Fig. 9

Physiological effects, stimulation parameters and fiber activation. A Left: Amplitude of VNS-induced laryngeal twitches in S2, plotted against current amplitude; Middle and right: activation of A\(\beta\)-fibers, and activation of A\(\gamma\)- and B-fibers across different radial and longitudinal stimulation locations. B Changes in breathing rate in subject S8 (pulse width 130\(\,\upmu\)s, frequency 5 Hz, train duration 1 s) in response to current (Left) A\(\gamma\)-fiber activation (Middle) and A\(\beta\)- and B-fibers activations (Right). Confidence intervals show one standard deviation for stimulations that were done more than once. Linear models are fitted for each of the two stimulation locations. The difference in slopes between the two contacts was significant for A\(\beta\)-activation (ANOVA, \(F=7.68\), \(p<0.01\)), and not for current (\(F=0.72\), \(p=0.40\)), A\(\gamma\)-fiber activation (\(F=0.53\), \(p=0.47\)) or B-fiber activation (\(F=0.29\), \(p=0.60\)). C Left: change in heart rate in response to current and frequency changes of stimuli in S3 (pulse width 500\(\,\upmu\)s, train duration 5 s). Right: the same change in heart rate, plotted in three dimensions against the activation of A\(\gamma\)- and B-fibers. 2D linear models are fitted for each frequency. (0, 0, 0) points are added to anchor the surfaces to the origin. All fiber activations are normalised based on the maximum fiber activations recorded across each subject