Perceptual and Neural Response to Affective Tactile Texture Stimulation in Adults with Autism Spectrum Disorders

TLDR

Autism spectrum disorders are linked to altered sensory sensitivity and affective responses, yet the neural mechanisms remain largely unknown. The study used psychophysics and fMRI to examine how adults with ASD and controls respond to textured surfaces varying in roughness and pleasantness. Participants with ASD rated pleasant and unpleasant textures more extreme and varied more on neutral textures, and fMRI revealed reduced BOLD responses to pleasant and neutral textures but heightened responses to the most unpleasant texture in affective somatosensory regions, with insular activation correlating with social impairment, indicating altered affective touch processing that may underlie social reward deficits. Published in *Autism Research* 2012,5:231–244; © 2012 International Society for Autism Research, Wiley Periodicals, Inc.

Abstract

Autism spectrum disorders ( ASD ) are associated with differences in sensory sensitivity and affective response to sensory stimuli, the neural basis of which is still largely unknown. We used psychophysics and functional magnetic resonance imaging ( fMRI ) to investigate responses to somatosensory stimulation with three textured surfaces that spanned a range of roughness and pleasantness in a sample of adults with ASD and a control group. While psychophysical ratings of roughness and pleasantness were largely similar across the two groups, the ASD group gave pleasant and unpleasant textures more extreme average ratings than did controls. In addition, their ratings for a neutral texture were more variable than controls, indicating they are less consistent in evaluating a stimulus that is affectively ambiguous. Changes in brain blood oxygenation level‐dependent ( BOLD ) signal in response to stimulation with these textures differed substantially between the groups, with the ASD group exhibiting diminished responses compared to the control group, particularly for pleasant and neutral textures. For the most unpleasant texture, the ASD group exhibited greater BOLD response than controls in affective somatosensory processing areas such as the posterior cingulate cortex and the insula. The amplitude of response in the insula in response to the unpleasant texture was positively correlated with social impairment as measured by the Autism Diagnostic Interview‐Revised ( ADI‐R ). These results suggest that people with ASD tend to show diminished response to pleasant and neutral stimuli, and exaggerated limbic responses to unpleasant stimuli, which may contribute to diminished social reward associated with touch, perpetuating social withdrawal, and aberrant social development. Autism Res 2012,5:231–244 . © 2012 International Society for Autism Research, Wiley Periodicals, Inc.