RETINOTOPY AND COLOR SENSITIVITY IN HUMAN VISUAL CORTICAL AREA V8

Prior studies suggest the presence of a color-selective area in the in ferior occipital-temporal region of human visual cortex. It has been p roposed that this human area is homologous to macaque area V4, which i s arguably color selective, but this has never been tested directly. T o test this model, we compared the location of the human color-selecti ve region to the retinotopic area boundaries in the same subjects, usi ng functional magnetic resonance imaging (fMRI), cortical flattening a nd retinotopic mapping techniques. The human color-selective region di d not match the location of area V4 (neither its dorsal nor ventral su bdivisions), as extrapolated from macaque maps. Instead this region co incides with a new retinotopic area that we call 'V8', which includes a distinct representation of the fovea and both upper and lower visual fields. We also tested the response to stimuli that produce color aft erimages and found that these stimuli, like real colors, caused prefer ential activation of V8 but not V4.