Laboratory of Brain and Cognition, National Institute of Mental Health, Bethesda, MD 20892, USA.
Neuroimage. 2010 Jan 1;49(1):1099-107. doi: 10.1016/j.neuroimage.2009.07.036. Epub 2009 Jul 23.
Verbal fluency tasks have been widely used to evaluate language and executive control processes in the human brain. FMRI studies of verbal fluency, however, have used either silent word generation (which provides no behavioral measure) or cued generation of single words in order to contend with speech-related motion artifacts. In this study, we use a recently developed paradigm design to investigate the neural correlates of verbal fluency during overt, free recall, word generation so that performance and brain activity could be evaluated under conditions that more closely mirror standard behavioral test demands. We investigated verbal fluency to both letter and category cues in order to evaluate differential involvement of specific frontal and temporal lobe sites as a function of retrieval cue type, as suggested by previous neuropsychological and neuroimaging investigations. In addition, we incorporated both a task switching manipulation and an automatic speech condition in order to modulate the demand placed on executive functions. We found greater activation in the left hemisphere during category and letter fluency tasks, and greater right hemisphere activation during automatic speech. We also found that letter and category fluency tasks were associated with differential involvement of specific regions of the frontal and temporal lobes. These findings provide converging evidence that letter and category fluency performance is dependent on partially distinct neural circuitry. They also provide strong evidence that verbal fluency can be successfully evaluated in the MR environment using overt, self-paced, responses.
言语流畅性任务已被广泛用于评估人类大脑中的语言和执行控制过程。然而，言语流畅性的 fMRI 研究要么使用无声单词生成（无法提供行为测量），要么使用提示生成单个单词，以应对与言语相关的运动伪影。在这项研究中，我们使用一种新开发的范式设计来研究在明显的、自由回忆、单词生成过程中的言语流畅性的神经相关性，以便在更接近标准行为测试要求的条件下评估性能和大脑活动。我们调查了字母和类别提示的言语流畅性，以评估特定的额颞叶部位的差异参与，这是由先前的神经心理学和神经影像学研究提出的。此外，我们还纳入了任务转换操作和自动语音条件，以调节对执行功能的要求。我们发现，在类别和字母流畅性任务中，左半球的激活程度更高，而在自动语音中，右半球的激活程度更高。我们还发现，字母和类别流畅性任务与额颞叶特定区域的差异参与有关。这些发现提供了一致的证据，表明字母和类别流畅性表现依赖于部分不同的神经回路。它们还提供了强有力的证据，表明可以在磁共振环境中使用明显的、自我调节的、反应来成功地评估言语流畅性。
