Spectral EEG correlates of dream recall.

Recent studies have shown that dreaming is not limited to rapid eye movement (REM) sleep, but can be found to varying degrees in any stage of sleep. This study attempted to quantify the EEG correlations of dreaming during Stage 2 sleep. Six normal volunteers were studied for 24 nights in the sleep laboratory. Electroencephalogram (EEG) recording prior to awakening from Stage 2 sleep and from other stages without awakening were subjected to computer spectral analysis. Although awakenings associated with dream recall tended to have lower total power, mean frequency in the beta band proved to be the best correlate of mental activity in Stage 2 sleep. Mean frequency had its highest values in REM sleep and wakefulness and declined in Stage 2 and Stage 4 sleep, in keeping with the decline in mental activity reported from these stages. Implications of these findings are discussed with regard to models of dream recall and clinical states.