Caregivers and clinicians have long known that profoundly neglected infants grow into children with behavioral issues: studies of children rescued from dismal Romanian orphanages often show a wide range of neurological and psychological deficits, known collectively as “Reaction Attachment Disorder.” The exact mechanisms behind these changes were not known.
Now, a groundbreaking new study conducted by researchers from Children’s Hospital Boston and Harvard Medical School has provided the world with a neurobiological model for how isolation can damage the developing brain:
By studying mice that had been isolated early in life, researchers led by Gabriel Corfas of Children’s Hospital Boston and Harvard Medical School hoped to uncover how social deprivation can affect the developing brain. After the mice had weaned, the researchers put them into one of three environments: One was a deluxe suite, enriched with fresh toys every other day and populated by friends of similar ages, one was a standard laboratory cage holding four mice, and one was a holding cell for total isolation.
After two weeks, mice in the deluxe suite and the regular cage showed no abnormalities in their behavior or brains. But mice that were isolated showed big changes. These animals were socially stunted, showing less signs of exploratory behavior and a diminished working memory. What’s more, the researchers uncovered stunted development in the brain’s white matter, which helps nerve cells communicate.
In a brain region called the prefrontal cortex, isolated mice had less of a fatty insulating substance called myelin that wraps around nerve cells and helps carry their messages. This part of the brain is thought to be crucial for high-level tasks like social interactions. Myelin-making cells called oligodendrocytes were also stunted. Normally these cells have elaborate, winding tendrils full of complex branches. But isolated mice’s oligodendrocytes were smaller and less elaborate, with fewer branches. The result “shows how sensitive the development of myelin is to experience,” Corfas says.
The two-week period after weaning was critical. If isolation happened three weeks after weaning, the mice didn’t show these deficits. Nor could the isolation effects be reversed later by moving the isolated mice into a better situation.
Human infants are born with very little myelin, but produce more of it as they get older. Mental stimulation is a crucial part of the development of human myelin. Corfas described the first two years of a child’s life as being a crucial window for development, and stated that Romanian infants removed from their orphanages before two years of age had a much better prognosis for development than those removed later.
The development of Reaction Attachment Disorder isn’t exclusive to Romanian orphans, but these victims of negligent state institutions have provided the best opportunity for study and, hopefully, the development of effective therapies.
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