Dreaming without REM sleep

To test whether mental activities collected from non-REM sleep are influenced by REM sleep, we suppressed REM sleep using clomipramine 50 mg (an antidepressant) or placebo in the evening, in a double blind cross-over design, in 11 healthy young men. Subjects were awakened every hour and asked about their mental activity. The marked (81%, range 39–98%) REM-sleep suppression induced by clomipramine did not substantially affect any aspects of dream recall (report length, complexity, bizarreness, pleasantness and self-perception of dream or thought-like mentation). Since long, complex and bizarre dreams persist even after suppressing REM sleep either partially or totally, it suggests that the generation of mental activity during sleep is independent of sleep stage.

► Healthy subjects with clomipramine-induced REM sleep drastic reduction still report dreams in NREM sleep.
► The dreams are as long, complex, pleasant, and bizarre with clomipramine than with placebo.
► These results show that NREM sleep dreams are not remnants of previous REM sleep.
► They suggest that the generation of mental activity during sleep is independent from sleep stage.