Slow alpha variant during REM sleep.

REM sleep resembles wakefulness or drowsiness. The pattern can be low-voltage, or else alpha-like. Alpha frequencies are present only during the tonic phases of REM sleep and, compared to wakefulness tracings, alpha activities are slightly slower by 1-2 Hz and are more monomorphic. The slow alpha-variant rhythm or subharmonic alpha pattern consists of rhythmic notched theta waves. It shares the same topography and reactivity with the alpha rhythm. We report its presence during the tonic phases of REM sleep without any modification in its morphology in the first case. In the second case, its morphology was similar to awakening but with slower amplitude. No alpha frequencies were found in REM sleep but only its slow alpha variant. This study provides evidence that REM sleep is a stage of sleep that contains rhythms similar to those seen during wakefulness and drowsiness.