A new study offers a preliminary explanation for one of the symptoms of autism spectrum disorder (ASD). Many people with ASD are hyper-sensitive to the sensation of touch and fail to recognize the social import of touching. The study, from the Yale Child Study Center finds that the brains of children with ASD respond differently to social touches, like a light graze of the arm, than children without ASD. The findings could help research understand some of autism’s social deficits.
The researchers used functional magnetic resonance imaging (fMRI) to assess 19 children with ASD and 19 controls. During the fMRI, the researchers lightly touched the participants with a soft brush, gently grazing the children’s forearms and palms. Touching participants’ arms was intended to activate a type of nerve called c-tactile afferents. These nerves, found in hair and skin, respond to social touches. In contrast, a touch to the palm of the hand activates nerves that interpret information about texture and environmental conditions.
The children in the control group had more brain activity in regions that process social information—the prefrontal cortex, fusiform gyrus, and amygdala—in response to the arm touch than to the palm touch. In contrast, the children with ASD had similar brain activity in response to both touches. This suggests that people with ASD may be unable to get social information from touch or that their brains process social information differently than people without ASD. The children with ASD also demonstrated a stronger response to the palm touch than the children in the control group.
“People without autism automatically interpret the social significance of the touch and start revving up the parts of the brain involved in processing social information. [People with autism] perceive the non-social aspects of touch, but they don’t perceive the significance,” explained lead researcher Kevin Pelphrey, professor of psychology.
The results may help researchers understand why some people with ASD dislike touching. The study may also offer evidence for the “intense world” theory of autism, which hypothesizes that the symptoms of autism are the result of heightened responses to everyday stimuli.
This research is published in the journal Cerebral Cortex.
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