Verb morphology impairment in a bilingual speaker with non-fluent aphasia

Introduction Current literature on bilingual aphasia offers little evidence regarding the manifestation of verb morphology impairment in two languages. De Diego Balaguer et al. (2004) report parallel impairment in the two languages of early, highly proficient Catalan-Spanish bilinguals with non-fluent aphasia, both demonstrating greater difficulty conjugating irregular than regular verbs on a sentence completion task. Further, greater difficulty with tense selection in verb production has been found in structured tests as compared to semi-spontaneous connected speech production (Faroqi-Shah & Dickey, 2009). The present study examined tense selection and verb conjugation in two languages of a bilingual on different tests of language production, to address the following question: What aspects of verb morphology should be considered to determine parallel or non-parallel impairment in the two languages of bilinguals with aphasia? Methods The participant was a 73-year-old Hebrew-English speaker with moderate non-fluent chronic aphasia. He has been exposed to English in an immersion context for 35 years and used both languages at the time of the CVA. The Western Aphasia Battery (WAB, Kertesz, 1982) administered in English revealed an aphasia quotient of 71. He underwent a comprehensive battery of language tests in both his languages in an alternating, counter-balanced order. The battery included a structured test, a modified version of the Verb Inflection Test (Faroqi-Shah, unpublished), and a semi-spontaneous picture sequence description task (based on the Narrative Story Cards, Helm-Estabrooks & Nicholas, 2003). Results In the Verb Inflection Test, the overall performance in Hebrew (L1) and English (L2) was comparable, but the error patterns varied. In Hebrew, 37% of verbs (10 out of 27) were produced in the appropriate tense and with the correct conjugation. The participant’s most frequent error on the remaining verbs (9 out of 27, 33%) was producing the verb in an inappropriate tense (e.g., “Tomorrow, girl painted pictures”). None of the errors in Hebrew were verb conjugation errors. In English, he provided correct responses for 33% of verbs. Errors in tense selection occurred as often as in Hebrew (33% of verbs); however, in English verb conjugation errors (e.g., “Yesterday, girl weared the skates) were also frequent. In the picture sequence description task, the participant was less impaired in Hebrew than in English. Specifically, out of 19 opportunities in Hebrew, he produced 16 verbs (84%), all of which were correctly conjugated. In English, he produced verbs in 8 out of 22 opportunities (36%). Out of these, 3 were correctly conjugated (38%). Conclusion Whereas accuracy levels on the structured task were comparable in the participant’s two languages, he was more accurate in L1 than in L2 on the semi-spontaneous task. Further, production in L1 revealed only tense-selection errors evident only in the structured task; production in L2 included both tense-selection and conjugation errors, and those were found on both tasks. Thus, what may appear as comparable impairment in producing conjugated verbs on a structured test could rather be construed as non-parallel levels of morphological deficit. These findings highlight the importance of considering both tense selection and conjugation across different tasks

