The Effects of Single-Session Cathodal and Bihemispheric tDCS on Fluency in Stuttering

Developmental stuttering is a fluency disorder that affects many aspects of a person’s life. Recent transcranial direct current stimulation (tDCS) studies have shown promise to improve fluency when paired with fluency enhancing conditions. To date, bihemispheric tDCS has not been investigated in people who stutter, although several studies associated it with improved speech and articulation skills in aphasic patients. In this study, we aimed to investigate the effects of single-session bihemispheric and unihemispheric cathodal tDCS on fluency in adults who stutter. We predicted that bihemispheric tDCS with anodal stimulation to the left IFG and cathodal stimulation to the right IFG would improve fluency better than the sham and cathodal tDCS to the right IFG. Seventeen adults who stutter completed this single-blind, crossover, sham-controlled tDCS experiment. All participants received 20 minutes of tDCS alongside metronome-timed speech during intervention sessions. Three tDCS interventions were administered: bihemispheric tDCS with anodal stimulation to the left IFG and cathodal stimulation to the right IFG, unihemispheric tDCS with cathodal stimulation to the right IFG, and sham stimulation. Speech fluency during reading and conversation was assessed before, immediately after, and one week after each intervention session. There was no significant fluency improvement in conversation for any tDCS interventions. Reading fluency improved following both bihemispheric and cathodal tDCS interventions. tDCS montages were not significantly different in their effects on fluency. This study has significant implications in developing and applying interventions for people who stutter.

发育性口吃是一种影响个人生活多方面的流畅性障碍。近期关于经颅直流电刺激（tDCS）的研究表明，当与流畅性提升条件结合使用时，tDCS有望改善流畅性。迄今为止，双半球tDCS尚未在口吃患者中研究，尽管有几项研究将其与流利性和发音技巧的提升关联起来，尤其是在失语症患者中。在本研究中，我们旨在探究单次双半球和单半球阴极tDCS对成年口吃者流畅性的影响。我们预测，通过阳极刺激左侧前扣带回皮层（IFG）和阴极刺激右侧IFG的双半球tDCS将比安慰剂和右侧IFG的阴极tDCS更有效地改善流畅性。十七位成年口吃者完成了这项单盲、交叉、安慰剂控制的tDCS实验。所有参与者在接受干预期间均接受了20分钟的tDCS，并伴随节拍器计时下的言语。实施了三种tDCS干预：双半球tDCS，阳极刺激左侧IFG，阴极刺激右侧IFG；单半球tDCS，阴极刺激右侧IFG；以及安慰剂刺激。在阅读和对话中的言语流畅性在干预前、干预后立即以及每次干预后一周进行评估。对于任何tDCS干预，在对话中的流畅性改善均无显著差异。阅读流畅性在双半球和阴极tDCS干预后均有所提高。tDCS配置在改善流畅性方面没有显著差异。本研究对于开发和应用针对口吃者的干预措施具有重要意义。