Neural correlates of real-world route learning

Classical theories of spatial microgenesis (Siegel and White, 1975) posit that information about landmarks and the paths between them is acquired prior to the establishment of more holistic survey-level representations. To test this idea, we examined the neural and behavioral correlates of landmark and path encoding during a real-world route learning episode. Subjects were taught a novel 3 km route around the University of Pennsylvania campus and then brought to the laboratory where they performed a recognition task that required them to discriminate between on-route and off-route buildings. Each building was preceded by a masked prime, which could either be the building that immediately preceded the target building along the route or immediately succeeded it. Consistent with previous reports using a similar paradigm in a virtual environment (Janzen and Weststeijn, 2007), buildings at navigational decision points (DPs) were more easily recognized than non-DP buildings and recognition was facilitated by in-route vs. against-route primes. Functional magnetic resonance imaging (fMRI) data collected during the recognition task revealed two effects of interest: first, greater response to DP vs. non-DP buildings in a wide network of brain regions previously implicated in spatial processing; second, a significant interaction between building location (DP vs. non-DP) and route direction (in-route vs. against-route) in a retrosplenial/parietal-occipital sulcus region previously labeled the retrosplenial complex (RSC). These results indicate that newly learned real-world routes are coded in terms of paths between decision points and suggest that the RSC may be a critical locus for integrating landmark and path information.