New Discoveries Question Our Understanding of Sleep

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Written by Baginda Tirtadji

On October 23, 2019

How much do we really know about sleep? We go to sleep every day for several hours, without thinking about how that process works. Sleeping is essential as breathing, and no matter how long we try to stay awake, eventually we will fall asleep. While we are sleeping, many vital processes are going on in our body, so our brain is not really resting, it is actually bursting with activity.

Have you ever wondered how do we fall asleep, and what happens in our brain when we start feeling tired? For a long time, this was one of many sleep-related mysteries. There is no such thing as a magical button or brain’s sleep switch to turn the lights off in our brain. However, recently, researchers from Aarhus University and the University of Oxford managed to make significant progress in this field with their international study about brain dynamics and transitions during Non-REM sleep and periods of wakefulness. 

 

How Much Do We Know About Sleep so Far?

During our sleep, every 90 to 120 minutes, we go through one sleep cycle, meaning that over the course of one night, we complete four or five sleep cycles. The first one is always the shortest, and it lasts around 90 minutes, after that every next one will last from 100 to 120 minutes. Every sleep cycle consists of four different stages of sleep.

Once we start falling asleep, first we go through three stages of Non-REM sleep, and then we fall into the REM stage. Stage 1 of Non-REM is the drowsy one, it does not last long, and it can be described as light sleep, or transition from wakefulness to sleep. You can still hear sounds, or be easily awoken, although your brain has stepped into sleep, you are not entirely aware that you are sleeping. 

After that comes the stage 2, which lasts significantly longer, making around 40-60% of our sleep time. This stage is also the stage of light sleep, but it is not so shallow as it is in the first stage. During this phase, our brain is processing memories and emotions, our metabolism is regulating, so there is still a lot going on, while our heart rate and breathing are slowly decreasing.

Stage 3 lasts longer in children, but in adults, it is quite short, this stage of deep sleep is also known as restorative. This is when our body and muscles get relaxed, and our body produces growth hormone, regulates its immune system; basically, it nurtures itself from the inside. Together, these three stages last roughly around 90 minutes, after that comes the REM sleep. 

While during the third stage of NREM it is all about the body, in REM, the central activity occurs in our brain. The REM stage is a phase when our dreams occur, the brain’s activity is at its highest, eyes are moving rapidly, heart rate increases, etc. After REM, the cycle goes again from the beginning, and we go again from the N1 stage through the REM. The first REM is the shortest, but as the night progresses, every next one will last slightly longer.

 

The Case Study

We spend one-third of our lives sleeping, so it is not surprising that many scientists are fascinated by sleep, and everything related to it. Researchers from Denmark and the US have joined their forces to question one particular problem that is common for both nations, sleep issues since both countries have a high percentage of the population dealing with various sleep disorders. They believe that their findings can be potentially revolutionary in terms of understanding what happens in our brain while we are sleeping. Besides that, it could also be significant for improving treatments and fighting sleep disorders.

So far, our understanding of sleep was based on classifying sleep into different stages; however, how the underlying brain dynamics work was not clear. Dividing sleep into stages is based on many conventions, which are not outdated, but they do not explain precisely enough what is going on in our brain. For the purpose of this study, researchers gathered 57 healthy adults and used Markovian data-driven way of analyzing continuous neuroimaging while participants were falling asleep. At the same time, they were simultaneously performing fMRI and EEG. By doing so, they were able to get a detailed and more precise idea of sleep, as a result of multiple brain networks that communicate through different patterns during sleep.

Their findings showed that our wake-NREM sleep complex is much more complex than we believed, certainly more than the traditional division into stages was suggesting. They used those transitional stages and projected them onto a probabilistic map of different relationships between whole-brain networks. By examining those transitions, researchers noticed a lowered whole-brain dynamics during the NREM stages. They consider that the activity of the brain network does not correspond to the traditional criteria for defining N1 sleep. Also, they find out that the activity in our brain is not on the same level before and after sleep. 

However, at the moment, their results are still not enough to understand what is going on in the brain of a person who suffers from insomnia, or what the role of sleep is in mental disorders. But, researchers are hoping that the next steps in their work will provide more information and success.

 

Key Takeaway

This type of research represents a modern outlook on something that was accepted and became a convention a long time ago. This is a step forward in understanding and getting to know more about the brain’s activity during sleep, and with every further research, it is going to get more and more complicated. Traditional sleep stages are not wrong; they can still be accepted as a simplified version of what is going on. However, with the progress of modern science, we can only expect that researches like this one will eventually break that division and come up with a new one, more detailed, more complicated, and more accurate.

This guest article was written by Selena Thomas. Selena Thomas is a content writer who loves sharing tips on healthy lifestyles. A writer by day and a reader by night, she’s fond of writing articles that can help people in improving both physical and mental health. Also, she loves traveling and inspires people on her blogs.

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