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The Effect Of Dynamic Synapses On Spatio Temporal Receptive Fields In Visual Cortex
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Book Synopsis The Effect of Dynamic Synapses on Spatio-temporal Receptive Fields in Visual Cortex by :
Download or read book The Effect of Dynamic Synapses on Spatio-temporal Receptive Fields in Visual Cortex written by and published by . This book was released on 1997 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Temporal dynamics are a well known feature of synaptic transmission. Recently temporal dynamics of synaptic transmission has been reported in neocortex. Here we examine the possible effects of these dynamics on the spatio-temporal receptive fields of simple cells in VI. We do this by examining a simple model of a cortical neuron that depends on an oriented thalamocortical projection. In our model, the receptive field (RF) structure is encoded either as a structured presynaptic probability of release or as a structured postsynaptic efficacy. We show that these different assumptions about the origin of receptive field structure lead to very different spatio-temporal dynamics. The structured efficacy model (SE) leads to tuning curves that are unimodal, and although the response magnitude changes in time, the preferred orientation does not. On the other hand, the structured probability model (PR) leads to tuning curves which are not unimodal and change their preferred orientation in time. We show that the temporal code induced by the dynamic synapses can be used for distinguishing between different input that induce the same average firing rate.
Book Synopsis Synaptic Mechanisms and Network Architecture Underlying Spatiotemporal Properties of Simple Cell Receptive Fields in Primary Visual Cortex In Vivo by : M. Morgan Taylor
Download or read book Synaptic Mechanisms and Network Architecture Underlying Spatiotemporal Properties of Simple Cell Receptive Fields in Primary Visual Cortex In Vivo written by M. Morgan Taylor and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Neurons in sensory cortex represent information about the environment and relay this information to other cells in the network using electrical and chemical signals. The study of neuronal receptive fields-descriptions of the sensory stimuli that best drive a neuron to fire-can yield insights into how different groups of cells transform sensory information. In layer 4 (L4) of primary visual cortex (V1), neurons called simple cells are responsive to the specific orientation and spatial phase of an edge-like stimulus. Relatedly, simple cell receptive fields are characterized by elongated, non-overlapping, spatially restricted subregions in which visual stimuli can either increase or decrease the cell's firing rate, depending on contrast.In this dissertation, we examine the synaptic and network mechanisms underlying the generation of simple cell receptive fields and their response characteristics to visual stimuli within their receptive fields. Our experimental data from in vivo, intracellular recordings provides a characterization of the spatiotemporal distribution of visually-evoked excitatory and inhibitory synaptic conductances. In contrast with a popular theory of functional connectivity in primary visual cortex, but consistent with anatomical studies of inhibitory neurons, we present evidence supporting unbiased connectivity arising from inhibitory simple cells in L4 of V1. In addition to our experimental findings, we provide two different network models of V1 L4 that combine anatomical and experimental data. Together, these models account for apparent discrepancies in experimental findings and offer mechanistic explanations for the characteristic delay between the onset of excitation and inhibition that has been observed across sensory cortex. The work here provides the most complete description to date of the spatial and temporal distribution of inhibition as it relates to simple cells in layer 4 of primary visual cortex.
