Sleep dependent memory consolidation during a daytime nap in adolescents

Abstract

Introduction: This study examined the sleep-dependent memory consolidation hypothesis through napping in adolescents in their naturalistic living environment. Previous controlled experimental studies suggested that a short nap could help support memory consolidation and learning in normally sleeping adults. This study attempted to extend previous findings by demonstrating memory consolidation effects of napping with multiple memory tasks in adolescents who commonly have inadequate sleep. Methods: Forty healthy adolescents, aged 15-19 were recruited at a full time boarding English-speaking high school in Hong Kong. Volunteering participants were matched in pairs on age, sex and sleepiness, using the Cleveland Adolescent Sleepiness Questionnaire. They were then randomly assigned to either the “nap” (n=21) or the “no-nap” condition (n=19). Three verbal learning and recall tasks - prose recall, word pair associates, and word list learning were adopted. Task stimuli were presented to all participants at around 2.00pm on the testing day. The nap group was then instructed to take a nap at their own dormitory room between 3.15pm and 4.15pm while the no-nap group was instructed to stay awake as usual. Re-testing of recall and recognition tasks and learning of a new word list was scheduled at 5.15pm. Results: The nap group was significantly better at recalling previously learnt proses [F (1,36) = 9.11, p= .005, η2= .202] and word pairs [F (1,36)=5.80, p =.021, η2=.139]. These effects were not associated with self-reported sleep duration in the preceding seven nights and daytime sleepiness. The nap group also performed better in learning a new word list after napping than the no-nap group [F (1,37) = 6.905, p = .012, η2=.157]. Conclusion: Our results suggested that a short nap can be of benefit to students of diverse sleep status. Planned, polyphasic sleep complementary to good sleep hygiene may be advisable to help adolescents cope with increasing cognitive demands in modern societies.