Brain white matter tract integrity and cognitive abilities in community-dwelling older people: The Lothian Birth Cohort, 1936.

Abstract

Objective: The present study investigates associations between brain white matter tract integrity and cognitiveabilities in community-dwelling older people (N 655). We explored two potential confounds of white mattertract cognition associations in later life: (a) whether the associations between tracts and specific cognitiveabilities are accounted for by general cognitive ability (g); and (b) how the presence of atrophy and whitematter lesions affect these associations. Method: Tract integrity was determined using quantitative diffusionmagnetic resonance imaging tractography (tract-averaged fractional anisotropy [FA]). Using confirmatoryfactor analysis, we compared first-order and bifactor models to investigate whether specific tract-abilityassociations were accounted for by g. Results: Significant associations were found between g and FA inbilateral anterior thalamic radiations (r range: .16 .18, p .01), uncinate (r range: .19 .26, p .001),arcuate fasciculi (r range: .11 .12, p .05), and the splenium of corpus callosum (r .14, p .01). Aftercontrolling for g within the bifactor model, some significant specific cognitive domain associations remained.Results also suggest that the primary effects of controlling for whole brain integrity were on g associations,not specific abilities. Conclusion: Results suggest that g accounts for most of, but not all, the tract cognitionassociations in the current data. When controlling for age-related overall brain structural changes, only minorattenuations of the tract cognition associations were found, and these were primarily with g. In totality, theresults highlight the importance of controlling for g when investigating associations between specific cognitiveabilities and neuropsychology variables.