Facial expressions and hand gestures are utilized in nonverbal communication to convey socially relevant information. One key process that mediates nonverbal communication is simulation. The mirror neuron system (MNS), which maps observed actions onto the motor representations used when producing those actions, likely plays a role in simulation. Previous neuroimaging experiments have identified a putative human MNS that includes the inferior parietal lobule (IPL) and the frontal operculum. Although understanding nonverbal communication presumably involves the MNS, it is unknown whether these two forms of nonverbal social communication have distinct representations within that system. Here we report the results of a functional magnetic resonance imaging experiment in which participants viewed, imitated, and produced facial expressions and social hand gestures. The observation and execution of facial expressions and social hand gestures activated the MNS, but the magnitude of response differed. Activation in the IPL was greater for social hand gestures, whereas activation in the frontal operculum was greater for viewing facial expressions. The locations of neural activity evoked by viewing facial expressions and social hand gestures in the frontal operculum were significantly different. These data argue that there are distinct representations of different types of social nonverbal communication in the MNS.

We compared two tasks that are widely used in research on mentalizing—false belief stories and animations of rigid geometric shapes that depict social interactions—to investigate whether the neural systems that mediate the representation of others' mental states are consistent across these tasks. Whereas false belief stories activated primarily the anterior paracingulate cortex (APC), the posterior cingulate cortex/precuneus (PCC/PC), and the temporo-parietal junction (TPJ)—components of the distributed neural system for theory of mind (ToM)—the social animations activated an extensive region along nearly the full extent of the superior temporal sulcus, including a locus in the posterior superior temporal sulcus (pSTS), as well as the frontal operculum and inferior parietal lobule (IPL)—components of the distributed neural system for action understanding—and the fusiform gyrus. These results suggest that the representation of covert mental states that may predict behavior and the representation of intentions that are implied by perceived actions involve distinct neural systems. These results show that the TPJ and the pSTS play dissociable roles in mentalizing and are parts of different distributed neural systems. Because the social animations do not depict articulated body movements, these results also highlight that the perception of the kinematics of actions is not necessary to activate the mirror neuron system, suggesting that this system plays a general role in the representation of intentions and goals of actions. Furthermore, these results suggest that the fusiform gyrus plays a general role in the representation of visual stimuli that signify agency, independent of visual form.