Definition: NREM sleep, also called non-REM sleep, consists of four stages of deep, restful sleep.

Quite Simply...


  • About every 90 minutes during sleep, we enter REM sleep which is marked by rapid eye movement (REM). It is in this stage that we experience dreaming. In between these stages of REM sleep there are periods of non-rapid eye movement, or NREM sleep,
  • There are 4 different stages of nREM (Stages 2-5) and each of them can last from 5-15 minutes.
  • Sleep talking and sleepwalking happen during NREM sleep.
  • As sleep time goes on, a sleeper will spend less and less time in the lower stages of NREM.

Stages of NREM Sleep...


  1. N1, Light Sleep: Marked by theta waves; this stage is the period right after someone falls asleep, and most of the time if they are wakened, they don't believe they fell asleep in the first place. People in this stage also experience vivid visual events called hypnogogic images or hallucinations (These are commonly interpreted as ghost visits, alien abductions, etc.)
  2. N2, Sleep Spindles: Marked by sleep spindles; as people drift further into sleep, the heart-rate begins to slow, and breathing becomes shallow and irregular.
  3. N3 (Stages 3 and 4), Deepest Sleep: Marked by delta waves; This is the deepest stage of sleep, often referred to as slow-wave sleep. The body is now at the lowest level of functioning, and the pituitary gland is now releasing the peak amount of GH (growth hormone). Adults and children alike are very hard to wake at this stage, but especially children because their bodies are hard at work growing and repairing themselves.

See Also...


  • REM Sleep - Rapid Eye Movement Sleep; The opposite of NREM sleep, REM consists of dreams, sleep paralysis, and emotional recovery.
  • Consciousness is the level of alertness about the world around you; NREM is an altered state of consciousness.
  • Sleep is a part of your Circadian Rhythms , it's your 25-hour biological clock.

Crash Course video on Sleep:


Sleep Cycle Graphs...


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