A central function of sleep is the consolidation of memories (Mednick et al. 2011). Specific sleep stages and electroencephalographic waveforms have been shown to correlate with improvements in discrete memory domains (Mednick et al 2003, Fogel et al 2007). However, it is not known whether experimental manipulation of specific sleep features via pharmacological intervention will modulate performance. Here, in a repeated measures crossover design, we examine the effects of zolpidem (ZOL) (10mg), sodium oxybate (SO) (2.5g) and placebo (PBO) on perceptual, verbal and motor memory during a morning (9AM) nap. We tested perceptual learning with the texture discrimination task, declarative verbal memory with the word pair associates task, and motor learning with the motor sequence task before (6AM) and after (3PM) the naps. We show that ZOL decreased perceptual learning and increased verbal memory, and did not change motor learning, compared with SO or PBO. Drug effects on sleep showed that ZOL decreased rapid eye movement (REM) sleep and increased sleep spindle density, while SO increased slow wave sleep (SWS), compared to PBO. Thus, ZOL showed a trade-off between increased verbal and decreased perceptual memory, likely related a similar trade-off between spindle density and REM sleep. The magnitude of verbal memory improvement was correlated with the amount of sleep spindles in all three drug conditions, indicating that enhancements with ZOL represent an augmentation of a normal consolidation process during sleep, and are independent of drug pharmacology. These results demonstrate a causal change in perceptual and verbal memory consolidation due to pharmacological manipulation of sleep, and indicate sleep spindles as an important mechanism for memory consolidation. Furthermore, the performance gains in verbal memory exceeded those of sleep alone or with a control drug, and therefore demonstrate the capacity for "exceptional" memory enhancement with pharmacologically-specified sleep.
Meeting abstract presented at VSS 2012