Selective reactivation of value- and place-dependent information during sharp-wave ripples in the intermediate and dorsal hippocampus

Abstract

Reactivation of place cells during sharp-wave ripples (SWRs) in the hippocampus transfers newly acquired information to the neocortex and thus is important for memory consolidation. However, whether hippocampal reactivation is affected by the values of events experienced by the animal is largely unknown. Here, we investigated whether place cells in the dorsal (dHP) and intermediate (iHP) hippocampus are differentially reactivated depending on the value associated with a place. Rats were trained to learn the places associated with higher-value rewards in a T-maze, with concurrent simultaneous recording of single units in the dHP and iHP. Place cells in the iHP representing the high-value location were reactivated significantly more frequently during SWRs in both task and subsequent sleep periods than those representing the low-value location. The amount of reactivation during sleep was positively correlated with learning speed the next day. In contrast, these characteristics were not observed in the dHP. Instead, place-cell activities coding the routes leading to high-value locations were replayed more in the dHP than in the iHP. Our findings suggest that value-based differential reactivation patterns along the septotemporal axis of the hippocampus may play essential roles in goal-directed spatial-learning optimization for maximal reward.