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A study shows the complex choreography of brain activity during sleep

So reveals a study led by Morten Kringelbach, a researcher at the University of Oxford, involving Gustavo Deco, director of the Center for Brain and Cognition, published on 4 March in Nature Communications. Data for the study on brain state when falling asleep were obtained by functional magnetic resonance imaging (fMRI).

06.03.2019

 

In many respects, sleep remains a scientific mystery despite taking up about a third of our lives. Understanding what happens during sleep depends inseparably on our ability to categorize and derive patterns of brain activity. This scientific task began in the 1930s when it was first possible to record neuronal action potentials in the brain during sleep by means of electroencephalography (EEG) techniques, which provide data on the width and frequency of brain waves.

Currently, there is consensus among the experts that human sleep passes through four stages, plus a period of REM sleep (Rapid eye movement), or paradoxical sleep stage, in which various processes take place. Despite the major advances in modern technology to record brain activity, “our vision remains unnecessarily narrow”, says the author of a study published in Nature Communication.

In this study, for the first time, scientists have used fMRI to identify recurring states of unique configurations of interactions between brain regions and transition states between them that are “not very different from the choreographies used in music and dance”

An international team of researchers, including Gustavo Deco, director of the Center for Brain and Cognition (CBC) and ICREA research professor at UPF’s Department of Information and Communication Technologies (DTIC), used recordings of images obtained by functional magnetic resonance imaging (fMRI) to find out more about the underlying whole brain activity in the conventional stages of sleep in humans. The results of this study were published on 4 March 2019 in the open access journal Nature Communications.

Until now, the different stages of sleep were based on the observation of recordings obtained using electroencephalograms. In this study, for the first time, scientists have used fMRI to identify recurring states of unique configurations of interactions between brain regions and transition states between them that are “not very different from the choreographies used in music and dance”, state the authors.

When comparing recordings of the different stages of sleep obtained by fMRI techniques with those obtained by conventional EEG, the findings with fMRI display higher resolution and greater complexity than those observed using traditional EEG techniques. “Instead of being reduced to a matter of general changes in EEG frequencies, we have seen how the differences between states of wakefulness and sleep are reflected in the large-scale reorganization of the brain networks”, they explain. “The boundary between wakefulness and sleep, the loss of consciousness that we experience every night, has challenged the staging of conventional sleep for decades, and the results based on data confirm that the definitions at present are inconsistent”, they add.

Today, we have a consistent understanding of what happens in the brain when sleep suffers, in insomnia, but also in psychiatry, where sleep disruption is present ubiquitously.

“We expect that a more complete representation based on data concerning the changes in the neural network throughout the brain during sleep will help to develop better models of the role of sleep in such disorders”

These findings could change the way we understand sleep and how sleep disorders such as insomnia are dealt with. Sleep and the changes associated with consciousness are not just a matter of scientific perplexity, but are a vital requirement for the healthy functioning of the body. Today, we have a consistent understanding of what happens in the brain when sleep suffers, in insomnia, but also in psychiatry, where sleep disruption is present ubiquitously. “We expect that a more complete representation based on data concerning the changes in the neural network throughout the brain during sleep will help to develop better models of the role of sleep in such disorders”, the authors assert.

Professor Morten Kringelbach, a researcher at the University of Oxford (UK) and principal author, adds: “Our findings show the complex choreography of brain activity during normal sleep. Besides breaking the bases of our understanding of sleep, we have also taken the unorthodox step of seeking new ways to listen to the findings. We have worked closely with composer Milton Mermikidis who has interpreted our scientific data to produce a beautiful musical composition: ’Sound asleep’, the music of the brain falls asleep and awakens”.

For more information

A. B. A. Stevner, D. Vidaurre, J. Cabral, K. Rapuano, S. F. V. Nielsen, E. Tagliazucchi, H. Laufs, P. Vuust, G. Deco, M. W. Woolrich, E. Van Someren & M. L. Kringelbach (2019), “Discovery of key whole-brain transitions and dynamics during human wakefulness and non-REM sleep”, Nature Communications, vol. 10, 1035.

 

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