INTRODUCTION: Perceiving and understanding the emotional state of other individuals is critical to react adaptively in social environments. Facial and bodily expressions convey important information about another person’s feelings and intentions. Nevertheless, to date most studies have focused on the neural correlates of perception of facial, rather than bodily, emotional expressions. 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). METHODS: We used single-pulse Transcranial Magnetic Stimulation to explore corticospinal motor excitability in the right and left hemispheres. MEPs were recorded from the controlateral FDI hand muscle during observation and active categorization of pictures of emotionally positive (joyful) and negative (fearful) expressions, neutral gestures (i.e. actions with implied movement comparable to emotional body expressions but with no emotional meaning) and static neutral postures (baseline). To explore the time course of motor modulation during emotion perception, motor excitability was assessed at 150 and 300 ms after stimulus presentation (Fig1). After TMS, subjects completed the Interpersonal Reactivity Index (IRI) (Davis, 1996). RESULTS: In the early time window (150 ms after stimulus onset) seeing emotionally positive and negative expressions reduced motor excitability in the right hemisphere relative to neutral gestures (Fig.2). Such inhibitory response to emotional bodies correlated with participants’ score at the Personal-Distress subscale of the Interpersonal Reactivity Index (IRI) (Fig.3) and was absent in the left hemisphere. Conversely, at 300 ms, greater excitability for positive, negative and neutral gestures relative to neutral static body postures was found in both hemispheres (Fig.4). This later motor facilitation marginally correlated with the IRI’s Perspective-Taking subscale (Fig.5). CONCLUSIONS: We explored the temporal dynamics of human corticospinal system during the perception of emotional and neutral gestures. Our findings demonstrate that the motor system is firstly influenced by the emotional meaning and then the motion features of the observed bodily expressions. We found a relatively early (150 ms) inhibitory response to emotionally arousing body expressions that was specific for the right hemisphere. This inhibitory response was independent from “motion” features of the gesture and it was absent when seeing neutral gestures. Moreover it was greater in participants with higher interpersonal anxiety-related personality traits (personal distress) and likely reflected a freezing-like orienting response toward emotional body cues. The later facilitatory response (300 ms) occurred in both hemispheres independently from the emotional meaning of the gestures and was greater in participants with higher cognitive empathy. This later response likely reflected the simulation of the body movement implied in the observed gestures that occurred independently from its emotional meaning. 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. References: Davis, M. H. (1996). Empathy: A social psychological approach. Boulder, CO: Westview Press.