We know that people with autism spectrum disorder (ASD) do not process facial expressions and emotions the same way that people without ASD do. However, there is little agreement about the cause of these deficits. Researchers at Children’s Hospital Los Angeles and Columbia University recently conducted a study to find out how individuals with ASD process facial expressions compared to typically developing (TD) individuals. The study reveals that people with ASD have more neural activity in response to expressions like happiness or fear. The findings may help scientists understand why people with ASD process emotional stimuli differently.
The researchers used functional magnetic resonance imaging (fMRI) to assess brain activity in 51 individuals with ASD and 84 TD individuals. They were specifically interested in two neurophysiological systems: valence and arousal. “Valence” refers to how positive or negative an emotion is. “Arousal” refers to how much something commands attention. For example, a “happy” response might arise from a strong positive valence with moderate positive arousal. The researchers showed the participants a range of facial expressions and then correlated their responses with the neural activity they measured with the fMRI.
Both the ASD and TD groups demonstrated a comparable response, yet there were significant differences in their neural activity. The ASD participants had more neural activity in response to arousing facial expressions like happiness or fear. In contrast, TD participants had greater activity when viewing less arousing, more impassive expressions.
The results suggest that TD and ASD individuals find different aspects of emotional stimuli relevant. The findings may help explain how these atypical responses to interpersonal and emotional experiences develop in people with ASD.
“Human beings imbue all experiences with emotional tone. It’s possible, though highly unlikely, that the arousal system is wired differently in individuals with ASD. More likely, the contrast in activation of their arousal system is determined by differences in how they are experiencing facial expressions. Their brain activity suggests that those with ASD are much more strongly affected by more arousing facial expressions than are their typically developing counterparts,” stated principal investigator Bradley Peterson, MD, director of the Institute for the Developing Mind at Children’s Hospital Los Angeles.
This research is published in the journal Brain Mapping.
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