Patterns of decline and recovery in bilingual speakers with primary progressive aphasia

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Project Summary Primary progressive aphasia (PPA) is a neurodegenerative disorder characterized by a decline in speech and language abilities, with relative sparing of other cognitive abilities. In recent years, significant advances have been made regarding the nature and treatment of PPA in monolingual speakers, however; the nature and treatment of bilingual speakers with this diagnosis has been relatively unexplored. Through the use of a historical dataset, this proposal will investigate differences in the trajectory of behavioral and neural decline in untreated bilingual speakers relative to monolingual speakers with PPA (within each variant), so that the long- term benefits of treatment can be discerned in future cases. In addition, this proposal will compare the trajectory of decline between monolinguals and bilinguals with PPA (within each variant), to observe whether bilingualism provides a behavioral or neural advantage in this focal dementia. Performance on selected speech-language and cognitive assessments will also be compared between groups. Structural neuroimaging will be used to examine longitudinal change in gray matter volumes. In this study, we will also prospectively implement two behavioral speech-language interventions (lexical retrieval training and a script training approach), and will systematically manipulate treatment targets in order to facilitate cross-linguistic generalization. We use a cognitive-neuroanatomical framework to predict differential responsiveness to cognate loading and to each treatment approach on the basis of each PPA variant’s distinctive cognitive-linguistic and neural profile. Ten Spanish-English bilingual individuals with PPA will receive speech language intervention. In rehabilitative studies of stroke-induced aphasia, cross-linguistic cognates have been observed to both facilitate and impede generalization, with no cost to within language gains. Therefore, this study will manipulate the density of cognate inclusion in stimulus sets, to determine the proportion of cognates that maximizes cross-linguistic generalization and minimizes competition. The relevance of this project to public health lies in its attempts to understand the nature and treatment of behavioral and neural changes in bilingual speakers with PPA. One goal of the Healthy People 2020 program is to reduce the morbidity and costs associated with, and maintain or enhance the quality of life for persons with dementia. PPA is a form of dementia that has been understudied, and bilinguals with PPA have been historically underserved. The findings from this proposal will provide clinically relevant evidence regarding the rate of decline and potential benefit of treatment in bilinguals with PPA. This project will provide the applicant with a unique training experience, which will include learning new methodologies and data analysis techniques. The applicant’s sponsors and consultants will provide expertise and mentorship in the areas of intervention, neuroimaging, bilingualism, experimental design and statistics; thus, preparing her to become an independent researcher in the fields of bilingual aphasia and dementia.