Bose Arpita, Patra Abhijeet, Antoniou Georgia Eleftheria, Stickland Rachael C, Belke Eva
School of Psychology and Clinical Language Sciences, University of Reading, Reading, UK.
Manchester Metropolitan University, Manchester, UK.
Int J Lang Commun Disord. 2022 May;57(3):593-614. doi: 10.1111/1460-6984.12710. Epub 2022 Mar 23.
Verbal fluency tasks are routinely used in clinical assessment and research studies of aphasia. People with aphasia produce fewer items in verbal fluency tasks. It remains unclear if their output is limited solely by their lexical difficulties and/or has a basis in their executive control abilities. Recent research has illustrated that detailed characterization of verbal fluency performance using temporal characteristics of words retrieved, clustering and switching, and pause durations, along with separate measures of executive control stands to inform our understanding of the lexical and cognitive underpinnings of verbal fluency in aphasia.
To determine the locus of the verbal fluency difficulties in aphasia, we compared semantic and letter fluency trials between people with aphasia and healthy control participants using a wide range of variables to capture the performance between the two groups. The groups were also tested on separate measures of executive control to determine the relationship amongst these tasks and fluency performance.
METHODS & PROCEDURES: Semantic (animal) and letter (F, A, S) fluency data for 60s trials were collected from 14 people with aphasia (PWA) and 24 healthy adult controls (HC). Variables, such as number of correct responses, clustering and switching analyses, were performed along with temporal measures of the retrieved words (response latencies) and pause durations. Participants performed executive control tasks to measure inhibitory control, mental-set shifting and memory span.
OUTCOMES & RESULTS: Compared with HC, PWA produced fewer correct responses, showed greater difficulty with the letter fluency condition, were slower in getting started with the trials, showed slower retrieval times as noted in within- and between-cluster pause durations, and switched less often. Despite these retrieval difficulties, PWA showed a similar decline in the rate of recall to HC, and had similar cluster size. Executive control measures correlated primarily with the letter fluency variables: mostly for PWA and in one instance for HC.
CONCLUSIONS & IMPLICATIONS: Poorer performance for PWA is a combination of difficulties in both the lexical and executive components of the verbal fluency task. Our findings highlight the importance of detailed characterization of fluency performance in deciphering the underlying mechanism of retrieval difficulties in aphasia, and illustrate the importance of using letter fluency trials to tap into executive control processes.
What is already known on the subject PWA typically show impaired performance in verbal fluency tasks. It is debated whether this impaired performance is a result of their lexical difficulties or executive control difficulties, or a combination of both. This debate continues because previous studies have mostly used semantic fluency condition without including letter fluency condition; used a limited range of variables (e.g., number of correct responses); and not included separate executive control measures to explain the performance pattern in aphasia. This research addresses these outstanding issues to determine the specific contribution of lexical and executive control processes in verbal fluency in aphasia by including: both semantic and letter fluency conditions; a wide range of variables to identify the relative contribution of lexical and executive control mechanisms; and independent measures of executive control. What this paper adds to existing knowledge Using the multidimensional analysis approach for verbal fluency performance from both semantic and letter fluency conditions, this is the first study to systematically demonstrate that PWA had difficulties in both lexical and executive control components of the task. At the individual level, PWA had greater difficulty on the letter fluency condition compared with semantic fluency. We observed significant correlations between the executive control measures and verbal fluency measures primarily for the letter fluency condition. This research makes a significant contribution to our understanding of lexical and executive control aspects in word production in aphasia. What are the potential or actual clinical implications of this work? From a clinical perspective, this research highlights the importance of using a full range of verbal fluency and executive control measures to tap into the lexical as well as executive control abilities of PWA, and also the utility of using letter fluency to tap into the executive control processes in PWA.
言语流畅性任务常用于失语症的临床评估和研究。失语症患者在言语流畅性任务中产出的项目较少。目前尚不清楚他们的产出是否仅受词汇困难的限制和/或是否有执行控制能力方面的基础。最近的研究表明，利用所检索单词的时间特征、聚类和转换以及停顿持续时间对言语流畅性表现进行详细表征，再结合执行控制的单独测量，有助于我们理解失语症患者言语流畅性的词汇和认知基础。
为了确定失语症患者言语流畅性困难的根源，我们使用广泛的变量比较了失语症患者和健康对照参与者之间的语义和字母流畅性试验，以了解两组之间的表现差异。还对两组进行了单独的执行控制测量，以确定这些任务与流畅性表现之间的关系。
从14名失语症患者（PWA）和24名健康成人对照（HC）中收集了60秒试验的语义（动物）和字母（F、A、S）流畅性数据。进行了诸如正确反应数量、聚类和转换分析等变量分析，同时还测量了所检索单词的时间特征（反应潜伏期）和停顿持续时间。参与者执行执行控制任务以测量抑制控制、心理定势转换和记忆广度。
与健康对照相比，失语症患者产生的正确反应较少，在字母流畅性条件下表现出更大的困难，试验开始时较慢，聚类内和聚类间停顿持续时间显示检索时间较慢，且转换频率较低。尽管存在这些检索困难，但失语症患者的回忆率下降与健康对照相似，且聚类大小相似。执行控制测量主要与字母流畅性变量相关：主要针对失语症患者，在一个实例中针对健康对照。
失语症患者表现较差是言语流畅性任务中词汇和执行成分都存在困难的综合结果。我们的研究结果强调了在解读失语症患者检索困难的潜在机制时，对流畅性表现进行详细表征的重要性，并说明了使用字母流畅性试验来探究执行控制过程的重要性。
关于该主题已知的信息是，失语症患者在言语流畅性任务中通常表现受损。关于这种受损表现是由于他们的词汇困难还是执行控制困难，或者是两者的结合，存在争议。这场争论仍在继续，因为以前的研究大多使用语义流畅性条件，而未包括字母流畅性条件；使用的变量范围有限（例如正确反应的数量）；并且未包括单独的执行控制测量来解释失语症患者的表现模式。本研究通过纳入：语义和字母流畅性条件；广泛的变量以确定词汇和执行控制机制的相对贡献；以及执行控制的独立测量，解决了这些突出问题，以确定词汇和执行控制过程在失语症患者言语流畅性中的具体贡献。本文对现有知识的补充：使用来自语义和字母流畅性条件的言语流畅性表现的多维分析方法，这是第一项系统证明失语症患者在任务的词汇和执行控制成分方面都存在困难的研究。在个体层面，与语义流畅性相比，失语症患者在字母流畅性条件下困难更大。我们观察到执行控制测量与言语流畅性测量之间存在显著相关性，主要针对字母流畅性条件。这项研究对我们理解失语症患者单词生成中的词汇和执行控制方面做出了重大贡献。这项工作的潜在或实际临床意义是什么？从临床角度来看，这项研究强调了使用全面的言语流畅性和执行控制测量来探究失语症患者的词汇以及执行控制能力的重要性，以及使用字母流畅性来探究失语症患者执行控制过程的实用性。
