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Author: Matthew Lindsay Patten Publisher: ISBN: Category : Languages : en Pages :
Book Description
How does the human visual system convert two-dimensional projections from our eyes into a three-dimensional percept? One primary method is from binocular disparities, which result from having two horizontally separated eyes and are used to provide a powerful cue to depth in our environment. In this thesis, I use human fMRI to investigate the cortical signals associated with binocular disparity. I address several core issues, including the relationship between cortical activity and perception, the significance of the reference plane on depth configurations, and the topography of disparity signals on the cortical surface. In measuring responses to coarse and fine disparities, researchers typically engage two respective tasks: a signal-in-noise and a feature difference task. In the first chapter, we decouple the disparity magnitude from the perceptual task and examine cortical responses to both of these tasks when using fine disparities. Further, we manipulated performance and identified visual areas whose activity varied in line with perceptual judgments. We reveal that responses in later dorsal regions VIPS and POIPS were closely related to perception for both tasks. In the second chapter, we used a similar manipulation to investigate cortical regions that have solved the correspondence problem and whose responses were consistent with the depth percept of the observer, and reveal that this takes place in V7 and VIPS. The third chapter examines the importance of the reference in disparity calculations. We performed several classifications based on depths that were considered relative to fixation or relative to the surround. We found that early visual areas were most sensitive to disparity edges; dorsal visual areas used both the fixation plane and the surround in computing disparity whereas ventral visual areas processed disparity with reference to the surround. In the fourth chapter, we attempt to identify a topographic organisation of binocular disparity in the visual cortex. We estimate the disparity preferences of each voxel in two distinct ways, and displayed these preferences on a flatmap of the cortical surface. Although we did not observe a topographic map of disparity, we observed a cluster in intermediate dorsal regions (V3A, V3B/KO, V7) that consistently showed a bias towards crossed disparities of a larger magnitude.
Author: Matthew Lindsay Patten Publisher: ISBN: Category : Languages : en Pages :
Book Description
How does the human visual system convert two-dimensional projections from our eyes into a three-dimensional percept? One primary method is from binocular disparities, which result from having two horizontally separated eyes and are used to provide a powerful cue to depth in our environment. In this thesis, I use human fMRI to investigate the cortical signals associated with binocular disparity. I address several core issues, including the relationship between cortical activity and perception, the significance of the reference plane on depth configurations, and the topography of disparity signals on the cortical surface. In measuring responses to coarse and fine disparities, researchers typically engage two respective tasks: a signal-in-noise and a feature difference task. In the first chapter, we decouple the disparity magnitude from the perceptual task and examine cortical responses to both of these tasks when using fine disparities. Further, we manipulated performance and identified visual areas whose activity varied in line with perceptual judgments. We reveal that responses in later dorsal regions VIPS and POIPS were closely related to perception for both tasks. In the second chapter, we used a similar manipulation to investigate cortical regions that have solved the correspondence problem and whose responses were consistent with the depth percept of the observer, and reveal that this takes place in V7 and VIPS. The third chapter examines the importance of the reference in disparity calculations. We performed several classifications based on depths that were considered relative to fixation or relative to the surround. We found that early visual areas were most sensitive to disparity edges; dorsal visual areas used both the fixation plane and the surround in computing disparity whereas ventral visual areas processed disparity with reference to the surround. In the fourth chapter, we attempt to identify a topographic organisation of binocular disparity in the visual cortex. We estimate the disparity preferences of each voxel in two distinct ways, and displayed these preferences on a flatmap of the cortical surface. Although we did not observe a topographic map of disparity, we observed a cluster in intermediate dorsal regions (V3A, V3B/KO, V7) that consistently showed a bias towards crossed disparities of a larger magnitude.
Author: HyungGoo R.. Kim Publisher: ISBN: Category : Depth perception Languages : en Pages : 186
Book Description
"When we move through the world, the motion of objects provides a sufficient cue for depth perception. For accurate depth measurements, the brain needs to resolve the depth-sign of objects (that is, whether the object is near or far relative to fixation). This is no easy task as depth-sign can be ambiguous based solely on visual motion. MT neurons are selective for depth-sign from motion parallax by combining retinal inputs and eye movement signals. We addressed three fundamental questions about how the brain uses motion parallax to code depth information. In the first experiment, we asked whether MT neurons are functionally linked to the perception of depth from motion parallax. Responses were recorded while macaque monkeys judged the depth-sign of visual stimuli containing motion parallax cues. We found that trial-by-trial variability of neural responses was correlated with the animal's perceptual decisions in the discrimination task. Greater responses predicted choices toward the depth preference of the recorded neurons. These results provide evidence that MT neurons may be involved in the perception of depth from motion parallax. In the second study, we investigated the nature of response modulation by eye movements. Direction-dependent modulation by eye movements yields the depth-sign selectivity of MT neurons. Responses of near-preferring neurons are suppressed when the eye moves toward the anti-preferred direction of neuron, whereas responses of far-preferring neurons are suppressed during eye movements toward the preferred direction. This response modulation exhibited both multiplicative and additive components, but the depth-sign selectivity of neurons was predicted only by the multiplicative gain change component. Using computer simulations, we show that a population of gain-modulated MT neurons can compute depth from motion parallax. Movement of an observer produces large background motion. In the third study, we hypothesized that neurons can use a visual consequence of self-motion (dynamic perspective cues) to compute depth-sign from motion parallax. We show that MT neurons can disambiguate depth-sign based on large-field background motion, in the absence of eye movements, and that these depth-sign preferences are correlated with those obtained when the animal is physically translated. MT neurons also contribute to depth perception from binocular disparity. It is likely that both eye movements and large field motion modulate MT responses to binocular images in a systematic way to encode the 3D spatial information of objects. These insights provide a deeper understanding of 3D information processing during navigation"--Pages v-vi.
