Visual mechanisms for the analysis of spatial pattern.

After a brief outline of the structure and electrophysiology of the normal visual pathways, the responses, as revealed by psychophysical studies, of the visual system to spatially and temporally varying stimuli are reviewed. An appropriate network model, involving two sequentially organized classes of visual channel, is presented. Examples are given in which the psychophysical methods developed to analyse the normal visual pathways are applied to cases in which these pathways are defective (amblyopia, albinism, hemianopia, parietal cortical lesion, inhibitory central colour vision defect). These cases not only illustrate the value of psychophysical techniques in analysing disturbances of visual function but are also suggestive of the mechanisms involved in higher processing of the retinal image.