No Myelin, No Learning
The crucial role that myelin plays in learning and retaining new skills has been confirmed by a study just published in the journal Science,from a group at the University College London (UCL).
In a functioning brain, neurons communicate with one another by sending electrical signals down their axons to interact with neighbouring neurons. To maximise the efficiency of this information transfer, the axon is insulated through the formation of a fatty myelin sheath that surrounds it and prevents any leakage of this electrical signal as it travels down the axon. These myelin sheaths primarily compose the brains white matter and during the process of learning a novel motor skill (e.g. learning to ride a bike), this is restructured as new neural connections are made. These connections are strengthened as electrical signals are fired more frequently down the axon. Therefore, it has previously been suggested that the formation of these myelin sheaths play an important role in facilitating the learning process and this is exactly what was demonstrated in this study by McKenzie and colleagues at UCL.
Here, two groups of mice were compared on their ability to master running on a “complex” wheel that had irregularly spaced rungs. In the experimental group, the mice were genetically engineered so that the production of oligodendrocytes (the cells which produce myelin) was blocked. By preventing myelin production, these mice were actually unable to successfully master the complex wheel, whereas those in the control group were unimpaired. In a second experiment, all the mice were allowed to learn how to run on the complex wheel prior to any genetic manipulations. This time, following the genetic prevention of myelin production, all of the mice were able to immediately master running on the complex wheel upon reintroduction to it.
Together, these results demonstrate that myelin production is essential to the restructuring of white matter that occurs when learning a new motor skill, but it is not necessary for the recall or performance of a pre-learned motor skill. It has previously been suggested that myelin production is important in skill learning given its fundamental role in facilitating neuron-to-neuron communication – however, this is the first time it has been experimentally demonstrated. These results are important in our understanding of the learning process and the next step will be to investigate whether the production of myelin is equally important for the learning of non-motor skills, such as maze navigation.
McKenzie, I., Ohayon, D., Li, H., Paes de Faria, J., Emery, B., Tohyama, K., & Richardson, W. (2014). Motor skill learning required active central myelination. Science, 346, 318-322.
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