Children with autism have distinctive patterns of brain activity

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Children with autism have distinctive patterns of brain activity

Researchers say they have identified a unique 'signature' of autism in the

brains of children with the condition

guardian.co.uk, Monday 15 November 2010 20.00 GMT

Autism: Lone boy Children with autism had reduced activity in specific brain

regions.

The pattern of brain activity of children with autism spectrum disorder (ASD) is

markedly different from that of children without the condition, according to a

new brain-imaging study.

The work, which shows that ASD has a " signature " in the brain, may lead to a

better understanding of which parts of the brain the condition interferes with

and how some people, despite having a high genetic risk of developing the

condition, manage to compensate for its effects.

ASD is a genetically influenced condition that affects the development of

children's brains, with symptoms that include difficulties with social

communication, interaction and imagination.

Hundreds of genes may contribute to the condition and scientists believe that

individual cases of ASD could correspond to different patterns of genetic

variation, which could lead to measurable differences in the way that the brains

of autistic children function.

Dr Martha Kaiser and Professor Pelphrey of Yale University led a team of

researchers that explored this idea by studying how children's brains responded

to videos of people moving around them.

" As intrinsically social creatures, humans typically exhibit robust visual

sensitivity to other people's movements, " they write today in the journal

Proceedings of the National Academy of Sciences.

" This is well illustrated by the discovery that point-light displays (ie videos

created by placing lights on the major joints of a person and filming them

moving in the dark), although relatively impoverished stimuli, contain

sufficient information to identify the kind of motion being produced (eg

walking, dancing, reaching) as well as the identity of the agent. "

Previous research found that two-year-olds with autism did not turn to face

point-light displays of " biological motion " .

In their study, Kaiser and Pelphrey placed 62 children aged from 4 to 17 years

old into functional magnetic resonance imaging (fMRI) scanners and monitored

their brain activity as they watched a point-light display of biological motion

and another of scrambled dots.

In the group, 25 children had ASD, 20 were the siblings of children with ASD but

did not display any symptoms themselves, and the remainder were " typically

developing " children.

The researchers identified three signatures of brain activity that corresponded

to the different children's responses to the point-light displays.

Relative to the other groups, there was reduced activity in specific brain

regions in children with ASD when they were watching biological motion compared

with scrambled motion.

These included the right amygdala and the ventromedial prefrontal cortex, areas

which other research has identifed as having changed activity in adults with

ASD.

The researchers found additional brain regions that showed reduced activity in

both the siblings group and the ASD group, relative to the typically developing

group.

They interpreted this result as a reflection of the underlying genetic

vulnerability that the siblings group might have to ASD.

The scientists also found what they called " compensatory activity " in the

siblings group – brain regions that were working harder than normal and might be

helping the children overcome their increased genetic risk of ASD.

These included the right posterior temporal sulcus and the ventromedial

prefrontal cortex, which have been implicated in social perception and social

cognition.

" These regions might reflect the absence of additional genetic or environmental

factors that confer risk for ASD, " the researchers wrote.

" Alternatively, they could represent a process through which brain function was

altered over development to compensate for an increased genetic risk to develop

ASD. "

Dorothy Bishop, a professor of developmental neuropsychology at Oxford

University, said: " This is a potentially interesting study that looks for brain

markers of underlying abnormality in children with autism in response to viewing

dot patterns that indicate biological motion. "

But she added: " More controversially, the authors also propose that other brain

regions are under-responsive to biological motion in siblings of children with

autism, as well as in those with autism.

" Yet other regions are reported to be overactive in the siblings, and this is

interpreted as compensatory activity.

" Since these siblings had no subclinical symptoms of autism, and were selected

to have no other relatives with any autistic features, they are unlikely to

constitute a group with strong genetic risk for autism, and so this aspect of

the results is puzzling and it would be important to replicate it in another

sample. "

The researchers themselves admitted that further studies would be needed to

determine the precise functions of the " compensatory " brain activity that they

had identified.

But if confirmed, they said, these could " represent important targets for

treatments and provide a measure of the effectiveness of intervention, as well

as a better understanding of the mechanisms through which successful treatments

function " .

* guardian.co.uk © Guardian News and Media Limited 2010