Color responsiveness argues against a dorsal component of human V4

Abstract

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.

A Conceptual Lemon: Theta Burst Stimulation to the Left Anterior Temporal Lobe Untangles Object Representation and Its Canonical Color

“…Given the established role of the V4 complex in color-related processing, could stimulating the ATL interfere with neural processing of V4, thereby abolishing the color effect? If this were the case, we would expect that stimulation of the OP ( V1 of the visual cortex) would similarly abolish the color effect, as it is anatomically closer to V4 than is the ATL and hosts multiple color-sensitive subregions that send signals to V4 for further processing (Goddard, Mannion, McDonald, Solomon, & Clifford, 2011;Shapley & Hawken, 2011). Contrary to this possibility, however, our results showed that the color congruency effect remained robust after the stimulation of the OP, making this an unlikely explanation.…”

Regions of Mid-level Human Visual Cortex Sensitive to the Global Coherence of Local Image Patches

“…Standard criteria were used to delineate the borders of the low-level visual areas V1, V2, and V3 (Dougherty et al, 2003; Schira, Tyler, Breakspear, & Spehar, 2009). The ventral mid-level human V4 region (hV4) was defined as a full contralateral hemifield representation extending posterior to the ventral V3 border (Arcaro, McMains, Singer, & Kastner, 2009; Goddard, Mannion, McDonald, Solomon, & Clifford, 2011; Wade, Brewer, Rieger, & Wandell, 2002). We delineated three regions of dorsal mid-level cortex; LO1, LO2, and V3A/B.…”

Categorical Clustering of the Neural Representation of Color

“…Whereas some have argued that human V4 consists of a dorsal and ventral part (V4v and V4d) (Hansen et al, 2007), differences in retinotopy and functional properties suggest that these two human cortical regions are distinct. Unlike V4v, putative human V4d does not respond more strongly to color than to grayscale stimuli (Tootell and Hadjikhani, 2001;Wade et al, , 2008Winawer et al, 2010;Goddard et al, 2011). Macaque V4v (adjacent to V3v) and V4d (adjacent to V3d) represent complementary parts of the contralateral hemifield.…”