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This chapter reviews the general physiology of the visual system. The discussions cover the eye; visual pathways and decussation; the lateral geniculate nucleus; visual cortex; the stimulus tuning of cortical cells; the columnar organization of the cortex; other visual areas; and midline interactions.

The physiology of the mammalian visual system is reviewed, with an emphasis on mechanisms related to the perception of depth in monkeys and humans. The structure and functions of the eye, the visual pathways, and the lateral geniculate nucleus are described. An account of neurophysiological procedures used in the study of the brain is followed by an account of the organization of areas of the brain serving visual depth perception. The account starts in the primary visual cortex and progresses through the many in-parallel and in-series visual areas. The description of visual areas is followed by an account of our knowledge of the functions they serve. Special attention is devoted to the columnar organization of the visual cortex, especially to columns related to the perception of depth. The chapter ends with a discussion of the physiology of attention.

This chapter considers the reorganization of the primary visual cortex of the cat following monocular or binocular retinal lesions. These studies reveal the importance of horizontal connections within the visual cortex. The mechanisms of reorganization are investigated utilizing molecular, pharmacological, and electrophysiological techniques.

Studies have shown that the prefrontal cortex (PFC) is involved in at least some types of working memory functions. Neurodynamics helps us understand the underlying mechanisms that implement the working memory-related activity observed in the primate PFC. This chapter reviews the application of these techniques for the analysis of experimental measurements gained at different levels (single-cell, functional magnetic resonance imaging (fMRI)) of the prefrontal and inferior temporal (IT) visual cortex that result in a better understanding of the neural mechanisms of visual memory. It also considers the mechanisms that enable the IT visual cortex to set up view-invariant representations of objects — a process that involves not just storing information in a long-term form of memory, but also building suitable object representations to be stored.

This chapter is concerned with invariant representations of faces and objects in the inferior temporal visual cortex. It also covers computational approaches to invariant object recognition, feature spaces, structural descriptions and syntactic pattern recognition, template matching and the alignment approach, invertible networks that can reconstruct their inputs, and feature hierarchies. A theory of invariant object recognition learning systems in the brain is given.

This chapter reviews the general growth of the visual system and, in particular, the pre- and post-natal growth of the binocular system. The discussions cover subcortical development; the development of visual cortex; and the growth of cortical neurones.

The consequences of focal injury to the cerebral cortex in the immature brain differ from the consequences caused by similar damage of the mature cerebrum. In the immature brain, some distant neurons are more vulnerable to the injury, whereas others survive and expand their projections to bypass damaged or degenerated structures. The net result is the sparing of neural processing and behaviors. This chapter summarizes both the modifications in the visual pathways resulting from primary visual cortex damage sustained early in development, and the neural and behavioral processes that are spared or permanently impaired.

Perception depends on proper recurrent interactions among separate visual areas. Within such a cooperative network, the primary visual cortex plays a unique part. It is the main recipient of visual information, and it is at the end stage of top-down influences. In recent years, it has become clear that the primary visual cortex plays a prominent role in producing visual perception. This chapter gives an overview of the latest neurophysiological findings on figure-ground segmentation in the monkey primary visual cortex and discusses how those findings relate to visual perception.

This chapter discusses the paradoxical difference between the results of visual cortex damage in humans and other primates, especially the greater apparent residual function in animals despite the fact that all primates have several parallel visual input pathways that remain intact after visual cortex damage. The historical accounts of the subject from the 19th century onwards are reviewed, including the classical accounts by William James, Munk, Holmes, Luciani, Popplereuter, Klüver, Teuber, and others. Contemporary evidence on the effects of visual cortex damage and plasticity in monkeys is summarized, further highlighting the contrast between the animal and human claims.

This chapter discusses the neural correlates of human action perception, specifically the perception of bodies and body movements. It also provides a brief discussion on the likely connection of this network to additional cortical areas associated with more abstract properties of action perception, such as perceived intentionality. An introduction to the primary perceptual pathways in the visual cortex for generalized motion and form perception is presented, as well as some preliminary evidence for specialized circuits dedicated to biological motion perception.

This chapter reviews the anatomy of the visual system. There are parallel pathways, starting in the retina, then going through the lateral geniculate nucleus, primary visual cortex (V1), secondary visual cortex (V2), then to areas specialized for color and form (V4), and motion and depth (V5). The system for inspecting objects goes on to ventral areas of the brain, including temporal cortex, and is known as the “what pathway.” The system for noticing objects goes on to dorsal areas of the brain, including parietal and frontal cortices, and is known as the “where pathway.” The pathways are kept separate in layers in the lateral geniculate and V1, and in columns in all areas of cortex. Psychophysical experiments support the separation of different aspects of vision in the analysis of objects.

