Transcutaneous Auricular Vagus Nerve Stimulation Enhances Emotional Bias Toward Happiness in Healthy Young Adults: A Comparative Study of Electric and Ultrasound Stimulation
June Christoph Kang, Ji You Ng, Marcus Kaiser, Hyuk Choi, Jae-Jun Song, JeYoung Jung
Neuromodulation: Technology at the Neural Interface 2026 · 10.1016/j.neurom.2026.04.016
Abstract
Introduction Transcutaneous auricular vagus nerve stimulation (taVNS) is an emerging neuromodulation technique showing promise in modulating affective processing. However, comparative evidence between electric and ultrasound modalities remains limited. This study aimed to investigate and compare the acute effects of electrical (E-taVNS) and ultrasound (U-taVNS) modalities on emotional bias in healthy young adults. Materials and methods A total of 59 healthy participants were randomly assigned to E-taVNS or U-taVNS group and completed a single-blind, sham-controlled, within-subject study. Emotional bias was assessed using a facial emotion categorization task using morphed expressions at pre-, during-, and post stimulation phases. Results Active taVNS significantly enhanced emotional bias scores relative to sham when both stimulation modalities were pooled (t(58) = 2.09, p = 0.020, d = 0.27), shifting categorization of ambiguous faces toward more positive interpretations. Within each modality, active stimulation produced significant pre-to-post increases in bias scores, though the active-versus-sham contrast did not reach statistical significance for either modality individually (E-taVNS: p = 0.107; U-taVNS: p = 0.063, one-tailed). No significant between-modality differences were detected. In addition, individual differences in interoceptive awareness correlated with treatment response magnitude. Conclusions When pooled, active electric and ultrasound taVNS acutely modulated emotional bias relative to sham stimulation. These findings support taVNS as a promising noninvasive, well-tolerated intervention for research on emotional bias, with potential for further investigation of personalized treatment based on interoceptive awareness.
Abstract via europepmc.
Exposures
Exposure 1: U-taVNS (ultrasound taVNS, right cymba conchae)
Target: vagus nerve — “auricular branch of the vagus nerve (right cymba conchae)”
Device: other named manufacturer · NeurGear Inc. · ZenBud ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 5,300 | ✓✓✓ |
| Pulse duration (ms) | not reportedimplied by duty cycle ÷ PRF: 12.1951 ms (not stated by the paper) | ⚑ |
| Pulse repetition frequency (Hz) | 41 | ✓✓✓ |
| Duty cycle (%) | 50 | ✓✓✓ |
| Sonication duration (s) | 1,800 | ✓✓✓ |
| Free-field pressure (kPa) | not reported | |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | not reported | |
| In-situ pressure (kPa) | not reported | |
| In-situ Isppa (W/cm²) | not reported | |
| In-situ Ispta (W/cm²) | not reported | |
| Pressure, domain unspecified (kPa) | 1,030 | ✓✓✓⚑ |
| Isppa, domain unspecified (W/cm²) | 0.081 | ✓✓✓ |
taVNS was administered for 30 minutes; the initial 15 minutes served as a stabilisation period, after which the emotional bias task was repeated during stimulation, and again after the 30-minute stimulation period ended (post-stimulation phase).
Consistency checks: intensity pressure inconsistent unspecified domain.
Flags from extraction
blinding— Abstract states 'single-blind, sham-controlled, within-subject study'; no further detail on who was blinded.exposures[0].unspecified_domain.pressure_kpa— The sentence labels 1.03 MPa as 'an average intensity', but MPa is a pressure unit, not an intensity unit; recorded as stated (converted to kPa) rather than corrected, and the same sentence redundantly repeats 'a centre frequency of 5.3 MHz' twice, suggesting a drafting error in the parameter list.exposures[0].timing.pulse_duration_ms— Only duty cycle (50%) and PRF (41 Hz) are stated for U-taVNS; per-pulse duration is not explicitly stated and was not computed from DC/PRF.direction_of_effect— Within-modality active-vs-sham contrast for U-taVNS alone was only marginally significant (one-tailed p=0.051); pooled-modality effect was significant, so direction is recorded as mixed/unclear rather than a clear excitatory effect.