Chromatic and Form Processing in Macaque Primary Visual Cortex PDF Download
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Author: Sylvia David Elfar
Publisher:
ISBN:
Category :
Languages : en
Pages : 484
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Author: Sylvia David Elfar
Publisher:
ISBN:
Category :
Languages : en
Pages : 484
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Author: Galina V. Paramei
Publisher: Frontiers Media SA
ISBN: 288919857X
Category : Psychology
Languages : en
Pages : 136
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Starting from psychophysics, over the last 50 years, most progress in unravelling the mechanisms of color vision has been made through the study of single cell responses, mainly in LGN and striate cortex. A similar development in the study of form perception may seem to be underway, centred on the study of temporal cortex. However, because of the combinatorial characteristics of form perception, we are also observing the opposite tendency: from single-cell activity to population coding, and from static receptive field structures to system dynamics and integration and, ultimately, a synthetic form of psychophysics of color and form perception. From single cells to system integration: it is this development the present Research Topic wishes to highlight and promote. How does this development affect our views on the various attributes of perception? In particular, we are interested in to what extent evolving knowledge in the field of color perception is relevant within a developing integrative framework of form perception. The goal of this Research Topic is to bring together experimental research encompassing both color and form perception. For this volume, we planned a broad scope of topics – on color in complex scenes, color and form, as well as dynamic aspects of form perception. We expect that the Research Topic will be attractive to the community of researchers whose work straddles the boundary between the two visual perception fields, as well as to the wider community interested in integrative/systems neuroscience.
Author: Abhishek De
Publisher:
ISBN:
Category :
Languages : en
Pages : 184
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Vision is critical for survival. We can easily identify objects, guide actions, and avoid collisions if our eyes are open but these abilities are severely impaired if our eyes are closed. This tremendous feat of vision appears simplistic but is implemented by complex biological processes performed by the eye and brain. Therefore, a central goal in visual neuroscience is to understand how neurons in the brain represent scenes, and how the neural activity in turn helps guide behavior. Scenes are composed of spatial and chromatic variations, herein referred to as spatiochromatic variations. In the primary visual cortex (V1) of macaque monkeys, some neurons jointly analyze edges and color, making them an ideal substrate for understanding human spatiochromatic vision. Double-opponent (DO) cells in V1 respond strongly to adjacently placed lights of opposite color and weakly to spatially uniform light of one color. These properties make them well suited for processing of color across space. However, we do not know precisely what information DO cells represent and how. Understanding how DO cells function will advance the field of visual neuroscience in three ways. First, it will help us understand how DO cells are connected to other neurons, thereby shedding light on the organization of cells in V1. Second, it will help link the neuronal responses to behavioral phenomena in color vision. Third, it will advance mathematical models of visual processing that will guide research in other fields. How information about scenes is used for behavior is incomplete without understanding the link between neural activity and behavior. A mechanistic understanding of how V1 neural activity impacts visual perception will be important for understanding the role of V1 in diseases and designing brain-machine interfaces. Using a combination of electrophysiological measurements, monkey behavior and state-of-the-art techniques, I investigated the role of V1 DO cells in the spatiochromatic processing of light, and the role of V1 neural activity in visual perception. I compared my findings about DO cells to simple cells--the best understood functional cell type in V1 that represent oriented luminance edges in scenes, and integrate signals across space roughly linearly. I pursued my research in the form of three different projects, and I report the key findings from each of the projects below. In project 1, I investigated the representation of edges by DO cells. I found that DO cells represent chromatic edges the same way as simple cells represent luminance edges. In project 2, I investigated how DO cells integrate color signals across space. I found that DO cells integrate spatial signals as linearly as simple cells meaning that both these classes of neurons simply weigh and sum the incoming light to generate a spiking response. In interpreting this result, it is important to realize that linearity is not the default mode of visual neurons but rather implies a specialized wiring. My results suggest that the specialized wiring creates linear luminance edge detectors and chromatic edge detectors in V1. Together, the results from project 1 and project 2 suggest that DO cells are similar to simple cells in many ways, and these classes of neurons have a similar mechanism of processing edges than previously thought. This property has major implications in understanding the neural circuitry of these cell classes and their contributions to image processing, which I discuss in Chapters 2 & 3. In project 3, I investigated the impact of silencing neural activity on behavior by pioneering a fast and powerful neural inactivation technique in monkey cortex. The advantage of this technique is that the neural inactivation can be reversed on a trial-by-trial basis, which was difficult to achieve previously. Inactivation of V1 led to reduced sensitivity for visual detection by monkeys suggesting that V1 neural activity impacts visual perception. This result opens doors for possible therapeutic treatments of visual impairments and investigations of many outstanding questions in the domain of perception, action and cognition, which I discuss in Chapter 4. Collectively, my research has made important strides in the field of visual neuroscience by advancing our understanding of spatiochromatic processing by DO cells, and the impact of V1 neural activity on visual perception.
