distinction between so-called linear and circular conceptions of time. The presentation of these theories is accompanied by some of the critiques they have provoked, in order to enable the reader to form her or his own opinion of them.

  2. Quantum control and representation theory

    Ibort, A; Perez-Pardo, J M

    2009-01-01

    A new notion of controllability for quantum systems that takes advantage of the linear superposition of quantum states is introduced. We call such a notion von Neumann controllability, and it is shown that it is strictly weaker than the usual notion of pure state and operator controllability. We provide a simple and effective characterization of it by using tools from the theory of unitary representations of Lie groups. In this sense, we are able to approach the problem of control of quantum states from a new perspective, that of the theory of unitary representations of Lie groups. A few examples of physical interest and the particular instances of compact and nilpotent dynamical Lie groups are discussed

  3. Berry phase in Heisenberg representation

    Andreev, V. A.; Klimov, Andrei B.; Lerner, Peter B.

    1994-01-01

    We define the Berry phase for the Heisenberg operators. This definition is motivated by the calculation of the phase shifts by different techniques. These techniques are: the solution of the Heisenberg equations of motion, the solution of the Schrodinger equation in coherent-state representation, and the direct computation of the evolution operator. Our definition of the Berry phase in the Heisenberg representation is consistent with the underlying supersymmetry of the model in the following sense. The structural blocks of the Hamiltonians of supersymmetrical quantum mechanics ('superpairs') are connected by transformations which conserve the similarity in structure of the energy levels of superpairs. These transformations include transformation of phase of the creation-annihilation operators, which are generated by adiabatic cyclic evolution of the parameters of the system.

  4. Representation theory of finite monoids

    Steinberg, Benjamin

    2016-01-01

    This first text on the subject provides a comprehensive introduction to the representation theory of finite monoids. Carefully worked examples and exercises provide the bells and whistles for graduate accessibility, bringing a broad range of advanced readers to the forefront of research in the area. Highlights of the text include applications to probability theory, symbolic dynamics, and automata theory. Comfort with module theory, a familiarity with ordinary group representation theory, and the basics of Wedderburn theory, are prerequisites for advanced graduate level study. Researchers in algebra, algebraic combinatorics, automata theory, and probability theory, will find this text enriching with its thorough presentation of applications of the theory to these fields. Prior knowledge of semigroup theory is not expected for the diverse readership that may benefit from this exposition. The approach taken in this book is highly module-theoretic and follows the modern flavor of the theory of finite dimensional ...

  5. Temporal Representation in Semantic Graphs

    Levandoski, J J; Abdulla, G M

    2007-08-07

    A wide range of knowledge discovery and analysis applications, ranging from business to biological, make use of semantic graphs when modeling relationships and concepts. Most of the semantic graphs used in these applications are assumed to be static pieces of information, meaning temporal evolution of concepts and relationships are not taken into account. Guided by the need for more advanced semantic graph queries involving temporal concepts, this paper surveys the existing work involving temporal representations in semantic graphs.

  6. Experience representation in information systems

    Kaczmarek, Jan

    2014-01-01

    This thesis looks into the ways subjective dimension of experience could be represented in artificial, non-biological systems, in particular information systems. The pivotal assumption is that experience as opposed to mainstream thinking in information science is not equal to knowledge, so that experience is a broader term which encapsulates both knowledge and subjective, affective component of experience, which so far has not been properly embraced by knowledge representation theories. This ...

  7. Experience representation in information systems

    Kaczmarek, Jan

    2014-01-01

    This thesis looks into the ways subjective dimension of experience could be represented in artificial, non-biological systems, in particular information systems. The pivotal assumption is that experience as opposed to mainstream thinking in information science is not equal to knowledge, so that experience is a broader term which encapsulates both knowledge and subjective, affective component of experience, which so far has not been properly embraced by knowledge representation theories. Th...

