Williams Syndrome, a personality type that features extremely extroverted yet anxious behavior, is triggered by the abnormal development of a circuit center buried deep in the front center of the brain, according to scientists at the National Institutes of Health.
Researchers used three different kinds of brain imaging to identify the suspect area in the brains of people with Williams Syndrome, a rare genetic disorder.
When the scans were matched to scores on a personality rating scale, it became clear that the stronger these personality/temperament traits appeared in an individual with Williams Syndrome, the more abnormalities there were in a specific brain structure, called the insula.
“Scans of the brain’s tissue composition, wiring, and activity produced converging evidence of genetically-caused abnormalities in the structure and function of the front part of the insula and in its connectivity to other brain areas in the circuit,” explained Karen Berman, M.D., of the NIH’s National Institute of Mental Health (NIMH).
In Williams Syndrome, there is a deletion of some 28 genes, many involved in brain development and behavior, in a specific part of chromosome 7. Individuals with the syndrome lack visual-spatial skills and a tendency to be overly friendly with people, while overly anxious about non-social events, such as spiders or heights. Often, those with the disorder are learning disabled, but some have normal IQs.
“This line of research offers insight into how genes help to shape brain circuitry that regulates complex behaviors — such as the way a person responds to others — and thus holds promise for unraveling brain mechanisms in other disorders of social behavior,” said NIMH Director Thomas R. Insel, M.D.
Earlier imaging studies by the NIMH researchers found irregular tracts of the neuronal fibers that carry out long-distance communications between brain regions — probably a result of neurons moving to the wrong destinations during early development.
For the study, researchers evaluated 14 intellectually normal Williams Syndrome volunteers and 23 healthy controls.
It was revealed through magnetic resonance imaging (MRI) that patients had decreased gray in the bottom front of the insula, which integrates mood and thinking. However, they had increased gray matter in the top front part of the insula, which has been linked to social and emotional processes.
There was also reduced white matter — the brain’s long-distance wiring — between the thinking and emotion centers. These structural and functional abnormalities in the front of the insula correlated with the Williams Syndrome personality profile.
“Our findings illustrate how brain systems translate genetic vulnerability into behavioral traits,” explained Berman.
The study is published online in the journal Proceedings of the National Academy of Sciences.
Source: National Institutes of Health