Computing distance information from landmarks and self-motion cues - Differential contributions of anterior-lateral vs. posterior-medial entorhinal cortex in humans.

Landmarks and path integration cues are two important sources of spatial information for navigation. For example, both can be used to compute positional information, which, in rodents, has been related to computations in the entorhinal cortex. In humans, however, if and how the entorhinal cortex supports landmark-based navigation and path integration is poorly understood. To address this important question, we developed a novel spatial navigation task in which participants learned a target location and judged relative positions of test locations in relation to the target. Landmarks and path integration cues were dissociated, and their reliability levels were manipulated. Using fMRI adaptation, we investigated whether spatial distances among the test locations were encoded in the BOLD responses, separately for landmarks and self-motion cues. The results showed that the anterior-lateral entorhinal cortex adapted to the distance between successively visited test locations when landmarks were used for localization, meaning that its activation decreased as the distance between the currently occupied location and the preceding location decreased. In contrast, the posterior-medial entorhinal cortex adapted to between-location distance when path integration cues were used for localization. In addition, along with the hippocampus and the precuneus, both entorhinal subregions showed stronger activation in correct trials than incorrect trials, regardless of cue type and reliability level. Together, these findings suggest that subdivisions of entorhinal cortex encode fine-grained spatial information for different spatial cues, which provides important insights into how the entorhinal cortex supports different modes of spatial navigation.