It is known that maturation of oligodendrocytes is necessary for motor skill learning. The structure of the white matter changes after motor skill training (e.g., juggling or playing piano).

It is well known that oligodendrocytes myelinates axons. In addition, oligodendrocyte dysfunction causes severe neurological disorders, such as multiple sclerosis. So better understanding of the interactions between oligodendrocytes and neuronal axons has important medical applications.

However, the difficulty of identifying the interaction between oligodendrocytes and neuronal axons in the brain was due to the high density of oligodendrocytes in white matter, preventing researchers from detecting the precise morphology of each oligodendrocyte.

The Japanese research group used a viral vector to label single oligodendrocytes in the white matter. With multiple viral vector injections, neuronal axons derived from distinct brain region (motor cortex or sensory cortex) and oligodendrocytes in the white matter were simultaneously labeled. Surprisingly, the research group found that oligodendrocytes did not just ensheath axons randomly some oligodendrocytes selectively myelinated axons from a particular brain region.

They found that some populations of oligodendrocytes in the corpus callosum predominantly ensheathed axons derived from motor cortex or sensory cortex, while others ensheathed axons from both brain regions, suggesting heterogeneity in preference of myelination toward a particular subtype of neurons. 

This method developed by the research group is available for demyelination in an animal model to assess demyelinating diseases. "Now, we plan to analyze oligodendrocyte morphology and myelination in demyelinating mouse models," says corresponding author. "Furthermore, axon selective myelination for a specific neuronal subtype found in this study encourages us to investigate physiological relevance of multiple myelination to higher brain function."

http://www.nips.ac.jp/eng/release/2016/10/_--.html