0056 Overnight Memory Consolidation in Adolescents: Effects of Change in DLMO Phase After Sleep Restriction

Abstract Introduction Sleep aids learning and memory. Limited studies have examined how circadian rhythms moderate this process, particularly in adolescents who experience developmental changes in circadian biology. Here we examine how sleep restriction, memory consolidation, and circadian biology interact in youth with distinct circadian phase preferences. Methods Adolescents were recruited based on circadian phase preference on the Morningness/Eveningness (M/E; Carskadon et al., 1993) scale. Sixteen participants entered the current analysis (6F, 2 Non-White; age 10-15, mean±sd:12.69±1.76 years; M/E 22-40; mean±sd: 33.38±5.78; 1 Evening-Type [M/E≤23]; 4 Neither Type [23>M/E< 34]; 11 Morning type]). All completed 19 nights of stabilization on a self-selected 9-hour in bed schedule followed by 7 nights of sleep restriction (6.5 hours in bed; bedtime delayed and rise time advanced equally). In-lab dim-light-melatonin-onset (DLMO) assessment occurred on the final nights of stabilization and restriction. Overnight memory consolidation was indexed on the motor sequence task (MST; Walker et al., 2006) across the final night of sleep restriction. Memory outcomes included speed (# correct sequences), # of errors, and precision (speed-error trade-off). We examined overnight improvement (morning-evening) in MST performance and associations between improvement, phase preference score, stabilized DLMO phase, and the DLMO phase change after restriction (negative numbers indicate phase delay). Regressions controlled for age where statistically justified. Results MST speed improved (t(15)=-3.44, p<.01, d=0.86) for the morning (12.94±6.89) test session compared to evening (10.81±5.69). There were no overnight changes in errors or precision (d’s<.14, p’s>.34). Overnight improvement was not related to M/E phase preference (Adj. R2’s< 0.17; p’s>.05); however, there was a significant association between the change in DLMO phase (mean±sd: 10.34±41.69 minutes) and memory consolidation for both speed (Adj. R2=0.54, F(2,13)=9.79, p<.01) and errors (Adj. R2=0.21, F(1,15)=4.94, p<.05). Specifically, children with a greater delay in DLMO phase demonstrated greater overnight improvement on the MST. Conclusion These data indicate a potential link between circadian biology and the cognitive benefits of sleep during adolescence. These findings are significant given the shifts in circadian rhythms occurring across adolescence. Understanding the influence of circadian rhythms in sleep-dependent memory may inform discussions of how sleep loss affects learning in school-aged youth. Support (if any) R01NR08381 and P20GM139743