Frontiers in human neuroscience
January 1, 2022
Arnfinn Aamodt, André Sevenius Nilsen, Rune Markhus et al.
29 citations
In a follow-up EEG sleep study, brain signal complexity (Lempel-Ziv complexity, LZC) decreased progressively from wakefulness into deeper non-REM sleep. However, within NREM2 sleep, there was no significant difference in LZC between dream and non-dream awakenings, and no correlation between LZC and subjective ratings of dream vividness, diversity, or perceptual quality. The authors failed to reproduce their earlier finding that posterior LZC increased with more perceptual dream experiences. This raises doubts about whether EEG LZC is a reliable marker of richness of experience within the same sleep stage.
Frontiers in Psychology
April 23, 2021
Arnfinn Aamodt, André Sevenius Nilsen, Benjamin Thürer et al.
24 citations
Signal diversity in EEG recordings, measured by Lempel-Ziv complexity and other metrics, decreases with deeper non-REM sleep stages, consistent with theories linking consciousness to complex cortical dynamics. However, signal diversity did not significantly differ between dreaming and non-dreaming periods within the same sleep stage. A positive correlation was found between Lempel-Ziv complexity over the posterior cortex and the thought-perceptual quality of dream contents, suggesting that specific aspects of dream experience may relate to local cortical signal diversity.
Nature communications
August 13, 2025
William Wong, Rubén Herzog, Kátia Cristine Andrade et al.
10 citations
A new open database, the DREAM database, combines standardized sleep magneto/electroencephalography (M/EEG) recordings with dream reports from 505 participants across 20 datasets, totaling 2,643 awakenings. Each awakening includes at least 20 seconds of high-resolution sleep EEG (≥100 Hz, ≥2 electrodes) and a classification of the sleeper's reported experience. Analyses showed that reports of conscious experiences during sleep can be predicted from objective EEG features in both REM and NREM sleep. The database aims to overcome limitations of small sample sizes and methodological variability in dream research, enabling larger-scale investigations of the neurocognitive basis of dreaming.
Brain sciences
September 13, 2024
André Sevenius Nilsen, Johan Frederik Storm, Bjørn Erik Juel
Measures of consciousness based on signal diversity of spontaneous or perturbed EEG are not affected by cognitive load, whereas the P300b event-related potential is. In 12 participants, EEG was recorded during passive attention to sensory stimuli and during a demanding working memory task. The P300b, which reflects conscious awareness of auditory deviance, was significantly reduced by the concurrent memory task. In contrast, several signal diversity measures, including the perturbational complexity index, were unchanged. These findings suggest that signal diversity measures may remain reliable for assessing consciousness in clinical settings where attention, sensory processing, or command following are impaired.