The role of the entorhinal cortex in reward-guided spatial navigation

The concept of a cognitive map posits that the brain maintains an internal representation of space. This map is represented in cells of the hippocampus and entorhinal cortex, which carry information about the animal’s location in an environment. These representations are adaptable to changes in the environment; for example, the number of hippocampal place cells that encode a particular location will increase if a reward is delivered at that location. We aimed to investigate what information the two regions of the entorhinal cortex – medial and lateral – may contribute during reward-guided spatial navigation.

To this end, we compared activity across populations of neurons from three regions (CA1 of the hippocampus, MEC: medial entorhinal cortex, and LEC: lateral entorhinal cortex) during a spatial navigation task. As expected, we found an enrichment in the number of CA1 place cells at the rewarded location of the track. In stark contrast, however, we found little to no preference of MEC cells for the rewarded location but a dramatic increase in the number of LEC cells active near the reward location. Moreover, we found that the reward representation in the LEC is stable across locations and environments. These results establish a dichotomy between the entorhinal cortices in spatial navigation. Further, they provide a possible framework for the types of information and behavior they may be involved in. While the MEC has a well-established role in encoding spatial locations, our results indicate that the LEC provides a more dynamic, contextual representation that interfaces information from goals and rewards with the spatial navigation system in a flexible manner.