Stephan, A. M. | bioRxiv Science

bioRxiv2023

Non-REM parasomnia experiences share EEG correlates with dreams

Sleepwalking and related parasomnias result from sudden and incomplete awakenings out of slow wave sleep. Clinical observations suggest that behavioral episodes can occur without consciousness and recollection, or in relation to dream-like experiences. To understand what accounts for these differences in consciousness and amnesia, we recorded parasomnia episodes with high-density EEG and interviewed participants immediately afterwards. Compared to reports of unconsciousness (19%), reports of conscious experience (81%) were preceded, during prior sleep, by high-amplitude slow waves in anterior cortical regions and an activation of posterior cortical regions. Reduced posterior slow wave activity was also present during the episode when patients displayed elaborate behaviours in relation to dream-like scenarios. Amnesia for the experience (25%) was modulated by right medial temporal activation during prior sleep and fronto-parietal slow wave activity during the episode. Thus, the neural correlates of parasomnia experiences are similar to those previously reported for dreams and therefore likely reflect core physiological processes involved in sleep consciousness.

neuroscience↗

bioRxiv2021

The determinants of the subjective perception of sleep: insights from a high-density EEG study with serial awakenings

What accounts for the feeling of being deeply asleep? Standard sleep recordings only incompletely reflect subjective aspects of sleep and some individuals with so-called sleep misperception frequently feel awake although sleep recordings indicate clear-cut sleep. To identify the determinants of the subjective perception of sleep, we performed 787 awakenings in 20 good sleepers and 10 individuals with sleep misperception and interviewed them about their subjective sleep depth while they underwent high-density EEG sleep recordings. Surprisingly, in good sleepers, sleep was subjectively lightest in the first two hours of Non-rapid eye movement (NREM) sleep, generally considered the deepest sleep, and deepest in rapid eye movement (REM) sleep. Compared to good sleepers, sleep misperceptors felt more frequently awake during sleep and reported lighter REM sleep. At the EEG level, spatially widespread high-frequency power was inversely related to subjective sleep depth in NREM sleep in both groups and in REM sleep in misperceptors. Subjective sleep depth positively correlated with dream-like qualities of reports of mental activity. These findings challenge the widely held notion that slow wave sleep best accounts for feeling deeply asleep. Instead, they indicate that subjective sleep depth is inversely related to a neurophysiological process that predominates in early NREM sleep, becomes quiescent in REM sleep and is reflected in high-frequency EEG-activity. In sleep misperceptors, this process is more frequently active, more spatially widespread, and abnormally persists into REM sleep. These findings help identify the neuromodulatory systems involved in subjective sleep depth and are relevant for studies aiming to improve subjective sleep quality.

neuroscience↗