Sleep-Wake State Stability
A normal sleep-wake cycle requires the coordinated timing and stability of three distinct states: wakefulness, non-REM sleep, and REM sleep.1-5
Three sleep-wake states are defined by distinct neurophysiologic characteristics.3,5
What is wakefulness?
Normally, wakefulness is promoted during the day by multiple interconnected neuronal systems, including acetylcholine, dopamine, histamine, norepinephrine, and serotonin neurons.1,2 Wakefulness is characterized by high muscle tone and fast-frequency neuronal activity that is necessary for alertness and higher-order neurocognitive functioning.3,5
What is non-REM sleep?
Non-REM sleep is a sleep state with slower-frequency neuronal activity and light to deep stages of non-REM sleep.3,5 Skeletal muscle tone is lower than during wakefulness.3,5 Nighttime sleep normally begins with an episode of non-REM sleep.3
What is REM sleep?
During REM sleep, which is associated with dreaming and skeletal muscle atonia, neuronal activity is faster and desynchronized, with distinct wave patterns (e.g., sawtooth waves) on electroencephalogram (EEG).3,5,7 Episodes of REM sleep typically occur at night after non-REM sleep and become longer over the course of the night.3
Circadian timekeeping coordinates sleep and wakefulness with the daily light/dark cycle.3
A normal sleep-wake cycle is generally characterized by consolidated wakefulness during the day and predictable, alternating periods of non-REM and REM sleep at night, with generally infrequent awakenings.2,3,7
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- Scammell TE. The neurobiology, diagnosis, and treatment of narcolepsy. Ann Neurol. 2003;53(2):154-166.
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- Broughton R, Valley V, Aguirre M, Roberts J, Suwalski W, Dunham W. Excessive daytime sleepiness and the pathophysiology of narcolepsy-cataplexy: a laboratory perspective. Sleep. 1986;9:205-215.
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