Previous transcranial magnetic stimulation (TMS) studies have demonstrated cortical inhibition (CI) abnormalities in patients with schizophrenia. However, the relationship between changes in CI and changes in psychopathology and cognition resulting from antipsychotic treatment is not known. This is an 8 week follow up study which aims to evaluate the relation of the CI with the symptoms and cognitive functions of the patients who are switched to new atypical antipsychotic treatment, and to compare the TMS measurements of patients with those of controls. Method: Thirteen patients and 13 control subjects matched according to age, sex, and educational level were included in the study. Patients were assessed with TMS, Positive and Negative Syndrome Scale (PANSS), and a neurocognitive battery at baseline and at 8 weeks post-treatment, while the control group was evaluated with the neurocognitive battery and TMS at baseline only. CI parameters evaluated by TMS include resting motor threshold, cortical silent period, ipsilateral silent period (ISP), short interval intracortical inhibition (SICI) and intracortical facilitation. Results: Intracortical facilitation (ICF) was weaker and ISP was longer in patients relative to control subjects both at baseline and at the end of the eight weeks. Intracortical facilitation decreased following 8 weeks of antipsychotic treatment, indicating an increase in CI. The decrease in PANSS general psychopathology score was directly correlated with the decrease in ICF. SICI positively correlated with cognitive test performance in both cross-sectional and longitudinal analyses. Conclusion: Our findings suggest that increase in CI is associated with the improvement in the symptoms and the action of the atypical antipsychotics.

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