A transcranial magnetic stimulation study of transcallosal inhibition and facilitation in schizophrenia

Deficits in cortical inhibition (CI) have been implicated in the pathophysiology of schizophrenia, including decreased transcallosal inhibition (TCI). A closely related phenomenon, which has not yet been studied in schizophrenia, is transcallosal facilitation (TCF). TCI and TCF are thought to maintain a complimentary existence, allowing for the performance of tasks such as unilateral voluntary movement. Therefore, deficient TCI may lead to abnormal expression of TCF. This study aims to confirm the presence of TCI deficits in schizophrenia, and to examine TCF. Thirty consenting participants took part in the study (15 with schizophrenia and 15 healthy controls), although not all were able to complete all aspects of the study. TCI and TCF were measured using dual-pulse transcranial magnetic stimulation methodologies. Patients with schizophrenia exhibited significantly less TCI than controls; there was no difference in TCF, however. The lack of significant TCF findings is discussed in light of the methodological limitations, while the theoretical significance of deficient TCI to the pathophysiology of schizophrenia is considered.