Insula modulation effects of transcutaneous auricular vagus nerve stimulation treating functional dyspepsia

Previous clinical studies have demonstrated that transcutaneous auricular vagal nerve stimulation (taVNS) alleviates functional dyspepsia (FD) symptoms. But the underlying brain functional mechanism remains unclear. This study aimed to explore the brain modulation effects of taVNS treating FD by using resting-state functional magnetic resonance imaging (rs-fMRI).

Twenty-one patients with FD and 30 healthy controls (HCs) were enrolled. The FD subjects (FDs) were treated by taVNS and conducted with brain fMRI scans before and after 8-week treatment, HCs underwent one fMRI scan upon inclusion. Voxel-based functional connectivity (FC) and correlation analyses were used to explore the brain modulation effects of taVNS on FDs.

After treatment, FD patients showed significant improvement in symptoms. At baseline, FD patients exhibited significantly increased functional connectivity (FC) between the left dorsal anterior insula (dAI) and the left dorsolateral prefrontal cortex (DLPFC) compared with healthy controls. After taVNS treatment, FC between insular subregions-particularly the anterior insula (AI)-and multiple brain regions, including the DLPFC, amygdala, parahippocampus, and cuneus/lingual/calcarine gyrus, was widely reduced.

This study demonstrated that FD patients exhibit abnormal FC between the AI and DLPFC. TaVNS effectively alleviated clinical symptoms in FD, which may be associated with its modulation of FC between the AI with central executive network (CEN), limbic system, and visual network (VN).