What happens in REM sleep ?

REM sleep is one of the five sleep phases we go through every night and is often referred to as dream sleep. We explain here what exactly happens in REM sleep and why it is so important for our health and brain performance.

Table of contents

1. sleep phases at a glance
2. What happens during REM sleep?
3. Why do we need REM sleep?
4. How much REM sleep do we need?
5. REM sleep disorders
6. Conclusion

1. Sleep phases at a glance

Every night we go through several sleep cycles, which are divided into different sleep phases The falling asleep and light sleep phase is followed by deep sleep, which then changes into the well-known REM sleep. REM stands for "Rapid Eye Movement" because in this stage the eyes move quickly back and forth under the closed eyelids.

In each phase of sleep, various important bodily processes take place, all of which contribute to making sleep restful overall. While deep sleep is primarily about energy balance and growth processes, REM sleep is fundamental to cognitive and emotional processing that takes place in the brain. It is also known as dream sleep because dreams are experienced particularly intensely and remembered more often here.

2. What exactly happens during REM sleep?

REM sleep is the last phase of a sleep cycle and follows immediately after regenerative deep sleep. Blood flow and brain activity increase, blood pressure rises, and heart rate and breathing become more irregular. In the EEG Instead of the slow delta waves that dominate deep sleep, higher frequency theta waves are measured. Scientific studies have also shown that the areas of the brain responsible for processing emotions (the limbic system) are even more active than when awake, while the brain regions responsible for planning thinking, such as the prefrontal cortex, show less activity than when awake.

This contributes to dreams are experienced particularly intensely in REM sleep. The body is in what is known as sleep paralysis, in which the brain stem blocks the transmission of commands to the muscles. The only movement that should then take place is the characteristic horizontal eye movement. This mechanism protects the dreamer from acting out the dream events and injuring themselves or others with uncontrolled movements.

The likelihood of waking from REM sleep is generally greater than from deep sleep because it is the last phase of a sleep cycle and is associated with higher brain activity and alertness.

3. Why do we need REM sleep?

During REM sleep, many important processing and learning processes take place in the brain and procedural memory, which forms the basis for subconscious skills such as automated movement sequences and motor learning, is formed. In addition, the emotions and experiences of the day are processed. REM sleep therefore plays an important role in cognitive performance and mental and emotional health.

4. How much REM sleep do we need?

newborns and toddlers require more REM sleep than adults for brain development and memory formation and therefore spend almost half of their sleep in the REM phase, i.e. around 8 hours a day. However, with age, the sleep structure changes and the proportion of REM sleep decreases.In adulthood, we still spend about 2 hours per night in REM sleep.

We provide more information on the changes in sleep structure with age here.

5. Disorders of REM sleep

Too little REM sleep

Less REM sleep is associated with poorer physical and mental health and, according to studies, can also worsen mortality. In addition, too little REM sleep appears to negatively affect learning processes and cognitive performance.

REM sleep behavior disorder (RBD)

In REM sleep behavior disorder, the sleep paralysis not or only partially, and muscle movements are no longer suppressed correctly during dreams. This leads to those affected acting out their dream experience by moving in bed, sitting up, kicking around or expressing themselves verbally, e.g. by talking, screaming, laughing or swearing.

According to studies, people with REM sleep behavior disorder have an 80% chance of suffering from a neurodegenerative disease such as Parkinson's or Alzheimer's within the next 15 years.

narcolepsy

Narcolepsy is a neurological dysfunction of the areas of the brain that control sleep and wakefulness. It changes sleep-wake behavior and manifests itself, among other things, in extreme sleepiness or uncontrollable bouts of sleep during the day, in which those affected suddenly tire in unusual situations and go from being awake directly into REM sleep. We explain what exactly happens with narcolepsy here.

nightmare disorder

Due to the intense dream experience, nightmares particularly common in REM sleep. When processing emotions, stressful, frightening or distressing dream content can arise and lead to negative dream experiences.

6. Conclusion

• REM sleep is one of five sleep stages that occur every night.

• During REM sleep, intense dreaming as well as emotional and cognitive processing take place.

• Healthy adults spend about 2 hours in REM sleep each night.

• Too little or disturbed REM sleep can harm health and performance in the long term and promote neurodegenerative diseases such as Alzheimer's or Parkinson's.

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