It's well known that adults abused as children frequently exhibit violent behavior. Now a new study with laboratory rats suggests a direct link between stress in childhood and brain alterations that may explain the violence.
Swiss researchers have found evidence that neurological changes apparently caused by abusive or stressful events in an individual's early life might trigger aggressive behavior in adulthood.
Scientists at the Ecole Polytechnique Federale de Lausanne or EPFL in Switzerland investigated the effects of psychological stress in 43 young rats. Study co-author Guillaume Poirier says they found that the rat pups which were exposed to frightening situations during their early development, were more aggressive as adults than normal rats.
When he and his colleagues studied electrical activity in the stressed rodents’ brains, comparing them to the brains of normal rodents, Poirier says they found significant differences in two regions of the brain associated with aggressive behavior -- the amygdala and orbitofrontal cortex:
“One can think of the amygdala as a sort of a quote-end-quote hot spot for emotion, and the orbitofrontal cortex is part of more so-called executive decisional processes,” Poirier said.
Poirier says there was a decrease in the activity of the orbitofrontal cortex, which normally has a calming effect in stressful situations, helping individuals reason their way through negative emotions.
In the rat models, researchers also identified changes in the activity of two genes that pre-dispose humans to aggressive emotions.
One of those genes, called MAOA, was more active in the stressed rats’ prefrontal cortex. Poirier says drugs known as MAOA inhibitors -- which are used to treat depression in humans -- soothed the rats' aggressive and anti-social behavior.
“And, in fact, when we administered this drug to the individuals (rats) that were more aggressive, it normalized their behavior, suggesting that it’s not that if you’ve experienced these early life events, that’s it - that you are into a single track of emotional disturbances and mayhem,” Poirier said.
An article on the impact of youthful stress on aggressive adult behavior is published in the journal Translational Psychiatry.