31604
Knowing about Others Versus Feeling about Others: Neural Basis of Understanding the Meaning of Socio-Affective Touch in Adults with Autism Spectrum Disorders
Humans can grasp the socio-affective implications of touch during mere observation. This ability can be explained by the theory of mind (ToM) and embodied resonance account. Individuals with autism spectrum disorder (ASD) exhibit impairments in the use of nonverbal communication such as social and reciprocal touch. Despite the importance of interpersonal touch in social communication and the pervasiveness of touch aversion in ASD, the neural basis underlying these difficulties is largely unknown.
Objectives:
The purpose of the current study is to identify the neural basis of social impairment related to socio-affective touch processing in individuals with ASD. In particular, we examined the involvement of the ToM and somatosensory resonance system in observed touch processing.
Methods:
Twenty-one individuals with ASD and twenty-one age-, gender-, and IQ-matched neuro-typical (NT) participants took part in the current study. They assessed the valence and arousal of 75 video clips showing social and non-social touch events, followed by participating in fMRI scanning sessions during which they watched the same videos. Also, we stimulated each participant's arm with pleasant and unpleasant touch materials during fMRI sessions in order to select an individual’s touch-sensitive area as a part of regions of interest (ROI). Other ROIs implicated in visual processing and social cognition, including the core ToM region (i.e., the temporoparietal junction (TPJ)), were also functionally defined and included as ROIs. Using multi-voxel pattern analysis (MVPA) methods, we created a group averaged neural representational dissimilarity matrix (RDM) for each ROI in each group. We predicted each neural RDM based on the perceived overall affect (a combination of valence and arousal ratings) of stimuli with multiple regression analysis while controlling for the effects of low-level visual features. Lastly, we measured the relationship between the strength of affective representations in touch-selective regions and individual differences in autistic traits and attitudes toward social touch.
Results:
The results from valence ratings suggest that positive touch was perceived as pleasant, negative touch as negative, and non-social touch as neutral. Concerning arousal ratings, both groups perceived social touch as exciting and non-social touch as calm. Despite the high similarity in their judgments, we observed that individuals with ASD perceived positive touch slightly less pleasant. At the brain level, the overall affective meaning of touch was well represented in TPJ in both groups (Figure 1). Conversely, we found significant group differences in the somatosensory regions as individuals with ASD did not show affective representations in these areas (Figure 1). Lastly, we found a link between the absence of affective representations in the somatosensory regions and individual characteristics (high scores on autistic traits and more negative attitudes toward social touch).
Conclusions:
Our findings reveal the involvement of the ToM mechanism in interpreting the socio-affective meaning of observed touch in both individuals with and without ASD, implying intact ToM ability in ASD. Individuals with ASD, on the other hand, did not show embodied resonance in relation to somatosensory experiences of others, which may be related to social touch aversion and impaired social functioning in daily life.