Pictures of disgusting foods and disgusted facial expressions suppress the tongue motor cortex

Abstract

The tongue holds a unique role in gustatory disgust. However, it is unclear whether the tongue representation in themotor cortex (tM1) is affected by the sight of distaste-related stimuli. Using transcranialmagnetic stimulation (TMS) in healthy humans, we recorded tonguemotor-evoked potentials (MEPs) as an index of tM1 cortico-hypoglossal excitability. MEPs were recorded while participants viewed pictures associated with gustatory disgust and revulsion (i.e. rotten foods and faces expressing distaste), non-oral-related disgusting stimuli (i.e. invertebrates like worms) and control stimuli. We found that oralrelated disgust pictures suppressed tM1 cortico-hypoglossal output. This tM1 suppression was predicted by interindividual differences in disgust sensitivity. No similar suppression was found for disgusting invertebrates or whenMEPs were recorded froma controlmuscle. These findings suggest that revulsion-eliciting food pictures trigger anticipatory inhibitionmechanisms, possibly preventing toxin swallowing and contamination. A similar suppression is elicited when viewing distaste expressions, suggesting vicariousmotor inhibition during social perception of disgust. Our study suggests an avoidant-defensive mechanismin human cortico-hypoglossal circuits and its 'resonant' activation in the vicarious experience of others' distaste. These findings support a role for themotor system in emotion-drivenmotor anticipation and social cognition.