Mesoscale functional organization of face and body areas in the macaque brain.

Segregated networks of mesoscale functional units convey highly specific functional signals within and across early visual areas. However, it remains unclear whether higher-order category-selective areas exhibit a similar mesoscale functional organization. In this study, we investigated the mesoscale functional architecture of face-, body-, and object-selective regions in macaque monkeys using sub-millimeter fMRI (0.22 mm3 voxels) combined with single-cell recordings. Our findings reveal that these category-selective areas are subdivided into spatially clustered mesoscale functional units, which are highly consistent across subjects. Notably, mesoscale functional units of the same type exhibit segregated interhemispheric functional connectivity, forming long-range mesoscale functional networks. Single-cell recordings from a body-selective area confirmed this mesoscale organization and showed a remarkable correspondence between fMRI-defined mesoscale functional units and neuronal tuning profiles. These mesoscale functional units also displayed sharp functional boundaries and response similarity decay patterns, similar to those observed in previous single-unit recordings. Our findings suggest that mesoscale functional networks are a fundamental feature of primate cortex and highlight the power of high-resolution, high-sensitive fMRI in mapping neural circuitry at mesoscale level.