A conversation with Dr. Brahim Nait-Oumesmar, a Paris Brain Institute Group Leader, Team “Regain-MS: Regeneration in Demyelinating Diseases: From Biology to Clinical Translation”
“But, as immaterial as they may seem, thoughts too need a point of support; otherwise, they begin to spin around themselves in a mad whirl.”
Stefan Zweig, Chess
Neuroscientists consistently emphasize the importance of certain daily habits for brain health: sleeping well, engaging with others, reading, exercising, walking around the block, or running around Central Park’s reservoir. Even letting the mind wander and, above all, avoiding stress at all costs can protect the brain and help prevent neurological diseases.
At a New York salon conversation hosted by Helena Skarstedt and Yayane Verbuyt on behalf of Paris Brain Institute America and its chair, publisher Martine Assouline, guests even posed unexpected questions to Dr. Brahim Nait-Oumesmar, a neuroscientist at the Paris Brain Institute: Could empathy, learning and making love also contribute to brain health? His response was simple and definitive: “All of the above,” he replied, smiling.
Just as the protagonist of Zweig’s final novel clings desperately to a chess book—reading and rereading it obsessively—to keep from losing his mind while imprisoned in Nazi isolation, we, too, need social interactions and movement to sustain our mental well-being. At the heart of this process lies one of the brain’s most overlooked yet crucial components: myelin—a fatty substance that insulates nerve fibers and plays a vital role in how our brain functions.
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Myelin is part of the brain’s white matter and is produced by the oligodendrocytes – one of the glial cells of the central nervous system. For decades, neuroscientists believed that this mushy mass merely served as a support system for neurons—the star cells responsible for memory, movement, and communication. Dr. Nait-Oumesmar has devoted his career to studying glial cells and multiple sclerosis yet challenges this perception. “I have always wanted to understand their physiology, function, and role in cerebral processes,” he explains.
Without myelin, pianists cannot play, actors forget their lines, and athletes lose their performances. Over time, as myelin degrades, fundamental body functions deteriorate. Diseases such as multiple sclerosis, dementia, Parkinson’s, and Alzheimer’s all share one common trait: a lack of myelin.
A lack of stimulation—whether physical, cognitive, or social—negatively impacts myelin formation and can accelerate cognitive decline.
Dr. Nait-Oumesmar
Dr. Nait-Oumesmar’s research into multiple sclerosis led him to investigate the link between the brain’s inability to produce myelin and mental disorders such as schizophrenia.
This intersection of neuroscience and neuropsychiatry—where the science of the brain meets the study of the mind—marks a paradigm shift in mental health. Advances in myelin research could open new avenues of treatments as the world grapples with the destigmatization and increasing prevalence of mental disorders. In the United States alone, 23% of adults—roughly 60 million people—experienced a mental illness in 2024. Among them, 14.1 million suffered from Serious Mental Illnesses (SMIs), with young adults aged 18 to 25 being the most affected. Women, more than men, continue to bear the brunt of these disorders.
“We have discovered that myelin is a component that can be regenerated. In multiple sclerosis, the structure of myelin is destroyed by autoimmune mechanisms—in other words, an attack on one’s own myelin, which leads to lesions. Our work then focuses on the mechanisms that regulate myelin regeneration, also called remyelination“, explains Dr Nait-Oumesmar.
The realization that reading Zweig’s novels, playing chess in Washington Square, or practicing outdoor basketball on the streets of New York could promote myelin formation and slow down cerebral aging suggests that new therapeutic perspectives could be envisioned for mental health disorders.
JC Agid: What is the role of this fatty, white substance called ‘Myelin?”
Dr. Brahim Nait-Oumesmar: Myelin acts as an insulating sheath around nerve fibers and helps speed up the transmission of nerve impulses, meaning the messages between neurons. You can compare it to the plastic insulation around an electrical wire that protects it and ensures good current conduction. Without this protection, information travels very slowly or not at all.
Do we all have the same amount of myelin at birth?
It is partly something we acquire at birth, but it continues developing well after! Myelin formation in humans continues until age 20-30, especially in cortical regions.
What is the advantage of having a lot of myelin?
Myelin provides many benefits! The first, acquired through evolution in jawed fish, is predation and the ability to move quickly to escape predators! One of myelin’s essential functions is ensuring speed and coordination of movements, especially locomotion. Myelin is also an evolutionary advantage that ensures the proper functioning of cognitive abilities such as thinking, learning, memory, and emotions.
Can we recreate or stimulate myelin regeneration in our brain?
Myelin is a “plastic” structure, meaning that it remodels itself and is capable of regenerating in the adult brain. This plasticity is linked to these immature cells, which can respond to environmental stimuli through the activity of nerve fibers. We call this adaptive myelination. This is a relatively recent discovery in brain plasticity—about 30 years ago—well after synaptic plasticity was discovered.
