Later On

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The Making of a Bully

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Interesting article in The Scientist by Bhavana Weidmann:

Like neonates, adolescent rats are also vulnerable to childhood trauma, becoming aggressive and pathologically violent later in life, according to a study published earlier this month (January 15) inTranslational Psychiatry.

The team of researchers at the Brain Mind Institute in Lausanne, Switzerland, observed adult rats that had undergone traumatic experiences as adolescents, and found evidence of altered brain activity and epigenetic changes in the pre-frontal cortex that may explain the animals’ aggressive behavior. Because the findings match those from previous studies in humans, the study offers a robust rat model to further investigate the underlying neuro-biological causes and potential treatment avenues for increased aggression resulting from childhood trauma.

“This work represents a critical advancement in our understanding of how our environment influences our behaviors and shapes our brains,” Fiona Hollis, a neuroscientist at the Brain Mind Institute, who did not participate in the study, wrote in an e-mail to The Scientist. “By demonstrating a link between early-life trauma and adult pathological aggression, we can better understand, and perhaps even reverse, the mechanisms underlying the cycle of violence, that is too often observed in society.”

Previous studies in rats, have clearly demonstrated the negative effects of stress, incurred soon after birth. Young pups, when separated from their mother, for example, develop into more aggressive adults. But whether stress incurred through adolescence had similar effects was unclear.

To investigate this question, the Brain Mind Institute’s Carmen Sandi and colleagues exposed 28- to 42-day-old adolescent rats to a fox odor or placed them in a vulnerable position on an elevated platform under bright light for a few minutes every day for 7 days. Rats exposed to such fearful stimuli grew up to become “bullies,” displaying pathological violence against any new rat introduced to their cage. Control rats that were not exposed to fearful stimuli as adolescents, one the other hand, were significantly less aggressive toward intruders, as adults.

Rats stressed in adolescence also presented anxiety and depression-like behaviors as adults; exhibited increased activity in the amygdala, the part of brain associated with fear responses; and showed lowered activity in the orbito-frontal cortex, a part of the pre-frontal cortex. These specific brain activity patterns have been linked to aggression and violence in humans. Additionally, the stress-exposed adolescent rats, as adults, displayed hormonal irregularities, namely high testosterone and low corticosterone levels—another pattern associated with increased aggression and violence in humans.

The effects of early-life adversity percolated right down to the level of the rats’ DNA. . .

Continue reading.

Written by LeisureGuy

28 January 2013 at 11:25 am

Posted in Mental Health, Science

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