Functional segregation within pars opercularis of the inferior frontal gyrus: evidence from fMRI studies of imitation and action observation.

Recent neuroimaging studies have suggested that the inferior frontal gyrus (IFG) is important for action observation and imitation. In order to further explore the role of IFG in action observation and imitation, we pooled data from seven functional magnetic resonance imaging studies involving observation and imitation of simple finger movements performed in our laboratory. For imitation we found two peaks of activation in the pars opercularis, one in its dorsal sector and the other in its ventral sector. The dorsal sector of the pars opercularis was also activated during action observation, whereas the ventral sector was not. In addition, the pars triangularis was activated during action observation but not during imitation. This large dataset suggests a functional parcellation of the IFG that we discuss in terms of human mirror areas and the computational motor control architecture of internal models.