Sex differences in the neuroanatomy of human mirror-neuron system: a voxel-based morphometric investigation.

Females frequently perform better in empathy, interpersonal sensitivity, and emotional recognition than do males. The mirror-neuron system has been proposed to play an important role in social cognition. It remains to be clarified, however, whether the neuroanatomy underlying the human mirror neuron system exhibits sex differences. With the use of voxel-based morphometry analysis, a whole-brain unbiased technique to characterize regional cerebral volume differences in structural magnetic resonance images, concurrent with the dispositional empathy measures, we demonstrate that young adult females (n=25) had significantly larger gray matter volume in the pars opercularis and inferior parietal lobule than matched males (n=25) participants. Moreover, higher self-report scores in the emotional empathic disposition was tightly coupled with larger gray matter volume of the pars opercularis across all female and male participants (P=0.002). These results indicate that the existence of neuroanatomical sex differences in the human mirror-neuron system. They also suggest that the network of the human mirror-neuron system is strongly linked to empathy competence.