The way the gray matter in the brain is wired appears to be different in people with autism, new research shows.
Specifically, those with the disorder are more likely to have enhanced connections in the brain that are associated with common autism symptoms, such as narrow interests and repetitive behaviours, the scientists reported.
"Our study [and others] reliably and repeatedly demonstrate that the brain in autism is built and functions differently, which explains a variety of autistic symptoms," said study author Christine Ecker, a lecturer in neuroimaging at King's College London.
"From neuropsychology we also know that people with autism often have a preference for processing [fine details] over global features (the ability to integrate piecemeal information into a coherent whole)," she said. "Our findings may therefore represent a neuroanatomical correlate of these behaviours, although a direct causal link remains to be established."
Results of the study were published online July 22 in the Proceedings of the National Academy of Sciences.
Autism spectrum disorders are a group of neurodevelopmental disorders, common symptoms of which include impaired social communication, social reciprocity and repetitive behaviours, according to background information included in the study. Experts believe that differences in the brain account for these behaviours, but the exact changes that might occur in someone with autism aren't yet clear, according to the study.
The current study looked at 34 adult males with autism and 34 males without autism to serve as the control group. All of the study volunteers underwent MRI.
The researchers found that there were significant differences in the length of the connections between regions of the brain when they compared people with autism to those without. The minimum length of these connections in the cortical gray matter was dubbed "wiring costs" by the researchers. These wiring costs were significantly reduced in people with autism, meaning the lengths of their connections were shorter.
"These differences are predominantly observed in brain regions that we know are anatomically different in autism, and that are underlying autistic symptoms and traits," Ecker said. "We think that such differences in neuronal wiring may lead to locally over-connected networks in the brains of [patients with autism spectrum disorders] that could explain some autistic symptoms, such as repetitive behaviours."
One expert said the findings help define the biological basis of autism more clearly.
"We've known that there is a history of wiring differences that appear in individuals with autism. What's novel is that they used structural imaging to assess whether neurons are connected in the same way structurally," said Daniel Smith, senior director of discovery neuroscience at Autism Speaks.
"Gray matter connections are referred to as microcircuits, and they're everywhere," Smith said. "They're very important in the cerebral cortex, and the highest levels of thinking occur in the cerebral cortical regions of the brain."
"This study is another component in building our knowledge base," he added. "It's a step toward better understanding of what's happening in the brain and, ultimately, that will help lead to new treatments. But this study won't lead to an immediate impact on treatment."
No immediate changes
Dr Andrew Adesman, chief of developmental and behavioural paediatrics at the Steven and Alexandra Cohen Children's Medical Center in New Hyde Park, NY, agreed that this study won't lead to any immediate changes in the field.
"Unfortunately, despite the many advances in our ability to study the brain and identify a range of structural and functional differences associated with autism, we are still left with more questions than answers," Adesman said.
"[But] studies such as this bring us one step closer to understanding the neurobiological underpinnings of the mysterious and enigmatic condition known as autism spectrum disorder," he said.
Ecker said she hopes to conduct a study that follows young people as their brains are developing to see how the connections in the brain behave over time in people with autism.
Learn more about autism from Autism Speaks.