The Relationship of the Change in Symptoms and Cognitive Functions With the Change in Cortical Inhibition Parameters Measured by Transcranial Magnetic Stimulation: An Eight-Week Follow-Up Study

Objective: Transcranial magnetic stimulation (TMS) studies show cortical inhibition (CI) abnormalities in patients with schizophrenia. However, the relationship between the changes in CI and the changes in psychopathology and cognition caused by antipsychotic treatment is not known. This is an 8 week follow up study which aims to evaluate the relationship of the change in the symptoms and cognitive functions with the change in the CI of the patients, who are switched to new atypical antipsychotic treatment, and to compare the TMS measures of patients with those of controls. Method: Thirteen patients and age, sex, education matched 13 controls were included in the study. Patients were assessed with TMS, Positive and Negative Syndrome Scale (PANSS) and neurocognitive battery at baseline and 8th week, while the control group was evaluated once, with neurocognitive battery and TMS. The CI parameters studied by TMS were resting motor threshold, cortical silent period, ipsilateral silent period (ISP), short interval-intracortical inhibition (SICI) and intracortical facilitation. Results: Intracortical facilitation (ICF) was weaker, ISP was longer in patients than the controls both at the baseline and at the end of the eight weeks. Intracortical facilitation decreased with 8 weeks of antipsychotic treatment indicating an increase in CI. The decrease in PANSS general psychopathology score was related positively with the decrease in ICE SICI was related positively with cognitive test performances cross-sectionally and longitudinally. Conclusion: Our findings suggest that increase in CI is associated with the improvement in the symptoms and the action of the atypical antipsychotics.