Published January 2, 2013
Animals that are socially isolated for long periods make less myelin in the region of the brain responsible for complex emotional and cognitive behavior, according to researchers at UB and Mt. Sinai School of Medicine.
Their findings, published online in Nature Neuroscience, show that brain plasticity—the brain’s ability to adapt to environmental changes—occurs not only in neurons but myelin-producing glial cells as well.
“This research provides the first explanation of the mechanism behind brain plasticity,” says Karen Dietz, PhD, research scientist in pharmacology and toxicology and one of the paper’s lead authors.
Dietz and her colleagues found that the stress of social isolation disrupts the sequence in which oligodendrocytes, the myelin-making cells, are formed.
Their experiment involved isolating adult mice for eight weeks to induce a depressive-like state. Although mice are typically social, the isolated animals showed no interest in interacting with a mouse they hadn’t seen before.
Brain tissue analyses of the isolated mice revealed that the oligodendrocytes had significantly lower than normal levels of heterochromatin, a tightly packed form of DNA, in the prefrontal cortex.
DNA compaction signifies that the oligodendrocytes have matured. This, in turn, allows the oligodendrocytes to produce normal amounts of myelin, the fatty material crucial for a properly functioning nervous system.
“As adults age, you would normally see more compaction, but when social isolation interferes, there’s less compaction and, therefore, less myelin being made,” Dietz says.
The research also showed that myelin production returned to normal after a four-week period of social integration, suggesting that environmental intervention reverses the negative effects of adult social isolation.
Although myelin changes have been previously observed in psychiatric conditions, this study is the first to indicate that myelin plays a role in adult psychiatric disorders, Dietz says.
Demyelinating disorders, which result in a loss of normal nerve function, have been associated with depression, so the new research also has implications for questions about multiple sclerosis and other demyelinating conditions, she adds.
“The research suggests that recovery from an MS episode might be enhanced by social interaction. It opens another avenue of investigation of how mood and myelin disorders may interact with one another.”
The new research—together with another group’s showing myelin changes triggered by social isolation early in life—is expected to broaden investigations into brain plasticity.
Dietz conducted the study while a postdoctoral researcher at Mt. Sinai. It was funded by the National Institutes of Health.
David Dietz, PhD, assistant professor of pharmacology and toxicology, is one of the paper’s co-authors.
Their collaborators from Mt. Sinai are: