Feeling addressed! The role of body orientation and co-speech gesture in social communication

During face-to-face communication, body orientation and coverbal gestures influence how information is conveyed. The neural pathways underpinning the comprehension of such nonverbal social cues in everyday interaction are to some part still unknown. During fMRI data acquisition, 37 participants were presented with video clips showing an actor speaking short sentences. The actor produced speech-associated iconic gestures (IC) or no gestures (NG) while he was visible either from an egocentric (ego) or from an allocentric (allo) position. Participants were asked to indicate via button press whether they felt addressed or not. We found a significant interaction of body orientation and gesture in addressment evaluations, indicating that participants evaluated IC-ego conditions as most addressing. The anterior cingulate cortex (ACC) and left fusiform gyrus were stronger activated for egocentric versus allocentric actor position in gesture context. Activation increase in the ACC for IC-ego>IC-allo further correlated positively with increased addressment ratings in the egocentric gesture condition. Gesture-related activation increase in the supplementary motor area, left inferior frontal gyrus and right insula correlated positively with gesture-related increase of addressment evaluations in the egocentric context. Results indicate that gesture use and body-orientation contribute to the feeling of being addressed and together influence neural processing in brain regions involved in motor simulation, empathy and mentalizing.