How?
Through activities that engage our brain circuits and body—such as social interactions, sports, learning new movements, or even reading.
Producing myelin throughout life can be seen as a way to combat brain aging and neurodegeneration linked to diseases such as multiple sclerosis, Parkinson’s, Alzheimer’s, or certain forms of dementia.
Dr. Nait-Oumesmar
Do we produce myelin while we sleep?
Yes, but indirectly. Sleep acts like a “vacuum cleaner” that helps cleanse our brains. Myelin formation, like many other brain functions, requires this detoxification process. A system called the glymphatic system drains toxins from our brain, improving the function of glial cells. That said, while sleep is essential for preserving myelin, it is not necessarily produced while we sleep.
Good sleep, physical activity, and avoiding a sedentary lifestyle are all crucial for maintaining a healthy brain!
What happens if I remain inactive and do not allow my brain to adapt to its environment?
A lack of stimulation—whether physical, cognitive, or social—negatively impacts myelin formation. This can accelerate cognitive decline and increase the risk of neuropsychiatric disorders.
So, is it essential to protect and maintain my myelin levels?
Producing myelin throughout life can be seen as a way to combat brain aging and neurodegeneration linked to diseases such as multiple sclerosis, Parkinson’s, Alzheimer’s, or certain forms of dementia.
Without myelin, do I accelerate the progression of these diseases?
Yes, most certainly! Myelin has a neuroprotective role. Without myelin, nerve fibers and neurons are gradually lost as these diseases progress. That’s why myelin is a significant focus of research in multiple sclerosis, a disease in which the myelin’s own immune system attacks it.
In many cognitive disorders, such as autism or schizophrenia, myelin struggles to regenerate or remodel itself.
Dr. Nait-Oumesmar
How does this relate to psychiatric disorders?
In many cognitive disorders, such as autism or schizophrenia, myelin struggles to regenerate or remodel itself. This results in a blockage of adaptive myelin formation. We don’t fully understand why this blockage occurs. However, our research shows that we may be able to correct this myelin deficiency, especially in higher brain regions like the cortex, potentially improving cognitive function. Enhancing memory and learning ability partly depends on generating new myelin.
Are neuropsychiatric disorders like autism or schizophrenia caused by a lack of myelin, or does the lack of myelin worsen these conditions?
It depends on the pathology. In some neuropsychiatric conditions, myelin damage, influenced by environmental factors or excessive stress, could be a primary cause, which may later lead to white matter impairment. This could partly explain certain cognitive symptoms.
For autism and schizophrenia, the situation is more complex. These disorders likely result from a combination of genetic predisposition, environmental factors, and epigenetic influences that disrupt neural network activity, ultimately leading to myelin impairment.
If we link all this information together, could the social isolation caused by COVID-19 and the stress from job loss, contracts, illness, and related loss of friends or family members be responsible for an increase in mental health disorders, especially among young adults?
It is correct that the COVID-19 period was a catalyst for the rise in mental health issues. The pandemic revealed the critical importance of social interactions. For instance, we know that social isolation has long-term consequences on myelin development and increases the risk of neuropsychiatric disorders.
Certain activities can enhance myelin growth, including:
- Physical exercise (e.g., running, walking, and playing sports)
- Cognitive engagement (e.g., reading, learning new skills, playing chess, practicing piano)
- Social interactions (e.g., conversations, teamwork, emotional connection)
- Good sleep hygiene (supports the glymphatic system, which clears toxins and aids in brain function)
Did you anticipate that your research on myelin regeneration for multiple sclerosis would have implications for neuropsychiatric disorders?
Our growing knowledge of myelin led us to explore its role in cognitive processes. We realized that modifying myelin also influences a series of cognitive behaviors. This was not our initial focus, but we have demonstrated a key role for myelin in neuropsychiatric disorders thanks to interdisciplinary approaches at the intersection of neuroscience and cognitive science.
Isn’t that the essence of research? With this knowledge, is it possible to stimulate myelin regeneration with medications, which could impact patients with mental health conditions?
My primary research goal in multiple sclerosis is to promote myelin regeneration in brain or spinal cord damage cases. We aim to stimulate myelin repair using pharmacological molecules. Strategies developed for multiple sclerosis could also help us understand the therapeutic potential of remyelination for neuropsychiatric disorders. However, we are only at the very early stages of this research.
Might this also lead to increased research at the intersection of neuroscience and neuropsychiatry?
Many studies are ongoing, especially at the Brain Institute, on psychiatry-related areas—such as cognition and human behavior, including motivation and decision-making. The strength of the Paris Brain Institute lies in having researchers and doctors working across multiple levels, from cellular studies to human applications, creating a true synergy between fundamental and clinical research in neurology.
