Author: David C. Van Essen
Publisher:
ISBN:
Category :
Languages : en
Pages : 26
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Book Description
This report used a combination of physiological and anatomical approaches to elucidate the functional organization of visual cortex in the macaque monkey. One project was a single cell analysis of texture vision, using texture patterns of the type developed by Julesz for human psychophysical studies. Many cells tested in area V2 responded to static or moving texture gradients in ways which were not predictable on the basis of responses to individual texture elements and which correlated with the preattentive discriminability of these texture patterns to human observers. A second project involved the development of a computerized technique for generating two-dimensional maps of cerebral cortex. An algorithm based on simulated annealing procedures was used to construct a complete map of primary visual cortex, thereby demonstrating its suitability for dealing with anatomical data from highly convoluted regions of cortex. A third project involved the use of voltage-sensitive dyes to monitor activity patterns in visual cortex. This technique offers great promise for analyzing the organization of large neural ensembles with high spatial and temporal resolution. Keywords: Cerebral cortex; Pattern recognition; Cortical mapping; Single neuron physiology.
Author: Martin James Tovée
Publisher:
ISBN:
Category : Visual cortex
Languages : en
Pages : 174
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Book Description
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.
Author: Gregory R. Bock
Publisher: John Wiley & Sons
ISBN: 0470514620
Category : Psychology
Languages : en
Pages : 256
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Book Description
Foremost neurophysiologists and psychophysicists provide pertinent information on the nature of representation at the earliest stages as this will constrain the disposition of all subsequent processing. This processing is discussed in several different types of visual perception.
Author: Helga Kolb
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: Nathan Cheuck Lam Kong
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Animals continuously and dynamically process sensory information in service of both flexible and inflexible behaviours. To understand the brain's complex information-processing pipeline by which such behaviours arise, we must first understand how the brain transforms sensory information from its raw form. This will then allow us determine what information is accessible downstream in the process. In this dissertation, we try to understand how the brain processes visual information, which entails building and evaluating computational models that can predict how the animal will respond to novel visual inputs. We focus on a class of models known as convolutional neural networks (CNNs) and demonstrate ways in which they can be evaluated against and be built for primates and for rodents to better understand how the mammalian visual system supports behaviour. We first demonstrate a time-resolved correspondence between a feedforward CNN and whole-brain neural responses during human object processing and develop a data-driven optimization approach to improve upon correlations achieved between the model and the neural data. Motivated by extensive empirical work in rodents on navigational and on decision-making behaviours and by the desire to integrate models of cortical and of subcortical areas that support these behaviours, we build quantitatively accurate CNN models of the mouse visual system. Although CNNs are state-of-the-art models of primate and of rodent visual processing, they are extremely brittle. We therefore examine the nature of their brittleness and show the existence of representational differences between primary visual cortex of non-human primates and the models. Finally, we suggest that building less-brittle models will require us to incorporate the temporally-continuous nature of the visual inputs that animals receive. Looking forward, we hope that models of sensory cortex can be integrated with computational models of downstream cortical and subcortical areas, so that we can better understand how flexible and inflexible behaviours arise.
Author: Jonathan Stone
Publisher: Springer
ISBN:
Category : Computers
Languages : en
Pages : 466
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Book Description
In the mid-sixties, John Robson and Christina Enroth-Cugell, without realizing what they were doing, set off a virtual revolution in the study of the visual system. They were trying to apply the methods of linear systems analysis (which were already being used to describe the optics of the eye and the psychophysical performance of the human visual system) to the properties of retinal ganglion cells in the cat. Their idea was to stimulate the retina with patterns of stripes and to look at the way that the signals from the center and the antagonistic surround of the respective field of each ganglion cell (first described by Stephen Kuffier) interact to generate the cell's responses. Many of the ganglion cells behaved themselves very nicely and John and Christina got into the habit (they now say) of calling them I (interesting) cells. However. to their annoyance, the majority of neurons they recorded had nasty, nonlinear properties that couldn't be predicted on the basis of simple summ4tion of light within the center and the surround. These uncoop erative ganglion cells, which Enroth-Cugell and Robson at first called D (dull) cells, produced transient bursts of impulses every time the distribution of light falling on the receptive field was changed, even if the total light flux was unaltered.
