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.
Dreams incorporate specific information from waking experiences, and this incorporation may aid memory consolidation. Participants listened to an audiobook while falling asleep and were awakened during the night to report dreams. Blind raters could identify which audiobook a participant had heard based solely on dream reports, for both NREM and REM sleep dreams. Participants whose dreams more strongly incorporated the audiobook content tended to recognize more of that content later. The findings suggest that salient daytime experiences resurface in dreams and that content selected for memory consolidation during sleep is more strongly incorporated into dreams.
Dreams incorporate recent experiences, and memory-related brain activity is reactivated during sleep, suggesting a tight link between dreaming, memory consolidation, and reactivation. In this study, participants listened to different audiobooks before falling asleep. Brain activity during rapid eye movement (REM) sleep, particularly in the beta range, carried information about the audiobook. Global beta power during REM sleep was associated with better memory performance, but the amount of neural reinstatement did not correlate with memory retention. Blind raters could determine which audiobook participants had studied based on dream reports. Participants who dreamt of the audiobook showed stronger neural reinstatement. Reprocessing of pre-sleep experiences during sleep may thus shape brain activity, dreams, and memories.