Chapter 21 Long-term changes in visual mechanisms following differential stimulation of color and luminance channels during development

Publisher Summary

The anatomical and physiological data of the mammalian visual system strongly support that visual information is processed through parallel channels. Consistent correlations in the morphological and physiological characteristics of cells (e.g., soma size, dendritic spread, conduction velocity, receptive field size, response linearity, sustained or transient nature of response, ON-, OFF-, or ON-OFF center response), have resulted in investigators classifying retinal ganglion cells and thalamic neurons into functional groups, such as the W-, X-, and Y-cell classification developed in cat, and the color-opponent (parvocellular, chromatic, narrow-band) and luminance channel (magnocellular, achromatic, broad-band, brightness) distinction in monkey. Human psychophysical studies strongly support the existence of parallel visual channels. Recent psychophysical studies have tried to relate visual performance to underlying channels by determining thresholds under highly constrained stimulus and adaptation conditions. As a result of recent advances in the characterization of these channels at the neural level, there has been a corresponding resurgence of interest in how the responses of visual channels relate to visual perception. Attempts to parcel out the functions of these channels have included a variety of approaches; for example, neuroanatomical pathway tracing, electrophysiological recording, histochemical correspondences, selective chemical lesions, and psychophysical tests at isoluminance. Another approach to investigating structure/function relationships is through selective deprivation during development. An animal model is utilized that possesses a well-developed central visual system based on a relatively simple photoreceptor organization to stimulate the opponent-color and luminance channels during development.