Tom Booth, Mark E Bastin, Lars Penke, Susana Munoz Maniega, Catherine Murray, Natalie A Royle, Alan J Gow, Janie Corley, Ross D Henderson, Maria C Valdes Hernandez, John M Starr, Joanna M Wardlaw, and Ian J Deary (2013)

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

Neuropsychology, 27:595-607.

Objective: The present study investigates associations between brain white matter tract integrity and cognitive abilities in community-dwelling older people (N = 655). We explored two potential confounds of white matter tract cognition associations in later life: (a) whether the associations between tracts and specific cognitive abilities are accounted for by general cognitive ability (g); and (b) how the presence of atrophy and white matter lesions affect these associations. Method: Tract integrity was determined using quantitative diffusion magnetic resonance imaging tractography (tract-averaged fractional anisotropy [FAD. Using confirmatory factor analysis, we compared first-order and bifactor models to investigate whether specific tract-ability associations were accounted for by g. Results: Significant associations were found between g and FA in bilateral 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). After controlling 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-cognition associations in the current data. When controlling for age-related overall brain structural changes, only minor attenuations of the tract-cognition associations were found, and these were primarily with g. In totality, the results highlight the importance of controlling for,g when investigating associations between specific cognitive abilities and neuropsychology variables.

cognitive ability; tractography; white matter integrity; bifactor model