Two cortical navigation systems and their differential development

A couple of recent neuroimaging studies together led us to hypothesize-perhaps counterintuitively-that the occipital place area (OPA), which supports "visually-guided navigation" (ie making our way through the immediately visible environment, avoiding boundaries and obstacles), develops later than the retrosplenial complex (RSC), which supports "map-based navigation" (ie finding our way from a specific place to some distant, out-of-sight place). But is this true? We directly test this hypothesis using functional magnetic resonance imaging (fMRI) adaptation in 5- and 8-year-old children and ask when OPA and RSC represent left and right information-information that both regions represent in adulthood, albeit for different kinds of navigation. Our results revealed that in 5-year-olds, OPA does not represent left/right information and only does so in 8-year-olds. By contrast, RSC in 5-year-olds represents left/right information, like in 8-year-olds. These findings strongly support our hypothesis: the OPA, which is involved in visually-guided navigation, develops later than the RSC, which supports map-based navigation. This developmental timeline not only demonstrates that OPA and RSC develop at different rates but also strengthens the case that these regions serve distinct roles in adult human navigation-since a single system cannot follow two separate developmental trajectories.