Tonic is one of the categories of REM sleep. REM sleep in adult humans typically occupies 20–25% of total sleep, about 90–120 minutes of a night’s sleep. During a normal night of sleep, humans usually experience about four or five periods of REM sleep; they are quite short at the beginning of the night and longer toward the end. The function of REM sleep is not well understood; several theories have been proposed.


~ by mladenkesic on 29. May 2011..

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