Analyses of brain activity taken while people navigated a virtual map of London, published in Nature Communications this week, shed light on how the human brain simulates future routes to plan how to reach a destination. The study shows that two aspects of human navigation - the number of potential routes possible to take and recalling street layouts - are processed by two distinct parts of the same brain structure: the hippocampus.
Hugo Spiers and colleagues asked 24 participants to learn the layout of a part of Soho in London. Then, once the participants were familiar with the layout, the authors would show participants a photograph of a current location and one of a goal location and asked them to navigate through the virtual neighborhood. Measurements of brain activity taken during this navigation show that the right anterior hippocampus activity pattern corresponds to the details of the actual street participants entered and that right posterior hippocampal activity simulates the number of future routes possible. Sometimes, the authors forced participants to take detours, and showed that the re-planning process engages areas of the prefrontal cortex (a region of the brain responsible for evaluating potential future actions), the activity of which correlates with the difficulty of the detour.
Taken together, these results show how the human brain computes the number of potential future possibilities, and how it can re-plan and re-evaluate these possibilities if its initial plan was prevented.