REM Sleep

REM stands for "rapid-eye-movement" because the eyes dart back and forth in bursts of activity beneath the closed eyelids. REM sleep is a stage of sleep with the following major characteristics:

• brain activity is similar to that seen when people are awake and alert (beta-like waves);
• muscle tone is at a very low level, so that few muscle movements are possible beyond twitching of the face, hands, and feet;
• genital arousal frequently occurs;
• dreaming frequently occurs.