An Introduction to the Visual System

An Introduction to the Visual System was exactly as advertised. The relatively quick read provides an overview of the entire visual system of the brain. The book begins with a detailed description of the physiology of the eyes and the relevant physical and biochemical functional structures. The optical physics and photochemistry are glossed over in favor of giving the reader a slightly broader systems view of the eyes. Color vision is discussed in detail discussing the way three types of human cones allow for color vision. The biochemical properties of photopigments are glossed over in favor of a broader perspective. The evolutionary basis of color vision and problems arising in color defects are briefly explained. The text next discusses the organization of the visual system in a very broad sense. Cortical localization and the anatomy of visual organization are discussed with emphasis on the primary visual cortex. The modular organization of the primary visual cortex is emphasized, discussing cortical receptive fields, color vision, directionality, texture, based on the modular organization of the primary visual cortex. The remainder of the text discusses higher level visual functions. Development of the neural system is discussed in detail citing numerous animal studies of monocular and binocular deprivation. A chapter is devoted to the complex task of maintaining color constancy. Various studies are cited demonstrating the very complex nature of organizing a system of cortical neurons, some wavelength dependent and others "color context" dependent in order to use color recognition of objects for our benefit. The higher level brain functions of object perception and recognition and motion were especially fascinating. Citing various studies the author seems to suggest that complex higher cortical regions of the brain have large cortical receptive fields that integrate lower level cortical processing to respond to specific types of objects. "It has been suggested that the simple shapes coded for by the elaborate cells can form a `visual alphabet' from which a representation of an object can be constructed" (p.130). This proposition has tremendous implications for the study of visual perception if not consciousness itself. The discussion of motion processing the visual system in equally engrossing. The techniques of saccades, (rapid movement of the eye) stereoscoping (using differences in each eyes perception to create depth perception) and the organization of directional modularity in the V5 section of the brain provide neural basis for generating what the author refers to as "The illusion of continuity". An entire chapter is devoted the perception of the face. A seemingly trivial matter, the author explains through the use of PET scan and fMRI evidence that the primate brain really has sections and pathways devoted towards face recognition. The evolutionary significance of face recognition is briefly but effectively explained. The book ends a discussion of how the brain is able to integrate the multitude of complex processes into image formation. Neural oscillation and temporal binding theory are discussed , although the author seems to personally favor a more hierarchal organizing model. Overall the book is an excellent read for anyone interested in neuroscience, optics, or medicine. The book doesn't get bogged down in technical details in is very concise. Most of the information and claims presentation and supported with a plethora of references to neuroscience experiments. Perhaps best of all each chapter ends with a bullet point summary of the key concepts. I highly recommend this book.

Pretty good overview of the visual system, although I have seen better explanations in a neural physiology book.