A new approach to assessing intra-subject variability in single-subject designs

Research Aim: One of the methodological challenges of single-subject designs is accounting for intra-individual variability in performance, which is commonly assessed by applying the same testing materials on multiple sessions (McReynolds & Thompson, 1986). This approach might be less feasible in some individuals, such as bilingual speakers with aphasia, who would need to be tested, using the same materials, on several occasions within as well as across languages. Repetitive exposure to the same testing materials can increase practice effects and further reduce the validity of the testing. In the present study, we explored an alternative approach to measuring stability in performance by comparing the use of identical vs. different (but comparable) testing materials. Method: Participants were five monolinguals with non-fluent aphasia following a single left CVA. Participants performed an action-naming task and two narrative tasks: a picture sequence and a personal narrative. There were two testing times, several weeks apart using identical materials. Each testing time included three consecutive sessions, using different materials. Action-naming performance was assessed by the number of correct verbs produced. The verbal output in the narrative tasks was scored for amount (number of utterances), grammaticality (percentage of grammatical sentences), and verb diversity (number of different verbs). Pearson correlation coefficients (r) were computed to establish the intra-subject variability across testing times and across sessions. The magnitude of the correlations was evaluated using published guidelines (Strauss, Sherman, & Spreen, 2006). Results: For action naming, the correlations ranged from high to very high (.87 to .98) across testing times and from adequate to very high across sessions (.74 to .96). For the narrative tasks, the correlations between the number of utterances across testing times ranged from adequate to very high (.76 to .97) and from low to very high across sessions (.47 to .99). There were low to very high correlations between the percentage of grammatical sentences across testing times (.27 to .93) and across sessions (.02 to .95). The number of different verbs showed adequate to very high correlations across testing times (.75 to .99) and marginal to very high correlations across sessions (.69 to .99). Conclusions: The findings indicate that repeated testing using identical and comparable materials result in correlations of similar magnitude, suggesting that comparable and identical testing materials yield similar information about intra-individual variability in performance. Given these findings, it seems methodologically sound to use non-identical stimuli to establish stability in performance and in this way minimize practice effects in testing procedures for patients with aphasia. McReynolds, L. V., & Thompson, C. K. (1986). Flexibility of Single-Subject Experimental Designs. Part I: Review of the Basics of Single-Subject Designs. Journal of Speech and Hearing Disorders, 51(3), 194-203. doi: 10.1044/jshd.5103.194 Strauss, E., Sherman, E. M. S., & Spreen, O. (2006). A compendium of neuropsychological tests: Administration, norms, and commentary. New York: Oxford University Press

Language mixing patterns in a bilingual individual with non-fluent aphasia

Background: Language mixing in bilingual speakers with aphasia has been reported in a number of research studies, but the reasons for the mixing and whether it reflects typical or atypical behaviour has been a matter of debate. Aims: In this study, we tested the hypothesis that language mixing behaviour in bilingual aphasia reflects lexical retrieval difficulty. Methods & procedures: We recruited a Hebrew-English bilingual participant with mild-moderate non-fluent agrammatic aphasia and assessed his languages at three timepoints. We analysed the participant’s Hebrew and English production for retrieval during single-word naming, sentences, and discourse, and identified all instances of language mixing. Outcomes & Results: We found that there was a greater frequency of language mixing during production of more difficult lexical items, namely the post-morbidly less proficient language (compared to the more proficient language), function words (compared to content words), and single-word naming (compared to retrieval in the context of connected speech tasks), but not for verbs (compared to nouns). Conclusions: In this bilingual participant with non-fluent aphasia, language mixing behaviour closely resembles lexical retrieval difficulty. Thus, we suggest that bilingual speakers with aphasia may mix their languages as a strategy to maximise communication

The role of language proficiency and linguistic distance in cross-linguistic treatment effects in aphasia

Current findings from intervention in bilingual aphasia are inconclusive regarding the extent to which levels of language proficiency and degree of linguistic distance between treated and non-treated languages influence cross-language generalisation and changes in levels of language activation and inhibition following treatment. In this study, we enrolled a 65-year-old multilingual speaker with aphasia and administered treatment in his L1, Dutch. We assessed pre- and post-treatment performance for seven of his languages, five of high proficiency and two of lower proficiency. We asked whether treatment in L1 would generalise to his other languages or increase interference among them. Forty hours of treatment were completed over the course of five weeks. Each language was tested three times at pretreatment and at post-treatment. Testing included measures of narrative production, answering questions, picture description and question generation. Dependent measures examined language efficiency, defined as Correct Information Units (CIUs)/min, as well as language mixing, defined as proportion of code-mixed whole words. We found that our participant’s improved efficiency in Dutch was mirrored by parallel improvement in the four languages of high proficiency: English, German, Italian and French. In contrast, in his languages of lower proficiency, Norwegian and Spanish, improved efficiency was limited. An increase in code-mixing was noted in Spanish, but not in Norwegian. We interpret the increased code-mixing in Spanish as indication of heightened inhibition following improvement in a language of close linguistic proximity, Italian. We conclude that an interaction of language proficiency and linguistic similarity affects cross-language generalisation following intervention in multilingual aphasia