LivingWhy do we dream?

Why do we dream?

You run and never reach your destination. You fall off a cliff, but you never reach the end. At the most beautiful moment, you wake up…

Although many studies deal with them, dreams remain a great mystery to scientists today. What happens to the brain while dreaming? And what determines that we have a nice dream or that we have nightmares?

Dreams are realistic or fantastic stories that our brain creates while we sleep . Although they last a short time, they are repeated several times during the night, so sleep can last up to two hours.

When studying the dream , it can be done from a neuroscientific approach, where the structures that intervene in the production and organization of dreams are studied, or from a psychoanalytic approach, which is more oriented to the interpretation of the meaning of dreams.

sleep stages

The dream is not uniform. Generally, in one night there can be between 4 and 6 sleep cycles, which in turn are divided into several phases depending on the brain probes that are activated. That is why sometimes we do not remember what we have dreamed, or even think that we have not dreamed at all, because depending on the moment in which the person wakes up, they may or may not remember a dream.

It should be noted that not all cycles last the same. The first cycle is usually the shortest, 70-100 minutes, while later cycles are around 90-120 minutes. Also, sleep cycles can vary from person to person, and from night to night.

If we stop to analyze each of the cycles, we find that they are divided into four stages that show different patterns of brain activity throughout sleep.

The first stage is numbness , when the body is relaxing, and it usually lasts less than five minutes. It is the transition between being awake and going to sleep, and as you can imagine it is quite easy to wake someone up at this stage, but if they are not disturbed they will go to the next stage.

The second stage is light sleep and represents about half of total sleep. In it, it lowers body temperature and heart rate, in addition to relaxing muscles and breathing. At the same time, the pattern of brain waves changes from slow with occasional fast waves.

The third stage is deep sleep , so it becomes more difficult to wake someone up at this point in sleep, and when they wake up, the person needs time to get their bearings. In this stage, muscle tone, pulse rate, and respiratory rate continue to decrease as the body relaxes, while brain waves are extremely slow (delta waves). Generally lasting between 20 and 40 minutes, it tends to get shorter as the night goes on, “giving its time” to the REM sleep phase.

As for the stage of REM sleep ( Rapid Eye Movement ), there is a radical change, in which brain activity increases, approaching the activity levels of when a person is awake. For its part, the body loses tone completely, giving rise to a temporary muscular paralysis of the entire body, except for the eyes, which move very quickly and irregularly (hence its name), and the respiratory muscles, which increase the respiratory rate. They also increase blood pressure and heart rate. Generally, the REM phase begins after approximately 90 minutes of sleep. In the first cycles, this stage only lasts a few minutes, but as the night progresses, they lengthen and can last an hour. Under normal conditions, it represents 25% of the total sleep of an adult.

As for the act of dreaming, it can occur in any of the stages, but dreams are more vivid and frequent during the REM phase , due to the significant increase in brain activity.

What is the purpose of dreams?

It is not known exactly if there is a purpose per se, but one of the theories is that dreaming helps memorize and order important and complicated information . It is unknown how dreams affect information storage and block stimuli that could interfere with memory.

Still, research shows that if important information is learned before the sleep cycle, it is much easier to remember or reproduce than immediately after learning. This is because during sleep there is an adequate ordering and storage of information, and it is much easier to remember it.

But not everything is positive, although many wish it, sleep does not erase repressed memories , on the contrary, they return through dreams. In other words, repressed thoughts during the day return during sleep, causing stress and negative emotions. And even if you think that you have already forgotten about a topic, curiously, it may appear in your dreams up to 7 days after the last time you had it in mind.

Something that should be noted is that external stimuli affect emotions during sleep . If you have had a good day, you have been given a gift, or you have seen a romantic movie, it is most likely that you will have dreams related to positive themes, while if the movie is a horror movie, you have been given bad news, or you have had bad news. had sad thoughts before going to sleep, dreams will generate negative emotions.

It is not known exactly why there are some dreams that we remember, others that we forget a few minutes after waking up, and others that we do not forget, but it is believed that when we remember what we have dreamed it is because we have woken up in the middle of the cycle , when we were still actively dreaming .

Dreams, like sleep, are part of a cycle that the body needs to be emotionally and physically adapted to the events and feelings of everyday life. It helps us get rid of fatigue and unnecessary information, as well as store necessary and important memories.

References:

Cai, D.J., Mednick, S.A., Harrison, E.M., Kanady, J.C & Mednick, S.C. (2009, 23 de Junio). REM, not incubation, improves creativity by priming associative networks. PNAS, 106(25). https://doi.org/10.1073/pnas.0900271106
Eiser, A. S. (2005, Marzo). Physiology and Psychology of Dreams. Seminars in Neurology, 25(01), 97–105. https://doi.org/10.1055/s-2005-867078
‌Fischer, S., Diekelmann, S., & Born, J. (2010, 17 de Agosto). Sleep’s role in the processing of unwanted memories. Journal of Sleep Research, 20(2), 267–274. https://doi.org/10.1111/j.1365-2869.2010.00881.x
Kröner-Borowik, T., Gosch, S., Hansen, K., Borowik, B., Schredl, M., & Steil, R. (2013, 16 de Mayo). The effects of suppressing intrusive thoughts on dream content, dream distress and psychological parameters. Journal of Sleep Research, 22(5), 600–604. https://doi.org/10.1111/jsr.12058

Malinowski, J. E., & Horton, C. L. (2014, 19 de Febrero). Memory sources of dreams: the incorporation of autobiographical rather than episodic experiences. Journal of Sleep Research, 23(4), 441–447. https://doi.org/10.1111/jsr.12134
‌Patel, A. K., Reddy, V., & Araujo, J. F. (2021, 22 de Abril). Physiology, Sleep Stages. Nih.gov; StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK526132/
Rasch, B., & Born, J. (2013, 1 de Abril). About Sleep’s Role in Memory. Physiological Reviews, 93(2), 681–766. https://doi.org/10.1152/physrev.00032.2012

Schönauer, M., & Pöhlchen, D. (2018, 8 de Octubre). Sleep spindles. Current Biology, 28(19), PR1129–PR1130. https://doi.org/10.1016/j.cub.2018.07.035
Suni, E. (2021, 20 de Diciembre). Stages of Sleep. Sleep Foundation. https://www.sleepfoundation.org/stages-of-sleep
‌Tirapu-Ustarroz J. (2012, July 16). Neuropsychology of dreams. Journal of Neurology , 55(2), 101–110. https://doi.org/10.33588/rn.5502.2012149
Vectorpouch (s.f.). Whale swims in deep space illustration Free Vector [Imagen]. Flickr. https://www.freepik.com/vectorpouch

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