Book Synopsis Recurrent Network Dynamics in Visual Cortex by : Jeroen Joukes
Download or read book Recurrent Network Dynamics in Visual Cortex written by Jeroen Joukes and published by . This book was released on 2016 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a data-driven computational approach for studying neural systems. In this approach one starts with experimental stimuli (inputs) and measured neuronal responses (outputs). The relationship between the inputs and outputs is modeled with an artificial recurrent neural network (ARNN). A detailed investigation of the network weights and response properties of the connected elements, together with simulated experiments performed on the ARNN leads to significant new insights and new hypotheses about the underlying neural mechanisms. We first applied this approach to motion responses of neurons in the macaque middle temporal area (MT). This provided the novel insight that recurrent networks dynamics can explain complex motion tuned response dynamics found in MT neurons, without the need for feedforward temporal delay lines. In our second study we used this approach to model the early visual form processing pathway of the macaque brain. Neurons in the secondary visual cortex (V2) were stimulated with textured stimuli designed to probe the visual systems for complex visual shapes. The approach led to the novel hypothesis that selectivity for complex form depends on selectivity for motion. For the third study we extended the approach by taking advantage of chronically implanted microelectrode arrays (FMA) in primary visual cortex (V1) of the awake behaving macaque. With the FMA we collected V1 responses on day one, fitted an ARNN, explored the detailed properties of the ARNN the following days, and tested model predictions with a V1 validation experiment within the same week. We found that V1 selectivity for form is much more complex than commonly thought and includes spatiotemporal interactions between multiple hotspots in the receptive field. With this approach we found complex V1 tuning properties that are currently thought to primarily arise higher up in the visual processing stream. We conclude that ARNNs can offer a useful tool set for systems neuroscience; the powerful computational approach, together with carefully designed experiments, provides novel hypotheses and insights into the complexity of neural function.
Book Synopsis Spike Timing Dependent Plasticity of Receptive Fields in Primary Visual Cortex by : Chad Daniel Meliza
Download or read book Spike Timing Dependent Plasticity of Receptive Fields in Primary Visual Cortex written by Chad Daniel Meliza and published by . This book was released on 2005 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Visual Cortex by : Stephane Molotchnikoff
Download or read book Visual Cortex written by Stephane Molotchnikoff and published by BoD – Books on Demand. This book was released on 2012-09-26 with total page 427 pages. Available in PDF, EPUB and Kindle. Book excerpt: The neurosciences have experienced tremendous and wonderful progress in many areas, and the spectrum encompassing the neurosciences is expansive. Suffice it to mention a few classical fields: electrophysiology, genetics, physics, computer sciences, and more recently, social and marketing neurosciences. Of course, this large growth resulted in the production of many books. Perhaps the visual system and the visual cortex were in the vanguard because most animals do not produce their own light and offer thus the invaluable advantage of allowing investigators to conduct experiments in full control of the stimulus. In addition, the fascinating evolution of scientific techniques, the immense productivity of recent research, and the ensuing literature make it virtually impossible to publish in a single volume all worthwhile work accomplished throughout the scientific world. The days when a single individual, as Diderot, could undertake the production of an encyclopedia are gone forever. Indeed most approaches to studying the nervous system are valid and neuroscientists produce an almost astronomical number of interesting data accompanied by extremely worthy hypotheses which in turn generate new ventures in search of brain functions. Yet, it is fully justified to make an encore and to publish a book dedicated to visual cortex and beyond. Many reasons validate a book assembling chapters written by active researchers. Each has the opportunity to bind together data and explore original ideas whose fate will not fall into the hands of uncompromising reviewers of traditional journals. This book focuses on the cerebral cortex with a large emphasis on vision. Yet it offers the reader diverse approaches employed to investigate the brain, for instance, computer simulation, cellular responses, or rivalry between various targets and goal directed actions. This volume thus covers a large spectrum of research even though it is impossible to include all topics in the extremely diverse field of neurosciences.
Book Synopsis The Speed of Thought by : Martin James Tovée
Download or read book The Speed of Thought written by Martin James Tovée and published by . This book was released on 1998 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book deals with information processing in the primate temporal visual cortex, one of the higher visual association areas, which is believed to be important for the representation of complex stimuli and may also play a role in visual memory. Here, the need for rapid information processing shapes the functional architecture of all sensory systems, acting to reduce, where possible, wiring length and the number of synapses, to allow faster processing.
