(Sept 22, 2014) A new study suggests that measuring how fast the brain responds to sights and sounds could help objectively identify severity and subtypes of autism spectrum disorder (ASD). The authors express hope that their simple test might also help diagnose autism earlier.
"One of the challenges in autism is that we don't know how to classify patients into subgroups or even what those subgroups might be," says study leader Sophie Molholm. "This has greatly limited our understanding of the disorder and how to treat it." In addition, Dr. Molholm says, autism diagnosis tends to be “highly subjective and require a tremendous amount of clinical expertise. “ We clearly need a more objective way to diagnose and classify this disorder."
An earlier study by Dr. Molholm’s team suggested that brainwave electroencephalogram (EEG) recordings might be useful in measuring the severity of autism. That study found that children with autism process sensory information such as sight, sound and touch less rapidly than typically developing children do.
In their new study, Dr. Molholm’s team looked at how sensory-processing varies along the autism spectrum. Participants included 43 children, ages 6 to 17, affected by autism but without intellectual disability. (All had IQ scores of at least 80.) While monitoring the children’s brainwave activity, the researchers presented each participant with either a sound (a simple tone), a visual image (red circle) or the tone and image combined. They instructed the children to press a button as soon as they received one of these cues.
Overall, the time it took to process the sound signal – as gauged by reaction time and EEG signals – strongly correlated with the severity of a child’s autism symptoms. The more delayed the response, the more severe the symptoms.
The study found a significant but weaker correlation between the severity of symptoms and the speed of processing the combined audio-visual signals. The researchers saw no association between symptoms and reaction to the visual prompt alone.
"This is a first step toward developing a biomarker of autism severity—an objective way to assess someone's place on the ASD spectrum," Dr. Molholm says. "Using EEG recordings in this way might also prove useful for objectively evaluating the effectiveness of ASD therapies."
In addition, EEG recordings might help diagnose autism earlier, the authors say. "Early diagnosis allows for earlier treatment, which we know increases the likelihood of a better outcome," Dr. Molholm says. Currently, fewer than 15 percent of children with autism receive their diagnosis before age 4.
“The greater importance of this study may rest in underscoring the importance of sensory processing in autism,” comments developmental pediatrician Paul Wang, Autism Speaks head of medical research. “It’s possible that these sensory impairments are at the root of the social and communicative problems,” Dr. Wang explains. “We need to better understand how these sensory differences arise and how they can be best addressed.” Only recently (2013) were sensory processing difficulties added to the criteria used to diagnose ASD.
Dr. Molholm discusses her research in the video below.
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