Open Access Dissertation
Date of Award
Numerous studies over the past decade have used diffusion tensor imaging (DTI) to examine associations between age, diffusion and anisotropy measures of cerebral white matter (WM), and cognitive performance. However, few have examined relationships between intra-individual change in DTI measures of WM and cognitive function. It is possible that the extant cross-sectional findings are a poor representation of age-related change in WM and cognition. The present study used latent difference-score modeling (LDM) to assess change over two years in DTI indices fractional anisotropy (FA), radial diffusivity (DR), axial diffusivity (DA) and mean diffusivity (MD). In addition, we examined the effects of WM change on concomitant change in age-sensitive cognitive domains, while controlling for individual differences in duration of hypertension treatment, a common marker of vascular risk. A sample of 96 healthy participants spanning the adult lifespan underwent DTI scanning and cognitive testing at baseline and following a two-year delay. Univariate LDM analyses showed cross-sectional associations between DTI measures and age did not accurately describe actual change in WM. Regions including the genu of the corpus callosum, forceps major, and forceps minor showed reliable reductions in FA and increases in MD. In addition, change differed between DR and DA, suggesting the importance of evaluating these measures separately, rather than relying solely on MD as an index of diffusivity. Comparison of change in DTI measures and memory revealed baseline individual differences in FA, DA, and DR in dorsal and ventral cingulum bundle predicted two-year change in associative memory, while baseline DR and FA in multiple regions predicted change in recognition performance. The present findings demonstrate the necessity of longitudinal evaluation of change in WM and cognition.
Bender, Andrew Robert, "Changes In Cerebral White Matter, Vascular Risk And Cognition Across The Adult Lifespan" (2014). Wayne State University Dissertations. 872.