Download or read book Brain Theory written by Adrianus Aertsen and published by . This book was released on 1993-05-28 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt: Emerging from the Fourth International Meeting on Brain Theory, Held in Trento, Italy, April 1992, this collection of papers brings together new insights and concepts from various branches of experimental and theoretical neuroscience, partly in the form of review chapters, partly in short, focused contributions, or critical essays. The volume is divided into four sections: space-time aspects of brain function--sensory perception; space-time aspects of brain function--control of action; space-time dynamics of neuronal activity in the working brain; and the brain--the organization of perception and action. No index. Annotation copyright by Book News, Inc., Portland, OR
Book Synopsis Encyclopedia of Computational Neuroscience by : Dieter Jaeger
Download or read book Encyclopedia of Computational Neuroscience written by Dieter Jaeger and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Theory of Cortical Plasticity by : Leon N. Cooper
Download or read book Theory of Cortical Plasticity written by Leon N. Cooper and published by World Scientific. This book was released on 2004 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt: This invaluable book presents a theory of cortical plasticity and shows how this theory leads to experiments that test both its assumptions and consequences. It elucidates, in a manner that is accessible to students as well as researchers, the role which the BCM theory has played in guiding research and suggesting experiments that have led to our present understanding of the mechanisms underlying cortical plasticity. Most of the connections between theory and experiment that are discussed require complex simulations. A unique feature of the book is the accompanying software package, Plasticity. This is provided complete with source code, and enables the reader to repeat any of the simulations quoted in the book as well as to vary either parameters or assumptions. Plasticity is thus a research and an educational tool. Readers can use it to obtain hands-on knowledge of the structure of BCM and various other learning algorithms. They can check and replicate our results as well as test algorithms andrefinements of their own.
Download or read book Brain Dynamics written by Hermann Haken and published by Springer Science & Business Media. This book was released on 2007-12-22 with total page 331 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is an excellent introduction for graduate students and nonspecialists to the field of mathematical and computational neurosciences. The book approaches the subject via pulsed-coupled neural networks, which have at their core the lighthouse and integrate-and-fire models. These allow for highly flexible modeling of realistic synaptic activity, synchronization and spatio-temporal pattern formation. The more advanced pulse-averaged equations are discussed.
Book Synopsis Spatiotemporal Dynamics in Neocortex by : Lyle Muller
Download or read book Spatiotemporal Dynamics in Neocortex written by Lyle Muller and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: It has only recently been acknowledged to what large extent the internal dynamics of neural networks could play a role in their function. In this respect, synaptic "noise" -- that is, the influence of the cortical network on single neurons exerted through the massive recurrent circuity that is the hallmark of neocortex -- has recently been shown to have a profound effect on neuronal integrative properties, changing the responses of single neurons across brain states, sometimes within the matter of a few seconds. These internally generated activity states, shaped by and continually shaping the plastic synaptic recurrent connections, then combine with the external inputs to produce a rich repertoire of responses to sensory stimuli in primary cortical regions. In this thesis, we have focused on the {\it spatial} aspect of these internal dynamics, specifically the spatial structure of cortical oscillations, spontaneous and stimulus-evoked. Along the way, we have made an extensive review of the literature concerning propagating waves in thalamus and cortex, and studied network models to investigate how waves depend on network state. We have also introduced new tools for the characterization of spatiotemporal activity patterns in noisy multichannel data. The culmination of this work is a demonstration, using voltage-sensitive dye imaging data taken from the awake monkey, that the population response to a small visual stimulus propagates like a wave across a large extent of primary visual cortex during the awake state, a result contradicting a range of previous studies which seemed to suggest that propagating waves disappear in this case. Moving forward, we have begun to investigate the spatiotemporal structure of local field potential and spiking activity in multielectrode recordings taken from the human and monkey in various states of arousal, to address questions prompted by our initial voltage-sensitive dye imaging study in the monkey. In parallel, we have initiated an analysis of the extent to which neural connectivity can be characterized by the "small-world" effect, the main result of which is that neural graphs may in fact reside outside the small-world regime. The results from these PhD studies thus span the spectrum of scales in neuroscience, from macroscopic activity patterns to microscopic connectivity profiles. It is my sincere hope to expound in these pages a unified theme for these results, and a foundation for further work in neuroscience -- a search for structure within the internal architecture of the system under study.
