Daytime naps improve procedural motor memory
ABSTRACT To investigate the impact of a short daytime nap on procedural and declarative memory consolidation.
Following a normal night's sleep, 34 young healthy subjects were randomly assigned to a nap or wake condition of about 45min in the early afternoon after learning procedural and declarative memory tasks. Subjects were controlled for alertness and cortisol secretion.
The afternoon naps were dominated by sleep stage 2 but contained some slow wave sleep (SWS) and rapid eye movement (REM) sleep as well. Naps significantly improved procedural, but not declarative, memory. Females showed more improvement than males in the declarative memory tasks irrespective of nap or wake. There was no difference between groups with respect to cortisol secretion or alertness.
A short nap is favorable for consolidation of procedural memory. The possibly confounding effect of gender should always be considered in research on sleep and memory.
- SourceAvailable from: Klaus Junghanns[Show abstract] [Hide abstract]
ABSTRACT: Sleep architecture as well as memory function are strongly age dependent. Slow wave sleep (SWS), in particular, decreases dramatically with increasing age, starting already beyond the age of 30. SWS normally predominates during early nocturnal sleep and is implicated in declarative memory consolidation. However, the consequences of changes in sleep across the life span for sleep-associated memory consolidation have not been evaluated so far. Here, we compared declarative memory consolidation (for word-pair associates) during sleep in young and middle-aged healthy humans. The age groups (18-25 vs. 48-55 yr) did not differ with regard to learning performance before retention periods that covered, respectively, the first and second half of nocturnal sleep. However, after early retention sleep, where the younger subjects showed distinctly more SWS than the middle-aged (62.3 +/- 3.7 min vs. 18.4 +/- 7.2 min, P < 0.001), retrieval of the word pairs in the middle-aged was clearly worse than in the young (P < 0.001). In contrast, declarative memory retention did not differ between groups after late sleep, where retention was generally worse than after early sleep (P = 0.005). Retention of declarative memories was the same in both age groups when sleep periods containing equal amounts of SWS were compared, i.e., across late sleep in the young and across early sleep in the middle-aged. Our results indicate a decline in sleep-associated declarative memory consolidation that develops already during midlife and is associated with a decrease in early nocturnal SWS.Learning & memory (Cold Spring Harbor, N.Y.) 06/2007; 14(5):336-41. DOI:10.1101/lm.470507 · 4.38 Impact Factor
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ABSTRACT: Alpha/theta neurofeedback training is supposed to enhance cognitive performance as well as alleviate psychiatric disorders. Sleep during this training is regarded a confounding factor, although it is usually not controlled. Here, the amount of sleep, the impact of sleep on frequency results and the validity of subjective judgments of having fallen asleep were investigated. 40 healthy young subjects participated in 31 training units of real or mock feedback. It turned out that stage 2 sleep occurred in 10-14 % of training time, in 95 % of the subjects and in 1/3 of all training units. Sleep significantly influenced the theta/alpha ratio and theta but not alpha amplitudes. Only about 2/3 of the subjective judgements were correct and no more than 13 % of the participants could reliably identify sleep. These data demonstrate that sleep can easily occur during alpha/theta neurofeedback training and should be controlled by objective means.Applied Psychophysiology and Biofeedback 04/2015; 40(2). DOI:10.1007/s10484-015-9278-9 · 1.13 Impact Factor
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ABSTRACT: Many young females take exogenous hormones as oral contraceptive (OC), a condition rarely controlled for in studies on sleep and memory consolidation even though sex hormones influence consolidation. This study investigated the effects of OCs on sleep-related consolidation of a motor and declarative task, utilizing a daytime nap protocol. Fifteen healthy, young females taking OCs came to the sleep lab for three different conditions: nap with previous learning, wake with previous learning and nap without learning. They underwent each condition twice, once during the 'pill-active' weeks and once during the 'pill-free' week, resulting in 6 visits. In all conditions, participants showed a significant off-line consolidation effect, independent of pill week or nap/wake condition. There were no significant differences in sleep stage duration, spindle activity or spectral EEG frequency bands between naps with or without the learning condition. The present data showed a significant off-line enhancement in memory irrespective of potential beneficial effects of a nap. In comparison to previous studies, this may suggest that the use of OCs may enhance off-line memory consolidation in motor and verbal tasks per se. These results stress the importance to control for the use of OCs in studies focusing on memory performance. © 2015 S. Karger AG, Basel.Neuropsychobiology 02/2015; 70(4):253-261. DOI:10.1159/000369022 · 2.30 Impact Factor