It has been hypothesized that REM (rapid eye movement) sleep has an important role in memory consolidation. The evidence for this hypothesis is reviewed and found to be weak and contradictory. Animal studies correlating changes in REM sleep parameters with learning have produced inconsistent results and are confounded by stress effects. Humans with pharmacological and brain lesion-induced suppression of REM sleep do not show memory deficits, and other human sleep-learning studies have not produced consistent results. The time spent in REM sleep is not correlated with learning ability across humans, nor is there a positive relation between REM sleep time or intensity and encephalization across species. Although sleep is clearly important for optimum acquisition and performance of learned tasks, a major role in memory consolidation is unproven.

https://science.sciencemag.org/content/sci/294/5544/1058.full.pdf

The REM Sleep-Memory Consolidation Hypothesis

Changes in sleep cycle patterns with age

Overnight verbal memory retention correlates with the number of sleep spindles.

This research evaluated parent reports of sleep behaviors of four groups of children: those with Autism or Pervasive Developmental Disorders, those with General Mental Retardation alone, those attending Special Education classes (with no MR diagnosis), and a control group of similar aged children without a developmental diagnosis. Diagnostic classification and demographic information were determined through parent report, report of classroom registration, and the Gilliam Autism Rating Scale (Gilliam, 1995). To evaluate sleeping behavior the study used a 28-item, five-factor scale (Behavioral Evaluation of Disorders of Sleep/BEDS; Schreck, 1997/1998) constructed from the diagnostic criteria for childhood sleep disorders found in the International Classification of Sleep Disorders: Diagnostic and Coding Manual (ICSD, American Sleep Disorders Association, 1990). Findings suggest that reports of parents with children with autistic characteristics exhibit expected quantities of sleep, but parent perception of their sleep difficulties and sleep quality is different for children with autism than for children in all other study groups.

Parental report of sleep problems in children with autism.

We tested the hypothesis that EEG sleep stages 3 and 4 (slow-wave sleep, SWS) would be increased as a function of either acute of chronic exercise. Ten distance runners were matched with 10 nonrunners, and their sleep was recorded under both habitual (runners running and nonrunners not running, 3 night) and abruptly changed (runners not running and nonrunners running, 1 night) conditions. Analyses of both visually scored SWS and computer measures of delta activity during non-rapid eye-movement (NREM) sleep failed to support the SWS-exercise hypothesis. The runners showed a significantly higher proportion and a greater absolute amount of NREM sleep than the nonrunners. The runners showed less rapid eye-movement activity during sleep than the nonrunners under both experimental conditions, indicating a strong and unexpected effect of physical fitness on this measure. Modest afternoon exercise in nonrunners was associated with a strong trend toward elevated heart rate during sleep. Mood tests and personality profiles revealed few differences, either between groups or within groups, as a function of exercise.

M Braun

Papers

Eeg sleep patterns in mental retardation