Mirror neuron deficit in schizophrenia: Evidence from repetition suppression.

Background: Schizophrenia is associated with impaired cognition, especially cognition in social contexts. The mirror neuron system (MNS) serves as an important neuronal basis for social cognitive skills; however, previous investigations on the integrity of MNS function in schizophrenia remain approximate.

Methods: We employed a repetition suppression paradigm that allows for measuring neuronal responses to gesture observation and gesture execution. Cross-modal repetition suppression, i.e., adaptation between observe/execute and execute/observe conditions, was defined as the decisive experimental condition characterizing the unique sensori-motor properties of mirror neurons. Event-related potentials (ERPs) were assessed in 15 schizophrenia patients and 15 matched controls.

Results: We isolated an ERP signature of specific adaptation effects to identical hand gestures. Of critical importance, this ERP signature indicated intact intra-modal adaptive pattern, i.e., observe/observe and execute/execute, of comparable magnitude between groups, but deficient cross-modal adaptation, i.e., observe/execute and execute/observe, in schizophrenia patients.

Conclusion: Our data provide robust evidence that pure perception and execution of hand gestures are relatively intact in schizophrenia. In contrast, visuo-motor transformation processes mediated by the MNS seem to be specifically disturbed in schizophrenia. These results unambiguously demonstrate MNS deficits in schizophrenia and extend our understanding of the neuronal bases of social dysfunction in this disorder.