Somatosensory Evoked Potentials reveal reduced embodiment of emotions in autism

In the past two decades, research has shown the contribution of the somatosensory system to emotion recognition, supporting the embodied emotion hypothesis. Atypical processing of emotional expressions in Autism Spectrum Disorder (ASD) has been mainly investigated at a visual level, here we aim to test if ASD individuals show atypical responses in the somatosensory system during emotion recognition, compared to typically developed (TD) individuals. We presented neutral, fearful and happy faces and asked our participants to pay attention to the emotional expression (emotion task) or the gender (control task) while recording their brain activity with a 64-channels EEG. We measured the visual evoked potentials (VEPs) over the occipital lobe and the somatosensory evoked potentials (SEPs) over sensorimotor areas. SEPs were evoked by applying a tactile stimulation on their index finger during the visual processing in 50% of trials. To isolate the somatosensory activity related to emotion processing from visual carryover effects, we subtracted the neural responses recorded in the visual condition from activity in the visuo-tactile condition (Sel et al., 2014). Interestingly, we found significant task*group and task*group*region interactions in the 100-130ms time window (corresponding to P100 SEPs component), showing enhanced difference between the two groups in the emotion task, in particular in frontal sensorimotor regions. Moreover, simple linear regressions revealed that autistic traits measured by Autism Quotient (AQ) and Social Responsiveness Scale (SRS) significantly predicted SEPs amplitude evoked during the emotion task. EEG signal was source localized in the right primary and secondary somatosensory cortex and in the right supplementary motor area. Our study provides novel evidence of atypical responses in the somatosensory system during recognition of emotional expressions in individuals with ASD.