Interrelatedness of Mental Activity During Sleep

A paper by Aserinsky and Kleitman1in 1953 initiated renewed interest in the scientific study of dreams. They reported that subjects related dreams on 74% of awakenings from periods of sleep characterized by a low-voltage, desynchronized EEG pattern and rapid eye movements (REM periods). The subjects rarely reported dreams when awakened from periods of sleep characterized by EEG delta and sleep spindle activity and no rapid eye movements (NREM periods). A more extensive study by Dement and Kleitman3yielded 80% dream recall on REM awakenings and 7% dream recall on NREM awakenings. They considered that the small amount of recall obtained on NREM awakenings probably represented dreams experienced during earlier REM periods and incorrectly assigned by the subject to the NREM period immediately preceding the awakening. Using the REM period as the criterion of dreaming, Dement and Kleitman2established that three