The impact of sleep duration and subject intelligence on declarative and motor memory performance: how much is enough?
Recent findings clearly demonstrate that daytime naps impart substantial memory benefits compared with equivalent periods of wakefulness. Using a declarative paired associates task and a procedural motor sequence task, this study examined the effect of two lengthier durations of nocturnal sleep [either a half night (3.5 h) or a full night (7.5 h) of sleep] on over-sleep changes in memory performance. We also assessed whether subject intelligence is associated with heightened task acquisition and, more importantly, whether greater intelligence translates to greater over-sleep declarative and procedural memory enhancement. Across both tasks, we demonstrate that postsleep performance gains are nearly equivalent, regardless of whether subjects obtain a half night or a full night of sleep. Remarkably, the over-sleep memory changes observed on both tasks are very similar to findings from studies examining performance following a daytime nap. Consistent with previous research, we also observed a strong positive correlation between amount of Stage 2 sleep and motor skill performance in the full-night sleep group. This finding contrasts with a highly significant correlation between spectral power in the spindle frequency band (12-15 Hz) and motor skill enhancement only in the half-night group, suggesting that sigma power and amount of Stage 2 sleep are both important for optimal motor memory processing. While subject intelligence correlated positively with acquisition and retest performance on both tasks, it did not correlate with over-sleep changes in performance on either task, suggesting that intelligence may not be a powerful modulator of sleep's effect on memory performance.
Tucker
Matthew A
MA
Department of Psychiatry, Center for Sleep and Cognition, Harvard Medical School, Boston, MA 02215, USA. mtucker1@bidmc.harvard.edu
Fishbein
William
W
D001288:Attention / Q000502:physiology; D002540:Cerebral Cortex / Q000503:physiopathology; D004569:Electroencephalography; D005260:Female; D005583:Fourier Analysis; D006801:Humans; D007360:Intelligence / Q000502:physiology; D008297:Male; D011939:Mental Recall / Q000502:physiology; D010153:Paired-Associate Learning / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology; D012691:Serial Learning / Q000502:physiology; D012815:Signal Processing, Computer-Assisted; D012890:Sleep / Q000502:physiology; D012892:Sleep Deprivation / Q000503:physiopathology / Q000523:psychology; D012894:Sleep Stages / Q000502:physiology; D055815:Young Adult