The Modulatory Effects of 2-Hz rTMS Treatment on the Prefrontal Cortex in Patients with Major Depressive Disorder: An fNIRS Study

Background: Previous studies have shown the antidepressant effect of 2 Hz repetitive transcranial magnetic stimulation (rTMS) to the right dorsolateral prefrontal cortex (DLPFC) in patients with major depressive disorder (MDD); however, its underlying neural mechanisms are poorly understood. The aim of this study was to examine the effects of 2Hz rTMS to the right DLPFC on the cortical activation of the PFC in MDD patients, using functional near-infrared spectroscopy (fNIRS).Methods: Twenty-two patients with MDD and twenty-five healthy controls were enrolled in this study. Patients underwent 4 weeks of 2 Hz TMS delivered to the right DLPFC. fNIRS was used to measure the activation of the PFC during a verbal fluency task in patients with MDD at baseline and after 4 weeks of treatment. Clinical response to treatment was determined using the Hamilton Rating Scale (HAMD).Results: Compared with the healthy controls, the activation of the PFC was significantly lower in patients with MDD. After 4 weeks rTMS treatment, depression symptoms and the activation of the PFC in MDD patients were significantly improved. The severity of depression was negatively correlated with the level of oxy-hemoglobin (oxy-Hb) in the right inferior frontal gyrus. The baseline oxy-Hb concentration in middle frontal gyrus was positively correlated with the HAMD reduction after treatment.Conclusions: This study suggests that the function of the PFC in patient with MDD was significantly impaired and could be improved after 2 Hz right rTMS.Trial registration: Chinese Clinical Trials Registry (registration No.126 ChiCTR2100046806)Ethics: All participants provided written informed consent. This study was approved by the West China Hospital Clinical Trials and Biomedical Ethics Committee of Sichuan University (No. of ethical approval: [2021]-428) on April 30, 2021.Funding: This work was financially supported by the National Natural Science Foundation of China (No. 81873354) and the Key Project of Science and Technology of Sichuan Province (No. 2020YFS0284).Competing interests: None