The Effects of Transcutaneous Auricular Vagus Nerve Stimulation (taVNS) on Anxiety Responses and Emotional Regulation

Transcutaneous auricular vagus nerve stimulation (taVNS) is a non-invasive method for modulating vagal nerve function and has shown potential efficacy in alleviating anxiety symptoms and improving emotional regulation. But the neural mechanisms of how taVNS affects anxiety and emotional regulation remain unclear. Therefore, we focus on this question by combining behavioral meausres, skin conductance response, heart rate variability and fMRI in this study. A participant-blinded, sham-controlled, between-subject design is employed in this study. In a randomised order, a total of 140 healthy males and females with or without high trait anxiety are recruited and receive the stimulation of taVNS on their tragus (experimental group) or earlobe (sham control group). After the participants arrive at the laboratory, they first complete a roughly 30-minute personality trait questionnaire and prepare for the experiment. Then, they undergo a 7-minute resting-state fMRI scan, followed by a 15-minute taVNS session. Next, they complete a 7-minute resting-state scan and a 60-minute task-based scan (a modified emotional regulation task). During the entire procedure, saliva samples will be collected three times for subsequent physiological hormone analyses, and participants' skin conductance and electrocardiogram data will also be recorded. During the modified emotional regulation task, subjects are instructed to regulate their emotional responses to negative pictures (high vs. low intensity) using reinterpretation/distance strategies or to only look these pictures. We also record subjects' rating scores on their anxiety levels during these conditions ("reinterpretation" vs. "distance" vs. "look") and successful usage of emotional regulation strategies. Questionnaire scores including State-Trait Anxiety Inventory, Beck Depression Inventory II, Beck Anxiety Inventory, Autism Spectrum Quotient, Toronto Alexithymia Scale, Social Responsiveness Scale, Emotion Regulation Questionnaire, Cognitive Emotion Regulation Questionnaire, Multidimensional Assessment of Interoceptive Awareness, Positive and Negative Affect Schedule will also be collected.

• Skin conductance responses (SCR) in the emotional regulation task during fMRI scanning [Time frame: 60 minutes]
• HRV in resting-state fMRI and emotional regulation task [Time frame: 75 minutes during scanning]
• Saliva samples analysis [Time frame: Three time points: pre-taVNS (baseline, 0 minute), immediate post-taVNS (60 minutes post-taVNS), and the end of experiment (70 minutes post-scanning).]