The Effects of taVNS on Motivation in MDD With Anhedonia

Anhedonia is the core symptom of MDD, which means they have deficits in processing rewards.MDD get lesser positive feelings than healthy controls from rewards as they could not use the reward outcome to update the value of a stimulus, which in consequence impedes their reward motivation or response inhibition and worsen their symptom. This study is dedicated to revealing how reward motivation or response inhibition ability could be intervened by taVNS intervention, which has been proven is highly relevant to reward motivation and response inhibition ability. Implementing a safer intervention of taVNS stimulation might help us to prove a better treatment for patients. All patients underwent a medical evaluation that included physical examination and routine laboratory studies before and after taVNS stimulation treatment. Before and after the taVNS treatment, depression symptom of each participant was assessed by the Hamilton Depression Scale and the Beck Depression Self-Rating Scale. The anhedonia severity was evaluated by The Temporal Experience of Pleasure Scale, the Self-Report Apathy Evaluation Scale, the Positive Valence system scale and the Motivation and Pleasure Scale. The neuroimaging data are collected using event-related potentials during the effort reward task and stop signal task before and after the intervention. Patients were randomly allocated into an active group and a sham group. This study plans to enroll a minimum total sample size of 30 participants in active and sham group respectively according to the Power and Sample Size program. The decision to enroll a patient was always made prior to randomization. Each patient will be treated for 4 weeks with 25Hz taVNS. Each participant was interviewed in detail about the adverse event of the taVNS intervention during 10 days. Every participant should take part in the study voluntarily and sign an informed consent form before the study.