There is currently no objective test to help doctors diagnose autism, a developmental disorder that strikes about 1 in 100 children, typically before age 3. Children with autism struggle with language and communication, social interaction, and may exhibit repetitive movements like rocking or flicking a wrist.
The study, which is published in the journal BMC Medicine, used electroencephalograms (EEGs) to study patterns of electrical activity in the brains of nearly 1,000 children. About half of the children had been diagnosed with autism. The other half did not have autism and were used for comparison. All the kids were between the ages of 2 and 12.
The kids in the study wore a cap of 24 electrodes that recorded patterns of brain activity while they were awake and alert. A technologist kept a close eye on the recording to flag any spikes in activity that could have been caused by slight movements like blinking, yawning, or drowsiness.
Researchers discovered 33 specific patterns, or factors, that reliably distinguished children with autism from their normal peers.
Most of the patterns showed areas of decreased brain activity. That diminished activity was especially apparent on the left side of the brain, the area responsible for language and communication.
But about 30% of the patterns showed increased activity, leading researchers to guess that the brain may be working harder in certain regions to overcome the local areas of faulty communication.
"They may be the brain's attempt to overcompensate for the regions that should be working together but aren't working together so well," says researcher Frank H. Duffy, MD, a developmental neurophysiologist at Boston Children's Hospital and an associate professor at Harvard Medical School.
Another explanation, Duffy tells WebMD, may have something to do with seizures.
"There's also a high association of autism with seizure disorders," he says. "An over-connected brain may be more prone to seizures than an under-connected brain."
The next step, Duffy says, will be to compare the patterns of brain activity seen in autism to the EEGs of children who have other kinds of developmental disorders to see how much they overlap.
If the overlap is minimal, researchers think EEGs may one day be a help to doctors as they make an autism diagnosis.
Another way the test could potentially be used is to see whether treatments like drugs or behavioral therapies are working.
Geraldine Dawson, PhD, the chief science officer of the nonprofit group Autism Speaks, says the study is one of the largest to show that children with autism have these patterns of reduced coordination across brain regions.
"This reduced functional connectivity in the brain helps us understand the impairments associated with autism," Dawson, who is also a professor of psychiatry at the University of North Carolina at Chapel Hill, says in an email. "The hope is that early behavioral intervention can help [modify] these functional impairments helping to form the connections that naturally develop in typical children."