REM sleep (REMS) has long been a field of interest for both the public and scientists who wanted to know more about what exactly happens during our sleep and why it is so. One of the reasons why REM has drawn so much attention may be the fact that out of all sleep stages our brains are the most active during REM, or that this is when we have the most vivid dreams. People who are REM sleep deprived experience a number of symptoms, such as eating disorders, memory and learning problems, emotional instability and more. So what makes this mysterious sleep stage so important?
What is REM sleep?
REM sleep or rapid eye movement sleep is the time of sleep during which eye muscles move quickly. REMS is one of four sleep stages – our body goes through three stages of light and deep Non-REM sleep before reaching the rapid eye movement (an example of a sleep cycle might look like this: Stage 1 – Stage 2 – Stage 3 – Stage 2 – REM). REM is the fourth stage of sleep. It’s worth noting that until 2008 Stage 3 was divided into two stages (3 and 4), which is why some sources present REM as the fifth stage.
Discovered in the 1950s, REM has been of high scientific interest ever since. When brain waves recorded by an EEG (electroencephalograph) are compared to those of a fully alert person, they show almost the same level of brain activity.
REM is also known as paradoxical sleep or desynchronized sleep because brain activity is on the high, eyes move rapidly, but the rest of the body experiences muscle atonia, or a kind or temporary paralysis. This happens when pons, a brain area from which REM sleep signals are sent out, blocks signals sent to the spinal cord. It leaves the body motionless so that we are safe from hurting ourselves while sleeping. If this wasn’t so, we would be able to act out our dreams freely and pose a threat to ourselves or others.
Is REM the same as deep sleep?
REM doesn’t equal deep sleep. Deep sleep is one of three NREM sleep stages – actually, it is the deepest NREM stage. Also known as slow-wave sleep or restorative sleep, it is very important for our health and we should make sure to have plenty of deep sleep every night.
How long does REM last?
The first REM phase lasts for about 10 minutes and happens about 90 minutes into sleep. As the night progresses, REM lasts longer – it can even take as much as one or two hours. During one night, people go through several sleep cycles, which means we reach the REM sleep stage about 3-5 times. We spend about 20% of our sleep time in this stage, so if you sleep seven or eight hours per night, you are likely to dream for about one hour and a half.
What happens during REM sleep?
There is a number of physical, physiological and cognitive processes which happen while we are in the REM stage of sleep:
- Brain activity increases while muscles remain paralyzed (REM atonia)
- Eyes move rapidly
- Breathing becomes irregular and shallow
- Heart rate increases
- Neural connections are formed (information from the day before is processed)
- Serotonin and dopamine levels are replenished
- Vivid dreams happen
- Brain waves are similar to those during wakefulness
Although it has been widely believed that dreams only occur during REM sleep, it has been recently discovered that dreams occur in NREM sleep as well. These dreams, however, are not as vivid as those during REM.
Why does REM sleep occur?
Even the scientists haven’t found a single explanation they all agree on. However, taking a look in the above list may help us easily understand some of the theories surrounding REM sleep.
REM – Learning and memory consolidation
REM sleep may help our learning – this is what most of us will agree with, considering that many people report dreaming of doing exactly those activities they had learned some time before. However, some authors claim that only certain parts of our learning, that is, our visual skills, are strengthened by REM. NREM seems to be in charge of learning movements and storing information from short-term into long-term memory.
One of the reasons which go in favor of REM being responsible for memory consolidation is that individuals who have been REM sleep deprived have issues learning and remembering. On the other hand, those who have had enough REM sleep before and after being exposed to new information were more likely to remember that particular information.
As stated above, experiences from the previous day are replayed in our dreams and that way memory is consolidated or strengthened. This happens with some help of the emotional center of the brain – the amygdala, which is also known to detect fear and respond to emergencies. Knowing that sleep deprivation negatively affects learning, memory, and emotional consolidation, some scientists have come to an interesting idea.
They have successfully treated trauma-exposed victims with sleep deprivation in order to prevent stressful events from consolidation. This study has shown hope for early treatment of possible victims of post-traumatic stress disorder (PTSD).
REM and brain development
According to the National Sleep Foundation, newborns spend about 50% out of their 12-16-hour sleep time in the REM stage. We know that new neural connections are formed in REMS, and this may be the reason why babies need it so much.
REM as a wake-up preparation
An author has hypothesized that REM may be a preparation of our body to wake up. Some of the arguments for the hypothesis are as follows:
- REM periods get longer and more frequent towards the morning
- A sleeper is the subject who observes or acts out dreams
- The last awakening in the night’s sleep happens either during or at the end of a REM stage
- Brain activity during REM is progressively increased to that which is required for wakefulness
This hypothesis seems to make even more sense once we consider the following changes which occur in REM and are not present in NREM: rising of body temperature, increased heart rate and breathing, accompanied by higher brain activity.
What are the benefits of REM?
There are numerous studies suggesting the benefits of those who get enough REM sleep.
- Better ability to read other people’s emotions. It has been proven that after reaching REM sleep, people are more able to recognize emotions on photographs showing various facial expressions.
- Emotional response to stress is lower. It seems that after a good night’s rest our emotional center the brain is less sensitive and more able to cope with difficult situations.
- Lower risk of developing Alzheimer’s disease. During sleep, our brain clears off of certain neurotoxins, including those found in Alzheimer’s disease patients. Having plenty of sleep may be connected with lowering the risk of this disease.
