Transcutaneous auricular Vagus nerve stimulation for working memory enhancement: A comparative study of electrical and ultrasound stimulation

Alicia Falcon-Caro, Nicholas Myers, Marcus Kaiser, Hyuk Choi, Jae-Jun Song, JeYoung Jung

2026 · 10.64898/2026.03.06.710106

human healthyhealthybehaviour

Abstract

Objectives Transcutaneous auricular vagus nerve stimulation (taVNS) is a non-invasive neuromodulation technique that has shown potential to enhance cognitive function, including working memory. This study investigated the acute effects of both electrical (E-taVNS) and ultrasound (U-taVNS) modalities on working memory using a 3-back task in healthy young adults. We hypothesized that active taVNS would enhance working memory performance relative to sham, and that both stimulation modalities would engage similar neuromodulatory mechanisms. Materials and Methods Fifty-nine participants underwent a single-blind, sham-controlled, within-subject design study, with working memory performance assessed using a 3-back task before and after stimulation. Primary performance measures included correct rejection rate, error false alarm, and sensitivity ( d ′). Statistical analyses compared pre- and post-stimulation performance across modalities. Results E-taVNS significantly enhanced working memory performance through an increase in correct rejection rate and sensitivity (measured by d’ ), alongside a reduction in error of false alarm. U-taVNS showed a similar directional trend across performance measures, although these effects did not reach statistical significance. Baseline anxiety levels significantly predicted individual responsiveness to taVNS. In terms of tolerability, a higher proportion of participants receiving E-taVNS reported skin irritation compared to those receiving U-taVNS. Conclusions E-taVNS can acutely enhance working memory performance, while U-taVNS may offer a comparable, better tolerated alternative. Our findings highlight the potential of taVNS to support memory function, while showing the importance of further research to clarify modality-specific effects and optimize stimulation parameters.

Abstract via europepmc.

Specieshuman

Subjects29 participants

Sessions per subject1

Randomisedyes

Blindingsingle

Sham / controlinactive transducer

Auditory controlnot reported

Readout timingoffline

Anaesthesianot applicable

Readoutsbehaviour — 3-back working memory task (correct rejection rate, error false alarm rate, sensitivity d'); side-effects questionnaire

Direction of effectno effectU-taVNS showed a similar directional trend to E-taVNS across working memory performance measures (d', correct rejection rate) but active vs sham differences did not reach statistical significance (e.g. d' ratio: t(28)=0.50, p=0.619). Post-hoc pre-to-post comparisons within the active U-taVNS condition showed significant increases in d' and overall accuracy, but a similar pattern was seen in the U-taVNS sham condition.

Adverse eventsobservedA higher proportion of participants receiving E-taVNS reported skin irritation compared to U-taVNS (E-taVNS: 20.0%; U-taVNS: 3.4%; chi2=3.86, p=0.049); ear pain was reported by both groups (E-taVNS: 16.7%; U-taVNS: 10.3%) with no significant difference between modalities.

Exposures

Exposure 1: Ultrasound taVNS (U-taVNS) to right cymba conchae

Target: vagus nerve — “right cymba conchae (auricular branch of the vagus nerve)”
Device: other named manufacturer · NeurGear Inc., Rochester, NY, USA · ZenBud ✓

Pulse timing
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	✓✓✓

Pressure and intensity, by domain
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	✓✓✓⚑

Protocol, in the paper’s words

Participants received 30 minutes of taVNS per session; each participant completed two sessions (one active, one sham) separated by at least five days, with session order counterbalanced. Sham stimulation used an identical sham device that delivered no active ultrasound.

Consistency checks: intensity pressure inconsistent unspecified domain.

Flags from extraction

n_subjects — 29 participants were allocated to U-taVNS, but one female participant was excluded from analysis for missing sham-session data ('Due to missing data from Sham session, one female participant from U-taVNS was excluded from the analysis'; 'Therefore, a total of 58 participants were analyzed, 30 for E-taVNS and 28 for U-taVNS.'); n_subjects reflects the enrolled/allocated total (29) rather than the analysed total (28).
exposures[0].unspecified_domain.pressure_kpa — The paper labels this 1.03 MPa value 'average intensity', though MPa is a pressure unit not an intensity unit; recorded as pressure_kpa (1030 kPa) rather than an intensity field.
exposures[0].unspecified_domain.isppa_w_cm2 — 'Peak mechanical output of 0.081 W/cm2' is not explicitly labelled ISPPA or ISPTA; assigned to ISPPA given the word 'peak', but this is an inference.
exposures[0].timing.pulse_duration_ms — Duty cycle (50%) and PRF (41 Hz) are stated but pulse duration is not; not computed per the no-arithmetic rule.
exposures[0].free_field — The paper does not state whether the reported pressure/intensity values are free-field or in-situ; recorded under unspecified_domain.