MIB challenges the traditional understanding of human sleep stages in a new study

08. March 2019

Researchers from the DNRF’s Center for Music in the Brain (MIB) at Aarhus University are leading an international study that, by mapping underlying sleep patterns, challenges the traditional understanding of human sleep stages. The study was recently published in the scientific journal Nature Communications.  

(Photo: Ömürden Cengiz/Unsplash)
(Photo: Ömürden Cengiz/Unsplash)

An international research team led by the DNRF’s Center of Excellence MIB has recently published a study in the scientific journal Nature Communications. In the study, researchers, for the first time, map underlying sleep patterns and dynamics in the brain. The participants from MIB include lead author post-doc Angus Stevner, senior author Professor Morten Kringelbach, and head of center Peter Vuust.

The modern understanding of human sleep has long been based on the classification of four stages of sleep. This consensus stems from studies in the 1930s and is based on so-called electroencephalography (EEG), a technique that registers parts of the brain’s electrical activity with the help of electrodes. Despite the great technological developments in the measurement of brain activity, the traditional understanding has created an unnecessarily narrow view of brain activity during sleep.

“Sleep and the associated changes in consciousness are not just a topic of scientific puzzlement; they represent a vital need for healthy functioning. Today, we lack a consistent understanding of what happens in the brain when sleep suffers, in conditions such as insomnia but also in psychiatry where sleep disruption is ubiquitously present. It is our hope that a more complete and data-driven representation of whole-brain network changes during sleep can assist in the development of better models of the role of sleep in such disorders,” said Stevner, a post-doc at MIB and the lead author of the study.

In the new study, the research team has, for the first time, mapped complex patterns and dynamics in the brain during sleep. By using so-called fMRI (functional magnetic resonance tomography) scanning to map brain activity and measure changes associated with bloodstreams, the researchers have received improved scanning images than hitherto achieved. Also, the researchers have used a complete data-driven representation of changes in the brain, unlike the traditional definition of sleep stages that is generally based on human experts’ observations of EEG. Stevner and the rest of the international research team then compared the results with the more conventional EEG measurements and found that, during sleep, there is a much more complex network of brain activity between the brain regions than hitherto assumed.

The boundary between being awake and being asleep, the point where we slowly drift out of consciousness and further into sleep, has long challenged the conventional understanding of sleep and its four stages. Stevner and the research team’s new results confirm that the hitherto dominant definitions in the field are inconsistent, a result that can change the way we understand sleep, not to mention the way we approach sleep disorders such as insomnia.

“The findings show the complex choreography of brain activity during normal sleep. In addition to breaking new ground in our understanding of sleep, we have also taken the unorthodox step of finding new ways to listen to the findings. We have worked closely together with composer Milton Mermikides to use our findings to produce beautiful musical compositions such as “Sound asleep,” the music of your brain falling asleep and waking up,” said Professor Kringelbach from MIB and senior author of the study.

Read the scientific article in Nature Communications here

Read more about the study in a press release from MIB here