Author: Giedrius T. Buračas
Publisher:
ISBN:
Category :
Languages : en
Pages : 516
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Book Description
Author: Thomas A. Portocello
Publisher:
ISBN: 9781604565300
Category : Visual cortex
Languages : en
Pages : 0
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Book Description
All visual information that the human mind receives is processed by a part of the brain known as visual cortex. The visual cortex is part of the outermost layer of the brain, the cortex, and is located at the dorsal pole of the occipital lobe; more simply put, at the lower rear of the brain. The visual cortex obtains its information via projections that extend all the way through the brain from the eyeballs. The projections first pass through a stopover point in the middle of the brain, an almond-like lump known as the Lateral Geniculate Nucleus, or LGN. From there they are projected to the visual cortex for processing. Visual cortex is broken down into five areas, labelled V1, V2, V3, V4, and MT, which on occasion is referred to as V5. V1, sometimes called striate cortex because of its stripey appearance when dyed and put under a microscope, is by far the largest and most important. It is sometimes called primary visual cortex or area 17. The other visual areas are referred to as extrastriate cortex. V1 is one of the most extensively studied and understood areas of the human brain. Neurons in the visual cortex fire action potentials when visual stimuli appear within their receptive field. By definition, the receptive field is the region within the entire visual field which elicits an action potential. But for any given neuron, it may respond to a subset of stimuli within its receptive field. This property is called tuning. In the earlier visual areas, neurons have simpler tuning. For example, a neuron in V1 may fire to any vertical stimulus in its receptive field. In the higher visual areas, neurons have complex tuning. For example, in the inferior temporal cortex (IT), a neuron may only fire when a certain face appears in its receptive field. The visual cortex receives its blood supply primarily from the calcarine branch of the posterior cerebral artery. This book presents the latest research in the field from around the globe.
Author: Juri D. Kropotov
Publisher: Academic Press
ISBN: 008092297X
Category : Medical
Languages : en
Pages : 601
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Book Description
While the brain is ruled to a large extent by chemical neurotransmitters, it is also a bioelectric organ. The collective study of Quantitative ElectroEncephaloGraphs (QEEG-the conversion of brainwaves to digital form to allow for comparison between neurologically normative and dysfunctional individuals), Event Related Potentials (ERPs - electrophysiological response to stimulus) and Neurotherapy (the process of actually retraining brain processes to) offers a window into brain physiology and function via computer and statistical analyses of traditional EEG patterns, suggesting innovative approaches to the improvement of attention, anxiety, mood and behavior.The volume provides detailed description of the various EEG rhythms and ERPs, the conventional analytic methods such as spectral analysis, and the emerging method utilizing QEEG and ERPs. This research is then related back to practice and all existing approaches in the field of Neurotherapy - conventional EEG-based neurofeedback, brain-computer interface, transcranial Direct Current Stimulation, and Transcranial Magnetic Stimulation - are covered in full. While it does not offer the breadth provided by an edited work, this volume does provide a level of depth and detail that a single author can deliver, as well as giving readers insight into the personl theories of one of the preeminent leaders in the field. Provide a holistic picture of quantitative EEG and event related potentials as a unified scientific field Present a unified description of the methods of quantitative EEG and event related potentials Give a scientifically based overview of existing approaches in the field of neurotherapy Provide practical information for the better understanding and treatment of disorders, such as ADHD, Schizophrenia, Addiction, OCD, Depression, and Alzheimer's Disease
Author: Alistair J. Bray
Publisher:
ISBN:
Category : Bionics
Languages : en
Pages : 84
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Book Description
Abstract: "This document describes an activity-based model of information processing in the early mammalian visual pathway. The work has been published previously in an abbreviated form [9], so this report is intended to present a more complete story. The model describes the retina, lateral geniculate nucleus (LGN), and development of simple cells in visual cortex (layer IVc of V1). In the retina we employ a non-adaptive model of on-centre and off-centre retinal ganglion cells (the tonic cells only) that is a non-linear approximation to difference-of-Gaussian processing. The output of this provides input to the LGN where the On and Off channels are kept separate. Here we simulate the effects of local inhibitory lateral interactions; this stage is also non-adaptive. Simple cells in the cortical model receive feedforward excitation from both the On and Off channels projecting out of the LGN. We propose a dual population model in which one population excites close neighbours while the other inhibits all neighbours within a greater area. We simulate this dynamic feedback using an iterative method, and when the network activity is stable we adapt all feedforward weights connecting simple cells to the LGN using a Hebbian (correlation-based) learning rule. We find that when presenting the network with many samples from natural images, the simple cells' feedforward weights adapt to become 'edge' and 'bar' detectors with receptive fields extremely similar to Gabor functions. These edge and bar detectors are orientation selective, and the orientation preference of different simple cells varies smoothly across the cortical surface. When plotting preferred orientation we get 'orientation maps' qualitatively similar to those documented in neurophysiological literature (in terms of smoothness & singularities). We examine these maps (and others) in terms of their auto-correlation matrix and orientation distribution. Finally we describe preliminary experiments in which the lateral connections within the cortex are adaptive; we find that regions of simple cells develop within which the cells have similar receptive fields but between which the cells have different receptive fields."