Book Synopsis The Functional Impact of Neurons in the Dorsal Lateral Geniculate Nucleus on the Awake Visual Cortex by : Carl Richard Stoelzel
Download or read book The Functional Impact of Neurons in the Dorsal Lateral Geniculate Nucleus on the Awake Visual Cortex written by Carl Richard Stoelzel and published by . This book was released on 2007 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Cognitive Thalamus by : Yuri B. Saalmann
Download or read book The Cognitive Thalamus written by Yuri B. Saalmann and published by Frontiers Media SA. This book was released on 2015-06-17 with total page 127 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cognitive processing is commonly conceptualized as being restricted to the cerebral cortex. Accordingly, electrophysiology, neuroimaging and lesion studies involving human and animal subjects have almost exclusively focused on defining roles for cerebral cortical areas in cognition. Roles for the thalamus in cognition have been largely ignored despite the fact that the extensive connectivity between the thalamus and cerebral cortex gives rise to a closely coupled thalamo-cortical system. However, in recent years, growing interest in the thalamus as much more than a passive sensory structure, as well as methodological advances such as high-resolution functional magnetic resonance imaging of the thalamus and improved electrode targeting to subregions of thalamic nuclei using electrical stimulation and diffusion tensor imaging, have fostered research into thalamic contributions to cognition. Evidence suggests that behavioral context modulates processing in primary sensory, or first-order, thalamic nuclei (for example, the lateral geniculate and ventral posterior nuclei), allowing attentional filtering of incoming sensory information at an early stage of brain processing. Behavioral context appears to more strongly influence higher-order thalamic nuclei (for example, the pulvinar and mediodorsal nucleus), which receive major input from the cortex rather than the sensory periphery. Such higher-order thalamic nuclei have been shown to regulate information transmission in frontal and higher-order sensory cortex according to cognitive demands. This Research Topic aims to bring together neuroscientists who study different parts of the thalamus, particularly thalamic nuclei other than the primary sensory relays, and highlight the thalamic contributions to attention, memory, reward processing, decision-making, and language. By doing so, an emphasis is also placed on neural mechanisms common to many, if not all, of these cognitive operations, such as thalamo-cortical interactions and modulatory influences from sources in the brainstem and basal ganglia. The overall view that emerges is that the thalamus is a vital node in brain networks supporting cognition.
Book Synopsis Spatiotemporal Receptive Fields of Simple Cells in Early Visual Cortex by : Vargha Talebi
Download or read book Spatiotemporal Receptive Fields of Simple Cells in Early Visual Cortex written by Vargha Talebi and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Collectively, the three studies in this thesis demonstrate the powerful potential of natural image stimuli and regularized regression system identification techniques, making them ideal candidates for routine use in visual neuroscience studies. RF models derived from natural images have revealed that physiological response..." --
Book Synopsis Micro-, Meso- and Macro-Dynamics of the Brain by : György Buzsáki
Download or read book Micro-, Meso- and Macro-Dynamics of the Brain written by György Buzsáki and published by Springer. This book was released on 2016-05-02 with total page 181 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book brings together leading investigators who represent various aspects of brain dynamics with the goal of presenting state-of-the-art current progress and address future developments. The individual chapters cover several fascinating facets of contemporary neuroscience from elementary computation of neurons, mesoscopic network oscillations, internally generated assembly sequences in the service of cognition, large-scale neuronal interactions within and across systems, the impact of sleep on cognition, memory, motor-sensory integration, spatial navigation, large-scale computation and consciousness. Each of these topics require appropriate levels of analyses with sufficiently high temporal and spatial resolution of neuronal activity in both local and global networks, supplemented by models and theories to explain how different levels of brain dynamics interact with each other and how the failure of such interactions results in neurologic and mental disease. While such complex questions cannot be answered exhaustively by a dozen or so chapters, this volume offers a nice synthesis of current thinking and work-in-progress on micro-, meso- and macro- dynamics of the brain.
