PARALLEL-PROCESSING STREAMS IN HUMAN VISUAL-CORTEX

THIS study shows the existence in humans of independent neural process ing streams in early visual cortex, which had previously been demonstr ated in macaque monkeys. This evidence was obtained by controlled fixa tion testing of a subject who had suffered a small stroke in the right fusiform gyrus. The patient showed a severe disruption of color perce ption, shape discrimination and contrast sensitivity for stationary gr atings in the upper left quadrant of his visual field. However, motion perception and contrast sensitivity for drifting gratings were relati vely preserved. These results support the view that there are independ ent visual processing streams early in human visual cortex, and that t hese streams may subserve such functions as motion and color/form perc eption.