Transcutaneous Auricular Vagus Nerve Stimulation Enhances Emotional Bias Toward Happiness in Healthy Young Adults: A Comparative Study of Electric and Ultrasound Stimulation

Abstract Transcutaneous auricular vagus nerve stimulation (taVNS) is an emerging neuromodulation technique demonstrating promise in emotional regulation. This study investigated the acute effects of both electrical (E-taVNS) and ultrasound (U-taVNS) modalities on emotional bias using a facial emotion categorization task in healthy young adults. Fifty-nine participants underwent a single-blind, sham-controlled, within-subject design, with emotional bias assessed at pre-, during-, and post-stimulation phases. Our findings revealed that both E-taVNS and U-taVNS significantly enhanced emotional bias scores, shifting the perception of neutral and ambiguous faces towards positive interpretations and reducing negative emotional bias. No significant differences in efficacy were observed between the two stimulation modalities. Furthermore, individual differences in interoceptive awareness were found to be associated with the observed taVNS effects. These results suggest that both electrical and ultrasound taVNS can acutely modulate emotional regulation, highlighting the potential of taVNS as a non-invasive, well-tolerated alternative for interventions targeting emotional bias and mood disorders. Highlights taVNS reduces negative emotional bias toward ambiguous stimuli. Both electrical and ultrasound taVNS shifted emotional bias toward more positive interpretations of ambiguous facial expressions. Ultrasound taVNS (U-taVNS) demonstrated comparable efficacy to electrical taVNS (E-taVNS). The subscale of the Multidimensional Assessment of Interoceptive Awareness predicted individual variability in taVNS-induced emotional bias change.