Early development of navigationally relevant location information in the retrosplenial complex.

Representing the locations of places so that we can use them as landmarks is critical to our ability to navigate through large-scale spaces-a process referred to as "map-based navigation." While many neuroimaging studies in adults have revealed that this ability involves the retrosplenial complex (RSC)-a scene-selective region in the medial parietal cortex-nothing is known about how this cortical system develops. So, does it develop only late in childhood, as generally assumed from some behavioral studies? Or is it, perhaps counterintuitively, present in the first few years of life? To test this question, using functional magnetic resonance imaging (fMRI) multivoxel pattern analysis and a virtual town paradigm, we investigated the representation of location information in the RSC of 5-y-olds. We found that i) the RSC in 5-y-olds already represents the locations of particular buildings in the town (e.g., the ice cream store by the mountain versus by the lake), but not their category membership (e.g., ice cream store, regardless of location), and ii) this neural representation is correlated with their performance on a location task. Using multidimensional scaling, we also found that the neural representation of the buildings in RSC reflects the actual layout of the virtual town. Finally, the parahippocampal place area-a scene-selective region implicated in scene categorization, not map-based navigation-did not represent location information, but instead category information, the exact opposite of RSC. Taken together, these findings reveal the early development of navigationally relevant location information in RSC and thus the early origins of map-based navigation.