Author: David Alais Publisher: MIT Press ISBN: 9780262012126 Category : Binocular rivalry Languages : en Pages : 416
Book Description
Recent work on perceptual ambiguity and its implications for the correlation between neural events and perceptual experience. Researchers today in neuroscience and cognitive psychology increasingly turn their attention to binocular rivalry and other forms of perceptual ambiguity or bistability. The study of fluctuations in visual perception in the face of unchanging visual input offers a means for understanding the link between neural events and visual events, including visual awareness. Some neuroscientists believe that binocular rivalry reveals a fundamental aspect of human cognition and provides a way to isolate and study brain areas involved in attention and selection. The eighteen essays collected in Binocular Rivalry present the most recent theoretical and empirical work on this key topic by leading researchers in the field. After the opening chapter's overview of the major characteristics of binocular rivalry in their historical contexts, the contributors consider topics ranging from the basic phenomenon of perceptual ambiguity to brain models and neural networks. The essays illustrate the potential power of the study of perceptual ambiguity as a tool for learning about the neural concomitants of visual awareness, or, as they have been called, the "neural correlates of consciousness."
Author: Ian P. Howard Publisher: OUP USA ISBN: 019976414X Category : Psychology Languages : en Pages : 672
Book Description
The three-volume work Perceiving in Depth is a sequel to Binocular Vision and Stereopsis and to Seeing in Depth, both by Ian P. Howard and Brian J. Rogers. This work is much broader in scope than the previous books and includes mechanisms of depth perception by all senses, including aural, electrosensory organs, and the somatosensory system. Volume 1 reviews sensory coding, psychophysical and analytic procedures, and basic visual mechanisms. Volume 2 reviews stereoscopic vision. Volume 3 reviews all mechanisms of depth perception other than stereoscopic vision. The three volumes are extensively illustrated and referenced and provide the most detailed review of all aspects of perceiving the three-dimensional world.Volume 1 starts with a review of the history of visual science from the ancient Greeks to the early 20th century with special attention devoted to the discovery of the principles of perspective and stereoscopic vision. The first chapter also contains an account of early visual display systems, such as panoramas and peepshows, and the development of stereoscopes and stereophotography. A chapter on the psychophysical and analytic procedures used in investigations of depth perception is followed by a chapter on sensory coding and the geometry of visual space. An account of the structure and physiology of the primate visual system proceeds from the eye through the LGN to the visual cortex and higher visual centers. This is followed by a review of the evolution of visual systems and of the development of the mammalian visual system in the embryonic and post-natal periods, with an emphasis on experience-dependent neural plasticity. An account of the development of perceptual functions, especially depth perception, is followed by a review of the effects of early visual deprivation during the critical period of neural plasticity on amblyopia and other defects in depth perception. Volume 1 ends with accounts of the accommodation mechanism of the human eye and vergence eye movements.
Author: Olivier A. Coubard Publisher: Frontiers Media SA ISBN: 2889196550 Category : Binocular vision Languages : en Pages : 266
Book Description
Binocular vision is achieved by five neurovisual systems originating in the retina but varying in their destination within the brain. Two systems have been widely studied: the retino-tectal or retino-collicular route, which subserves an expedient and raw estimate of the visual scene through the magnocellular pathway, and the retino-occipital or retino-cortical route, which allows slower but refined analysis of the visual scene through the parvocellular pathway. But there also exist further neurovisual systems: the retino-hypothalamic, retino-pretectal, and accessory optic systems, which play a crucial role in vision though they are less understood. The retino-pretectal pathway projecting onto the pretectum is critical for the pupillary or photomotor reflex. The retino-hypothalamic pathway projecting onto the suprachiasmatic nucleus regulates numerous behavioral and biological functions as well as circadian rhythms. The accessory optic system targeting terminal lateral, medial and dorsal nuclei through the paraoptic fasciculus plays a role in head and gaze orientation as well as slow movements. Taken together, these neurovisual systems involve 60% of brain activity, thus highlighting the importance of vision in the functioning and regulation of the central nervous system. But vision is first and foremost action, which makes perception impossible without movement. Binocular coordination is a prerequisite for binocular fusion of the object of interest on the two foveas, thus ensuring visual perception. The retino-collicular pathway is sufficient to elicit reflexive eye movements with short latencies. Thanks to its motor neurons, the superior colliculus activates premotor neurons, which themselves activate motor neurons of the oculomotor, trochlear and abducens nuclei. At a higher level, a cascade of neural mechanisms participates in the control of decisional eye movements. The superior colliculus is controlled by the substancia nigra pars reticulata, which is itself gated by subcortical structures such as the dorsal striatum. The superior colliculus is also inhibited by the dorsolateral prefrontal cortex through a direct prefrontotectal tract. Cortical areas are crucial for the triggering of eye movements: the frontal eye field, supplementary eye field, and parietal eye field. Finally the cerebellum maintains accuracy. The focus of the present research topic, entitled Neural bases of binocular vision and coordination and their implications in visual training programs, is to review the most recent findings in brain imaging and neurophysiology of binocular vision and coordination in humans and animals with frontally-placed eyes. The emphasis is put on studies that enable transfer of knowledge toward visual training programs targeting visual field defects (e.g., hemianopia) and binocular functional disorders (e.g., amblyopia).
