Brain complexity: new tasks make more myelin (Introduction)

by David Turell , Wednesday, January 24, 2018, 14:41 (2277 days ago) @ dhw

When an area of the brain becomes more active the axon fibers are coated with more myelin to speed transmission:

https://cosmosmagazine.com/biology/active-brain-regions-make-more-myelin

"New research shows that increased electrical activity in an individual neuron leads to a thicker myelin coating around its axon, which can help speed up the transmission of neural signals.

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"These axons are coated with a fatty layer of myelin that insulates the nerve fibres and facilitates conductivity. The more myelin, the faster the signal.

"Myelin is produced when oligodendrocyte progenitor cells (OPCs) in the central nervous system detect a “need more myelin” signal and mature into the oligodendrocytes that actually make it.

"It’s also known that learning new skills such as juggling or playing piano can induce long-term changes in the structure of white matter in humans. Moreover, mice that are unable to make new myelin have trouble learning complex motor tasks.

"Toby Merson of the Australian Regenerative Medicine Institute at Monash University in Melbourne, Australia, explains that through these and other studies “we’ve come to understand that electrical activity within axons in the central nervous system is able to stimulate more myelin to be produced”.

"However, it was unknown if it is a general process where more activity in a brain area leads to more myelin, or whether it is a precise mechanism where the myelin is targeted to the active axons.

"To find out, Merson and his colleagues increased the activity of a subset of neurons in the brains of mice, then checked to see if myelination also increased in these particular neurons.

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"When we looked at the [active] axons we found they were more myelinated,” says Merson. “The adjacent axons that we hadn’t modified were unchanged.”

"To determine how myelin-making cells responded when the neurons became more active, the researchers tagged OPCs with a gene for a fluorescent protein, so that they glowed as they matured into active oligodendrocytes.

"Visual analysis confirmed these cells were not responding randomly.

“'They were preferentially myelinating the axons that we had activated,” explains Merson.
It appears there is a precise mechanism enabling myelin to be recruited to the axons that need it most.

“"In development or in plasticity of the brain, you would want those axons to be functioning more efficiently and firing faster, and myelination is the mechanism through which that can be achieved,” says Merson.

"Now that he knows how finely tuned the myelination response can be, he is investigating whether the electrical activity of the axon brings this about through direct interaction with nearby OPCs. "

Comment: Looks like a great designed system to me. It had to be created all at once for this reason: when the brain started to activate a region to handle a new task it is beneficial to happen quickly and adding more insulation to speed impulses is a necessary step. All the parts have to work together from the beginning. Too many parts to develop stepwise.