This chapter begins with a brief discussion of contextual effects in the physiological responses of single neurons in cats and primates. It reviews the physiological investigations of contextual visual phenomena in human visual cortex made possible by noninvasive functional neuroimaging techniques. It addresses two important topics concerning filling-in and related contextual effects. First, it asks the question: What are the contributions of feedforward, feedback, and lateral anatomical connections? Second, it asks: How large is the neural network that contributes to particular classes of contextual effects? Finally, the chapter discusses how single-neuron properties can be related to population indices and how the organization of the primate visual system may impact thoughts about filling-in.

All neurons in the mature nervous system are mapped onto the neurons to which they connect; and therefore, understanding how neural mappings are achieved could be considered synonymous with understanding how every aspect of the connectivity of the nervous system is established. This chapter discusses the development of topographically ordered maps of connections, hypotheses for map formation, the development of topographic maps in non-cortical systems, rhe role of fibre ordering in map-making, cytodifferentiation hypothesis, neighbour matching hypothesis, induction of specificity hypothesis, timing hypothesis, development of topographic maps in cortical systems, thalamo-cortical projection and whether the cortical map is specified prior to innervation, mapping to specific cortical areas, the development of callosal and ipsilateral corticocortical projections, the development of feature maps in the visual system, development of geniculate projections to the visual cortex, the effects of neural activity (especially with respect to functional deprivation), models for map-making, models for the development of topography, models based on chemoaffinity, and models for the development of cortical feature maps.

Long-term potentiation (LTP) was first described in the mammalian hippocampus and was also elicited in the visual cortex of rats. LTP is most strongly expressed during early postnatal development when synaptic plasticity is high. To test the hypothesis that lesion-induced reorganization in the visual cortex is associated with increased LTP, this chapter examines synaptic plasticity in slices of the lesioned rat visual cortex in vitro. Characteristic changes are in plasticity are observed in the surround of lesions, supporting the hypothesis of enhanced LTP being involved in reprogramming of the visual cortex in response to local damage in the adult visual cortex.

This chapter reviews experimental work in macaque monkeys concerning the processing of visual information for object recognition. Going from the primary visual cortex, area V1, to the inferior temporal cortex (IT), the end station of the ventral visual stream, neurons become selective for complex object features and display a greater tolerance for stimulus changes that preserve object identity. Single IT neurons code for object properties such as shape, texture, and color. Current data suggest that IT neurons do not represent whole visual objects or visual categories, but rather represent features less complex than a whole object (except perhaps in facial representation). The responses of IT neurons are affected by changes in the image that preserve object identity, but their object feature preference is largely invariant to such changes. The stimulus selectivity of IT neurons facilitates the read-out of visual categories and object identity in the regions to which IT projects.

This chapter describes the behavioral deficits observed following lesions of the primary visual cortex in both mature and infant macaque monkeys. Overall, the consequences of such lesions are far more severe in adulthood than during development. The chapter also presents anatomical evidence that alterations to the thalamocortical pathways may explain the greater behavioral abilities identified following visual cortex lesions incurred during development, but not maturity.

This chapter presents a Ferrier Lecture entitled “Functional Architecture of Macaque Monkey Visual Cortex”. The lecture considers a view of the cortex as containing a thousand sand machines of similar structure. Each machine contains two types of hypercolumns, whose functions are dovetailed with each other and with the topographical map. This dicing up into subdivisions is the way the cortex handles or represents orientation and ocular dominance besides the two obvious visual-field positional variables. An interesting aspect is the very orderliness of the architecture.

There is growing consensus that in the visual cortex, many cortical properties arise in whole or in part from the local circuits created by richly interconnected neuronal assemblies. While considerable progress has been made in determining the patterns of anatomical connectivity and functional interactions in the adult brain, relating specific circuits to specific function properties remains a challenge. One potentially powerful strategy employs correlative developmental analyses to relate the emergence of particular neuronal assemblies to emergence of a distinct visual response property, such as orientation. Uncovering the mechanisms by which such assemblies form may provide insight into the capabilities of the adult cortex and into the forces which drive its assembly. This chapter discusses recent experimental approaches aimed at deciphering these mechanisms, and relates these findings to the emergence of functional architecture, especially orientation selectivity in the visual cortex.

This chapter considers recent evidence suggesting that neurotrophins may function in the activity-dependent remodeling of connections during the development of the mammalian visual cortex. It begins by considering evidence of a requirement for a retrograde signal from the postsynaptic to the presynaptic neuron. It then reviews evidence that neurotrophins may be good candidates for this signal.