Barcelona, Spain: Scientists have discovered how damage to the myelin sheath – the insulating layer around nerve fibres – affects brain activity during sleep.
In research presented on Friday at the Federation of European Neuroscience Societies (FENS) Forum 2026 [1], Dr Mohit Dubey described how electroencephalogram (EEG) recordings in mice with damaged myelin showed electrical spikes, similar to those seen in patients with epilepsy or Alzheimer's disease (AD). These spikes occurred only when the mice were asleep. The findings may have implications for patients with multiple sclerosis (MS), AD and other neurodegenerative diseases. [2]
"Sleep disturbances are extremely common in neurological diseases such as multiple sclerosis and Alzheimer's disease, but the biological reasons for these problems remain poorly understood," said Dr Dubey, who is a ZonMw Memorable Dementia Fellow at the Netherlands Institute for Neuroscience in Amsterdam, The Netherlands.
"The myelin sheath helps electrical signals travel efficiently through brain circuits. In many neurodegenerative diseases myelin is damaged, which can disrupt communication between neurons. We wanted to understand whether myelin damage could also affect how brain circuits behave during sleep. By studying this link, we hope to better understand what causes sleep disturbances in neurological disease and whether sleep-related brain signals could serve as biomarkers for diseases that are yet to show clinical symptoms, as well as showing disease progression."
Dr Dubey and colleagues looked at EEG recordings taken over multiple nights over several weeks in mouse models with damaged myelin and AD, and compared them with EEG data from sleeping patients with MS.
They found that the abnormal electrical spikes in brain activity seen in the sleeping mice were tightly linked to sleep rhythms, including the bursts of brain activity that occur during the second stage of non-rapid eye movement (REM) sleep (known as sleep spindles). Furthermore, they discovered slowing of electrical rhythms that are exclusively observed during REM sleep.
"REM is a stage of sleep associated with dreaming and replay of daytime experiences. In this state the brain produces rhythmic electrical patterns called oscillations that help coordinate communication between neurons. Our findings show that these rhythms become disrupted and slower when myelin degenerates, and that the electrical spikes seen during sleep are closely linked to the stability of brain circuits affected by neurodegenerative diseases such as MS and AD," said Dr Dubey.
"This opens new research directions exploring how sleep rhythms depend upon the myelination status of the brain circuits. Sleep recordings may provide a non-invasive way to detect early changes in brain circuit myelination in neurological disease. This could eventually help clinicians monitor disease progression, and we want to investigate whether sleep recordings could be used as biomarkers to detect early changes in brain circuit function.
"Sleep disturbances are already known to affect quality of life in people with MS and AD. They contribute to fatigue and cognitive decline. Therefore, understanding the biological link between sleep and brain circuit dysfunction could help guide future strategies for improving sleep and brain health in these conditions.
"Sleep plays a fundamental role in maintaining healthy brain function, but it has often been overlooked in the study of neurodegenerative disease."
Dr Dubey's future research will focus on understanding the cellular and molecular mechanism linking myelin degeneration, sleep rhythms and abnormal electrical activity in the brain.
As yet, there are no treatments that can repair damaged myelin, although there are some drugs that aim to slow the immune system's attack on the myelin sheath in MS. Understanding the biological basis for how myelin damage affects sleep could help researchers to design non-invasive approaches that might be able to repair myelin during sleep.
A strength of the research is that it combines sleep neuroscience with the study of demyelinating brain circuits, allowing researchers to examine how brain rhythms interact with disease-related changes. A limitation is that the work is mainly in mice and further studies are needed to understand how the mechanisms translate to human disease.
Professor Christina Dalla from the National and Kapodistrian University of Athens, Greece, is chair of the FENS Forum communication committee and was not involved in the research. she said: "Dr Dubey and his colleagues are to be congratulated on their work showing the effects of damaged myelin on the brains of sleeping mice, while also observing a slowing of REM sleep oscillations in patients with multiple sclerosis. This appears to be connected with disruptions in brain circuit stability and connectivity, as seen in mice with Alzheimer's disease. These observations open up interesting new avenues for further research on sleep quality and architecture as a biomarker for brain diseases and as a therapeutic target in humans."
