Neural Representation Of Multiple Moving Features In Extrastriate Visual Cortical Area Mt
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Neural Representation Of Multiple Moving Features In Extrastriate Visual Cortical Area Mt
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Author : Jianbo Xiao
language : en
Publisher:
Release Date : 2017
Neural Representation Of Multiple Moving Features In Extrastriate Visual Cortical Area Mt written by Jianbo Xiao and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.
Natural scenes often contain multiple entities. The ability to segregate visual scenes into distinct objects and surfaces, referred to as visual segmentation, is fundamental to vision. Transparent motion perception is the perception of multiple motion vectors within the same visual space. Transparent motion presents a difficult case for visual segmentation. Understanding neural representation of transparent motion is important to elucidating how the brain distinguishes multiple stimuli. In this dissertation, I studied the neural representation of transparent motion by recording from neurons in the middle temporal (MT) cortex of macaque monkeys while they performed either a visual fixation task or a motion discrimination task. In the first project, I investigated the neural representation of two transparently moving stimuli that have different signal strengths. I found that neuronal responses to the transparent motion stimuli can be well accounted for by the weighted summation of the component responses plus a non-linear interaction term between the component responses, and MT neurons weight the stimulus component that has the higher signal strength more strongly. In the second project, I investigated how MT neurons represent overlapping random-dot stimuli moving transparently in slightly different directions. I found that, although the population-averaged neuronal activity represents the vector-averaged direction of the two motion components, more than half of MT neurons preferentially represent the component directions. In the third project, I studied the neural representation of overlapping stimuli moving transparently at different depths and the effects of feature-based attention to understand how different motion features, which in this case are motion direction and binocular disparity, interact with each other to achieve visual segmentation. I found a tuned feature-based attention effect and that MT neurons preferentially represent the near stimulus component regardless of the attentional state and the neuron's binocular disparity selectivity. This dissertation research demonstrated the success of divisive normalization model in characterizing the neuronal representation of transparent motion, and discovered soub-populations of MT neurons that were capable of discriminating similar motion directions, and illustrated the dominant neural representation of the near component stimulus in response to multiple stimuli moving transparently at different depths.
Neural Mechanisms Of Motion Based Image Segmentation In Cortical Area Mt
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Author : Steven Wiesner
language : en
Publisher:
Release Date : 2021
Neural Mechanisms Of Motion Based Image Segmentation In Cortical Area Mt written by Steven Wiesner and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021 with categories.
Natural scenes often contain multiple visual entities. A fundamental function of vision, referred to as image segmentation, is to segregate visual objects from the background and each other to generate visual perception and guide behavior. Visual motion cues are particularly powerful for segmentation. In this dissertation, I studied how neurons in the middle temporal (MT) cortex, a cortical area important for processing visual motion information, encode multiple moving stimuli. I also investigated how the encoding rules characterized in my studies benefit the extraction of information about individual stimulus components from population neuronal responses. In the first project, I revealed the neural basis for the well-known perceptual phenomenon of direction repulsion, and demonstrated how direction repulsion benefits the segmentation of overlapping moving stimuli. I found that the shape of the population neuronal responses elicited by overlapping random-dot stimuli are widened at direction separations of 45℗ʻ and 60℗ʻ, compared to if neurons linearly pool responses to individual stimulus components. In the second project, I investigated how neurons in area MT represent multiple visual stimuli that compete in more than one feature domain. I found that MT neurons showed a bias towards a stimulus component with a higher contrast and lower motion coherence when overlapping, even though that stimulus component evoked a weaker response in MT compared to a stimulus with a lower contrast and higher coherence. I also found that how MT neurons represent multiple stimuli is dependent on the spatial arrangement, highlighting the impact of hierarchical processing on the representation of multiple stimuli. In the third project, I investigated the neural representation of multiple moving stimuli that are spatially separated within the receptive fields of MT neurons. I found that neurons in area MT showed a spatial bias towards the stimulus that elicited a stronger response when presented alone. These studies made several novel findings about how MT neurons pool inputs from multiple stimuli in a nonlinear fashion and the impact on population neuronal responses. Thanks to these response nonlinearities, the visual system is equipped with a population neural code that facilitates the segmentation of multiple visual entities in natural environments.
Visual Motion Analysis In Extrastriate Cortical Areas Mt And Mst
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Author : Hilary Whetu Heuer
language : en
Publisher:
Release Date : 2003
Visual Motion Analysis In Extrastriate Cortical Areas Mt And Mst written by Hilary Whetu Heuer and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2003 with categories.
Neural Mechanisms Of Visual Segmentation Using Motion And Depth Cues In Cortical Area Mt
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Author : Venkta Lakshmi Anjani Chakrala
language : en
Publisher:
Release Date : 2023
Neural Mechanisms Of Visual Segmentation Using Motion And Depth Cues In Cortical Area Mt written by Venkta Lakshmi Anjani Chakrala and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023 with categories.
