Figure 1. What is the best way home?

An ordinary paper map encodes location only, whereas a cognitive map is also involved in planning a route. Pfeiffer and Foster report that, just before a rat takes a journey, hippocampal place cells in its brain play out sequences predicting the animal’s future path. This suggests that the hippocampus functions much like a GPS unit that not only shows where you are, but also how to get home.