Joint Encoding Represents Fine-Scale Functional Specialization in Mouse Higher Visual Areas.

Functional specialization in the higher visual areas (HVAs) has traditionally been attributed to the segregation of distinct visual features; however, the role of feature integration remains poorly understood. In this study, we investigated the processing of color and motion in the visual cortex by developing a neuronal color-purity assessment strategy. Our results demonstrate that the joint encoding of color purity and motion distinguishes the functional roles of the four HVAs, whereas tuning preferences segregate them into two groups. Specifically, correlations between color purity and motion are area-specific across the HVAs, whereas tuning preferences follow the putative dorsal and ventral streams. The anatomical results suggest that joint encoding in the HVAs may be related to the primary visual cortex neurons with projections to multiple targets. Collectively, these findings reveal that feature integration, operationally defined via joint encoding, provides a finer dimension of functional differentiation than segregation alone, thereby establishing a novel mechanism underlying cortical functional specialization.