Bilingual Factors Associated with Cognitive Reserve and Linguistic Resilience in Hispanics with Primary Progressive Aphasia

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Project Summary/Abstract Society at large is facing a global “dementia epidemic” that is predicted to intensify with the growing aging population. Although there is currently no cure for this devastating and pervasive condition, one life experience shown to protect against the onset of Alzheimer’s disease and related disorders (ADRD) is that of bilingualism. Nevertheless, findings regarding bilingualism as a contributor to cognitive reserve are mixed. These mixed findings may, in part, be attributed to variability in the characterization of the bilingual experience across distinct sociocultural contexts in addition to the presence of potential confounding variables. Little attention has been directed towards examining bilingualism factors (e.g., language dominance, proficiency, use and age of acquisition) that may underly these findings. In addition, limited attention has been directed towards language- prominent dementia syndromes, such as primary progressive aphasia (PPA). Although speech and language impairments are ubiquitous features of ADRD, in the case PPA these debilitating deficits manifest as initial, predominant symptoms. Differential patterns of language decline have been observed in bilingual PPA, with resilience of the first learned language and parallel decline reported in the literature. However, a nuanced account establishing patterns of language decline across different linguistic domains has yet to be systematically examined in PPA. In addition, although positive effects of speech-language intervention are now well documented in monolingual speakers with PPA, there is a significant gap in the literature examining treatment optimized for bilingual speakers with PPA. Moreover, the behavioral, neural and bilingual factors associated with language re-learning have yet to be established in bilingual speakers with PPA. The overall aim of the proposed research is to establish associations between bilingualism factors and the onset, decline, and treatment response of Hispanic, bilinguals (Spanish-Catalan) with PPA. In Aim 1, we seek to identify bilingualism factors associated with a later age of onset in Hispanics with each PPA variant. In Aim 2, we seek to identify the bilingualism factors associated with differential patterns of language impairment in Hispanics with PPA using metrics derived from connected speech. In Aim 3, we will evaluate the benefits of tailored speech-language intervention in the largest behavioral rehabilitation study of bilingual Hispanics with PPA to-date. We will also identify the bilingualism factors, pre-treatment cognitive-linguistic measures, and brain regions implicated in bilingualism that predict the magnitude of within-language gains and cross-language transfer effects. In order to accomplish these aims, we will enroll 90 Hispanic, bilinguals with PPA who will undergo behavioral assessment, MRI, and speech-language treatment. This proposal will provide needed evidence regarding cognitive reserve and linguistic resilience by leveraging a large bilingual PPA cohort via an established international collaboration. Outcomes will also provide crucial knowledge regarding neural mechanisms of language re-learning and will address how specific bilingual factors influence cognitive reserve and linguistic resilience in language-prominent dementia.