0064 Trading sleep for learning time improves next-day recall, but with poorer retention of items learned during sleep deprivation

Abstract

Abstract Introduction Sleep is important for learning and memory retention. However, students often cram for examinations by staying awake late to study. We tested the hypothesis that trading sleep for learning time leads to better next-day recall, but items learned during sleep deprivation will be more poorly retained. Methods Seventy healthy adults (18–24 years; 32 males) participated in an overnight laboratory study and were tasked with learning the meanings of 120 pseudowords using digital flashcards. Half of participants were randomly assigned to 8 h of TIB for sleep (23:00 to 07:00) and the other half to 4 h of TIB for sleep with a later bedtime (03:00 to 07:00). The 8-h TIB group was given 3 learning sessions (17:50, 19:50, and 21:50) with each flashcard shown twice per session. The 4-h sleep group was given an additional 2 learning sessions that occurred during the night (23:50 and 01:50). Cued-recall performance was tracked during pre-sleep learning, and participants were tested the following morning (09:30) on 60 randomly selected flashcards. Results Prior to sleep, the 4-h TIB group learned more items than the 8-h TIB group (Mean score ± SD: 4-h TIB, 85.31% ± 20.92%; 8-h TIB, 63.76% ± 24.22%) because they successfully encoded new items during their additional nocturnal learning sessions. On the following morning, the 4-h TIB group had significantly higher scores on the cued-recall test compared with the 8-h TIB group (Mean score ± SD: 4-h TIB, 83.71% ± 23.50%; 8-h TIB, 70.10% ± 24.18%; Mann-Whitney U test, p< 0.001). However, items learned during the final learning session before sleep were retained significantly better in the 8-h TIB group compared with the 4-h TIB group (4-h TIB, 76.64%; 8-h TIB, 91.35%, Chi-squared = 20.43, p< 0.001). Conclusion There was a trade-off of exchanging sleep for additional learning time. More learning time at the expense of sleep resulted in better next-day test scores but recall performance was poorer for items newly learned during partial sleep deprivation. Our findings help to explain why students often sacrifice sleep for short-term gains in test performance despite poorer memory retention. Support (if any) National Research Foundation, Singapore (NRF2016-SOL002-001)