Overnight improvements in two REM sleep-sensitive tasks are associated with both REM and NREM sleep changes, sleep spindle features, and awakenings for dream recall.

Memory consolidation is associated with sleep physiology but the contribution of specific sleep stages remains controversial. To clarify the contribution of REM sleep, participants were administered two REM sleep-sensitive tasks to determine if associated changes occurred only in REM sleep. Twenty-two participants (7 men) were administered the Corsi Block Tapping and Tower of Hanoi tasks prior to and again after a night of sleep. Task improvers and non-improvers were compared for sleep structure, sleep spindles, and dream recall. Control participants (N = 15) completed the tasks twice during the day without intervening sleep. Overnight Corsi Block improvement was associated with more REM sleep whereas Tower of Hanoi improvement was associated with more N2 sleep. Corsi Block improvement correlated positively with %REM sleep and Tower of Hanoi improvement with %N2 sleep. Post-hoc analyses suggest Tower of Hanoi effects-but not Corsi Block effects-are due to trait differences. Sleep spindle density was associated with Tower of Hanoi improvement whereas spindle amplitude correlated with Corsi Block improvement. Number of REM awakenings for dream reporting (but not dream recall per se) was associated with Corsi Block, but not Tower of Hanoi, improvement but was confounded with REM sleep time. This non-replication of one of 2 REM-sensitive task effects challenges both 'dual-process' and 'sequential' or 'sleep organization' models of sleep-dependent learning and points rather to capacity limitations on REM sleep. Experimental awakenings for sampling dream mentation may not perturb sleep-dependent learning effects; they may even enhance them.

Differential effects of sleep deprivation on sleepwalking: Role of demographic and clinical profiles.

BACKGROUND: Although sleepwalking is one of the most prevalent and potentially injurious of the NREM parasomnias, it is still diagnosed primarily based on the patient's clinical history. Early pilot work suggested that sleep deprivation protocols could help obtain a polysomnographically-based (PSG) diagnosis of sleepwalking, but larger studies remain lacking. METHODS: We compared baseline PSG recordings with those obtained after 25hrs of sleep deprivation in a cohort of 124 consecutively assessed adult sleepwalkers. RESULTS: When compared to baseline recordings, post-sleep deprivation PSG assessments resulted in nearly twice as many somnambulistic episodes being recorded in the laboratory and significantly increased the proportion of patients (from 48 % to 63 %) experiencing at least one lab-based episode. Moreover, while 17 % of patients experienced a sleepwalking event exclusively during recovery sleep, only 2 % of patients did so solely at baseline. Sleep deprivation had similar facilitating effects on patents' somnambulistic events regardless of age of onset and positive versus negative family history for sleepwalking. Younger age and higher home episode frequency both predicted a positive response to sleep deprivation. A separate group of 17 patients with comorbid sleep disorders showed a similar increase in their proportion experiencing at least one episode during recovery sleep. CONCLUSION: The results from this large series of sleepwalkers provide strong support for the use of sleep deprivation in facilitating the occurrence of somnambulistic events in the sleep laboratory.