Abstract
Sleep aids the encoding and consolidation of declarative memories, but many adolescents do not obtain the recommended amount of sleep each night. After a normal night of sleep, there is abundant evidence that a daytime nap enhances the consolidation of material learned before sleep and also improves the encoding of new information upon waking. However, it remains unclear how learning is affected when sleep is split between nocturnal and daytime nap periods during a typical school week of restricted sleep. We compared long-term memory in 58 adolescents who underwent two simulated school weeks of suboptimal continuous (6.5 h nocturnal sleep opportunity) or split sleep (5 h nocturnal sleep +1.5 h daytime nap at 14:00). In the first week, participants encoded pictures in the late afternoon on Day 5 and were tested after 2-nights of recovery sleep. On 3 consecutive days in the second week, participants learned about six species of amphibians in the morning, and six different amphibians in the late afternoon. Testing was performed in the evening following a night of recovery sleep. In the first week, the split sleep group recognized more pictures. In the second week, they remembered more facts about species learned in the afternoon. Groups did not differ for species learned in the morning. This suggests that under conditions of sleep restriction, a split sleep schedule benefits learning after a nap opportunity without impairing morning learning, despite less preceding nocturnal sleep. While not replacing adequate nocturnal sleep, a split sleep schedule may be beneficial for chronically sleep restricted learners.
Highlights
Sleep after learning stabilizes and integrates memories for longterm storage,[1] while sleep prior to learning prepares the brain to encode new information.[2]
A separate study found that a 2 h nap opportunity after a lecture was associated with better test performance in adolescents when compared to those who attended regular classes,[20] while a third study found a similar advantage when weekly lessons were followed by naps of longer than 30 min.[21]
Term-time sleep habits were actigraphically assessed for a oneweek period occurring within 5 months prior to commencement of the study
Summary
Sleep after learning stabilizes and integrates memories for longterm storage,[1] while sleep prior to learning prepares the brain to encode new information.[2]. 0.530 0.291 0.329 0.988 0.674 0.845 0.215 relative loss of nocturnal sleep in the split sleep group could impair their ability to encode in the morning.[6,25,26] the subsequent nap might compensate by enhancing consolidation of what was learned.[18] If memory were purely a function of total sleep obtained, memory for information learned in the morning or afternoon would not differ between split and continuous sleep schedules This design permits the evaluation of how splitting sleep affects learning that is similar to the way students study and revise across multiple episodes in school. Since the opportunity to consolidate during this retention interval was the same in the two sleep conditions, performance at retrieval provides a reliable measure of encoding success.[6,25] Prior work has shown improved encoding after a single daytime nap,[17] motivating us to test if encoding capacity would be enhanced under a habitual napping schedule where prior sleep was matched between nap and no-nap conditions
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