Emotional memory reactivation supports flexible sleep strategies

The interaction between sleep function and memory processing is widely observed in both animals and humans, especially in how sleep supports memory consolidation and forgetting. However, whether memory activity during sleep has any regulatory effect on sleep processes is poorly investigated. Here we find that sensory stimuli-triggered emotional memory reactivation significantly affects sleep strategies after learning, as negative memory promotes alertness in sleep while positive memory protects sleep from perturbation. By combining EEG/EMG recording and engram cell activity tracing, our data reveal that the activity of emotional memory engram cells is temporally correlated to the sleep phase transition. Furthermore, bidirectional manipulations of engram cells demonstrate the involvement of this reactivation in the regulation of wakefulness and sleep depth. Such regulatory effect of engram cell reactivation is supported by the projection from emotional engram cells to sleep-related brain regions. Thus, our data indicate that the reactivation of emotional memory during sleep links daily experiences to different sleep strategies and provides the neural basis for animals to achieve optimal sleep behaviors in an ever-changing environment.