Neural interactions between sensorimotor integration mechanisms play critical roles in voice motor control. We investigated how high-definition transcranial direct current stimulation (HD-tDCS) of the left ventral motor cortex modulates neural mechanisms of sensorimotor integration during voice motor control. HD-tDCS was performed during speech vowel production in an altered auditory feedback (AAF) paradigm in response to upward and downward pitch-shift stimuli. In one experiment, two groups received either anodal or cathodal 2 milliamp (mA) HD-tDCS to the left ventral motor cortex while a third group received sham (placebo) stimulation. In a second experiment, two groups received either 1 mA or 2 mA cathodal HD-tDCS to the left ventral motor cortex. Results of the first experiment indicated that the magnitude of vocal compensation was significantly reduced following anodal and cathodal HD-tDCS only in responses to downward pitch-shift AAF stimuli, with stronger effects associated with cathodal HD-tDCS. However, no such effect was observed following sham stimulation. Results of the second experiment indicate that there is not a differential effect of modulation from 1 mA versus 2 mA. Further, these results replicate the directional finding of the first experiment for vocal compensation in response to downward pitch-shift only. These findings suggest that neurostimulation of the left ventral motor cortex modulates sensorimotor mechanisms underlying voice motor control. We speculate that this effect is associated with the increased contribution of feedforward motor mechanisms, leading to reduced compensatory speech responses to AAF.

中文翻译：

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通过高清经颅直流电刺激左腹运动皮层调节声调。

感觉运动整合机制之间的神经相互作用在语音运动控制中起关键作用。我们调查了左腹运动皮质的高清经颅直流电刺激（HD-tDCS）如何在语音运动控制过程中调节感觉运动整合的神经机制。HD-tDCS是在语音元音生成过程中响应于向上和向下的音高变化刺激而在改变的听觉反馈（AAF）范式中执行的。在一个实验中，两组接受阳极或阴极2毫安（mA）HD-tDCS到达左腹运动皮层，而第三组接受假（安慰剂）刺激。在第二个实验中，两组接受了1 mA或2 mA的阴极HD-tDCS到左腹运动皮层。第一个实验的结果表明，在阳极和阴极HD-tDCS之后，仅对向下的音高偏移AAF刺激做出响应，声音补偿的幅度才显着降低，与阴极HD-tDCS相关的效果更强。然而，在假刺激后未观察到这种效果。第二个实验的结果表明，从1 mA到2 mA，调制没有不同的影响。此外，这些结果仅响应于向下的音调复制了第一个实验的声音补偿方向性发现。这些发现表明，左腹运动皮层的神经刺激调节了语音运动控制的感觉运动机制。我们推测这种影响与前馈运动机制的贡献增加有关，