During sleep, periods of rapid eye movement (REM) alternate with non-REM sleep in a cycle that recurs about every:
A) 30 minutes.
B) 50 minutes.
C) 60 minutes.
D) 90 minutes.

Question

Quizplus · Accepted Answer

The cycle of REM and non-REM sleep recurs about every 90 minutes. This cycle becomes longer throughout the night, with REM sleep periods increasing in duration and non-REM stages 3 and 4 (or deep sleep) becoming shorter.

During Sleep, Periods of Rapid Eye Movement (REM) Alternate with Non-REM