[Effect of transcutaneous auricular vagus nerve stimulation on functional connectivity in the related brain regions of patients with depression based on the resting-state fMRI].

OBJECTIVE: To explore the brain effect mechanism and the correlation between brain functional imaging and cognitive function in treatment of depressive disorder (DD) with transcutaneous auricular vagus nerve stimulation (taVNS) based on the resting-state functional magenetic reasonance imaging (rs-fMRI). METHODS: Thirty-two DD patients were included in a depression group and 32 subjects of healthy condition were enrolled in a normal group. In the depression group, the taVNS was applied to bilateral Xin (CO15) and Shen (CO10), at disperse-dense wave, 4 Hz/20 Hz in frequency and current intensity ≤20 mA depending on patient's tolerance, 30 min each time, twice daily. The duration of treatment consisted of 8 weeks. The patients of two groups were undertaken rs-fMRI scanning. The scores of Hamilton depression scale (HAMD), Hamilton anxiety scale (HAMA) and Wisconsin card sorting test (WCST) were observed in the normal group at baseline and the depression group before and after treatment separately. The differential brain regions were observed before and after treatment in the two groups and the value of degree centrality (DC) of fMRI was obtained. Their correlation was analyzed in terms of HAMD, HAMA and WCST scores. RESULTS: The scores of HAMD and HAMA in the depression group were all higher than those in the normal group (P<0.05). After treatment, the scores of HAMD and HAMA were lower than those before treatment in the depression group; the scores of total responses, response errors and perseverative errors of WCST were all lower than those before treatment (P<0.05). The brain regions with significant differences included the left inferior temporal gyrus, the left cerebellar peduncles region 1, the left insula, the right putamen, the bilateral supplementary motor area and the right middle frontal gyrus. After treatment, the value of DC in left supplementary motor area was negatively correlated to HAMD and HAMA scores respectively (r=-0.324, P=0.012; r=-0.310, P=0.015); the value of DC in left cerebellar peduncles region 1 was negatively correlated to the total responses of WCST (r=-0.322, P=0.013), and the left insula was positively correlated to the total responses of WCST (r=0.271, P=0.036). CONCLUSION: The taVNS can modulate the intensity of the functional activities of some brain regions so as to relieve depressive symptoms and improve cognitive function.

[Functional MRI-based study on neuromechanism of trans-auricular vagus nerve stimulation for treatment-resistant depression].

OBJECTIVE: To explore the neuromechanism of trans-auricular vagus nerve stimulation (taVNS) for treatment-resistant depression(TRD) based on functional brain network. METHODS: Twenty-eight patients with TRD were recruited from the psychiatric clinic or by the advertisement. The patients were treated by taVNS (5 Hz/20 Hz, 4-8 mA) at the auricular concha for 30 min, twice daily for 8 weeks. The symptom severity was assessed by 17-Item Hamilton Rating Scale for Depression (HAMD-17, ranging from 0 to 54 points, higher score indicates more severe conditions). Resting state fMRI data of the brain were collected to analyze changes of the regional homogeneity (ReHo), amplitude of low frequency fluctuation (ALFF) and resting state functional connectivity (rs-FC) before and after 8 weeks' taVNS by using DPARSF toolkit and the correlation between the rs-FC and clinical scale score was analyzed to assess the related brain mechanisms. RESULTS: Twenty-four patients finished the clinical study, and 23 patients finished the fMRI tests. After the treatment, the average score of HAMD-17 was significantly decreased (P<0.01), with the reduction rate being 66.95%; the ALFF and ReHo values of the right insula and putamen, the ReHo values of the right caudate nucleus and thalamus, as well as the rs-FC values of the right insula, left superior frontal gyrus and middle frontal gyrus were all significantly decreased (P<0.05). The reduced ReHo value in the right insular lobe was negatively correlated with the HAMD score reduction (P=0.001, r=-0.633). The rs-FC values of the right insula lobe and the left superior frontal gyrus were significantly negatively correlated with the reduced HAMD score(P=0.012, r=-0.512). CONCLUSION: TaVNS significantly relieves the symptoms of TRD patients, which may be related to its functions in regulating functional changes of the right insular and the left frontal gyrus network, and the limbic area and basal ganglia.