Myelin vital for learning new practical skills

New evidence of myelin's essential role in learning and retaining new practical skills, such as juggling or playing a musical instrument, has been uncovered by new research in the WIBR, published this month in the journal Science (McKenzie, Ohayon et al. 2014). Myelin is a fatty substance that insulates the brain's wiring and is a major constituent of 'white matter'. It is produced by cells called "oligodendrocytes" in the brain and spinal cord into early adulthood as it is needed for many developmental processes. The function of myelin is to allow electrical impulses to be conducted much more rapidly among different parts of the brain and spinal cord, and is essential to increase the brain's speed and computing power. Although earlier studies of human white matter hinted at the involvement of myelin in skill learning, this is the first time it has been confirmed experimentally.

The WIBR research team, headed by Prof Bill Richardson, devised a way of genetically manipulating mice so that production of new oligodendrocytes and myelin could be blocked after injection of a drug, without affecting myelin that had been formed up to that point. A group of modified mice treated with the drug was much worse at learning to run on a wheel with unevenly spaced rungs (a "complex wheel") compared to an unmodified "control" group that remained capable of generating new myelin. However, if genetically modified mice learned the complex wheel before receiving the drug they retained the ability to run at speed on the complex wheel subsequently, proving that new myelin formation is not required for mice to remember and perform a skill once it has been learned. New myelin needs to be laid down only when the mice first learn the skill.

Later experiments, not reported in the Science paper, showed that the different motor learning abilities of the myelinating and non-myelinating groups of mice developed very quickly - within 2 hours of being first introduced to the complex wheel. Prof Richardson said: "From earlier studies of human white matter using advanced MRI technology, we thought OLs and myelin might be involved in some way in skill learning, so we decided to attack this idea experimentally. We were surprised how quickly we saw differences in the ability of mice in the two groups to learn how to run on the complex wheel, which shows just how fast the brain can respond to wrap newly-activated circuits in myelin and how this improves learning. This rapid response suggests that a number of alternative axon pathways might already exist in the brain that can be used to drive a particular sequence of movements, but it quickly works out which of those circuits is most efficient and both selects and protects its chosen route with myelin.

Newborn Oligodendrocytes (OLs)