Transcutaneous Auricular Vagus Nerve Stimulation Modulates Performance but Not Pupil Size During Nonnative Speech Category Learning.
Jacie R McHaney, William L Schuerman, Matthew K Leonard and 1 others
PMID 37652065WHAT IT FOUND
Randomized taVNS groups did not differ in Mandarin tone learning accuracy or pupil size.
Exploratory analyses found lower amplitude associated with better accuracy, and stimulated trials with larger accuracy gains.
Key findings
01The two randomly assigned taVNS pairing groups did not differ in overall Mandarin tone learning accuracy or in how accuracy improved across training.
02Pupil size during the training task did not differ between taVNS groups for average or peak responses.
03Exploratory analyses suggested that higher taVNS amplitude was associated with fewer correct responses, and stimulated trials showed larger trial-by-trial accuracy gains than nonstimulated trials.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
Participants were healthy young adults with normal hearing and no tonal-language exposure, so results do not show effects in clinical populations. The main experiment compared two taVNS pairing conditions rather than taVNS versus no taVNS, and the positive amplitude findings were exploratory, not preregistered. Stimulation was subthreshold and often low amplitude, which the authors say may have been too low to drive pupil effects. The single-session task included long delays for pupillometry, including a 4-s delay before response and 2-s delayed feedback, which may have changed learning compared with immediate-feedback training. Final analysis included 38 participants, and response-time conclusions were limited because responses were made after a 4-s delay.
Declared interests
Funding came from the Defense Advanced Research Projects Agency Targeted Neuroplasticity Program under Contract No. N66001-17-2-4008 and from NIH Grant T32-DC011499. The supplied text reports no commercial sponsor, company funding, or author conflict-of-interest disclosures.
The easy way to misread this
Do not conclude that taVNS improves speech learning in patients. The randomized group comparison and pupil measures were null, and the amplitude and stimulated-trial effects were exploratory in healthy adults.