Book Synopsis Spatiotemporal Responses to Natural Images and Their Phase-shuffled Version in the Primary Visual Cortex by : Sepide Movaghati
Download or read book Spatiotemporal Responses to Natural Images and Their Phase-shuffled Version in the Primary Visual Cortex written by Sepide Movaghati and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "According to classical models of visual information processing, the visual cortex acts as a hierarchical structure in which information flow is unidirectional and transmitted from the primary visual cortex (V1) to higher visual areas. This model considers V1 as an inflexible processing unit, which filters local basic features of visual input, such as the spatial frequency and orientation of the changes in luminance. Contrary to this classical model, recent studies have reported variant activity in V1 based on the presence of higher-order features within visual inputs. In other words, specific characteristics, such as phase content or spatial coherence, potentially modulate the activity of V1. However, the explicit characteristics and the precise timing of their modulatory effect remain unclear. In this study, MagnetoEncephaloGraphy (MEG) was used to test whether the spatiotemporal response to natural images of animals is different from the response to their phase-shuffled counterparts. The frequency content and the total contrast of the images were maintained throughout the phase-scrambling approach. Meanwhile, higher-order image statistics, such as Kurtosis, were manipulated. We investigated the effect of this manipulation on the evoked response of V1 by taking advantage of (1) the high temporal resolution of the MEG technique and (2) the Minimum norm source localization method. The results of this thesis show that the modulation of activity associated with the presentation of natural images appears as early as 50ms post-stimulation. This effect can be observed in the power of the signals recorded by MEG sensors as well as in sources localized in the primary visual cortex. The phase scrambling of visual input increased the amplitude of the early response (30-70ms post-stimulation) and the M170 component (140-200ms post-stimulation). The weaker population response to natural images during the early response is consistent with a model proposing sparse neuronal coding for natural images. The increased M170 activation of V1 to non-natural phase-scrambled images is consistent with the predictive coding model. According to this model, the prediction error in lower order sensory areas increases with decreasing predictability of the sensory input. An increase in the power of gamma frequency (60-80Hz) was observed in response to phase-scrambled images. These findings are in accordance with a previous study that found prediction errors in auditory cortex to be predominantly conveyed via the high (gamma) frequency range. In addition, spatially coherent features in visual input induce a stronger surround suppression effect and reduce the population activity in V1. Therefore, the mechanisms underlying the late modulatory effect on the M170 component may also involve surround suppression in the visual cortex. Our findings suggest that feedback modulates the neuronal response of the primary visual cortex. Further, they identify V1 as a dynamic filter that can be modulated by the higher-order characteristics of visual input, as opposed to previous models that deem V1 to be an inflexible low-level processing unit." --
Book Synopsis Tutorials in Visual Cognition by : Veronika Coltheart
Download or read book Tutorials in Visual Cognition written by Veronika Coltheart and published by Routledge. This book was released on 2011-01-07 with total page 407 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the late-1980s, visual cognition was a small subfield of cognitive psychology, and the standard texts mainly discussed just iconic memory in their sections on visual cognition. In the subsequent two decades, and especially very recently, many remarkable new aspects of the processing of brief visual stimuli have been discovered -- change blindness, repetition blindness, the attentional blink, newly-discovered properties of visual short-term memory and of the face recognition system, the influence of reentrant processing on visual perception, and the surprisingly intimate relationships between eyeblinks and visual cognition. This volume provides up-to-date tutorial reviews of these many new developments in the study of visual cognition written by the leaders in the discipline, providing an incisive and comprehensive survey of research in this dynamic field.
