Perception of emotional bodies triggers fast motor reactions and motor resonance in the human corticospinal system

Imaging studies indicate that perceiving emotional bodies may recruit fronto-parietal regions involved in action execution. However, it is unclear whether activity in the motor system reflects “resonance” with the observed body postures (i.e. action mirroring) or an emotion-specific motor response (e.g. fight/flight reaction). To address this issue we used single-pulse Transcranial Magnetic Stimulation to explore corticospinal motor excitability in the right and left hemispheres, while participants observed pictures of emotionally positive (joy) and negative (fear) gestures, neutral actions, and static postures. To explore the time course of motor modulation during emotion perception, motor excitability was assessed at 150 and 300 ms after stimulus presentation. Relative to neutral postures, at 150 ms seeing emotionally positive and negative gestures reduced motor excitability in the right hemisphere. Such early freezing-like response to emotional bodies correlated with participants’ score at the Personal-Distress subscale of the Interpersonal Reactivity Index (IRI) (stronger inhibition in subjects with high interpersonal anxiety-related disposition) and was absent in the left hemisphere. Conversely, at 300 ms, greater excitability for positive, negative and neutral actions relative to static body postures was found in both hemispheres. This later motor facilitation marginally correlated with the IRI’s Perspective-Taking subscale (dispositional cognitive empathy) and reflected the simulation of the body movement implied in the emotional and neutral action stimuli. These findings highlight the motor system involvement during the perception of emotional bodies and suggest that fast reactions to emotional cues occur well before motor features of the observed emotional gesture are simulated in the motor system.