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- WASHINGTON (Reuters) - Murderers
and other people prone to violence have distinct brain patterns that can
be scanned and that might be changed with drugs and other therapies, researchers
said on Thursday.
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- They said in most people, the brain can rein in overreaction
to emotions such as fear and anger. But in pathologically violent people,
this control system gets short-circuited.
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- They said several studies have shown this rewiring can
be clearly seen in images such as PET (positron emission tomography) scans.
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- ``Impulsive, affective aggression may be the product
of a failure of emotion regulation,'' University of Wisconsin-Madison psychologist
Richard Davidson and colleagues wrote in their report, published in the
journal Science.
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- They said normal people can control their emotions, and
can respond to cues from other people, such as facial expressions of fear.
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- ``We suggest that individuals predisposed to aggression
and violence have an abnormality in the central circuitry responsible for
these adaptive behavioral strategies,'' they wrote.
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- Davidson and his team reviewed studies, including some
of their own, involving 500 violent people with aggressive personality
disorder, childhood brain injuries and convicted murderers.
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- They compared their brain function to nonviolent people.
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- They found dysfunction in the same brain regions in 41
murderers, in a group suffering from aggressive impulsive personality disorder
and in some people diagnosed with antisocial personality disorder.
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- The same brain regions were involved again and again,
Davidson's team found.
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- ``The evidence we have reviewed indicates that the orbitofrontal
cortex and the structures with which it is interconnected, including other
prefrontal territories, the anterior cingulate cortex, and the amygdala,
constitute core elements of a circuit that underlies emotion regulation,''
they wrote.
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- The orbital frontal cortex is important in holding back
impulsive outbursts, while the anterior cingulate cortex recruits other
brain regions in the response to conflict.
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- The amygdala, the almond-shaped structure linked with
fear and emotion, is also an important player. In violent people, its activity
essentially ran out of control, while other brain regions could calm it
down in normal people.
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- ``Abnormalities in serotonin function in regions of the
prefrontal cortex may be especially important,'' the researchers added.
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- Serotonin is an important message-carrying hormone, known
as a neurotransmitter, linked with mood and emotion. It is targeted by
antidepressant drugs.
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- Davidson said genetics and environment are probably both
involved. He said it may be possible to rewire these faulty circuits with
drugs or psychological therapy.
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- ``Given what we know about brain plasticity and the fact
that the brain really can change in response to experience, we have good
reason to expect that these treatments may, in fact, have beneficial consequences,''
he said in a statement.
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- Meanwhile, a second report in Science suggested that
aggression is not always bad.
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- Frans de Waal of the Yerkes Regional Primate Research
Centre in Atlanta said sometimes conflict led to closer relationships by
letting people literally kiss and make up.
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- ``For example, chimpanzees kiss and embrace after fight,
and other nonhuman primates engage in similar reconciliations,'' he wrote.
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