Chang Yichen, Peng Danhua, Zhao Yan, Chen Xi, Li Jingting, Wu Xiuqin, Liu Peng, Liu Hanjun
Department of Rehabilitation Medicine, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China.
Guangdong Provincial Key Laboratory of Brain Function and Disease, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China.
Front Neurosci. 2023 Jun 30;17:1208581. doi: 10.3389/fnins.2023.1208581. eCollection 2023.
A growing body of literature has implicated the left dorsolateral prefrontal cortex (DLPFC) in the online monitoring of vocal production through auditory feedback. Specifically, disruption of or damage to the left DLPFC leads to exaggerated compensatory vocal responses to altered auditory feedback. It is conceivable that enhancing the cortical excitability of the left DLPFC may produce inhibitory influences on vocal feedback control by reducing vocal compensations.
We used anodal transcranial direct current stimulation (a-tDCS) to modulate cortical excitability of the left DLPFC and examined its effects on auditory-motor integration for vocal pitch regulation. Seventeen healthy young adults vocalized vowel sounds while hearing their voice pseudo-randomly pitch-shifted by ±50 or ±200 cents, either during (online) or after (offline) receiving active or sham a-tDCS over the left DLPFC.
Active a-tDCS over the left DLPFC led to significantly smaller peak magnitudes and shorter peak times of vocal compensations for pitch perturbations than sham stimulation. In addition, this effect was consistent regardless of the timing of a-tDCS (online or offline stimulation) and the size and direction of the pitch perturbation.
These findings provide the first causal evidence that a-tDCS over the left DLPFC can facilitate auditory-motor integration for compensatory adjustment to errors in vocal output. Reduced and accelerated vocal compensations caused by a-tDCS over left DLPFC support the hypothesis of a top-down neural mechanism that exerts inhibitory control over vocal motor behavior through auditory feedback.
越来越多的文献表明，左背外侧前额叶皮质（DLPFC）参与通过听觉反馈对发声进行在线监测。具体而言，左DLPFC的破坏或损伤会导致对改变的听觉反馈产生夸张的代偿性发声反应。可以想象，增强左DLPFC的皮质兴奋性可能会通过减少发声代偿对发声反馈控制产生抑制作用。
我们使用阳极性经颅直流电刺激（a-tDCS）来调节左DLPFC的皮质兴奋性，并研究其对用于音高调节的听觉-运动整合的影响。17名健康的年轻成年人在左DLPFC接受主动或伪刺激a-tDCS期间（在线）或之后（离线）发出元音声音，同时听到他们的声音以±50或±200音分的方式伪随机变调。
与伪刺激相比，左DLPFC上的主动a-tDCS导致音高扰动的发声代偿的峰值幅度显著减小，峰值时间显著缩短。此外，无论a-tDCS的时机（在线或离线刺激）以及音高扰动的大小和方向如何，这种效应都是一致的。
这些发现提供了首个因果证据，即左DLPFC上的a-tDCS可以促进听觉-运动整合，以对发声输出中的错误进行代偿性调整。左DLPFC上的a-tDCS导致的发声代偿减少和加速支持了一种自上而下的神经机制假说，即通过听觉反馈对发声运动行为施加抑制控制。
