Influence of transcutaneous vagus nerve stimulation on cardiac vagal activity: Not different from sham stimulation and no effect of stimulation intensity
Influence of transcutaneous vagus nerve stimulation on cardiac vagal activity: Not different from sham stimulation and no effect of stimulation intensity
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DOI：
10.1371/journal.pone.0223848
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发表时间：
2019-10-11
期刊：
影响因子：
3.7
通讯作者：
Raab, Markus
中科院分区：
文献类型：
--
作者：
Borges, Uirassu;Laborde, Sylvain;Raab, Markus
本研究探讨了经皮迷走神经刺激对心脏迷走神经活动的影响，迷走神经的活动调节心脏功能。我们对左侧耳甲艇施加刺激，并测试不同刺激强度对迷走神经介导的心率变异性参数（即，连续差的均方根）以及对感知刺激强度的强度和由于刺激引起的不愉快的主观评级。进行了三个实验（受试者内设计，每个M = 61名健康参与者）：在实验1中，为了为后续研究选择一个固定刺激强度，我们比较了三个预设刺激强度（即，0.5、1.0和1.5 mA）。在实验2中，我们比较了设置刺激方法和自由刺激方法，其中参与者被指示自由选择强度。在实验3中，为了控制安慰剂效应，我们比较了两种方法（即，设置刺激与自由刺激）与它们各自的假刺激。在三个实验中，心脏迷走神经活动的增加被发现从休息到刺激阶段。然而，心脏迷走神经活动的这种增加不依赖于刺激强度（实验1），用于刺激的方法（即，设置与自由;实验2），或者刺激是主动的还是假的（实验3）。这种结果模式得到了贝叶斯估计的有力支持。在主观层面上，更高的刺激强度被认为是明显更强的，更强的刺激通常也被认为是更令人不快的。结果表明，心脏迷走神经活动可能类似的影响由主动和假刺激不同的刺激强度触发的传入迷走神经刺激。这些研究结果的潜在解释及其对未来研究的影响进行了讨论。
The present study investigated the effects of transcutaneous vagus nerve stimulation on cardiac vagal activity, the activity of the vagus nerve regulating cardiac functioning. We applied stimulation on the left cymba conchae and tested the effects of different stimulation intensities on a vagally-mediated heart rate variability parameter (i.e., the root mean square of successive differences) as well as on subjective ratings of strength of perceived stimulation intensity and 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 stimulation intensity 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 stimulation method with the free stimulation method, in which the participants were instructed to freely choose 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 the three experiments, an increase of cardiac vagal activity was found from resting to the stimulation phases. However, this increase in cardiac vagal activity was not dependent on stimulation intensity (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 solidly supported by Bayesian estimations. On the subjective level, higher stimulation intensities were perceived as significantly stronger and a stronger stimulation was generally also perceived as more unpleasant. The results suggest that cardiac vagal activity may be similarly influenced by afferent vagal stimuli triggered by active and sham stimulation with different stimulation intensities. Potential explanations for these findings and its implications for future research with tVNS are discussed.