Prioritized experience replays on a hippocampal predictive map for learning

Abstract

Hippocampal cells are central to spatial and predictive representations, and experience replays by place cells are crucial for learning and memory. Nonetheless, how hippocampal replay patterns dynamically change during the learning process remains to be largely elucidated. We found that when rats updated their behavioral strategies in response to a novel salient location, place cells increased theta sequences and sharp wave ripple-associated synchronous spikes that preferentially replayed salient locations and reward-related contexts in reverse order. The directionality and contents of the replays progressively varied with learning, including an optimized path that had never been exploited by the animals. Realtime suppression of sharp wave ripples during learning inhibited the rapid stabilization of optimized behavior. Our results suggest that hippocampal replays prioritize salient experiences and support the reinforcement of new behavioral policies. One-Sentence SummaryNeuronal network mechanisms to internally rehearse learned information for updating behavioral strategy are revealed