Dissertations, Theses, and Capstone Projects

Date of Degree

2-2024

Document Type

Dissertation

Degree Name

Ph.D.

Program

Speech-Language-Hearing Sciences

Advisor

Mira Goral

Committee Members

Jet M.J. Vonk

Elizabeth Galletta

Subject Categories

Nervous System Diseases | Neurosciences | Speech Pathology and Audiology

Keywords

cognitive reserve, frontotemporal dementia, primary progressive aphasia, sociobehavioral proxies, dementia

Abstract

Cognitive reserve refers to the brain’s ability to efficiently adapt in the presence of neuropathological disease. This is an active process influenced by individual differences (e.g., genetics) and lifetime experiences (e.g., education, occupation, leisure) (Cabeza et al., 2018; Stern et al., 2020). The cognitive reserve theory has recently been investigated in individuals with frontotemporal dementia (FTD), which refers to various disorders leading to frontotemporal neurodegenerative decline (Young et al., 2018); e.g., behavioral variant of FTD (bvFTD) and variants of Primary Progressive Aphasia (PPA): semantic (svPPA), nonfluent/agrammatic (nfvPPA), and logopenic (lvPPA). However, a clear consensus on the relationship among cognitive reserve, brain status, and clinical performance has not been reached for individuals with FTD and PPA. Thus, this dissertation aimed to investigate the current cognitive reserve literature for this population by conducting a systematic review (study 1), as well as investigating how education and occupation related to brain status measures, disease severity, and speech and language performance in a longitudinally followed cohort of individuals with PPA (study 2).

For study 1, 13 studies were included in the systematic review and all included studies reported statistically significant associations between a cognitive reserve measure and a brain status measure. However, only partial support was demonstrated for the cognitive reserve theory in individuals with FTD when education, occupation, and leisure involvement were utilized as sociobehavioral proxies in relation to brain status. For study 2, 143 individuals with PPA were included in the initial baseline analyses, and 80 of these participants were included in the longitudinal analyses. Specific speech and language measures were investigated for each PPA variant (e.g., lexical retrieval function was investigated for individuals with svPPA), and four brain status measures (i.e., two brain volume and two brain thickness measures) were incorporated to comprehensively examine how the sociobehavioral proxies related to brain status. The results provided partial support for the theory of cognitive reserve in individuals with PPA. Differences in education and occupation did not predict brain status patterns nor disease severity patterns at the initial and follow up MRI visits for this group of individuals with PPA. However, when incorporating specific lexical retrieval performance for individuals with svPPA, higher education and occupation levels related to better performance on lexical retrieval tasks at the initial MRI visit, as well as better performance on the phonemic fluency task when greater gray matter volume and thickness values were present. Further study is needed though, since results were not consistent across all measures and similar relationships were not found for individuals with nfvPPA and lvPPA, which could be related to relatively small sample sizes (i.e., n=27 for both nfvPPA and lvPPA groups at baseline).

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