Color responsiveness argues against a dorsal component of human V4

The retinotopic organization, position, and functional responsiveness of some early visual cortical areas in human and non-human primates are consistent with their being homologous structures. The organization of other areas remains controversial. A critical debate concerns the potential human homologue of macaque area V4, an area very responsive to colored images: specifically, whether human V4 is divided between ventral and dorsal components, as in the macaque, or whether human V4 is confined to one ventral area. We used fMRI to define these areas retinotopically in human and to test the impact of image color on their responsivity. We found a robust preference for full-color movie segments over a luminance-matched achromatic version in ventral V4 but little or no preference in the vicinity of the putative dorsal counterpart. Contrary to previous reports that visual field coverage in the ventral part of V4 is deficient without the dorsal part, we found that coverage in ventral V4 extended to the lower vertical meridian, including the entire contralateral hemifield. Together these results provide evidence against a dorsal component of human V4. Instead, they are consistent with human V4 being a single, ventral region that is sensitive to the chromatic components of images.