Nejati Vahid, Estaji Reza, Helisaz Zahra
Department of Psychology, Shahid Beheshti University, Tehran P.O. Box 1983969411, Iran.
Brain Sci. 2023 Aug 29;13(9):1257. doi: 10.3390/brainsci13091257.
Individuals with attention deficit hyperactivity disorder (ADHD) struggle with impaired verbal fluency as an executive function. The left and right dorsolateral prefrontal cortex (dlPFC) and the right inferior frontal gurus (IFG), which show reduced functionality in individuals with ADHD, are involved in verbal fluency. In this study, a total of thirty-seven children with ADHD participated in two separate experiments. Each experiment included three different stimulation conditions: anodal left dlPFC/cathodal right vmPFC stimulation, the reversed montage, and a sham stimulation in Experiment 1, and anodal right dlPFC, anodal right IFG with extracranial return electrode, and a sham stimulation in Experiment 2. During each session, participants performed semantic and phonemic verbal fluency tasks while receiving tDCS. The results revealed a significant main effect of stimulation condition on phonemic verbal fluency during anodal left dlPFC stimulation in Experiment 1, and on semantic verbal fluency during both real stimulation conditions in Experiment 2. In conclusion, this study suggests that anodal left dlPFC stimulation improves phonemic verbal fluency, while anodal right dlPFC and right IFG stimulation enhance semantic verbal fluency. This domain-specific improvement can be attributed to the distinct cognitive demands of phonemic and semantic verbal fluency tasks. Phonemic verbal fluency heavily relies on working memory processes, whereas semantic verbal fluency requires effective inhibitory control and cognitive flexibility.
患有注意力缺陷多动障碍（ADHD）的个体在作为执行功能的言语流畅性受损方面存在困难。左侧和右侧背外侧前额叶皮质（dlPFC）以及右侧额下回（IFG）在ADHD个体中功能降低，它们与言语流畅性有关。在本研究中，共有37名患有ADHD的儿童参与了两项独立实验。每个实验包括三种不同的刺激条件：实验1中的阳极左侧dlPFC/阴极右侧vmPFC刺激、反向组合以及假刺激，实验2中的阳极右侧dlPFC、带有颅外返回电极的阳极右侧IFG以及假刺激。在每个疗程中，参与者在接受经颅直流电刺激（tDCS）时执行语义和音素言语流畅性任务。结果显示，在实验1中阳极左侧dlPFC刺激期间，刺激条件对音素言语流畅性有显著的主效应，在实验2的两种真实刺激条件下，刺激条件对语义言语流畅性有显著的主效应。总之，本研究表明，阳极左侧dlPFC刺激可提高音素言语流畅性，而阳极右侧dlPFC和右侧IFG刺激可增强语义言语流畅性。这种特定领域的改善可归因于音素和语义言语流畅性任务的不同认知需求。音素言语流畅性严重依赖于工作记忆过程，而语义言语流畅性则需要有效的抑制控制和认知灵活性。