  8. Computing Visible-Surface Representations,

    1985-03-01

    Terzopoulos N00014-75-C-0643 9. PERFORMING ORGANIZATION NAME AMC ADDRESS 10. PROGRAM ELEMENT. PROJECT, TASK Artificial Inteligence Laboratory AREA A...Massachusetts Institute of lechnolog,. Support lbr the laboratory’s Artificial Intelligence research is provided in part by the Advanced Rtccarcl Proj...dynamically maintaining visible surface representations. Whether the intention is to model human vision or to design competent artificial vision systems

  9. Generalized oscillator representations for Calogero Hamiltonians

    Tyutin, I V; Voronov, B L

    2013-01-01

    This paper is a natural continuation of the previous paper (Gitman et al 2011 J. Phys. A: Math. Theor. 44 425204), where oscillator representations for nonnegative Calogero Hamiltonians with coupling constant α ⩾ − 1/4 were constructed. In this paper, we present generalized oscillator representations for all Calogero Hamiltonians with α ⩾ − 1/4. These representations are generally highly nonunique, but there exists an optimum representation for each Hamiltonian. (comment)

  10. Neural Representations of Physics Concepts.

    Mason, Robert A; Just, Marcel Adam

    2016-06-01

    We used functional MRI (fMRI) to assess neural representations of physics concepts (momentum, energy, etc.) in juniors, seniors, and graduate students majoring in physics or engineering. Our goal was to identify the underlying neural dimensions of these representations. Using factor analysis to reduce the number of dimensions of activation, we obtained four physics-related factors that were mapped to sets of voxels. The four factors were interpretable as causal motion visualization, periodicity, algebraic form, and energy flow. The individual concepts were identifiable from their fMRI signatures with a mean rank accuracy of .75 using a machine-learning (multivoxel) classifier. Furthermore, there was commonality in participants' neural representation of physics; a classifier trained on data from all but one participant identified the concepts in the left-out participant (mean accuracy = .71 across all nine participant samples). The findings indicate that abstract scientific concepts acquired in an educational setting evoke activation patterns that are identifiable and common, indicating that science education builds abstract knowledge using inherent, repurposed brain systems. © The Author(s) 2016.

  11. Spatial filtring and thermocouple spatial filter

    Han Bing; Tong Yunxian

    1989-12-01

    The design and study on thermocouple spatial filter have been conducted for the flow measurement of integrated reactor coolant. The fundamental principle of spatial filtring, mathematical descriptions and analyses of thermocouple spatial filter are given

  12. Impossibility Theorem in Proportional Representation Problem

    Karpov, Alexander

    2010-01-01

    The study examines general axiomatics of Balinski and Young and analyzes existed proportional representation methods using this approach. The second part of the paper provides new axiomatics based on rational choice models. New system of axioms is applied to study known proportional representation systems. It is shown that there is no proportional representation method satisfying a minimal set of the axioms (monotonicity and neutrality).

  13. Facilitating Mathematical Practices through Visual Representations

    Murata, Aki; Stewart, Chana

    2017-01-01

    Effective use of mathematical representation is key to supporting student learning. In "Principles to Actions: Ensuring Mathematical Success for All" (NCTM 2014), "use and connect mathematical representations" is one of the effective Mathematics Teaching Practices. By using different representations, students examine concepts…

  14. Computability and Representations of the Zero Set

    P.J. Collins (Pieter)

    2008-01-01

    htmlabstractIn this note we give a new representation for closed sets under which the robust zero set of a function is computable. We call this representation the component cover representation. The computation of the zero set is based on topological index theory, the most powerful tool for finding

  15. Lifts of matroid representations over partial fields

    Pendavingh, R.A.; Zwam, van S.H.M.

    2010-01-01

    There exist several theorems which state that when a matroid is representable over distinct fields F1,...,Fk , it is also representable over other fields. We prove a theorem, the Lift Theorem, that implies many of these results. First, parts of Whittle's characterization of representations of

  16. Equivalence of rational representations of behaviors

    Gottimukkala, Sasanka; Fiaz, Shaik; Trentelman, H.L.

    This article deals with the equivalence of representations of behaviors of linear differential systems. In general, the behavior of a given linear differential system has many different representations. In this paper we restrict ourselves to kernel and image representations. Two kernel

