REM, accounting for 20-25% of total sleep, is characterized by high frequency, low amplitude activity that resembles that during wakefulness and rapid eye movements. In this stage, muscles are also paralyzed and body temperature becomes unregulated. Vivid dreams are also often experienced during this stage, and the muscle atonia (paralysis) prevents the sleeper from acting them out.
REM佔總睡眠的20至25%,其特點是類似於清醒時的高頻率、低振幅的腦波活動以及快速的眼球活動。在這個階段,肌肉會被麻痺,體溫亦會變得不受調節。 REM睡眠中經常會出現生動的夢境,而肌肉麻痺會使睡眠者無法將其行動表現出來。