Atypical sensitivity to touch is common in children with autism spectrum disorders (ASD). Existing reports cover a wide array of behaviors, including under-sensitivity to pain, over-sensitivity to light touch, preference for deep pressure, and atypical reaction to social touch. Most of these reports have been either anecdotal or qualitative, however, and few studies exist with direct, quantitative measurements of sensitivity to social touch.
A new study published in Social Cognitive and Affective Neuroscience offers insight into why some people do not respond to physical touch and how families affected by autism may learn to show affection without overwhelming an child with autism’s senses.
Yale neuroscientists imaged their brain activity of young adults as a researcher lightly brushed them on the forearm with a soft brush. In some cases, the brushing was quick, and in others slow: prior studies have shown that slow brushing is perceived as affectionate contact, while the faster version is felt as less social and more uncomfortable.
The researchers evaluated the study subjects for autistic traits — things like a preference for sameness, order and systems, rather than social interaction. They found that participants with the highest levels of autistic traits had a lower response in key social brain regions — the superior temporal sulcus (STS) and orbitofrontal cortex (OFC) — to the slow brushing.
According to Martha Kaiser, senior author of the study and associate director of the Child Neuroscience Laboratory at the Yale Child Study Center, the STS is a critical hub of the social brain. “This region is important for perceiving the people around us, for visual social stimuli and for perceiving social versus nonsocial sounds,” she says.
A 2011 study at Yale looking at sensitivity to social touch in school-age children with Autism Spectrum Disorders found an altered sensitivity and response to social touch in those individuals with ASD. They determined that neurotypical children are trained from infancy to be able to recognize certain kinds of touch as social, and to react and respond in kind.
OFC helps the brain to determine if experiences are likely to be good or bad and if they involves pleasure or pain. “The brains of people high in autistic traits aren’t coding touch as socially relevant, that’s one interpretation,” says Kaiser of her findings. “The OFC is very important for coding reward so maybe they’re feeling the touch but in these individuals, their brains don’t code that type of touch as being as rewarding as in individuals with fewer autistic traits.”
The University of Californa, San Franscico Autism and Neurodevelopment Program is looking to do a study on how boys with autism process sound and touch and whether these sensory differences exist on a neurological level. They will be looking at where in the cortex activity is generated and how that activity looks in terms of timing and level of response.
Kaiser and her colleagues are already studying people with autistic spectrum disorders to explore these questions, particularly in children. Making social touch more rewarding early in development might further help autistic children learn social skills, since learning is heavily dependent on pleasure. And because later development relies on early experience, such a strategy could improve their overall development. “I think there are a lot of potential treatment applications for this work,” Kaiser says.