Local Changes in Sleep Following Declarative Learning

Traditionally, sleep has been viewed as a uniform, global state. This idea is contrasted by local sleep, which is characterized by transient periods of brain activity within specific brain regions, or even at the level of individual neurons during sleep. Previous studies have shown increased slow wave activity (SWA) in the parietal cortex during sleep following motor learning, indicating a local increase in sleep depth in response to motor learning. Here we ask a simple question: does this local use-dependent sleep response also occur during non-motor/declarative memory tasks? During one wake and one overnight session, participants completed a word pair learning task, consisting of an encoding phase, followed by immediate and delayed recall sessions. As a control, participants completed an overnight non-learning task, where they passively viewed sham word pairs. There was an increase in SWA following the declarative learning task compared to the control task, particularly in the fronto-central and left temporal regions, suggesting that localized SWA increases occur following non-motor learning. These localized changes in SWA were significantly correlated with memory recall performance when controlling for subjective sleepiness. These findings provide novel evidence for localized sleep responses following declarative memory tasks and suggest that SWA may be region-specific to task demands, though further investigation is needed to understand the relationship between SWA and memory consolidation in non-motor tasks.