In a new report, researchers document poor connections between brain regions that respond to the human voice and those that provide pleasure in children with autism.
As such, it could help explain why those with autism tend to miss the social and emotional aspects of human speech, the researchers conclude. “Weak brain connectivity may impede children with autism from experiencing speech as pleasurable, explains neuroscientist Vinod Menon, Ph.D., the study’s senior author.
The study may well reveal one source of the altered sensitivity to spoken communication that we see in autism, adds Daniel Smith, Ph.D., Autism Speaks senior director for discovery neuroscience. “It is important to improve our understanding of the causes of these verbal communication differences,” he says, "because it provides a peek at the type of biological features we might be able to use to better diagnose and treat autism.”
Following the brain connections
The study included 20 children with autism and 19 unaffected by the disorder. All had normal IQ and could speak and read. However, those with autism had difficulty holding conversations and understanding emotional cues in a person's voice.
The investigators compared functional magnetic resonance imaging brain scans while the children listened to human voices. In those with autism, the voice-processing centers on the left side of the brain connected only weakly to brain circuits that release dopamine. A messenger chemical, dopamine activates the brain's “reward” centers.
Among the children studied, those with weaker connections between these brain centers had the greatest problems with communication. Indeed, the researchers could use the strength of the brain connections to predict the children's scores on the verbal portion of a standard test of autism severity.
"The human voice is a very important sound. It not only conveys meaning but also provides critical emotional information to a child," says lead investigator Daniel Abrams, Ph.D. "We are the first to show that this insensitivity may originate from impaired reward circuitry in the brain."
Support for autism therapies that emphasize social communication
In theory, the findings support the effectiveness of autism therapies that emphasize pleasurable social communication, says co-investigator and autism therapist Jennifer Phillips, Ph.D. In doing so, such interventions may strengthen these vital brain connections. Future studies could test whether this is true.
“This study takes the field to a new level by using cutting-edge brain imaging tools," Dr. Smith says. "It reveals that specific brain circuits are altered in some children with autism.” People with autism are a very diverse group, he adds. “What our community needs to know next is whether this applies to very many or very few affected individuals."
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