Author: Benjamin Lankow Publisher: ISBN: 9781369616859 Category : Languages : en Pages :
Book Description
Throughout the brain, parallel processing streams compose the building-blocks of complex neural function. Perhaps the most salient of all parallel streams in the brain are the pathways carrying information from the two eyes. The interaction of these visual pathways has emerged as a promising model for establishing causal links between neural processing and visual perception, but much is unknown regarding where monocular information streams first interact in the brain and what types of neural circuitry support the processing of binocular signals. To address these points, we use psychophysical, physiological, and computational methods to develop an understanding of how the brain processes binocular visual information. We performed physiological and psychophysical experiments in the alert macaque monkey to determine where in the brain visual signals from the two eyes first interact; we demonstrate that visual information remains segregated in monocular streams prior to reaching the visual cortex. We then build on recent advances in the theory of dynamical neural networks to develop a computational framework for binocular combination and binocular rivalry. We demonstrate that surprisingly simple rules of connectivity that are inspired by functional connectivity in the visual cortex are sufficient to generate summation and rivalry in a network model of binocular vision.
Author: Donald House Publisher: Springer Science & Business Media ISBN: 1468463918 Category : Medical Languages : en Pages : 141
Book Description
Depth Perception in Frogs and Toads provides a comprehensive exploration of the phenomenon of depth perception in frogs and toads, as seen from a neuro-computational point of view. Perhaps the most important feature of the book is the development and presentation of two neurally realizable depth perception algorithms that utilize both monocular and binocular depth cues in a cooperative fashion. One of these algorithms is specialized for computation of depth maps for navigation, and the other for the selection and localization of a single prey for prey catching. The book is also unique in that it thoroughly reviews the known neuroanatomical, neurophysiological and behavioral data, and then synthesizes, organizes and interprets that information to explain a complex sensory-motor task. The book will be of special interest to that segment of the neural computing community interested in understanding natural neurocomputational structures, particularly to those working in perception and sensory-motor coordination. It will also be of interest to neuroscientists interested in exploring the complex interactions between the neural substrates that underly perception and behavior.
Author: Peter Thier Publisher: ISBN: Category : Medical Languages : en Pages : 664
Book Description
State-of-the-art overview of the current thinking on parietal lobe functions. Covers specific areas of anatomy and the contributions of the parietal lobes to eye movements, reaching and grasping, attention and perception, and the representation of space.
Author: Ian P. Howard Publisher: Oxford University Press, USA ISBN: 9780195084764 Category : Medical Languages : en Pages : 756
Book Description
This is a comprehensive survey of binocular vision, with an emphasis on its role in the perception of a three-dimensional world. The central theme is biological vision. Machine vision and computational models are discussed where they contribute to an understanding of living systems.
Author: V. A. Casagrande Publisher: Gulf Professional Publishing ISBN: 9780444516794 Category : Computers Languages : en Pages : 328
Book Description
Almost all of the messages that are received by the cerebral cortex from the environment or from the body's internal receptors come through the thalamus and much current thought about perceptual processing is based on sensory pathways that relay in the thalamus. This volume focuses on three major areas: the role of thalamocortical communication in cognition and attention; the role of the thalamus in communication between cortical areas; the hypothesis that much or all of the information relayed by thalamus, even to classical, pure "sensory" areas of cortex, represents a corollary message being sent simultaneously to motor centers. It presents a broad overview of important recent advances in these areas. * Provides a look at brain structures involved in perception and action * Includes summaries by leading investigators in the field * Presents recent advances in our understanding of brain functions
Author: Matthew Lindsay Patten
Author: Matthew Lindsay Patten
Author: HyungGoo R.. Kim
Author: David Alais
Author: Ian P. Howard
Author: Olivier A. Coubard
Author: Benjamin Lankow
Author: Donald House
Author: Peter Thier
Author: Ian P. Howard
Author: V. A. Casagrande