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Sleep-Wake Disorders: Lifespan Perspectives

Sleep is defined by both behavioral and physiologic criteria. The behavioral characteristics of sleep consist of dramatically reduced movement, a blunted response to external stimuli, and reversibility (unlike death, which shares the first two behavioral criteria with sleep but is not reversible). Physiologically, sleep is determined by specific changes in brain waves, eye movements, and muscle tone, as recorded on a polysomnogram.

The sleep of infants is made up of either active sleep (rapid eye movement [REM] or REM-like) or quiet sleep (non-REM [NREM] or NREM-like). By approximately 6 months of age, babies develop more clearly defined sleep stages. These include the NREM stages of N1, N2, and N3, as well as REM sleep. N1 sleep is light and transitional, N2 has a higher arousal threshold ...

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