Effects of non-invasive vagus nerve stimulation on pupil dilation are dependent on sensory matching.

Cecilia Vezzani, Rae-Marie Breakspear, Lilly Thurn, Ulrich Ettinger, Anne Kühnel, Nils B Kroemer

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Article in iScience, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.

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5 · Who and what money

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6 authors.

Cecilia VezzaniSection of Medical Psychology, Department of Psychiatry and Psychotherapy, University of Bonn, University Hospital Bonn, 53127 Bonn, North Rhine-Westfalia, Germany.

Rae-Marie BreakspearSection of Medical Psychology, Department of Psychiatry and Psychotherapy, University of Bonn, University Hospital Bonn, 53127 Bonn, North Rhine-Westfalia, Germany.

Lilly ThurnSection of Medical Psychology, Department of Psychiatry and Psychotherapy, University of Bonn, University Hospital Bonn, 53127 Bonn, North Rhine-Westfalia, Germany.

Ulrich EttingerDepartment of Psychology, University of Bonn, 53111 Bonn, North Rhine-Westfalia, Germany.

Anne KühnelSection of Medical Psychology, Department of Psychiatry and Psychotherapy, University of Bonn, University Hospital Bonn, 53127 Bonn, North Rhine-Westfalia, Germany.

Nils B KroemerSection of Medical Psychology, Department of Psychiatry and Psychotherapy, University of Bonn, University Hospital Bonn, 53127 Bonn, North Rhine-Westfalia, Germany.

Funding

No grant is acknowledged in the PubMed record.

6 · The paper itself

Abstract

Transcutaneous auricular vagus nerve stimulation (taVNS) is a promising tool to modulate motivation and affect, with prior studies showing greater pupil dilation compared to sham. However, sensory differences between conditions may confound results. In a randomized crossover study with 94 participants, we applied right-sided pulsed taVNS (1 s, 20 Hz, and 400 μs) and calibrated stimulation amplitude to match subjective sensation. Contrary to expectations, taVNS did not significantly increase pupil dilation versus sham. However, when participants perceived sham as less intense, taVNS effects were stronger. Differences in perceived sensation between taVNS and sham were mainly linked to sham-induced pupil dilation. Our findings suggest that right-sided pulsed taVNS only leads to greater pupil dilation when a sensory mismatch occurs, underscoring the difficulty of creating an effective sham.

Indexed as

affecteye observable entityNeurologyprocedure by devicesensory neuroscience

Identifiers

PMID41736856

DOI10.1016/j.isci.2026.114795

PMCPMC12927277

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Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.