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TableĀ 1 Sleep terminology

From: Sleep abnormalities associated with alcohol, cannabis, cocaine, and opiate use: a comprehensive review

Homeostatic sleep drive The drive to sleep that progressively builds with continued wakefulness
Insomnia A sleep disorder in which the quantity or quality of sleep is less than desired, usually characterized by difficulty falling or staying asleep, or waking too early, and experiencing daytime consequences of reduced sleep
Polysomnography (PSG) A technique that records brain activity, eye movements, and muscle tone in order to study sleep and diagnose sleep disorders
Rapid eye movement (REM) sleep The phase of sleep characterized by conjugate eye movements, paralysis of other muscles, and brain activity that is most similar to wakefulness
REM density The frequency of rapid eye movements occurring during REM sleep. REM density increases over the course of the sleep period and is greatest when homeostatic sleep drive (sleep pressure) is lowest
REM latency The amount of time from the onset of sleep to the onset of REM sleep
REM rebound The characteristic increase in REM sleep after REM sleep deprivation
Self-administration A method involving research participants administering a substance to themselves under observation in a clinical setting
Sleep architecture The structure of sleep, including non-REM (stages N1, N2, and N3) and REM (stage R) sleep
Sleep efficiency (SE) The percent of time in bed spent sleeping, calculated as total sleep time divided by time in bed
Sleep fragmentation Disruption in sleep characterized by awakenings and transitions to light (stage N1) sleep from deeper sleep
Sleep latency (SL) The amount of time from lights out to sleep onset
Slow-wave sleep (SWS) Also known as stage N3 sleep, slow wave sleep is characterized by low frequency and high amplitude waves
Total sleep time (TST) The amount of sleep in one complete episode of sleeping, usually reported in minutes
Wake after sleep onset (WASO) The amount of time awake after the onset of sleep and before final wakening