Non-Rapid Eye Movement Sleep (Paperback)

High Quality Content by WIKIPEDIA articles The sleep stages 1 through 3, previously known as stages 1 through 4, are collectively referred to as non-rapid eye movement, NREM, sleep. Rapid eye movement (REM) is not included. There are distinct electroencephalographic and other characteristics seen in each stage. Unlike REM sleep, there is usually little or no eye movement during this stage. Dreaming is rare during NREM sleep, and muscles are not paralyzed as in REM sleep. In addition, there is a parasympathetic dominance during NREM. Polysomnography (PSG) is a test used in the study of sleep; the test result is called a polysomnogram. Slow-wave sleep (SWS) is made up of the deepest stage of NREM, and is often referred to as deep sleep. The highest arousal thresholds (e.g. difficulty of awakening, such as by a sound of a particular volume) are observed in Stage 3. The major factor determining how much slow-wave sleep is observed in a given sleep period is the duration of preceding wakefulness.