Prefrontal control of hippocampal map reorganization during sleep

During wakefulness, exposure to novel experiences induces hippocampal remapping, in which place cell ensembles reorganize to form distinct representations of new information. Classical models of systems consolidation posit that subsequent sleep stabilizes these wake-formed representations and supports their gradual transfer to medial prefrontal cortex (mPFC) networks primarily via bottom-up hippocampal reactivations. Using miniscope Ca2+ imaging of CA1 place cells, we monitored hippocampal activity as mice explored a familiar environment followed by a similar novel one. As expected, place cells remapped in the novel context. However, a single episode of post-encoding sleep selectively reversed remapping dynamics by promoting the reinstatement of familiar place cell representations in the novel environment, an effect that was absent in the wake condition. This neural reinstatement was accompanied by behavioral indicators of familiarity, including reduced exploration and rearing. Chemogenetic inactivation of the mPFC during post-encoding sleep abolished this generalization effect, and instead preserved the novel hippocampal map. Thus, our results extend current models by showing that sleep not only consolidates wake-established hippocampal patterns, but actively shapes hippocampal maps via prefrontal control, thereby supporting memory generalization.