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Unaltered EEG spectral power and functional connectivity in REM microstates in frequent nightmare recallers: are nightmares really a REM parasomnia?

Gwen Van der Wijk, Borbála Blaskovich, Yeganeh Farahzadi, Péter Simor

Sleep Medicine November 1, 2020 DOI: 10.1016/j.sleep.2020.07.014 (opens in new tab)

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Study at a glance

AI-extracted from the abstract
Characteristics Observational cohort Peer reviewed
Sample size 44
Population Frequent nightmare recallers and healthy controls with high dream recall
Duration Two nights in the laboratory
Topics Dreaming
Keywords Functional connectivity Nightmare disorder Oscillations Rapid eye movement
Key findings No differences in REM sleep EEG power or functional connectivity were found between frequent nightmare recallers and healthy controls.

Abstract

Frequent nightmares show signs of hyperarousal in NREM sleep. Nevertheless, idiopathic nightmare disorder is considered a REM parasomnia, but the pathophysiology of REM sleep in relation to frequent nightmares is controversial. Cortical oscillatory activity in REM sleep is largely modulated by phasic and tonic REM periods and seems to be linked to different functions and dysfunctions of REM sleep. Here, we examined cortical activity and functional synchronization in frequent nightmare recallers and healthy controls, during phasic and tonic REM. Frequent nightmare recallers (N = 22) and healthy controls (N = 22) matched for high dream recall spent two nights in the laboratory. Phasic and tonic REM periods from the second nights' recordings were selected to examine differences in EEG spectral power and weighted phase lag index (WPLI) across groups and REM states. Phasic REM showed increased power and synchronization in delta and gamma frequency bands, whereas tonic REM featured increased power and synchronization in the alpha and beta bands. In the theta band, power was higher during tonic, and synchronization was higher during phasic REM sleep. No differences across nightmare and control participants or patterns representing interactions between the groups and REM microstates emerged. Our findings do not support the idea that abnormal REM sleep power and synchronization play a role in the pathophysiology of frequent nightmares. Altered REM sleep in nightmare disorder could have been confounded with comorbid pathologies and increased dream recall, or might be linked to more specific state factors (nightmare episodes).

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Study Year Design Participants
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Nightmare Prevalence, Nightmare Distress, and Self-Reported Psychological Disturbance Young adults with a mean age of 20 years 2002 Prospective observational study n = 116
Long-term effects of extreme situational stress on sleep and dreaming Survivors of traumatic events who complained of sleep disturbances, compared with... 1987 Case-control study n = 11
The relationship of nightmare frequency and nightmare distress to well‐being Adults who reported dreams 2004 Observational cohort n = 147
Dreaming in NREM Sleep: A High-Density EEG Study of Slow Waves and Spindles Healthy human subjects 2018 Observational cohort n = 14

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