Poster E92, Monday, March 27, 2:30 – 4:30 pm, Pacific Concourse
Memory replay during sleep in human intracranial recordings
Jessica Creery1, David Brang2, Vernon Towle3, James Tao3, Shasha Wu3, Ken A. Paller1; 1Northwestern University, 2University of Michigan, 3University of Chicago
A viable explanation for how sleep contributes to memory consolidation is that storage is facilitated when memories are replayed during sleep. However, additional evidence is needed to support the crux of this idea, ideally by observing neural evidence of memory replay during sleep and showing that replay benefits memory storage. The hippocampus has been implicated in sleep replay based on evidence of hippocampal place cell activity in rodents. Indirect evidence that replay benefits consolidation comes from sleep studies using targeted memory reactivation (TMR) — when sensory cues coupled with pre-sleep learning are re-presented during sleep, memory is superior post-sleep. Here we combined TMR with intracranial electroencephalography (iEEG) to observe activity in the hippocampus when specific memories are reactivated during sleep. We recorded activity from depth electrodes in three patients with epilepsy during a spatial learning task and subsequent sleep with TMR. We analyzed event-related spectral perturbations to sound cues during sleep and found an increase in hippocampal gamma (30-70 Hz) starting about 500 ms after sound onset. This response was larger for sounds associated with prior learning compared to novel sounds. Additionally, there was a larger increase in gamma when recall after sleep was better. Based on the inference that gamma reflects local neural activity, these findings indicate that the learning-related stimuli presented during sleep engaged hippocampal responses that predicted subsequent memory performance. We thus linked neural activation in the hippocampus during sleep replay to enhanced memory storage and consequently to consolidation.
Topic Area: LONG-TERM MEMORY: Episodic