Sub-perceptual-threshold tVNS evokes brainstem vagal potentials consistent with peripheral nerve engagement, and the pulse-evoked response follows an inverted-U function of stimulation intensity¶

Claim · All claims
Evidence · 1 study (2 entries) · causal r2 · q3
Currency · newest study 2020 · not yet checked against its sources · not reviewed by a person

Subclaims¶

q3 i? Sub-threshold tVNS pulses evoked three brainstem components (N1, P1, N2) at 2–15 ms latencies with magnitudes significantly above pre-pulse baseline. → Llanos 2020 q3 i? N1 and P1 peaks were stronger for intermediate intensities (1–2 mA) than for low or high intensities, suggesting a non-linear inverted-U relationship. → Llanos 2020 (2)

Evidence¶

Llanos 2020¶

Llanos, F., McHaney, J. R., Schuerman, W. L., Yi, H. G., Leonard, M. K. and Chandrasekaran, B. (2020). Non-invasive peripheral nerve stimulation selectively enhances speech category learning in adults. npj Science of Learning. https://doi.org/10.1038/s41539-020-0070-0

q3 · i? · causal · r2

EEG recorded during training from all stimulation participants, with pulse artifacts removed and responses averaged in a 15 ms window time-locked to pulse offset. Latencies of 2–15 ms were consistent with prior above-threshold tVNS work.

"we found three tVNS pulse-evoked brainstem components with peak magnitudes signi ficantly different from the pre-pulse baseline magnitude: N1 ( M = −1.07 µV, t40 = −2.96, p = 0.0051), P1 ( M = 0.27 µV, t40 = 4.75, p < 0.001), and N2 ( M = −0.15 µV, t34 = −5.77, p < 0.01)."

Llanos 2020 (2)¶

Llanos, F., McHaney, J. R., Schuerman, W. L., Yi, H. G., Leonard, M. K. and Chandrasekaran, B. (2020). Non-invasive peripheral nerve stimulation selectively enhances speech category learning in adults. npj Science of Learning. https://doi.org/10.1038/s41539-020-0070-0

q3 · i? · causal · r2

Correlational analysis of individual sensory thresholds against peak magnitudes found no significant linear correlations (e.g., N1: r = 0.051, p = 0.82); the intensity relationship instead followed a non-linear inverted-U pattern shown in Fig. 3a bottom.

"However, we found stronger N1 and P1 peaks for intermediate tVNS intensities (1 mA < intensity ≤ 2 mA), as compared to low (0.2 mA < intensity ≤ 1 mA) and high (2 mA < intensity ≤ 3 mA) intensities."

Discussion¶

Related Claims¶

• Brief tVNS paired with speech training produces no measurable change in the sensory representation of non-native pitch as indexed by frequency-following responses — related
• Pairing sub-perceptual tVNS with easier-to-learn Mandarin tone categories improves trial-by-trial speech category learning faster than training alone, and the enhancement is specific to the stimulated categories — related
• Pairing tVNS with feedback after correct responses does not enhance speech category learning, suggesting the enhancement is not driven by a reward signal — related
• The tVNS-easy group's performance falls outside the normal range of individual learning variability observed across 678 comparable unstimulated learners — related
• tVNS-enhanced speech category learning generalizes to new talkers' exemplars without accompanying stimulation or feedback — related
• tVNS paired with easier-to-learn categories increases retention of correct stimulus-response associations between training blocks — related