Differential development of selectivity for faces and bodies in the fusiform gyrus.

Viewing faces or bodies activates category-selective areas of visual cortex, including the fusiform face area (FFA), fusiform body area (FBA), and extrastriate body area (EBA). Here, using fMRI, we investigate the development of these areas, focusing on the right FFA and FBA. Despite the overlap of functionally defined FFA and FBA (54\%-75\% overlap), we found that these regions developed along different trajectories. With age (7-32 years old), the FFA gradually increased in size and selectivity, and was significantly larger and more face-selective in adults than children. By contrast, the size and selectivity of the FBA did not correlate with age, and were equivalent in children and adults. Whereas in adults the FFA and FBA were comparable in size, in children the FBA was on average 70\% larger than the FFA. These findings suggest that, in children, the fusiform gyrus is predominantly selective for bodies, with commensurate face-selective responses apparent later in development. Moreover, differences in the development of the FFA and FBA indicate that overlapping functional brain areas, supported by the same anatomical structure, can develop along different trajectories.