4 cycle progression of electrical activity that is recorded by an EEC. Stage 1 is marked by drowsiness; stage 2 is light sleeping, stage 3 and 4 show delta waves and consists of deep sleep. These stages are interrupted by REM sleep.

SLEEP STAGES: "The 4 sleep stages occur more than once each sleep."
Cite this page: N., Pam M.S., "SLEEP STAGES," in, April 13, 2013, (accessed April 22, 2021).