School of Psychology, Bangor University, Gwynedd, Wales, UK; Department of Communication Sciences and Disorders, Temple University, Philadelphia, PA, USA.
Department of Communication Sciences and Disorders, Temple University, Philadelphia, PA, USA.
Neuropsychologia. 2018 Mar;111:62-71. doi: 10.1016/j.neuropsychologia.2018.01.009. Epub 2018 Jan 11.
In a verbal fluency task, a person is required to produce as many exemplars of a given category (e.g., 'animals', or words starting with 'f') as possible within a fixed duration. Successful verbal fluency performance relies both on the depth of search within semantic/phonological neighborhoods ('clustering') and the ability to flexibly disengage between exhausted clusters ('switching'). Convergent evidence from functional imaging and neuropsychology suggests that cluster-switch behaviors engage dissociable brain regions. Switching has been linked to a frontoparietal network dedicated to executive functioning and controlled lexical retrieval, whereas clustering is more commonly associated with temporal lobe regions dedicated to semantic and phonological processing. Here we attempted to modulate cluster-switch dynamics among neurotypical adults (N = 24) using transcranial direct current stimulation (tDCS) delivered at three sites: a) anterior temporal cortex; b) frontal cortex; and c) temporoparietal cortex. Participants completed letter-guided and semantic category verbal fluency tasks pre/post stimulation. Cathodal stimulation of anterior temporal cortex facilitated the total number of words generated and the number of words generated within clusters during semantic category verbal fluency. These neuromodulatory effects were specific to stimulation of the one anatomical site. Our findings highlight the role of the anterior temporal lobes in representing semantic category structure and support the claim that clustering and switching behaviors have distinct substrates. We discuss implications both for theory and application to neurorehabilitation.
在言语流畅性任务中，要求一个人在固定的时间内尽可能多地列举出给定类别的示例（例如，“动物”或以“f”开头的单词）。成功的言语流畅性表现既依赖于语义/语音邻域内的搜索深度（“聚类”），也依赖于灵活地在耗尽的聚类之间脱离（“切换”）的能力。来自功能成像和神经心理学的综合证据表明，聚类切换行为涉及可分离的大脑区域。切换与专门用于执行功能和控制词汇检索的额顶网络有关，而聚类通常与专门用于语义和语音处理的颞叶区域有关。在这里，我们试图通过经颅直流电刺激（tDCS）在三个部位调节神经典型成年人（N=24）的聚类切换动态：a）前颞叶皮层；b）额叶皮层；c）颞顶叶皮层。参与者在刺激前/后完成字母引导和语义类别言语流畅性任务。前颞叶皮层的阴极刺激促进了语义类别言语流畅性中生成的单词总数和聚类中生成的单词数。这些神经调节效应是特定于一个解剖部位的刺激。我们的发现强调了前颞叶在表示语义类别结构中的作用，并支持聚类和切换行为具有不同的基础的观点。我们讨论了这对理论和神经康复应用的影响。
