REM sleep phase: what is it and why is it fascinating?

Today, a large majority of the population knows or has heard about the concept of REM phase or REM sleep. We know that it is part of our sleep and that, at least, it presents some differences with respect to the rest of sleep, the non-REM.

Many people do not know what it is that makes this dream such a necessary element for us. That is why in this article we are going to make a brief comment about what REM sleep is, and its peculiarities.

• Related article: "Types of brain waves: Delta, Theta, Alpha, Beta and Gamma"

The phases of sleep

Sleep is an essential need for human beings and for most living things. Our body is a structure that continuously consumes energy, requiring the elements of our resting "machinery" to function properly.

Sleeping is essential. However, the dream is not something uniform that appears abruptly. In fact, during sleep there are various cycles composed of different phases, in which different functions are altered and in which our brain reduces or increases certain types of bioelectric activity

. Specifically, we usually have between 4 and 9 of these cycles, each divided into five phases. These phases usually follow a certain order.

First, in phase 1 we find ourselves in a phase of numbness, in which our consciousness gradually decreases despite the fact that with the minimum stimulation we can clear ourselves. Our brain mainly registers waves of the alpha type, which are the usual ones for states of relaxation even when we are awake.

Later and if nothing interrupts it, we enter a second phase, in which eye movements are completely reduced and there is a marked decrease in muscle tone. We are more and more relaxed and disconnected from the environment. If we observe with a electroencephalogram the functioning of the brain at wave level we observe how theta waves prevail, with the peculiarity that oscillations appear in brain activity in the form of K complexes and sleep spindles.

After these phases, both of light sleep, we would enter phases 3 and 4 of sleep, known as deep sleep. These are the phases in which a true rest of the organism takes place. Physical activity is practically non-existent for most people, although there is an increase in muscle tone. The night terrors and other parasomnias such as somnambulism They occur during these phases of sleep. The brain wave recording would show a general prevalence of delta waves.

These phases correspond entirely to non-REM sleep. But behind them, we can still find one more phase, the REM or MOR phase.

• Related article: "The 5 phases of sleep: from slow waves to REM"

The REM or MOR phase

The REM phase (REM being the acronym for Rapid Eye Movement) or MOR (Rapid Eye Movements), is one of the most important phases of sleep. It is characterized by the presence of high brain activity, which may be visible when performing rapid and constant eye movements.

It is considered out of sync sleep. Brain activity is similar to what we would have awake or in the phases of numbness, there are abundant theta waves with saw teeth (the latter especially characteristic of the parietal areas of the brain) and beta. The body remains completely immobile and paralyzed, with complete disappearance of muscle tone except in the eyes and diaphragm.

It is in the REM phase of sleep that dreams and nightmares appear, as well as the ability to remember them. There is also an increase in physiological activation (despite muscle atony), increasing blood pressure, heart and respiratory rate and the appearance of erections is common. As the cycles go by, the amount of REM sleep increases.

Main function of this stage of sleep

The functions of this type of dream are not clearly delimited. However, it is considered that during REM sleep we reorganize our mental contents, fixing the new memories and integrating them into memory at the same time that we discard those information or memories considered irrelevant. Thus, this type of dream turns the experience into a memory stored in long-term memory.

Likewise, it is during these phases that the highest level of brain development occurs, being essential for its maturation especially during the growth stage. It is considered out of sync sleep.

This it is not only important on a cognitive level, but also with regard to sensory processing, as studies such as those of Marcos Frank at the National Institute of Health of the United States seem to indicate, by allowing, for example, that the ERK protein (a protein that is only activated in this phase of sleep) finishes fixing the changes in the visual cortex and adjusting the connections that allow the development of perception visual. The same goes for other skills.

Evolution throughout the life cycle

Throughout life our biorhythms and our sleep cycles vary enormously. We do not sleep the same during our first year of life as at thirty, and even less than at eighty years.

Newborns, for example, spend a large part of the day sleeping, with around 50% of this time being in the REM phase. From the fourth month on, this percentage drops to 40% and begins to be preceded by non-REM sleep. As the child grows, the time spent awake increases and the amount of sleep decreases. At the approximate age of six years, sleep patterns and cycles stabilize, resembling an adult's sleep.

During adulthood, the approximate proportion of REM sleep is 20%, the rest being non-REM sleep. With age, the total sleep time is reduced and fragmented, especially when we reach the third age, with lots of nocturnal awakenings. The amount of sleep is dramatically reduced, including REM sleep. Despite this, a lower latency of REM sleep is observed (it takes less time to appear).

Bibliographic references:

• McCarley, R.W. (2007). Neurobiology of REM and NREM sleep. Sleep Med, 8.