Complementary roles of dorsal and ventral hippocampus in the flexible adaptation of goal-directed behavior

The ability to adapt previously learned behaviors is crucial for survival in dynamically changing environments. The hippocampus has been implicated in associative learning, but how hippocampus activity along its septotemporal axis contributes to flexible adaptation is unknown. Using in vivo Ca²⁺ recordings and functional inhibition of dorsal CA1 (dCA1) and ventral CA1 (vCA1) neurons in mice during complementary cognitive flexibility tasks, we find that dCA1 is engaged and functionally required during consolidation of a learned contingency both before and after a rule change, whereas vCA1 is uniquely recruited during, and necessary for, early adaptation to a new contingency. This vCA1-dependent adaptation relies on a perseverative error signal, which is encoded in vCA1 and required for behavior updating. These results highlight a previously unknown division of labor within the hippocampus, in which vCA1 enables flexible adaptation when mismatches in expected and actual outcomes are detected, whereas dCA1 stabilizes newly learned information.