What happens in REM sleep?

REM sleep is one of the five sleep phases that we go through every night and is often referred to as dream sleep. Here we explain what exactly happens during 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 in REM sleep?
3. Why do we need REM sleep?
4. How much REM sleep do we need?
5. Disorders of REM sleep
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 phases are followed by deep sleep, which then transitions 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 sleep phase, various important body processes take place, all of which contribute to ensuring that sleep is overall restful. While deep sleep focuses primarily on energy balance and growth processes, REM sleep is fundamental for cognitive and emotional processing processes that take place in the brain. It is also known as dream sleep because dreams are experienced particularly intensively here and are remembered more often.

2. What exactly happens in REM sleep?

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

This contributes to the fact that dreams are experienced particularly intensely during 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 dreamers from acting out the dream event and injuring themselves or others with uncontrolled movements.

You are usually more likely to wake up from REM sleep than from deep sleep because it is the final 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 plays an important role, especially for cognitive performance and mental, emotional health.

4. How much REM sleep do we need?

Newborns and small children need 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 amount of REM sleep decreases. In adulthood we spend approx. 2 hours per night of REM sleep.

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

5. REM sleep disorders

Too little REM sleep

Less REM sleep is linked to poorer physical and mental health and research shows it 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, Sleep paralysis does not occur or only partially occurs and muscle movements are no longer correctly suppressed during dreaming. This leads to those affected acting out their dream experience by moving in bed, sitting up, kicking or expressing themselves verbally, e.g. b by speaking, shouting, laughing or swearing.

According to studies, those affected by REM sleep behavior disorder have an 80% chance of suffering from a neurodegenerative disease such as Parkinson's or Alzheimer's in the following 15 years.

Narcolepsy

Narcolepsy refers to 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 sleep attacks during the day, in which those affected suddenly become tired, even in unusual situations, and go directly from the waking state into REM sleep. We explain here what exactly happens with narcolepsy.

Nightmare Disorder

Due to the intense dream experience, Nightmares are experienced particularly frequently during REM sleep. When processing emotions, stressful, frightening or stressful dream content can arise and lead to negative dream experiences.

6. Conclusion

• REM sleep is one of 5 sleep phases that occur every night.

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

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

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

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