Neuroscience and Biobehavioral Reviews
April 1, 2023
Péter Simor, Philippe Peigneux, Róbert Bódizs
Dreaming and the forgetting of dreams are not meaningless byproducts of sleep but are integral to the brain's homeostatic functions, which both restore and anticipate future needs. Mental activity during sleep, especially in the second half of the night, is a self-focused, future-oriented cognitive process. Waking up shifts the brain to a constrained, goal-directed mode of thinking that competes for neural resources with dream production and recall, contributing to dream amnesia. Cortisol is highlighted as a potential factor in predictive homeostasis and forgetting dreams. This theoretical proposal reframes dreaming as part of a reactive and predictive homeostatic system.
NeuroImage. Clinical
January 1, 2022
Tamás Bogdány, Pandelis Perakakis, Róbert Bódizs et al.
Frequent nightmares are common and linked to mental health problems, but their biological basis is poorly understood. A small 2019 study reported that the heartbeat evoked potential (HEP) measured during REM sleep differed markedly between 11 nightmare sufferers and 11 controls, and correlated with depression in the nightmare group, suggesting HEP could be a biomarker. This replication attempt analyzed HEPs in two larger databases (39 and 41 participants each) using the same methods. No significant HEP differences between groups were found in either database, nor any association with depression scores. These results cast doubt on HEP as a reliable biomarker for nightmare disorder and indicate that interpreting HEP as a marker of impaired arousal and emotional processing during REM sleep is premature.
Mentálhigiéné és Pszichoszomatika
June 1, 2016
Piroska Sándor, Sára Szakadát, Róbert Bódizs
Children aged 4 to 8 years who have more emotional problems tend to report more dreams, and the negative quality of their dreams and the effect of dreams on daytime mood are linked to poorer emotional adaptation as measured by parent-reported behavioral difficulties. However, no relationship was found between the emotions children experience in their dreams and their waking emotional processing abilities. These findings partially support the idea that dreams play a role in emotional regulation during development, consistent with the neurocognitive dream theory proposed by Nielsen and Levine.
Brain and Cognition
November 1, 2014
Péter Simor, János Körmendi, Klára Horváth et al.
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.
Biological Psychology
December 1, 2013
Péter Simor, Klára Horváth, Péter P Ujma et al.
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.
Brain and Cognition
April 1, 2012
Péter Simor, Péter Pajkossy, Klára Horváth et al.
People who frequently experience nightmares show measurable impairments in certain thinking tasks during the day, particularly those requiring suppression of irrelevant information. In two studies, nightmare subjects were slower on emotional Go/NoGo and Stroop tasks, made more perseveration errors, and generated fewer words on a verbal fluency task compared to matched controls. These deficits appeared as an overall slowing regardless of whether the stimuli were emotionally positive, negative, or neutral. Poor sleep quality and waking anxiety accounted for some but not all of the differences. The findings suggest that frequent nightmares are linked to executive function difficulties involving the control of task-irrelevant semantic information.
Attachment & human development
March 1, 2011
Szilvia Csóka, Péter Simor, Gabor Szabo et al.
Adults who experienced early maternal separation (before age one and lasting at least one month) report more frequent nightmares and bad dreams. Depression fully explains the link between early separation and nightmare frequency but not the link between early separation and negative dream affect. The findings suggest a lasting increase in negative emotionality following early maternal separation, which shapes dream content and, when depression is present, also raises nightmare frequency.
Brain Research Bulletin
March 15, 2005
Róbert Bódizs, Melinda Sverteczki, Alpár Sándor Lázár et al.
During the wake-sleep transition, a REM-like 1.5-3.0 Hz rhythmic activity in the parahippocampal cortex increases, peaking after about 30 seconds of sleep onset and reaching 82% of the level seen during REM sleep. This activity follows the dropout of alpha waves but is not linked to short-term changes in alpha or sleep spindles. Non-REM slow activity below 1.25 Hz steadily increases in both scalp and parahippocampal recordings. The findings suggest that this REM-like parahippocampal slow activity results from the switching off of hypothalamic wake-promoting centers at sleep onset, which inhibits hippocampal function and may contribute to hypnagogic hallucinations.