Investigation of facial mimicry processes in emotion recognition: a TMS study

Abstract

Embodiment theories stipulate that observing emotional facial expressions leads to facial mimicry and that the feedback of this mimicry from the periphery to the somatosensory cortices, especially for the right hemisphere, plays a role in emotion recognition. This facial feedback would be necessary for, or at least can modulate, the understanding and the interpretation of perceived facial expressions. Several studies found that blocking mimicry affects emotion recognition (Oberman et al. 2007; Davis et al., 2010) but the exact interplay of face perception, facial mimicry generation and facial feedback processing, has not been clearly demonstrated yet. In this study, we aim at observing the involvement of mimicry generation and mimicry feedback in emotion recognition with the use of theta-burst rTMS to reduce motor cortex, or somatosensory cortex activation, prior to emotional facial expression evaluation tasks with EMG recording. Theta-burst TMS over motor cortex inhibition w ill reduce facial mimicry, whereas somatosensory stimulation will inhibits facial feedback only compared to the ‘sham’ vertex target. Behaviorally, we predicted lower intensity judgments of emotional expressions or slower recognition after rTMS over motor and/or somatosensory cortex vs. vertex. However, if somatosensory inhibition does not have an effect on speed or intensity, the emotion recognition would be independent of feedback and just based on mimicry generation. Whereas, facial mimicry would be performed in order to have a necessary feedback in emotion recognition. Our preliminary results suggest an involvement of both motor and somatosensory cortices, particularly observable with behavioral data after inhibitory rTMS over these areas.