- Better memory. A study has shown that REM sleep deprivation in rats reduces proliferation of cells in the part of the brain which takes part in long-term memory.
- Higher learning abilities. Getting the needed REM sleep is linked to better learning – individuals who were not able to reach REM demonstrated an inability to reproduce what they had been taught before falling asleep.
- Better mood. Not only does REM make us less prone to stress, but it also replenishes neurotransmitters that are responsible for good mood – serotonin and dopamine.
- Higher creativity. Some studies have shown that problem-solving capability was higher in those who have had REM sleep. Such capability was not observed in individuals who experienced Non-REM sleep only.
What are the consequences of not having enough REM sleep?
If you fall asleep, it doesn’t guarantee you will reach REM. These are the consequences of not having enough REM sleep:
- Reduced coping mechanisms. Skills needed in dangerous situations may become ineffective after a period of REM sleep deprivation.
- Frequent migraines. Lack of REM sleep may lead to migraines due to change of levels in certain proteins.
- Excessive weight. Individuals who don’t get enough sleep are prone to being overweight.
- Higher risk of anxiety, due to over-stimulated amygdala.
- Bad memory and learning skills.
Bear in mind that certain substances may reduce REM, such as alcohol. Although nightcap is a happy solution to many who want to fall asleep fast, it delays and reduces REM sleep. Apart from that, it increases the number of bathroom visits, which breaks up our sleep and interferes with our circadian rhythm. Many widely used drugs inhibit REM as well, such as amphetamines, for example.
Disorders linked to REM
REM sleep behavior disorder (RBD) is a sleep disorder characterized by REM sleep without atonia. This may be dangerous as numerous instances were recorded where otherwise calm individuals would turn violent towards their spouses. While dreaming about defending themselves or their families from dangers, they would kick or punch their spouses, causing injuries to them. However, RBD shouldn’t be compared to sleepwalking, which happens during NREM.
Those who run the highest risk of developing RBD are:
- white males over 50
- drug or alcohol addicts weaning off
- those who have stopped using sedatives
- those who currently take Mirtazapine, Selegiline, Tri-Cyclic and other types of antidepressants
- those who suffer from Parkinson’s disease
- those who have narcolepsy.
Narcolepsy is a disorder in which excessive daytime sleepiness is followed by suddenly falling asleep – directly into the REM stage. Another symptom is vivid hallucinations which appear just before falling asleep. This means that REM onset has happened during wakefulness, making dreams interfere with wakefulness.
Sleep paralysis happens after a person wakes up from a REM stage, but even though partially or fully conscious, is still unable to move. Sleep paralysis doesn’t pose a life threat, even though it is highly uncomfortable – it may be followed by REM episodes in which a person feels an unknown presence in the room or inability to breathe properly. Sleep paralysis rarely occurs with those who are well rested and healthy.
Both narcolepsy and sleep paralysis are linked to the brain systems responsible for switching between sleep and wakefulness known as the flip-flop switch.
How to get more REM sleep?
As it is a part of your regular sleep cycle, you can’t just isolate REM sleep and improve it. To make sure you have enough REM sleep, you should take care of your overall sleep habits.
- Respect your circadian rhythm. Get plenty of sleep every night by keeping a regular sleep schedule.
- Avoid alcohol and nicotine. Don’t drink any amounts of alcohol to ensure you get your REM. Nicotine is also known for interfering with REM sleep.
- Seek help for sleep disorders. People who suffer from obstructive sleep apnea stop breathing several times a night, which causes frequent wakings and disrupts a normal sleep cycle. The more you wake up, the less REM you get. Using CPAP machine to treat sleep apnea may help in REM normalization.
- Avoid nightly wakings. Make your sleep environment calm and quiet. Turn your phone off and don’t drink liquids which may cause frequent toilet visits.
- Don’t use your phone or computer before bed. Artificial lights may interfere with your sleep by confusing your circadian rhythm and delaying the onset of REM.
- Exercise for at least 30 minutes every day. Being active during the day helps your body function properly and promotes sleep. If possible, spend some time outside in the sunlight and avoid exercising before bed.
What is REM sleep rebound?
REM rebound is a change in sleep cycles caused by REM sleep deprivation. It happens after a period of not having REM sleep followed by a chance to ’catch up’ on the lost sleep. Our brain then tends to quickly cycle through the first three stages of sleep, reaching REM earlier and staying in it for a longer period of time. Patients struggling with untreated sleep apnea are likely to experience REM rebound once they start getting treatment.
Although having a REM sleep rebound means your brain is trying to make up for the lost REM, it doesn’t mean you are getting better sleep. While increasing the length of the REM stage, your brain is cutting back on other important sleep stages, such as Stage 2 and Stage 3. Sleep 3 (deep sleep) is known as restorative sleep during which cell restoration is promoted and the brain is prepared for new learning.
Too much REM sleep isn’t good
Having too little REM sleep is known to cause anxiety and irritability. The same goes for having too much sleep. We spend about 20% of our sleep time in REM, but if this percent gets much higher, or if you just sleep a lot longer than needed, there is a risk of getting too much REM sleep.
Being angry and irritable for a long time may lead to depression. A study has shown that depression can be successfully treated by sleep deprivation. Certain brain areas that were hyperactive in depressed individuals were normalized after a period of sleep restriction. Antidepressant benefits of this therapy were seen in the dopamine release correlated with the lack of sleep.
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