National Institutes of Health's (NIH) National Institute of Mental Health (NIMH) researchers found that a version of a gene previously linked to impulsive violence seems to weaken brain circuits that regulate impulses, emotional memory and thinking in humans. Brain scans showed that people with this gene version, especially males, tended to have relatively smaller emotion-related brain structures, a hyperactive alarm center and under-active impulse control circuitry.

The researchers reported their magnetic resonance imaging (MRI) study online in the Proceedings of the National Academy of Sciences during the week of March 20, 2006, which identifies neural mechanisms by which this gene likely contributes to risk for violent and impulsive behavior through effects on the developing brain.

"These new findings illustrate the breathtaking power of 'imaging genomics' to study the brain's workings in a way that helps us to understand the circuitry underlying diversity in human temperament," said NIH Director Elias A. Zerhouni, M.D., who conducted MRI studies earlier in his career.

The gene is one of two common versions that code for the enzyme monoamine oxydase-A (MAO-A), which breaks down key mood-regulating chemical messengers, most notably serotonin. The previously identified violence-related, or L, version, contains a different number of repeating sequences in its genetic code than the other version (H), likely resulting in lower enzyme activity and hence higher levels of serotonin. These, in turn, influence how the brain gets wired during development. The variations may have more impact on males because they have only one copy of this X-chromosomal gene, while females have two copies, one of which will be of the H variant in most cases.

Read more at NIMH press release.

News and Photo Source: NIMH