TY - JOUR
T1 - Influence of transcutaneous vagus nerve stimulation on cardiac vagal activity: Not different from sham stimulation and no effect of stimulation intensity
AU - Borges, Uri
AU - Laborde, Sylvain
AU - Raab, Markus
PY - 2019/10/24
Y1 - 2019/10/24
N2 - The present study investigated the effects of transcutaneous vagus nerve stimulation on cardiacvagal activity, the activity of the vagus nerve regulating cardiac functioning. We appliedstimulation on the left cymba conchae and tested the effects of different stimulation intensitieson a vagally-mediated heart rate variability parameter (i.e., the root mean square of successivedifferences) as well as on subjective ratings of strength of perceived stimulation intensityand unpleasantness due to the stimulation. Three experiments (within-subject designs, M =61 healthy participants each) were carried out: In Experiment 1, to choose one fixed stimulationintensity for the subsequent studies, we compared three preset stimulation intensities(i.e., 0.5, 1.0 and 1.5 mA) with each other. In Experiment 2, we compared the set stimulationmethod with the free stimulation method, in which the participants were instructed to freelychoose an intensity. In Experiment 3, to control for placebo effects, we compared both methods(i.e., set stimulation vs. free stimulation) with their respective sham stimulations. In thethree experiments, an increase of cardiac vagal activity was found from resting to the stimulationphases. However, this increase in cardiac vagal activity was not dependent on stimulationintensity (Experiment 1), the method used to stimulate (i.e., set vs. free; Experiment 2),or whether stimulation was active or sham (Experiment 3). This pattern of results was solidlysupported by Bayesian estimations. On the subjective level, higher stimulation intensitieswere perceived as significantly stronger and a stronger stimulation was generally also perceivedas more unpleasant. The results suggest that cardiac vagal activity may be similarlyinfluenced by afferent vagal stimuli triggered by active and sham stimulation with differentstimulation intensities. Potential explanations for these findings and its implications for futureresearch with tVNS are discussed.
AB - The present study investigated the effects of transcutaneous vagus nerve stimulation on cardiacvagal activity, the activity of the vagus nerve regulating cardiac functioning. We appliedstimulation on the left cymba conchae and tested the effects of different stimulation intensitieson a vagally-mediated heart rate variability parameter (i.e., the root mean square of successivedifferences) as well as on subjective ratings of strength of perceived stimulation intensityand unpleasantness due to the stimulation. Three experiments (within-subject designs, M =61 healthy participants each) were carried out: In Experiment 1, to choose one fixed stimulationintensity for the subsequent studies, we compared three preset stimulation intensities(i.e., 0.5, 1.0 and 1.5 mA) with each other. In Experiment 2, we compared the set stimulationmethod with the free stimulation method, in which the participants were instructed to freelychoose an intensity. In Experiment 3, to control for placebo effects, we compared both methods(i.e., set stimulation vs. free stimulation) with their respective sham stimulations. In thethree experiments, an increase of cardiac vagal activity was found from resting to the stimulationphases. However, this increase in cardiac vagal activity was not dependent on stimulationintensity (Experiment 1), the method used to stimulate (i.e., set vs. free; Experiment 2),or whether stimulation was active or sham (Experiment 3). This pattern of results was solidlysupported by Bayesian estimations. On the subjective level, higher stimulation intensitieswere perceived as significantly stronger and a stronger stimulation was generally also perceivedas more unpleasant. The results suggest that cardiac vagal activity may be similarlyinfluenced by afferent vagal stimuli triggered by active and sham stimulation with differentstimulation intensities. Potential explanations for these findings and its implications for futureresearch with tVNS are discussed.
M3 - Journal articles
SN - 1932-6203
VL - 14
JO - PloS one
JF - PloS one
IS - 10
M1 - e0223848
ER -