Fig. 15: Periodicity of RPS and "depth" of sleep

All night's sleep of 8 h 20 min duration in a normal adult. It is interrupted by four periods of RPS whose duration is 28 per cent of sleep.

Ordinate: E, arousal;

1-2-3-4, the four stages of sleep, and RPS (PRS).

Scale (in V) of the stimulator which triggered a loud speaker (1000 c/sec tone).

The white dots signal auditory stimulation which did not arouse the subject.

The black dots, auditory stimuli which did arouse the subject without recall of dream.

Black triangles, recall of dreams.

The two diagrams are continuous.

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