Hey Brain Rewirers,
Welcome to this week’s newsletter! We’re getting into some fatty goodness this week – and of course by that I mean myelin!
Myelin
I briefly mentioned myelin in my brain basics newsletter a few weeks ago, but I neglected to highlight its importance. Myelin is a fatty substance that surrounds the axon of a neuron. Think of the plastic insulation surrounding an electrical wire; myelin has a very similar job, it keeps all the electrical signals travelling across the neuron within the axon. Without myelin, neurons wouldn’t be able to send signals so quickly, and sometimes wouldn’t be able to send them at all1,2. In humans we know how detrimental this can be in disease like multiple sclerosis (MS), where myelin is damaged by the immune system3.
So myelin is important, right?
But what’s interesting is that different brain regions have different myelination. At a very high level, the brain can be broken down into white matter and grey matter. White matter is the bit with the myelin on it, giving it its white appearance, while grey matter is unmyelinated. But within white matter, axons can be myelinated with different thicknesses of myelin and different lengths of myelin4.
What causes these difference?
Myelin Plasticity
Recent research shows that much like neurons, myelin is plastic, and myelination patterns can change depending on an animals behaviour4,5. Importantly, these changes in myelin contribute to our long-term memory. Changes in myelination are critical in spatial memory, fear memory, and motor skills4. Additionally, myelination affects how neurons function at a singular level and how neurons work together as a circuit to produce behaviour4.
We see that when humans learn a new motor task, the underlying structure of white matter tracts is altered6. This suggests that the myelination pattern is being altered. We also see this in rats; learning new motor skills leads to changes in myelination7. Importantly, in rodents, if these myelin changes are blocked, the animals are unable to learn the motor skills8,9. Therefore, not only is myelin plastic, but this plasticity is required for learning and memory.
Myelin Personalities
Myelination patterns differ between individuals, and these differences affect our personalities. We see that different personality traits, such as compulsivity and impulsivity are linked to how our myelin develops10. We also know that in autism spectrum disorder (ASD), myelination often occurs more often or less often than in people without ASD, potentially linking differences we see in social behavior11. So just like how our neuron's connectivity and functionality will differ across individuals, so too does our myelin.
Me and My Myelin
Thus, it isn’t only our neurons we want to protect. Although we know that remyelination – the process of restoring lost myelin – does happen in humans, our remyelination capacity declines with age. This can lead to disability, as it does in MS, Alzheimers12, and Parkinsons13.
We should try to protect our brain and keep it as healthy as possible. There is limited knowledge available about what improves myelin health and myelination, but we do know that learning encourages myelin growth, so learning a new hobby as we get older is really important!
Other things that we have talked about before like sleeping well, getting sunlight, and being physically active, all help maintain our brain health.
If you want to learn more about maintaining and improving your brain health, check out my book!
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Until next week,
Nicole x
P.S. Leave a comment with requests for future newsletters!
References