Author: Helga Kolb
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Koen Nelissen
Publisher: Leuven University Press
ISBN: 9789058675415
Category : Rhesus monkey
Languages : en
Pages : 276
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In this thesis, we examined the monkey cortical regions involved in processing of color, visual motion information, and the recognition of actions done by others. The aim was to gain better insight in the functional organization of the monkey visual cortex using in-house developed functional imaging techniques. Two different functional imaging techniques were used in these studies, the double-label deoxyglucose technique (DG) and functional magnetic resonance imaging (fMRI) in the awake monkey (Chapter 2). Both techniques allow to obtain an overview of stimulus-related neural activity throughout the whole brain, integrated over a limited amount of time. The results of the color experiments (Chapter 3) clearly showed that color related information is processed within a group of areas belonging to the ventral stream, which is involved in the perception of objects. Color-related metabolic activity was observed in visual areas V1, V2, V3, V4 and inferotemporal cortex (area TEO and TE). These findings set to rest the longstanding controversial claims that color would be processed almost selectively in one extrastriate visual area (V4) (Zeki SM, Brain Res 1973 53: 422-427). These results also show the usefulness of whole brain functional mapping techniques, as a complimentary approach to single cell measurements. In Chapter 4, we investigated which regions in the superior temporal sulcus (STS) of the monkey are involved in the analysis of motion. While the caudal part of the STS has been studied extensively, including area MT/V5 and MST, little is known about motion sensitivity in more anterior-ventral STS regions. Using fMRI, we were able to localize and delineate six different motion sensitive regions in the STS. One of these regions, that we termed 1st (lower superior temporal), had not been described so far. We were able to further characterize the six motion sensitive regions, using a wide variety of motion-sensitivity tests. The results of the latter tests suggested that motion related information might be processed along a second pathway within the STS, in addition to the MT-MST path (which is involved in the perception of heading). This second pathway, which includes the more rostral motion sensitive STS regions (FST, 1st and STPm) is possibly involved in the visual processing of biological movements (movements of animate objects) and actions. Finally, we investigated how and where in the monkey brain visual information about actions done is processed (Chapter 5 and 6). We found (Chapter 5) that, in agreement with earlier single unit results, the observation of grasping movements activates several regions in the premotor cortex of the monkey. Remarkable is that these premotor regions predominantly have a motor function, coding different types of higher order motor acts (for instance grasping of an object). These results are in agreement with earlier suggestions that we are able to understand actions done by others, because observation of a particular motor act activates our own motor representation of the same act. Furthermore, these studies suggested that within the frontal cortex of the monkey, there is a distinction between context-dependent (a person grasping) and more abstract (a hand grasping) action representations. In Chapter 6 we studied two other regions which are involved in the processing of visual information of actions done by others, the superior temporal sulcus (STS) and the parietal cortex. In the parietal cortex, we found a similar distinction between context-dependent and more abstract action representations as observed in prefrontal cortex. These results suggest that the parietal cortex is not only involved in the visual control of action planning, but also in the visual processing of actions performed by others. Based upon anatomical connections between the STS, parietal and frontal regions and motion-, form- and action-related functional properties of the former regions, we tentatively suggest how information about actions done by others might be sent from the STS to the frontal cortex along three different pathways. The latter working hypothesis will be tested in the future by additional fMRI control experiments and by combining fMRI, inactivation and microstimulation experiments while monkeys perform grasping tasks and/or view actions performed by others.
