[Paleopsych] BBC: 'Over-friendly' brain clues found

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'Over-friendly' brain clues found
http://news.bbc.co.uk/2/hi/health/4664541.stm

Scientists have uncovered clues about what happens in the brain to make some 
people "over-friendly".

US National Institute of Mental Health experts looked at differences in the 
brains of people with an abnormality which makes them highly sociable.

Researchers used scans to identify areas which failed to work properly when 
they saw frightening faces.

In Nature Neuroscience, they say this could give clues for understanding social 
disorders in others.

Scary faces

People with the genetic condition Williams Syndrome lack around 21 genes on 
chromosome seven.

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This may be the first study to identify functional disturbances in a
brain pathway associated with abnormal social behaviour caused by a
genetic disorder
Thomas Insel, director of the National Institute of Mental Health
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Their lack of fear means they will impulsively engage in social situations, 
even with strangers.

But they often have heightened anxiety about non-human fears, such as spiders 
or heights.

The condition affects around one in 25,000 people.

The US team focused on the amygdala, an almond-shaped structure deep in the 
brain which has been thought to help regulate social behaviour.

fMRI (functional Magnetic Resonance Imaging) scans was used to study the brains 
of 13 healthy volunteers and 13 with Williams Syndrome.

All were shown pictures of angry or scary faces.

In healthy brains, seeing such images would provoke a strong response in the 
amygdala.

However the fMRI scans showed far less activity in those of people with 
Williams Syndrome.

Study participants were then shown pictures of threatening scenes, such as 
plane crashes, which did not have any people or faces in them.

The amygdala response was seen to be abnormally increased in participants with 
Williams Syndrome.

'Poor orchestration'

The researchers also identified three key areas of the prefrontal cortex, 
located in the front part of the brain, which did not behave normally in people 
with the syndrome.

They were the dorsolateral area - linked to establishing and maintaining social 
goals governing an interaction; the medial area - associated with empathy and 
regulating negative emotions; and the orbitofrontal region - involved in 
assigning emotional values to a situation.

Thomas Insel, director of the NIMH, said: "Social interactions are central to 
human experience and well-being, and are adversely affected in psychiatric 
illness.

"This may be the first study to identify functional disturbances in a brain 
pathway associated with abnormal social behaviour caused by a genetic 
disorder."