Introduction
As Alzheimer’s disease (AD) becomes more prevalent in bilingual individuals, concerns arise about the cognitive implications of AD on the language dynamics between first- and second-learned languages. Modern clinical studies suggest that AD leads to significant deterioration in the linguistic capabilities of the less dominant language. However, the current theoretical framework fails to address the non-uniform sensitivity to AD. This irregularity is reflected in the preserved linguistic abilities, including code-switching and semantic fluency, and the declined functions in translation, picture naming, and phonemic fluency, calling for improved therapy and testing practices.
Alzheimer’s Disease in Bilingual Individuals
Current preliminary clinical data indicate that bilingual individuals with AD (BIAD) showed higher cognitive-linguistic functions in their dominant first language than in the non-dominant second language. As Stilwell et al. (2016) note, their analysis indicates that “superior performances were reported for the dominant over the non-dominant language” for BIAD. Nevertheless, Stillwell et al. (2016) suggest the complex linguistic networks characteristic of bilingualism allow for “the rapid linguistic selection required during linguistic processing” (p. 3). Moreover, the simultaneous triggering of both languages “in the context of therapy that includes translation tasks” stimulates overlapping cognitive processes between the languages, particularly “cognitive control of language selection” (Ansaldo & Saidi, 2014, p. 5). This suggests that bilingualism’s high bilateral communication may help diminish AD’s deteriorating effects, informing effective therapy methods.
The candidates for these methods include semantic fluency and code-switching. Despite the transition’s promising results, Stilwell et al. (2016) research showed that BIAD translated words in the dominant language with higher performance. Furthermore, their study indicates during phonemic verbal fluency and picture naming tests, BIAD demonstrated higher accuracy in their dominant language. However, on the semantic fluency test, BIAD did not have “greater difficulty” in generating words in both languages, while the code-switching test “found no difference…between the two languages” (Stilwell et al., 2016, pp. 8-11). Additionally, less dominancy does not effectively determine the language’s “higher rates of speech disfluencies” (Byrd et al., 2015, p. 12). This inconsistency warrants refined therapy and testing of cognitive-linguistic facilities.
Conclusion
In summary, the clinical landscape has not reached a consensus on whether the dominance of a language decisively determines its higher chance of preservation. While dominance is attributable to the conservation of linguistic abilities, including translation, picture naming, and phonemic fluency, it showed little correlation with other functions, including code-switching and semantic fluency. The varying sensitivity of linguistic abilities to AD might inform the development of effective therapeutic and testing procedures.
References
Ansaldo, A. I., & Saidi, L. G. (2014). Aphasia therapy in the age of globalization: cross-linguistic therapy effects in bilingual aphasia. Behavioural neurology, 1–10.
Byrd, C. T., Watson, J., Bedore, L. M., & Mullis, A. (2015). Identification of stuttering in bilingual Spanish–English-speaking children. Contemporary issues in communication science & disorders, 42, 72–87.
Stilwell, B. L., Dow, R. M., Lamers, C., & Woods, R. T. (2016). Language changes in bilingual individuals with Alzheimer’s disease. International journal of language & communication disorders, 51(2), 113–127.