Area VO in human visual cortex is color selective as revealed by fMRI adaptation

摘要

Introduction: We use an fMRI adaptation paradigm to investigate the selectivity of the human visual cortex to red-green (RG) and achromatic (Ach) contrast, comparing regions in early visual cortex (V1, V2) with those in the dorsal (V3d, V3a, hMT+) and ventral (V3v, V4, VO) cortex. Methods: RG and Ach adaptation and no-adaptation conditions were contrasted within a block design. Test and adapting stimuli were high contrast sinewave counter-phasing rings (0.5cpd, 2Hz), as previously described (Chang et al, JOV, 2014, 14 (10) 983). Regions of interest (as listed above) were independently localized using standard procedures. We assume that cross-adaptation of responses to RG and achromatic stimuli indicates a common neural substrate for both, whereas a lack of cross-adaptation indicates selective neural responses within voxels. Selectivity was defined as significantly greater same-adaptation (RG on RG, or Ach on Ach) than cross-adaptation (RG on Ach, or vice versa), established by RM ANOVAs. Results: Adaptation was present in all areas except for hMT+, which showed no color adaptation. Areas V1 and V2 showed no selectivity of adaptation; specifically, both RG and Ach test stimuli were adapted as much by the cross adaptor as by the same adaptor. In the dorsal cortex, areas V3d, V3a, hMT+ showed significant selectivity for achromatic contrast. In the ventral cortex, VO showed significant selectivity for RG color contrast. Conclusion: Color-luminance responses are dominant in areas V1 and V2 with selectivity developing along the extrastriate pathways. While dorsal areas show selectivity for achromatic contrast, ventral cortex (VO) exhibits selectivity for RG color contrast. Area VO has previously been shown to be a color responsive area in human cortex. Here we show that it is also color selective, suggesting it plays a significant role in color processing.