The hippocampus and entorhinal cortex encode the path and euclidean distances to goals during navigation

Background: Despite decades of research on spatial memory, we know surprisingly little about how the brain guides navigation to goals. While some models argue vectors are represented for navigational guidance, other models postulate that the path to the goal is computed. Although the hippocampal formation has been implicated in processing spatial goal information it remains unclear whether this region processes path- or vector-related guidance information. Results: Here we report neuroimaging data collected from subjects navigating London’s Soho district (UK), which reveals that both the path and Euclidean distance to the goal are encoded by the hippocampus during navigation. While activity in the posterior hippocampus was sensitive to the distance along the path, activity in the anterior hippocampus and entorhinal cortex was correlated with the Euclidean distance component of a vector to the goal. During travel periods posterior hippocampal activity was greater the longer the path to the goal, but at decision points activity in this region increased the closer and more direct the path was to the goal. Importantly, sensitivity to the distance was abolished in these brain areas when subjects followed cued instructions on the direction to proceed at junctions. Conclusions: The results indicate that the hippocampus contains representations of both the Euclidean and path distance to goals during navigation. These findings argue for a flexible guidance system housed in the hippocampus that changes how it represents distance to the goal depending on the fluctuating demands of navigation.