Benefits of a Nap for the Consolidation of Newly Learned Words

A large body of evidence indicates that non-rapid eye movement (NREM) sleep contributes to the stabilization of newly acquired memories, whereas REM sleep has been proposed to support the integration of new information into pre-existing memory networks. Here, we examined memory consolidation and semantic integration within the same experimental paradigm. Fifty-two participants (M_age = 24.69 years, SD = 4.60, range = 18–37; Wake: n = 25; Sleep: n = 27) learned rare Spanish words paired with images and definitions and then either took a 90-min nap monitored with polysomnography or remained awake. Memory was assessed after training (TR2) and again following the retention interval (TS). Word recall did not differ between groups at training. Across the retention interval, word memory significantly decreased in the Wake group, whereas no significant decline was observed in the Sleep group. Accordingly, memory change differed significantly between groups, with greater forgetting in Wake. In contrast, change in definition memory did not differ between groups. No group differences were observed in semantic integration. Correlational analyses were subsequently performed to examine whether NREM slow-wave and spindle activity, as well as REM theta power, were associated with memory consolidation and semantic integration. These findings will be interpreted in the context of current models of sleep-dependent memory processing, particularly the active systems consolidation framework.