tVNS Increases Liking of Orally Sampled Low-Fat Foods: A Pilot Study

Figures

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  Figure 1. Order of tasks in a test session and approximate timing in minutes. Upon arrival at the laboratory, participants rated their hunger, fullness and thirst (“internal state”). Then a baseline spontaneous eye blink rate (SEBR) was assessed, then the stimulation device was turned on and the intensity for sham or tVNS stimulation was adjusted. Next VNS stimulation perception was assessed. Then the rest of the tasks were performed concurrent with stimulation: another SEBR measurement, internal state ratings, rating of food samples, internal state ratings and last ad libitum milkshake consumption. This entire procedure was repeated on two testing days, one session using sham stimulation on the earlobe, and one session using tVNS stimulation on the cymba conchae (order of sessions counterbalanced over participants).

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  Figure 2. Hedonic ratings of puddings and Jell-Os during sham vs. tVNS. (A) Liking ratings on LHS under sham (dark green) vs. tVNS (light green), plotted for the low fat puddings (upper left panel) and high fat puddings (upper right panel) separately. The boxplots indicate central tendencies and spread of the ratings, as follows: median (middle bar in box), first and third quartiles (lower and upper hinge), 1.5 × the interquartile range (top and bottom whiskers) and outlying points (separate solid black dots outside the whiskers). We overlaid individual data points on the boxplots (transparent gray dots) and connected the dots of an individual participant between the sham and tVNS bars to make it easier to inspect the difference within a single participant. Robustness check illustrating the effects of assigning more conservative Cauchy priors (wide and ultrawide, black and white circles, respectively) relative to the default user prior (gray circle) on Bayes factor values for the effect of sham vs. tVNS for liking ratings, plotted for the low fat puddings (lower left panel) and high fat puddings (lower right panel). (B) Wanting ratings for puddings on VAS under sham vs. tVNS and robustness…

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  Figure 3. SEBR and ad libitum consumption during sham vs. tVNS. (A) SEBR (relative to baseline) under sham (dark green) vs. tVNS (light green). (B) Robustness checks for effect of sham vs. tNVS on SEBR. (C) Ad libitum consumption (relative to total weight) under sham (purple) vs. tVNS (pink). (D) Robustness checks for effect of sham vs. tVNS on consumption. Details as in Figure 2.