Abstract
Growing evidence suggests that we understand others’ mental states by internally recreating, or simulating, their external actions. For example, both executing and observing movement decreases the “mu” rhythm (8-14 Hz) over sensorimotor cortex in electroencephalography (EEG). Reduced mu suppression has been reported in autism spectrum disorder, a finding recently extended to neurotypical individuals with high autistic tendencies (Siqi-Liu et al., 2018). However, this study did not directly compare mu suppression for action execution versus observation, raising questions about the extent to which these effects reflect motor simulation per se. Furthermore, the influence of emotional content on mu suppression is relatively unclear: although emotional body movements are more attentionally salient, neutral movements may be more readily simulated due to familiarity and/or ease of execution. Here we directly compared mu suppression associated with motor execution and action observation as a function of autistic tendencies in a neurotypical sample (n = 37). Participants completed separate blocks of finger-tapping and observation of point-light displays (PLDs) of emotional and neutral body movements. Autistic tendencies were indexed by Autism Quotient scores (AQ; Baron-Cohen et al., 2001), and participants were grouped by median split. We found significant mu suppression over sensorimotor cortex for action execution (AE) and action observation (AO), regardless of AQ subgroup. However, whereas both groups showed highly significant correlations in the scalp distribution of mu suppression for AE vs. neutral AO, mu suppression of emotional AO was only significantly correlated with AE in the high AQ subgroup. Contrary to the idea that action simulation indexed by mu suppression contributes to emotion perception, these results suggest that accessibility of simulation is greater for neutral, as opposed to emotional, movements. Individuals higher in autistic tendencies show more consistent mu suppression for observation of both neutral and emotional movements, with potential consequences for perceiving others’ emotions.