Author: Karen R. Dobkins
Publisher:
ISBN:
Category :
Languages : en
Pages : 514
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Author: Charles A. Hass
Publisher:
ISBN:
Category :
Languages : en
Pages : 131
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Vision is the culmination of countless biophysical events from the initial stages of sensory transduction to conscious perception. Despite the complexity of this process, our brains encode the visual world effortlessly in only a few hundred milliseconds. Color is a particularly salient visual cue yet we know relatively little about how color is encoded by neurons in the neocortex. Using a combination of neurophysiological, psychophysical, and theoretical approaches we investigated the role of neurons in the primary visual cortex (V1) in chromatic contrast detection in macaque monkeys. We recorded extracellularly from individual V1 neurons and tested the hypothesis that V1 neurons behave as the linear cardinal mechanisms at the observer's detection threshold. Although many neurons in V1 were active at detection threshold, we found that their responses were inconsistent with the cardinal mechanisms model. A subset of these neurons were responsive to both cardinal colors at detection threshold indicating that some V1 neurons are very broadly tuned to color even in response to low-contrast stimuli. Next, we investigated two sources of noise that affect the detectability of chromatic stimuli: eye-movements and noise in the phototransduction cascade. Monkeys made low amplitude (
Author: Bevil Richard Conway
Publisher:
ISBN: 9781475759549
Category :
Languages : en
Pages : 160
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Author: John S. Werner
Publisher: MIT Press
ISBN: 0262019167
Category : Science
Languages : en
Pages : 1693
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Book Description
A comprehensive review of contemporary research in the vision sciences, reflecting the rapid advances of recent years. Visual science is the model system for neuroscience, its findings relevant to all other areas. This essential reference to contemporary visual neuroscience covers the extraordinary range of the field today, from molecules and cell assemblies to systems and therapies. It provides a state-of-the art companion to the earlier book The Visual Neurosciences (MIT Press, 2003). This volume covers the dramatic advances made in the last decade, offering new topics, new authors, and new chapters. The New Visual Neurosciences assembles groundbreaking research, written by international authorities. Many of the 112 chapters treat seminal topics not included in the earlier book. These new topics include retinal feature detection; cortical connectomics; new approaches to mid-level vision and spatiotemporal perception; the latest understanding of how multimodal integration contributes to visual perception; new theoretical work on the role of neural oscillations in information processing; and new molecular and genetic techniques for understanding visual system development. An entirely new section covers invertebrate vision, reflecting the importance of this research in understanding fundamental principles of visual processing. Another new section treats translational visual neuroscience, covering recent progress in novel treatment modalities for optic nerve disorders, macular degeneration, and retinal cell replacement. The New Visual Neurosciences is an indispensable reference for students, teachers, researchers, clinicians, and anyone interested in contemporary neuroscience. Associate Editors Marie Burns, Joy Geng, Mark Goldman, James Handa, Andrew Ishida, George R. Mangun, Kimberley McAllister, Bruno Olshausen, Gregg Recanzone, Mandyam Srinivasan, W.Martin Usrey, Michael Webster, David Whitney Sections Retinal Mechanisms and Processes Organization of Visual Pathways Subcortical Processing Processing in Primary Visual Cortex Brightness and Color Pattern, Surface, and Shape Objects and Scenes Time, Motion, and Depth Eye Movements Cortical Mechanisms of Attention, Cognition, and Multimodal Integration Invertebrate Vision Theoretical Perspectives Molecular and Developmental Processes Translational Visual Neuroscience
Author: John Simon Werner
Publisher: MIT Press
ISBN: 0262033089
Category : Cell physiology
Languages : en
Pages : 975
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Book Description
An essential reference book for visual science.
