Animals that are socially isolated for prolonged periods make less myelin in the region of the brain responsible for complex emotional and cognitive behaviour, researchers at the University at Buffalo say.
The research sheds new light on brain plasticity, the brain's ability to adapt to environmental changes. It reveals that neurons are not the only brain structures that undergo changes in response to an individual's environment and experience, according to the lead author, Doctor Karen Dietz.
Researchers say that changes in the brain's white matter, or myelin, have been seen before in psychiatric disorders, and demyelinating disorders have also had an association with depression. Recently, myelin changes were also seen in very young animals or adolescents responding to environmental changes.
"This research reveals for the first time a role for myelin in adult psychiatric disorders," Dietz says. "It demonstrates that plasticity in the brain is not restricted to neurons, but actively occurs in glial cells, such as the oligodendrocytes, which produce myelin." Myelin is the crucial fatty material that wraps the axons of neurons and allows them to signal effectively. Normal nerve function is lost in demyelinating disorders, such as multiple sclerosis (MS) and the rare, fatal, childhood disease, Krabbe's disease.
This research reveals that the stress of social isolation disrupts the sequence in which the myelin-making cells, the oligodendrocytes, are formed. In the experiment, adult mice, normally social animals, were isolated for eight weeks to induce a depressive-like state.
They were then introduced to a "novel" mouse, one they had not seen before; while mice are normally highly motivated to be social, those who had been socially isolated did not show any interest in interacting with the new mouse, a model of social avoidance and withdrawal.