Perceptual and categorical processing and representation in color categorization

Abstract

We used fMRI to dissociate decisional and perceptual functions in color categorization. Participants viewed sequences of colored squares which varied in perceptual distance (0, 1 or 2 hue steps) and color (green, blue) and then judged whether one or two colors were present. Occipital, caudate, and anterior insula regions were active when more than one hue was presented, indicating a role in perceptual processing and attentional monitoring. Dorsolateral prefrontal cortex showed greater activity when two colors were present than a single color, indicating a role in coding color category. Cognitive control regions of the intraparietal sulcus and presupplementary motor area were sensitive to the interaction of decision and distance in perceptual space, indicating a role in combining these functions during decision making. These results support theories that colors are represented categorically at high levels of the cognitive hierarchy, and that visual cortex is sensitive to hue rather than color category.