The sense of touch may play a more crucial role in autism spectrum disorder (ASD) than previously assumed. The main findings of the doctoral research of Eliane Deschrijver of Ghent University, which are now published, show that individuals with ASD may have difficulties to determine which tactile sensations belong to the action of someone else.
ASD: Social problems and sensory sensitivities
Many individuals with ASD are over- or undersensitive to sensory information. Some feel overwhelmed by busy environments such as supermarkets, others are less sensitive to pain, or dislike being touched.
Large-scale queries in the scientific literature had reported already that the severity of daily social difficulties of individuals with ASD is strongly related to the extent to which they are sensitive to touch, more so than to the extent to which they show visual or auditory sensitivities. To determine why this is the case, Deschrijver and her colleagues investigated how the brain of individuals with and without ASD uses own touch to understand touch sensations in the actions of others.
Prof. Dr. Marcel Brass clarifies: "We think that the human brain uses the own sense of touch to distinguish one's self from others: When I perform an action that leads to a tactile sensation, for instance by making a grasping movement, I expect to feel a tactile sensation that corresponds to this. If my own touch tells me something else, the tactile sensation will probably belong to the other person, and not to me. The brain can thus effectively understand others by signaling tactile sensations that do not correspond to the own sense of touch."
In a series of experiments with electro-encephalography (EEG), the scientists showed that the brain activity of adults with ASD differs from that of adults without ASD while processing touch.
The research showed that the human brain of individuals without ASD indicated very quickly when a tactile sensation does not correspond to the own sense of touch. This means that the human brain is able to signal that a tactile sensation of a finger that touches a surface does not correspond to own touch.
This process occured otherwise in the brain of adults with ASD however. Their brain signaled to a much lesser extent when the external touch sensation did not correspond to their own touch. Those individuals that experienced stronger sensory difficulties showed a stronger disturbance of the neural process, while they were also the ones that experienced more severe social difficulties.
"It is to my knowledge the first time that a relationship could be identified between the way individuals with ASD process tactile information in their brain, and their daily social difficulties. The findings can yield a novel and crucial link between sensory and social difficulties within the autism spectrum," concludes Deschrijver.
"These findings primarily lead to a better understanding of the complex disorder, and of associated difficulties. It is yet too early to conclude on the impact on interventions. If the results can be confirmed in future studies of other groups with ASD, such as (young) children, they could provide a target for optimizing treatment," according to Prof. Dr. Jan Wiersema.
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Deschrijver E, Wiersema JR, Brass M. Action-based touch observation in adults with high functioning autism: Can compromised self-other distinction abilities link social and sensory everyday problems? Social Cognitive and Affective Neuroscience, Published Online September 9 2016. doi: 10.1093/scan/nsw126
Deschrijver E, Wiersema JR, Brass M. The interaction between felt touch and tactile consequences of observed actions: an action-based somatosensory congruency paradigm. Social Cognitive and Affective Neuroscience, Published Online July 7 2016. doi: 10.1093/scan/nsv081