  17. Tactile spatial resolution in blind braille readers.

    Van Boven, R W; Hamilton, R H; Kauffman, T; Keenan, J P; Pascual-Leone, A

    2000-06-27

    To determine if blind people have heightened tactile spatial acuity. Recently, studies using magnetic source imaging and somatosensory evoked potentials have shown that the cortical representation of the reading fingers of blind Braille readers is expanded compared to that of fingers of sighted subjects. Furthermore, the visual cortex is activated during certain tactile tasks in blind subjects but not sighted subjects. The authors hypothesized that the expanded cortical representation of fingers used in Braille reading may reflect an enhanced fidelity in the neural transmission of spatial details of a stimulus. If so, the quantitative limit of spatial acuity would be superior in blind people. The authors employed a grating orientation discrimination task in which threshold performance is accounted for by the spatial resolution limits of the neural image evoked by a stimulus. The authors quantified the psychophysical limits of spatial acuity at the middle and index fingers of 15 blind Braille readers and 15 sighted control subjects. The mean grating orientation threshold was significantly (p = 0.03) lower in the blind group (1.04 mm) compared to the sighted group (1.46 mm). The self-reported dominant reading finger in blind subjects had a mean grating orientation threshold of 0.80 mm, which was significantly better than other fingers tested. Thresholds at non-Braille reading fingers in blind subjects averaged 1.12 mm, which were also superior to sighted subjects' performances. Superior tactile spatial acuity in blind Braille readers may represent an adaptive, behavioral correlate of cortical plasticity.

  18. Learning semantic histopathological representation for basal cell carcinoma classification

    Gutiérrez, Ricardo; Rueda, Andrea; Romero, Eduardo

    2013-03-01

    Diagnosis of a histopathology glass slide is a complex process that involves accurate recognition of several structures, their function in the tissue and their relation with other structures. The way in which the pathologist represents the image content and the relations between those objects yields a better and accurate diagnoses. Therefore, an appropriate semantic representation of the image content will be useful in several analysis tasks such as cancer classification, tissue retrieval and histopahological image analysis, among others. Nevertheless, to automatically recognize those structures and extract their inner semantic meaning are still very challenging tasks. In this paper we introduce a new semantic representation that allows to describe histopathological concepts suitable for classification. The approach herein identify local concepts using a dictionary learning approach, i.e., the algorithm learns the most representative atoms from a set of random sampled patches, and then models the spatial relations among them by counting the co-occurrence between atoms, while penalizing the spatial distance. The proposed approach was compared with a bag-of-features representation in a tissue classification task. For this purpose, 240 histological microscopical fields of view, 24 per tissue class, were collected. Those images fed a Support Vector Machine classifier per class, using 120 images as train set and the remaining ones for testing, maintaining the same proportion of each concept in the train and test sets. The obtained classification results, averaged from 100 random partitions of training and test sets, shows that our approach is more sensitive in average than the bag-of-features representation in almost 6%.

  19. The Koslowski–Sahlmann representation: gauge and diffeomorphism invariance

    Campiglia, Miguel; Varadarajan, Madhavan

    2014-01-01

    The discrete spatial geometry underlying loop quantum gravity (LQG) is degenerate almost everywhere. This is at apparent odds with the non-degeneracy of asymptotically flat metrics near spatial infinity. Koslowski generalized the LQG representation so as to describe states labeled by smooth non-degenerate triad fields. His representation was further studied by Sahlmann with a view to imposing gauge and spatial diffeomorphism invariance through group averaging methods. Motivated by the desire to model asymptotically flat quantum geometry by states with triad labels which are non-degenerate at infinity but not necessarily so in the interior, we initiate a generalization of Sahlmann’s considerations to triads of varying degeneracy. In doing so, we include delicate phase contributions to the averaging procedure which are crucial for the correct implementation of the gauge and diffeomorphism constraints, and whose existence can be traced to the background exponential functions recently constructed by one of us. Our treatment emphasizes the role of symmetries of quantum states in the averaging procedure. Semianalyticity, influential in the proofs of the beautiful uniqueness results for LQG, plays a key role in our considerations. As a by product, we re-derive the group averaging map for standard LQG, highlighting the role of state symmetries and explicitly exhibiting the essential uniqueness of its specification. (paper)

  20. Alternative approach to nuclear data representation

    Pruet, J.; Brown, D.; Beck, B.; McNabb, D.P.

    2006-01-01

    This paper considers an approach for representing nuclear data that is qualitatively different from the approach currently adopted by the nuclear science community. Specifically, we examine a representation in which complicated data is described through collections of distinct and self-contained simple data structures. This structure-based representation is compared with the ENDF and ENDL formats, which can be roughly characterized as dictionary-based representations. A pilot data representation for replacing the format currently used at LLNL is presented. Examples are given as is a discussion of promises and shortcomings associated with moving from traditional dictionary-based formats to a structure-rich or class-like representation