A new open-access database, DREAM, combines sleep magneto/electroencephalography (M/EEG) recordings with standardized dream reports to enable large-scale neurocognitive research on dreaming. The initial release includes 20 datasets from 561 participants and 2649 awakenings, each with at least 20 seconds of high-frequency M/EEG data and a classification of the subject's experience. Analyses demonstrate that features extracted from EEG can predict whether a person reports having had a conscious experience during both REM and NREM sleep. The database aims to overcome the limitations of small sample sizes and methodological variability in dream research, allowing new questions to be addressed at a scale unattainable by individual labs.
Details from personally significant waking-life events are most likely to appear in REM-sleep dreams on the first two nights after the event and again five to seven nights later, a pattern known as the day-residue and dream-lag effects. In a 14-day diary study with 38 participants, only personally significant events showed this pattern, and only among the 19 participants who had fewer total correspondences between daily events and dreams. Major daily activities and major concerns did not show the effect. The U-shaped timeline may reflect REM-sleep-dependent memory consolidation, possibly linked to emotional memory processing. This study analyzed more dreams than any previous dream-lag study with trained participants.
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.
Daydreams more often incorporate major concerns from the previous two days than from earlier days, supporting a role for daydreams in processing current personal issues. However, personally significant events do not show this day-residue effect in daydreams, and there is no delayed incorporation from 5 to 7 days earlier, unlike what has been found for REM dreams. The study also failed to replicate the previously observed dream-lag effect for REM dreams, possibly due to methodological differences.