Neuro-Cardiac Interactions of Transcutaneous Auricular Vagus Nerve Stimulation: A Focus on Stress Effects

Abstract Transcutaneous auricular Vagus Nerve Stimulation (taVNS) has emerged as a promising non-invasive method for modulating the Autonomic Nervous System (ANS). However, its impact on cardiac autonomic regulation during acute stress remains underexplored. This study investigates taVNS effects on Heart Rate Variability (HRV) indices in response to psychological stress in healthy individuals across time and frequency domains. Sixty participants were randomly assigned to three groups: control, sham, and stimulation. Each underwent a three-phase experimental protocol: pre-stress, stress induction, and post-stress. Time domain (RR interval, pNN50, SDNN, RMSSD), frequency domain (HF, LF, LF/HF) were computed from ECG signals and analyzed using repeated-measures comparisons. Results revealed that stimulation group exhibited a sharper drop in RR intervals (753 ms pre-stress, 648 ms stress, and 745 ms post-stress), pNN50 (11.1% → 4.3% → 8.7%), and LF/HF rose from (0.6) under stress to (1.1) in recovery, suggesting enhanced vagal reactivation. While the sham group showed limited improvement, the control group demonstrated minimal restoration in pNN50. SDNN values for the stimulation group increased steadily (48.7 ms → 56.8 ms → 63.9 ms), indicating broader autonomic adaptability. These results indicate a targeted influence of taVNS on cardiac vagal tone and overall autonomic regulation, potentially promoting parasympathetic engagement under stress.