Verbal fluency performance in Bengali-English bilingual aphasia

Abstract

Event Abstract Back to Event Verbal fluency performance in Bengali-English bilingual aphasia Abhijeet Patra1 and Arpita Bose1* 1 University of Reading, School of Psychology and Clinical Language Sciences, United Kingdom Introduction: Research has shown that impairments in executive control may influence word production abilities in aphasia[1,2]. However, studies investigating the contribution of lexical retrieval and executive control processes during word production are mostly limited to monolingual aphasia[3,4]. Very little is known about bilinguals with aphasia (BWA). A better approach to understand the relationship between lexical retrieval and executive control processes might be to use a task that simultaneously draw upon these processes. In a verbal fluency task, lexical and executive contribution for semantic and letter fluency conditions are different; semantic fluency largely depends on lexical retrieval abilities, whilst letter fluency largely depends on executive control abilities. Characterisation of verbal fluency performance beyond number of correct responses (CR) (e.g., Fluency Difference Score FDS; cluster size; number of switches; temporal measures such as within- and between-cluster pauses), have enabled researchers to specifically speculate the components of performance that depends on lexical retrieval vs. executive control processes[5,6,7]. Previous research has shown that in semantic fluency, BWA produced fewer CR, smaller cluster sizes, and fewer number of switches compared to bilingual healthy adults (BHA)[5,6]. These studies have emphasised the greater role of lexical processes in performance differences between BWA and BHA. However, in absence of comparison to letter fluency, it remains inconclusive if it is only the lexical processes that are compromised in BWA. We compared semantic and letter fluency conditions between Bengali-English BWA and BHA to determine: a) if poor performance in aphasia is due to lexical retrieval and/or executive control difficulties; b) are the differences more exaggerated on measures which depend heavily on the executive control processes. Bengali is a South-Asian language spoken by 180.5 million speakers in the world[8]. Despite that aphasia research reporting Bengali speakers remain under-presented (only one study)[9]. We attempt to fill this gap in the literature. Methods & Procedure: Semantic (animals, fruits and vegetables) and letter fluency (/p/, /k/, /m/) 60-seconds trails were collected from eight non-fluent Bengali-English BWA and eight Bengali-English BHA in their dominant language (Bengali). The groups were matched for age, gender, years of education, and bilingualism measures (language proficiency, usage, dominance). We measured: CR, FDS ((CR.semantic fluency - CR.letter fluency)/CR.semantic fluency), cluster size, number of switches, within-and between-cluster pause. Results and Discussion: Table 1 presents results summary. Overall, on both fluency conditions, compared to BHA, BWA produced fewer number of CR, had higher FDS, made fewer switches, and had longer between-cluster pauses. These results are indicative of difficulty in the executive control component of the verbal fluency task in addition to their lexical difficulties[4,7]. Both groups performed similarly on cluster size and within-cluster pauses. Fewer number of CR, and fewer switches for BWA are consistent with the literature[5,6]. No difference in cluster size and within-cluster pause suggest similar search strategies used by BWA and BHA while accessing the mental lexicon. Our results demonstrate that inclusion of letter fluency and a full range of verbal fluency measures are necessary to understand the effect of lexical and executive control processes in verbal fluency performance. Acknowledgements We would like to thank all our participants for their time and effort. We also would like to acknowledge Felix trust, UK for the PhD fellowship.