Our dynamic world requires us to discern objects in complex environments to effectively interact with our surroundings. Our visual system has the remarkable ability to seamlessly segment objects from each other, unmatched by current machine vision systems, that enables us to understand visual scenes and guides actions. In natural vision, visual motion combined with other features like depth and cognitive abilities like attention is important to segment objects. Visual motion processing is widely studied at both perceptual and physiological levels. However, the neural mechanisms underlying the segmentation of multiple objects aided by motion combined with other features like depth and spatial location are not fully understood. The goal of this dissertation is to elucidate the neural mechanisms underlying the segmentation of multiple objects using motion direction, speed, depth (binocular disparity), and spatial location. Toward this, in chapter 2, I determined the neural representation of multiple objects, that differed in depth and motion direction and investigated the effect of selective attention on this representation. We designed a novel motion discrimination task, in which macaque monkeys selectively attended to one of two moving surfaces separated in depth. The task was paired with electrophysiological recordings from the middle temporal area (MT), known for its selectivity to visual motion and binocular disparity. Our results suggest that to represent multiple surfaces with different depths and motion direction, MT neurons leverage their preference to the binocular disparity of the constituent surfaces, so that the information about the two motion directions is distributed over neuronal subgroups defined by their disparity preferences (near and far-preferred neurons). Selective attention to one disparity enhanced the representation of the attended surface and its motion direction. In chapter 3, I investigated how MT neurons encoded two spatially separated stimuli moving at different speeds. Akin to chapter 2, we found that the MT neurons' spatial and speed preferences to single motion were preserved in their responses to two spatially separated speeds, which might help in their segmentation. Together, our results elucidate prevailing neural strategies of encoding multiple visual stimuli, and how the visual system exploits spatial cues either two-dimensional or three-dimensional, together with motion cues to segment multiple objects.
Multiple Visual Areas
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Author : Clinton N. Woolsey
language : en
Publisher: Springer Science & Business Media
Release Date : 2012-12-06
Multiple Visual Areas written by Clinton N. Woolsey and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-12-06 with Medical categories.
In April 1979 a symposium on "Multiple Somatic Sensory Motor, Visual and Auditory Areas and Their Connectivities" was held at the FASEB meeting in Dallas, Texas under the auspices of the Committee on the Nervous System of the American Physiological Society. The papers presented at that symposium are the basis of most of the substantially augmented, updated chapters in the three volumes of Cortical Sensory Organization. Only material in chap ter 8 of volume 3 was not presented at that meeting. The aim of the symposium was to review the present status of the field of cortical representation in the somatosensory, visual and auditory systems. Since the early 1940s, the number of recognized cortical areas related to each of these systems has been increasing until at present the number of visually related areas exceeds a dozen. Although the number is less for the somatic and auditory systems, these also are more numerous than they were earlier and are likely to increase still further since we may expect each system to have essentially the same number of areas related to it.
Brain Mapping
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Author :
language : en
Publisher: Academic Press
Release Date : 2015-02-14
Brain Mapping written by and has been published by Academic Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015-02-14 with Science categories.
Brain Mapping: A Comprehensive Reference, Three Volume Set offers foundational information for students and researchers across neuroscience. With over 300 articles and a media rich environment, this resource provides exhaustive coverage of the methods and systems involved in brain mapping, fully links the data to disease (presenting side by side maps of healthy and diseased brains for direct comparisons), and offers data sets and fully annotated color images. Each entry is built on a layered approach of the content – basic information for those new to the area and more detailed material for experienced readers. Edited and authored by the leading experts in the field, this work offers the most reputable, easily searchable content with cross referencing across articles, a one-stop reference for students, researchers and teaching faculty. Broad overview of neuroimaging concepts with applications across the neurosciences and biomedical research Fully annotated color images and videos for best comprehension of concepts Layered content for readers of different levels of expertise Easily searchable entries for quick access of reputable information Live reference links to ScienceDirect, Scopus and PubMed
Neural Representation Of Complex Motion In The Primate Cortex
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Author : Benedict Wild
language : en
Publisher:
Release Date : 2021
Neural Representation Of Complex Motion In The Primate Cortex written by Benedict Wild and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021 with categories.
This dissertation is concerned with how information about the environment is represented by neural activity in the primate brain. More specifically, it contains several studies that explore the representation of visual motion in the brains of humans and nonhuman primates through behavioral and physiological measures. The majority of this work is focused on the activity of individual neurons in the medial superior temporal area (MST) - a high-level, extrastriate area of the primate visual cortex. The first two studies provide an extensive review of the scientific literature on area MST. The ...
Large Scale Neuronal Theories Of The Brain
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Author : Christof Koch
language : en
Publisher: MIT Press
Release Date : 1994
Large Scale Neuronal Theories Of The Brain written by Christof Koch and has been published by MIT Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 1994 with Mathematics categories.
