What Is REM Sleep? Why Is It Important For You

REM Sleep

REM sleep plays an important role in brain development as well as other functions including mood, dreaming, and memory. Read on to know what is this sleep stage all about and how can you make the most of it each night.

What Is REM Sleep?

Rapid eye movement (REM) sleep is one of the four stages that the brain goes through during the sleep cycle. This period of the sleep cycle usually takes place about 90 minutes after a person first falls asleep. It is marked by a number of physiological changes that include muscle relaxation, eye movement, faster respiration, and increased brain activity.1

(Positron Emission Tomography (PET) scan of the human brain when it is awake. The colour-coding depicts active cerebral brain areas (red) through to inactive areas (blue). When awake the brain is alert, with high brainwave activity. The awake brain shows activity which resembles the phase of REM (rapid eye movement) sleep when the brain is dreaming. 
Source: sciencesource.com)

Signs of REM Sleep

The brain and body go through a number of changes that are characteristic of this stage of sleep. Some key signs of REM sleep include:

  • Body temperature changes
  • Body twitching, particularly in the face, arms, and legs
  • Increased blood pressure
  • Increased brain activity that is similar to awake states
  • Increased heart rate
  • Increased oxygen use by the brain
  • Rapid eye movements
  • Rapid, irregular breathing
  • Sexual arousal

Most people also experience a state of temporary paralysis known as atonia.

Read What Your Sleeping Position Reveals About Your Personality

Impact of REM Sleep

This sleep stage plays an important role in brain development as well as other functions including mood, dreaming, and memory.


Dreams happen during the rapid eye movement (REM) stage of sleep. In a typical night, you dream for a total of two hours, broken up by the sleep cycle.2

Researchers do not fully understand the exact reasons why we sleep. They do know that newborns dream and that depriving rats of REM sleep greatly shortens their lives. Other mammals and birds also have REM sleep stages, but cold-blooded animals such as turtles, lizards, and fish do not.

Dreams can take place during any of the stages of sleep, but those that occur during REM sleep tend to be the most frequent and vivid.3

Read 25 Common Dreams and Their Meanings

Brain Development

Research suggests that Rapid Eye Movement sleep serves an important role in the development of the central nervous system (CNS) during infancy.4 The high activity levels in the brain during this stage of sleep may play a role in developing and strengthening neural connections. 

Read Mental Health: The 10 Types of Sleep Disorders


Dreams may be one way that the brain consolidates memories. The dream time could be a period when the brain can reorganize and review the day’s events and connect new experiences to older ones. Because the body is shut down, the brain can do this without additional input coming in or risking the body “acting out” the day’s memories.

Some researchers believe that dreams are more like a background “noise” that is interpreted and organized. This activation-synthesis theory suggests that dreams are merely the brain’s attempt to make sense of random signals occurring during sleep.5

Some people have more control over their dreams than others. For these people, the last thoughts before going to bed may influence the content of a dream.


REM sleep plays an important role in a number of functions, including learning and memory. Interruptions to REM sleep can sometimes result in problems. As a result, the lack of REM sleep is linked to several health concerns, including the following.

Increased Weight

Reduced REM sleep is associated with changes in leptin levels and may be associated with increased appetite and weight.6

Read 13 Terrifying Health Effects of Sleep Deprivation

Memory Consolidation

The pons also sends signals to cerebral cortex by way of the thalamus (which is a filter and relay for sensory information and motor control functions deep in the brain). The cerebral cortex is the part of the brain involved with processing information (learning, thinking, and organizing).

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