Assessment of phase-locking factor with visual area-targeted transcranial magnetic stimulation-electroencephalography shows reduced connectivity in schizophrenia: A preliminary study.

As pathophysiological mechanisms of schizophrenia remain unclear, the development of reliable biomarkers for the disease is highly anticipated. Electroencephalogram with transcranial magnetic stimulation (TMS-EEG) is a developing technique for assessing mental condition. Phase-locking factors (PLFs) are a parameter of phase synchronization, which can assess the brain connectivity of specific areas. Both visual processing impairments and aberrant brain connectivity are implicated in the pathophysiology of schizophrenia. Here, we compared motor area PLFs using visual area-targeted TMS-EEG between three groups: 15 patients with schizophrenia (SZ), 15 patients with major depressive disorder (MD), and 15 healthy controls (HC). The PLF of the SZ group showed a significant decrease in the theta band compared to the HC group without confounding effects from TMS click noises or antipsychotic medication. The reduction of PLF in the theta band between the visual and motor area could reflect visual processing impairments in schizophrenia. Further experiments with larger sample size and appropriate cognitive tasks are required to confirm our conclusion.