Problems with myelin — demyelination (seen most dramatically in MS, but also in other forms of neurodegeneration, including normal aging and depression); failure to develop sufficient myelin (in children and adolescents) — are increasingly being implicated in a wide range of disorders. A new animal study adds to that evidence by showing that social isolation brings about both depression and loss of myelin.
In the study, adult mice were isolated for eight weeks (which is of course longer for a mouse than it is to us) to induce a depressive-like state. They were then introduced to a mouse they hadn’t seen before. Although typically very social animals, those who had been socially isolated didn’t show any interest in interacting with the new mouse — a common pattern in human behavior as well.
Analysis of their brains revealed significantly lower levels of gene transcription for oligodendrocyte cells (the components of myelin) in the prefrontal cortex. This appeared to be caused by a lower production of heterochromatin (tightly packed DNA) in the cell nuclei, producing less mature oligodendrocytes.
Interestingly, even short periods of isolation were sufficient to produce changes in chromatin and myelin, although behavior wasn’t affected.
Happily, however, regardless of length of isolation, myelin production went back to normal after a period of social integration.
The findings add to the evidence that environmental factors can have significant effects on brain development and function, and support the idea that socializing is good for the brain.
 Impaired adult myelination in the prefrontal cortex of socially isolated mice. Nature Neuroscience [Internet]. 2012 ;15(12):1621 - 1623. Available from: http://www.nature.com/neuro/journal/v15/n12/full/nn.3263.html