Effect of Short-Term Transcutaneous Vagus Nerve Stimulation (tVNS) on Brain Processing of Food Cues: An Electrophysiological Study

Figure 1. Positions of the ear-electrode (NEMOS®, Cerbomed Erlangen-Germany). (A) Transcutaneous stimulation of the auricular branch of the vagus nerve (tVNS), (B) stimulation of the auricular scaphoid fossa (sham). Stimulation parameters: 25 Hz, biphasic, 30 s ON and 30 s OFF interval, current intensity of 0.6 mA so that a tingly was perceptible.

Figure 2. EEG Oddball-Paradigm. During the EEG-Measurements pictures of food with high and low caloric content as well as unexceptional objects (control) were presented to the subjects. If the presented picture contained a green square, participants had to press the right mouse button with the index finger of the right hand as fast as possible.

Figure 3. Effects of tVNS on ERPs calculated with frequential statistics. Channel (A) shows positive potentials (P1 and P2), channel (B) negative potentials (N1 and N2) and channel (C) LPP potential. Line plots: mean change in electrical potentials (μV) in relation to a baseline (−100 to stimulus onset) over the time (x-axis) are shown for the conditions (lines). Bar plots: mean potential for each task condition pooled across electrodes. Abbreviations describe task conditions (stimulation and picture type; VF = tVNS Food, SF = Sham Food, VO = tVNS Object, SO = Sham Object). Horizontal lines signify statistical main effects. tp < 0.10, *p < 0.05, ***p < 0.001.

Figure 4. Effects of tVNS on ERPs calculated with Bayesian statistics. Graphics show the prior and posterior probability density for the stimulation main effect on (A,B) early latency phase components P1 and N1, (C,D) on middle latency phase components P2 and N2 and (E) on late latency phase component LPP. Cl describes the Bayesian credible interval. BF(10) is the Bayes factor in favour to the alternative hypothesis (H1) and BF(01) in favor of the null hypothesis. *Result of exploratory analysis.

Figure 5. Correlation of P2-amplitude and behavioral outcomes. P2 amplitudes are pooled across electrodes and task conditions. Significant relations were found for (A) only sham condition. (B) Both conditions. (C) Only sham condition.