non-REM sleep

noun

ˈnän-ˌrem- 

variants or NREM sleep

ˈen-ˌrem- 

: a state of sleep that occurs regularly during a normal period of sleep with intervening periods of REM sleep and is characterized by delta wave brain activity, little dreaming, and a reduced level of autonomic physiological activity

Non-REM sleep is a quiet sleep state. The muscles are relaxed but maintain some tone, breathing is regular, the cerebral cortex generates high-voltage waves, and consumption of energy by the brain is minimal.

—Jerome M. Siegel

For most people the few dreams found in non-REM sleep tend to have a rather thought-like character. During REM sleep, on the other hand, dreams occur more frequently and usually have a perceptual vividness …

—Francis Crick et al.

NREM sleep … is crucial to memory retention, and to acquiring and refining our motor skills.

—David Kamp

compare rem sleep, slow-wave sleep

Examples of non-REM sleep in a Sentence

Recent Examples on the Web

By injecting the animals with a fluorescent molecule that can trace the flow of cerebrospinal fluid, the researchers found that its levels, too, varied with norepinephrine levels during non-REM sleep. —Bymitch Leslie, science.org, 8 Jan. 2025

The previous night included at least six hours of sleep Sleep architecture (the pattern of rapid eye movement (REM) and non-REM sleep) was normal. —Anna Giorgi, Verywell Health, 12 Feb. 2025

According to the study, the correlation between the release of norepinephrine and changes in brain blood volume was stronger during the restful non-REM sleep than during the more active REM sleep or waking hours. —Margherita Bassi, Smithsonian Magazine, 10 Jan. 2025

Through this, the team was able to see that new memories were replayed and cemented in the brain during a fleeting moment in one of the non-REM sleep stage subsets, which corresponded with the animals' pupils appearing contracted. —New Atlas, 2 Jan. 2025

Though the eyes tend to stay stationary during non-REM sleep, the pupils oscillate between small and large diameters, reflecting the different substages and depths of slumber throughout the non-REM phase. —Sam Walters, Discover Magazine, 1 Jan. 2025

As the night goes on, the cycles contain less non-REM sleep and more REM sleep. —Beth Ann Malow, Discover Magazine, 24 Nov. 2024

Sleepwalking and sleep talking, which occur more often during childhood and adolescence, take place during non-REM sleep. —Diana Kwon, Scientific American, 1 Feb. 2023

Sleep research has shown that parasomnias often arise during the transitions to and from non-REM sleep. —Steve Nadis, Discover Magazine, 26 Nov. 2023

Word History

First Known Use

1963, in the meaning defined above

Rhymes for non-REM sleep

• asleep
• upkeep
• beep
• cheap
• creep
• deep
• heap
• jeep
• keep
• leap
• peep
• reap

Medical Definition

non-REM sleep

noun

-ˌrem- 

variants or NREM sleep

ˈen-ˌrem- 

: a state of sleep that occurs regularly during a normal period of sleep with intervening periods of REM sleep and is characterized by delta wave brain activity, little dreaming, and a reduced level of autonomic physiological activity

Non-REM sleep is a quiet sleep state. The muscles are relaxed but maintain some tone, breathing is regular, the cerebral cortex generates high-voltage waves, and consumption of energy by the brain is minimal.

—Jerome M. Siegel

NREM sleep … is crucial to memory retention, and to acquiring and refining our motor skills.

—David Kamp

called also orthodox sleep, S sleep, synchronized sleep

compare rem sleep, slow-wave sleep