Children with autism may have higher-than-normal connectivity between certain areas of the brain, suggests a small study that hints brain imaging might some day be used to diagnose the developmental disorder.
The findings come from MRI brain scans of 20 children with autism spectrum disorders and 20 children without autism. Researchers found that those with an autism spectrum disorder showed "hyperconnectivity" along five major brain networks.
The results, reported in the June 26 online issue of JAMA Psychiatry, suggest that the brain's "functional organisation" differs between kids with and without autism.
"The way different areas within those brain networks 'talk' to each other is quite different in children with autism, compared with typically developing children," said senior researcher Vinod Menon, a professor of psychiatry and behavioural sciences at Stanford University School of Medicine in California.
One network, called the salience network, showed the most hyperconnectivity -- which basically means that a greater-than-normal number of brain areas are activated at the same time. The salience network helps the brain decide which part of our environment deserves our attention at any given moment.
Restrictive and repetitive behaviours
Menon's team found that the more hyperconnectivity kids with autism had in the salience network, the more severe their "restrictive" and repetitive behaviours.
Those types of behaviours -- such as being completely engrossed in a single interest, or needing to follow precise daily routines -- are among the hallmarks of autism.
It's not clear that the hyperconnectivity actually causes those repetitive behaviours, but that is what the new findings "hint", Menon said.
Another possibility, he added, is that hyperconnectivity is involved in the exceptional skills seen in some kids with an autism diagnosis -- like being a whiz with numbers. For now, though, that's an "open question", Menon said.
Autism spectrum disorders, which affect about one in 88 US kids, are a group of developmental disorders that range widely in severity. Some people have mild problems socializing but have normal to above-normal intelligence; others have profound difficulties relating to others, speak very little and may have intellectual impairment as well.
An expert not involved in the current study said it could be a "starting point" for developing an objective way to help diagnose autism spectrum disorders, which is currently done by observing children's behaviour. This often delays diagnosis.
But there are still a lot of questions, said Daniel Smith, senior director of discovery neuroscience for the advocacy group Autism Speaks.
One is whether the same brain activity patterns are seen in young children with autism spectrum disorders -- the age at which you would want to diagnose them. The kids in this study were between 7 and 12 years old.
The children on the autism spectrum were also all "high-functioning" -- with normal IQs and language skills, but had problems with socialising and having conversations. So, studies need to include children with more severe autism, Smith and Menon said.
Right now, that's tricky, Menon pointed out. Kids need to be able to lie still for the MRI scans, which may be impossible for children with more severe forms of autism. Menon said he hopes the continually improving technology will help in that regard.
No one knows what causes autism, but experts believe that genetic vulnerability and some mix of environmental factors are at work.
Last week, the same Stanford team found that children with an autism spectrum disorder showed weaker connections between certain other brain areas -- namely, areas that process the human voice and those involved in feelings of "reward".
They speculated that these children may get less pleasure from the sound of the human voice, and that might help explain some of their communication difficulties.
"I think there will turn out to be an interplay between hyperconnectivity and hypoconnectivity in the brains of children with an autism spectrum disorder," Menon said.
The hope, he said, is that these early findings will eventually lead to reliable "biomarkers" of autism. Doctors then may be able to use brain scans to improve diagnosis at an earlier age. But that will take more time and study.
One of the "next critical steps" is to study young children, Menon said. "Our findings will help guide those studies."
Autism Speaks has more on autism spectrum disorders.