Consciousness during sleep changes dramatically across the night. Seven healthy participants were awakened 15–30 minutes apart across 44 nights and asked about their most recent conscious experience before the alarm. Recall with content occurred in 34% of non-REM awakenings and 77% of REM awakenings. Each sleep stage showed a distinct profile of features including thinking, perceiving, self-relatedness, and reflective consciousness. The serial awakening method yielded a large, representative sample of sleep consciousness with minimal disruption from sleep fragmentation, and may be especially useful when combined with brain imaging techniques.
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.