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

Here’s what experts had to say about the new study, how REM sleep and Alzheimer’s could be connected, and ways to increase your chances of getting healthy sleep. —Maggie O'Neill, Health, 6 Feb. 2025

Good sleep practices may help improve REM sleep and minimize dementia risk. —Tom Gavin, EverydayHealth.com, 4 Feb. 2025

The connection between the two measures wasn’t as tight when the animals were awake or in the other main sleep phase, REM sleep, when memories are consolidated. —Bymitch Leslie, science.org, 8 Jan. 2025

How To Sleep To Reduce Alzheimer's Risk The researchers advise people who are concerned about their own risk of Alzheimer's to practice healthy sleep habits that can help ease the transition from light into REM sleep. —Barbara A. Perry, Newsweek, 27 Jan. 2025

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