One of the ways in which individuals convey feelings and thoughts to one another is through touch. Although the neural responses to felt and observed tactile stimuli between an inanimate object and a part of the human body have been vastly explored, the neural responses to observed human interaction involving touch are not well understood. Considering that the observation of social touch involves vicarious sharing of emotions, we hypothesized that levels of empathic traits modulate the neural responses to observed touch and focused on the attenuation in the mu\alpha rhythm (8-13Hz), a neural marker that has been related to sensorimotor resonance. Fifty-four participants observed photos depicting social touch, nonsocial touch, or no touch while their electroencephalography (EEG) activity was recorded. Results showed that interindividual differences in levels of empathic traits modulated both behavioral and electrophysiological responses to human social touch, such that highly empathic participants evaluated human social touch as inducing more pleasant emotions and exhibited greater mu suppression upon observation of human social touch compared to less empathic participants. Specifically, both the behavioral and the electrophysiological responses to observed social touch were predicted by levels of personal distress, a measure of emotional contagion. These findings indicate that the behavioral and electrophysiological responses to observed social touch are modulated by levels of empathy.

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Although individuals with autism spectrum disorder (ASD) have impaired responses to interpersonal touch, the underlying neural correlates remain largely unknown. Here, we examined the neural correlates that underlie interpersonal touch perception in individuals with either high or low autistic traits. Fifty-three participants were classified as having either high or low autistic traits based on their performance on the autism quotient (AQ) questionnaire. We hypothesized that individuals with high AQ scores would have relatively high touch hypervigilance, reflected as earlier P1 and stronger late positive potential (LPP) responses, two components of event-related potentials that serve as electrophysiological markers of anxiety bias. We recorded each participant's electroencephalography activity during presentation of images depicting human touch, object touch, and non-touch control images. Consistent with our hypothesis, AQ scores were positively correlated with social touch aversion. Moreover, participants with high AQ scores had earlier P1 and stronger LPP responses when presented with human touch compared to the control images. Importantly, a regression model revealed that earlier P1 and larger LPP amplitude measured during social touch observation can accurately predict higher autistic trait levels. Taken together, these findings indicate that individuals with high levels of autistic traits may have a hypervigilant response to observed social touch. Autism Res 2017, 0: 000-000. © 2017 International Society for Autism Research, Wiley Periodicals, Inc. Autism Res 2017, 10: 1141-1154. © 2017 International Society for Autism Research, Wiley Periodicals, Inc.

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