Relationship between deficits of verbal short-term memory and auditory impairment among Cantonese speakers with aphasia

Background Patients with left hemisphere stroke often have co-morbid verbal short-term memory (STM) and language impairment. Studies have indicated that treatment on STM deficits generally have positive effect on patients’ responses to language therapy (Murray, 2012). Chinese is a logographic language and lack grapheme-phoneme relationship as English or other alphabetic languages. Law, Yeung, and Chiu (2008) found that absence of grapheme-phoneme correspondence results in poor phonological awareness among Cantonese speakers. Chen, Cowell, Varley, and Wang (2009) also suggested that shorter articulation time for digits in spoken Mandarin accounts for higher digit spans than English. Aim This study aimed to investigate the relationship between STM and auditory linguistic tasks in Cantonese speakers with aphasia. Specifically, whether the models used in explaining the relationship between STM and language processes and if STM treatment approaches in English can be applied to non-alphabetic languages was discussed. Procedures Fifteen left hemispheric stroke participants and fifteen controls were assessed with a series of immediate serial recall (ISR) tasks, including monosyllabic high frequency non-words, monosyllabic low frequency non-words, disyllabic non-words, monosyllabic real words, disyllabic high imageability real words, disyllabic low imageability real words, and auditory linguistic tasks, including auditory discrimination, lexical decision, and auditory word recognition. The stroke group was also administered the Cantonese version of the Western Aphasia Battery (CAB). Results The results showed statistically significant difference in all ISR and auditory linguistic tasks between the stroke control groups using Mann-Whitney Test (p<0.01). Multiple regression analysis in the stroke group showed that the auditory linguistic tasks statistically significantly predicted comprehension score in CAB, F(3,11)=, p<0.01, R2=38.65. Further tests showed that auditory discrimination task (β=0.52, p<0.01) and auditory word recognition tasks (β=0.10, p<0.01) but not the lexical decision task (β=0.11, p>0.05) statistically significantly predicted comprehension score in CAB. Spearman’s rho showed moderate to high correlations between auditory discrimination and word recognition tasks with almost all ISR tasks (0.57 to 0.92, p≤0.05) but moderate correlation between lexical decision task with only one ISR task. Wilcoxon Signed Rank test found statistical significant difference between real words and non-words in both monosyllabic and disyllabic words (p<0.01) of the two groups. Discussion Our results suggested that Cantonese speakers demonstrated more difficulties in non-words and lexical decision tasks, potentially due to the additional linguistic factor of lexical tone (Cutler & Chen, 1997).The importance of lexical tone in phonological processing of tonal languages, which warrants further investigation, should be highlighted for clinical assessment as well as intervention.

Abstract licence: CC BY

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