This book originated at a small and informal workshop held in December of 1992 in Idyllwild, a relatively secluded resort village situated amid forests in the San Jacinto Mountains above Palm Springs in Southern California. Eighteen colleagues from a broad range of disciplines, including biophysics, electrophysiology, neuroanatomy, psychophysics, clinical studies, mathematics and computer vision, discussed 'Large Scale Models of the Brain, ' that is, theories and models that cover a broad range of phenomena, including early and late vision, various memory systems, selective attention, and the neuronal code underlying figure-ground segregation and awareness (for a brief summary of this meeting, see Stevens 1993). The bias in the selection of the speakers toward researchers in the area of visual perception reflects both the academic background of one of the organizers as well as the (relative) more mature status of vision compared with other modalities. This should not be surprising given the emphasis we humans place on'seeing' for orienting ourselves, as well as the intense scrutiny visual processes have received due to their obvious usefullness in military, industrial, and robotic applications. JMD.
The Role Of Input Nonlinearities In The Primate Visual System
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Author : James Tsui
language : en
Publisher:
Release Date : 2013
The Role Of Input Nonlinearities In The Primate Visual System written by James Tsui and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
"When an observer views a moving object, the projection of the motion onto the retina is first converted into information about velocity in the primary visual cortex (V1). These motion signals are then sent to numerous visual cortical structures, known collectively as the extrastriate cortex. One such area is the middle temporal area (MT), which contains neurons that are highly selective for velocity. The outputs of MT are then sent to even higher cortical areas that are responsible for generating conscious motion perception. Many studies have devised sophisticated models to explain the process by which velocity selectivity arises in MT. In most of these models, complex computations are carried out on the inputs reaching MT from V1, which are typically modeled as linear filters of visual inputs. The outputs of such MT model are then used to infer perceptual behavior. While these models are often quite successful in capturing the relationship between MT neuronal responses and visual stimuli, they are often built on abstract mathematical assumptions about V1 processing. In particular the assumption that V1 neurons have responses that are linearly related to the visual stimulus is contradicted by the demonstration of multiple nonlinearities at this stage. Similarly, MT outputs presumably go through several nonlinear processing stages before affecting perception. Thus, in order to facilitate the development of biologically plausible models, it is important to first understand the relevant input nonlinearities. The present thesis explores this issue by analyzing electrophysiological data collected from awake-behaving macaques and through the development of novel computational models. In particular, this thesis shows how many of the seemingly complicated functions of MT can be explained largely on the basis of a realistic account of nonlinearities in the V1 inputs. The thesis also provides a new formulation of the individual contributions of the center and surround of MT neuron receptive fields, in the process revealing important nonlinear inhibitory inputs that had not previously been observed. Finally, this thesis shows how many of the perceptual phenomena that are thought to depend on center-surround antagonism in MT could actually arise from of the accumulation of nonlinearities along the visual pathway." --
Cortical Neural Network Models Of Visual Motion Perception For Decision Making And Reactive Navigation
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Author : Michael Beyeler
language : en
Publisher:
Release Date : 2016
Cortical Neural Network Models Of Visual Motion Perception For Decision Making And Reactive Navigation written by Michael Beyeler and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
Animals use vision to traverse novel cluttered environments with apparent ease. Evidence suggests that the mammalian brain integrates visual motion cues across a number of remote but interconnected brain regions that make up a visual motion pathway. Although much is known about the neural circuitry that is concerned with motion perception in the Primary Visual Cortex (V1) and the Middle Temporal area (MT), little is known about how relevant perceptual variables might be represented in higher-order areas of the motion pathway, and how neural activity in these areas might relate to the behavioral dynamics of locomotion.The main goal of this dissertation is to investigate the computational principles that the mammalian brain might be using to organize low-level motion signals into distributed representations of perceptual variables, and how neural activity in the motion pathway might mediate behavior in reactive navigation tasks. I first investigated how the aperture problem, a fundamental conceptual challenge encountered by all low-level motion systems, can be solved in a spiking neural network model of V1 and MT (consisting of 153,216 neurons and 40 million synapses), relying solely on dynamics and properties gleaned from known electrophysiological and neuroanatomical evidence, and how this neural activity might influence perceptual decision-making. Second, when used with a physical robot performing a reactive navigation task in the real world, I found that the model produced behavioral trajectories that closely matched human psychophysics data. Essential to the success of these studies were software implementations that could execute in real time, which are freely and openly available to the community. Third, using ideas from the efficient-coding and free-energy principles, I demonstrated that a variety of response properties of neurons in the dorsal sub-region of the Medial Superior Temporal area (MSTd) area could be derived from MT-like input features. This finding suggests that response properties such as 3D translation and rotation selectivity, complex motion perception, and heading selectivity might simply be a by-product of MSTd neurons performing dimensionality reduction on their inputs. The hope is that these studies will not only further our understanding of how the brain works, but also lead to novel algorithms and brain-inspired robots capable of outperforming current artificial systems.