People with frequent nightmares show an imbalance between sleep-protective and wake-promoting brain activity, according to a comparison of 22 nightmare participants and 22 healthy controls. Nightmare participants had less slow-wave sleep and increased high-frequency (beta and gamma) power during NREM sleep and the transition into REM sleep. Differences in low- and high-frequency power across pre-REM to post-REM transitions also distinguished the groups. Increased high-frequency power before REM was mainly driven by PTSD symptom intensity, whereas decreased low-frequency activity occurred regardless of PTSD severity. The findings suggest reduced sleep-protective activity and increased hyperarousal in nightmare participants.
People with nightmare disorder show signs of wake-like brain activity and reduced parasympathetic nervous system activity specifically during the transition into REM sleep, but not after REM periods. Compared to healthy controls, nightmare sufferers had increased alpha power in EEG recordings before REM sleep, indicating a more wake-like cortical state. They also lacked the normal increase in heart rate variability that typically occurs before REM, suggesting blunted parasympathetic activity. These differences were not explained by trait anxiety. The findings suggest that sleep is most disturbed during the transition into REM sleep in nightmare disorder, possibly reflecting altered emotional processing.
People with nightmare disorder show brain activity during REM sleep that resembles wakefulness more than healthy controls do. In a study of 19 individuals with nightmare disorder and 21 healthy controls, those with nightmares had increased high alpha (10-14.5Hz) power and increased fronto-central high delta (3-4Hz) power during REM sleep, along with a trend toward increased fronto-central low alpha (7.75-9Hz) power during NREM sleep. These differences were not explained by daytime emotional distress. The findings suggest that nightmare disorder involves wake-like electroencephalographic features during REM sleep, indicating impaired sleep regulation.