Large-Scale Color Biases in the Retinotopic Functional Architecture Are Region Specific and Shared across Human Brains.

Despite the functional specialization in visual cortex, there is growing evidence that the processing of chromatic and spatial visual features is intertwined. While past studies focused on visual field biases in retina and behavior, large-scale dependencies between coding of color and retinotopic space are largely unexplored in the cortex. Using a sample of male and female volunteers, we asked whether spatial color biases are shared across different human observers and whether they are idiosyncratic for distinct areas. We tested this by predicting the color a person was seeing using a linear classifier that has never been trained on chromatic responses from that same brain, solely by taking into account: (1) the chromatic responses in other individuals' brains and (2) commonalities between the spatial coding in brains used for training and the test brain. We were able to predict the color (and luminance) of stimuli seen by an observer based on other subjects' activity patterns in areas V1-V3, hV4, and LO1. In addition, we found that different colors elicited systematic, large-scale retinotopic biases that were idiosyncratic for distinct areas and common across brains. The area-specific spatial color codes and their conservation across individuals suggest functional or evolutionary organization pressures that remain to be elucidated.