rTMS stimulation improves the facial mimicry and detection response in an empathic emotional task

Facial expression detection and facial mimicry in response to an empathic situation were analyzed in the present research. Recent studies on emotions have revealed a wide range of areas activated in response to emotional cues, specifically the premotor cortex and the sensorimotor cortex, when a subject “mirrors” the perceived emotions. We supposed a “simulation mechanism” may be related to empathic response, and that it could be supported by some specific prefrontal cortical structures. High frequency (10 Hz) rTMS (repeated Transcranial Magnetic Stimulation) was applied to premotor area to induce an increased response to facial expression of emotions when subjects (n=26) were required to empathize with the emotional stimuli. The stimulus emotional valence was also varied (negative vs positive vs neutral faces) to explore the emotional content effect on empathic behavior. Autonomic (facial zygomatic and corrugator EMG subjective response) and detection (Correct Recognitions, CRs; Response Times, RTs,) measures were found to be modulated by the premotor cortex activity. Specifically, when prefrontal structures were activated (in comparison with sham effect and control site stimulation, parietal area) an increased performance was observed in terms of increased CRs and reduced RTs for face recognition from one hand; of increased emotion-specific EMG response from the other hand. In fact, zygomatic muscle was more responsive in case of positive emotion (happiness), whereas corrugator activity was related to negative emotions (fear, anger, disgust). A more significant effect was revealed for negative, and potentially aversive, faces in comparison respectively with positive (happiness) and neutral faces. Finally, a direct correlation was found between the autonomic and detection measures. Taken together, these results suggest a “simulation mechanism” and “embodied behavior” underlying empathic situations that includes both EMG and behavioral responses. This mechanism appears to be supported and regulated by the premotor area.