Excerpt from EEG Atlas: Normal Sleep EEG - Rapid Eye Movement Sleep
Synonyms, Key Words, and Related Terms: EEG atlas, normal sleep EEG, stage I sleep, stage II sleep, stage III sleep, stage IV sleep, EEG desynchronization, REM sleep, saw tooth wave, rapid eye movement sleep, non-REM sleep, nonrapid eye movement sleep, sleep stages, sleep-onset REM period, SOREMP, sleep waveforms
Loomis provided the earliest detailed description of various stages of sleep in the mid-1930s, and in the early 1950s Aserinsky and Kleitman identified rapid eye movement (REM) sleep. Sleep generally is divided in 2 broad types: nonrapid eye movement sleep (NREM) and REM sleep. On the basis of EEG changes, NREM is divided further into 4 stages (stage I, stage II, stage III, stage IV). NREM and REM occur in alternating cycles, each lasting approximately 90-100 minutes, with a total of 4-6 cycles. In general, in the healthy young adult NREM sleep accounts for 75-90% of sleep time (3-5% stage I, 50-60% stage II, and 10-20% stages III and IV). REM sleep accounts for 10-25% of sleep time. REM sleep normally is not seen on routine EEGs, because the normal latency to REM sleep (100 min) is well beyond the duration of routine EEG recordings (approximately 20-30 min). The appearance of REM sleep during a routine EEG is referred to as sleep-onset REM period (SOREMP) and is considered an abnormality. While not observed on routine EEG, REM sleep commonly is seen during prolonged (>24 h) EEG monitoring. Representative examples of waveforms described here can be seen in Images 1-6. For excellent patient education resources, visit eMedicine's Procedures Center. Also, see eMedicine's patient education articles Sleep: Understanding the Basics, REM Sleep Behavior Disorder and Electroencephalography (EEG).
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