Fig. 1. Visual cortex of the monkey. The monkey's cortex is depicted as unfolded and splayed flat. Area V1 (Brodmann's area 17) is the main recipient of parallel subcortical channels and a bottleneck for ascending inputs to maps of the visual fields located in extrastriate cortex. Area V1 connects reciprocally with V2, V3, and surrounding regions in early visual association cortex. It also connects directly and reciprocally with areas V5 (MT) and at least part of area V4. Area V4 receives a balance of M and P inputs; projects ventrally toward inferotemporal cortex (area IT); contains neurons modulated by attention, relevance, and perceptual context5,6; and may contribute to color and pattern processing.7,8 In contrast, V5 (MT) receives a predominance of M inputs, and projects dorsally toward the parieto-occipital regions. The neural complex that includes area MT and surrounding regions9,10 is probably important for the processing of motion, attention, and related visuospatial processes.11 Human vision and its disorders can be explained in terms of a homologous organization. (Felleman DJ, Van Essen DC: Distributed hierarchical processing in the primate cerebral cortex. Cereb Cortex 1:1, 1991)