Myelin plays a central role in allowing electrical signals to travel quickly and reliably between different regions of the brain.
In a new study published in Proceedings of the National Academy of Sciences, researchers report that sleep deprivation can weaken this insulation.
This is noteworthy because reduced concentration and slower reaction times have traditionally been explained by exhausted or overburdened nerve cells.
The findings instead point to changes in the brain’s white matter, which forms the network of connections between neurons.
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Animal experiments
The study is based on both human data and animal experiments.
MRI scans of 185 individuals with self-reported poor sleep quality showed structural changes in white matter.
The findings are consistent with previous studies but do not, in themselves, explain the cause.
To get closer to the underlying mechanism, the research team restricted sleep in rats over a period of ten days.
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Electrical measurements showed that signals between the brain’s hemispheres traveled significantly more slowly than normal.
When the brain tissue was later analyzed, the insulation around the nerve fibers was found to be markedly thinner than in well-rested animals.
An explanation emerges
It was only during the analysis of cholesterol metabolism that the picture began to change.
The researchers found that cholesterol was not being efficiently transported to myelin.
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Cholesterol is necessary to maintain stable and thick insulation, and the deficiency made the nerve fibers less efficient.
In experiments in which the substance cyclodextrin was used to release cholesterol, signal speed was normalized in the rats.
At the same time, the animals performed at the same level as the control group in behavioral tests.
The researchers emphasize that the results cannot yet be translated into treatments for humans.
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Nevertheless, the study points to a new understanding of why sleep deprivation may affect the brain more fundamentally than previously assumed.
Sources: Medical Xpress, and Proceedings of the National Academy of Sciences.
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