Japanese researchers say people with autism usually gauge warmth or hostility through verbal rather than visual indicators such as facial expressions, and have identified the area of the brain that determines the process, according to a study released Saturday.
The findings could lead to the development of an objective method to diagnose communication disorders or even a treatment for the symptoms, they said.
"Autistic patients are known to have difficulty understanding jokes or ironic remarks where facial expressions and verbal content are incongruent, and the latest results underline this," said Hidenori Yamasue, an associate professor at the University of Tokyo who participated in the study.
The research, published online by the PLoS ONE scientific journal, studied 15 adult males with autism spectrum disorders but no mental disabilities.
The subjects were shown videos of a smiling actor reading negative words such as "dirty," and another with a disgusted expression saying positive words, such as "great." They were then asked to determine if the actors were friendly or hostile while changes in their brain activity were monitored via functional magnetic resonance imaging.
The results showed they tended to place a greater emphasis on words instead of nonverbal cues and that brain activity diminished in the medial prefrontal area, which interprets other people's intentions or sentiments.
A similar study on 17 adult males without autism showed facial expressions were prioritized over verbal communication, with high activity recorded in the medial prefrontal area.
Communication disorders become increasingly severe the more such brain activity is diminished, according to the study, which can be viewed at www.plosone.org/home.action.