REM sleep

noun

: a state of sleep that recurs cyclically with non-REM sleep several times during a normal period of sleep, is characterized especially by greatly depressed muscle tone, dreaming with vivid imagery, rapid eye movements, and increased neuronal activity in certain brain regions (such as the pons), and typically comprises up to 25% of time spent in sleep

REM sleep, it soon became apparent, occurs in intervals throughout the night, usually four to six times, each lasting from ten minutes to an hour.

—Martin Gardner

People awakened during REM sleep usually report dreams with visual images and storylike narratives.

—Lis Harris

called also paradoxical sleep, rapid eye movement sleep

compare slow-wave sleep, non-REM sleep

Examples of REM sleep in a Sentence

Recent Examples on the Web

Cycles of REM sleep primarily occur in the last third of the night. —Lynne Peeples, TIME, 6 Jan. 2025

Essentially, sleep is divided into two stages – non-rapid eye movement (non-REM, which the researchers refer to as NREM) sleep and REM sleep – and it's widely understood both play distinct roles in memory and cognitive function. —New Atlas, 2 Jan. 2025

During a typical seven- to nine-hour night of sleep, most adults cycle through four to six cycles of non-REM (NREM) and REM sleep stages.1 Is REM or Deep Sleep Better? —Sohaib Imtiaz, Verywell Health, 10 Dec. 2024

According to a study from the Journal of Physiological Anthropology, heat exposure increases wakefulness and decreases time spent in deep sleep and REM sleep. —Nicole Kinning, WIRED, 21 Nov. 2024

Word History

First Known Use

1963, in the meaning defined above

Medical Definition

REM sleep

noun

: a state of sleep that recurs cyclically with non-REM sleep several times during a normal period of sleep, is characterized especially by greatly depressed muscle tone, dreaming with vivid imagery, rapid eye movements, and increased neuronal activity in certain brain regions (as the pons), and typically comprises up to 25% of time spent in sleep

REM sleep, it soon became apparent, occurs in intervals throughout the night, usually four to six times, each lasting from ten minutes to an hour.

—Martin Gardner

People awakened during REM sleep usually report dreams with visual images and storylike narratives.

—Lis Harris

called also desynchronized sleep, paradoxical sleep, rapid eye movement sleep

compare non-rem sleep