Studies of memory reactivation during sleep using intracranial recordings

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Sleep is crucial to the body's ability to function but scientists have yet to uncover all the reasons for why we sleep. Recent evidence shows that sleep contributes to memory, although how that happens is not yet well understood. This project explores the idea that the ability to remember depends on sleep-based changes in how memories are stored. The investigators have the special opportunity to obtain recordings of brain activity from sensors placed inside the human brain. In some patients with frequent epileptic seizures, when pharmacological treatments are ineffective, a surgical treatment can greatly enhance quality-of-life. Sensors placed in selected brain locations can isolate the source of abnormal activity, after which this brain tissue can be removed. These patients are usually willing and able to help the investigators understand what happens during sleep to preserve memories. The investigators will explore how the reactivation of new memories during sleep improves the ability to remember the information. This type of memory processing during sleep could constitute an essential ingredient for learning. Results from this project may have implications for educational advances and for approaches to improving memory across the lifespan. The investigator plans activities to increase public understanding of science and to bolster recognition of the vital benefits of sleep.A key hypothesis in the field is that a brain region known as the hippocampus functions during sleep to help consolidate memories. This can entail linking anatomically disparate components of a memory, gradually integrating new knowledge with prior knowledge, securing memory storage, and potentially transforming what is stored. The investigators will analyze recordings of brain activity from functional brain tissue to determine how memory storage is altered when audio input during sleep promotes memory reactivation. Brain oscillations identified previously (so-called slow oscillations, sleep spindles, and hippocampal ripples), and their precise temporal interrelationships, are hypothesized to be critical. Analyses of these signals obtained during memory reactivation are thus positioned to provide new knowledge about neural mechanisms of sleep-based memory improvement, thus advancing fundamental understanding of what allows a small subset of the massive number of memories people acquire each day to survive for the long term.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.