Post-training sleep and wakefulness promote explicit knowledge in children but not in adults

Previous research has extensively investigated the impact of post-training sleep and wakefulness on procedural memory consolidation across development. However, results regarding how offline processes specifically affect the explicit and implicit components of newly acquired procedural skills in children and adults remain controversial. To address this issue, we investigated differences between 42 children (9.7 ± 1.8 years) and 58 young adults (21.7 ± 2.5 years) in the consolidation and explicit knowledge of a visuo-motor sequence learned in a Serial Reaction Time Task. Participants were assigned to either a nocturnal sleep or a daytime wakefulness offline interval condition between learning and retest (~11 hours). Offline (between-session) and online (within-session) performance changes were assessed, and explicit sequence knowledge was quantified using the Process Dissociation Procedure (PDP). Results showed similar offline performance improvements in the two age groups and offline interval conditions. PDP results revealed that children had higher explicit knowledge of the sequence as compared to adults, irrespective of the offline interval condition. Furthermore, children exhibited a shift from online performance deterioration to online performance improvements that was consistent across sleep and wake conditions. The absence of a differential impact of sleep vs. wakefulness intervals suggests that mostly time-dependent mechanisms primarily drive procedural memory consolidation and the development of stronger related explicit knowledge in children. Our findings also highlight a developmental dissociation between the offline consolidation of procedural learning skills, which appears age-invariant, and the resulting explicit knowledge, which developed more strongly in children.