Regional leukoaraiosis and cognition in non-demented older adults

Frontal lobe-executive functions are heavily dependent on distal white matter connectivity. Even with healthy aging there is an increase in leukoaraiosis that might interrupt this connectivity. The goal of this study is to learn 1) the location, depth, and percentage of leukoaraiosis in white matter among a sample of non-demented older adults and 2) associations between these leukoarioasis metrics and composites of cognitive efficiency (processing speed, working memory, and inhibitory function), and episodic memory. Participants were 154 non-demented older adults (age range 60-85) who completed a brain MRI and neuropsychological testing on the same day. Brain MRIs were segmented via Freesurfer and white matter leukoaraiosis depth segmentations was based on published criteria. On average, leukoaraiosis occupied 1 % of total white matter. There was no difference in LA distribution in the frontal (1.12%), parietal (1.10%), and occipital (0.95%) lobes; there was less LA load within the temporal lobe (0.23%). For cortical depth, leukoaraiosis was predominantly in the periventricular region (3.39%; deep 1.46%, infracortical 0.15%). Only increasing frontal lobe and periventricular leukoaraiosis were associated with a reduction in processing speed, working memory, and inhibitory function. Despite the general presence of LA throughout the brain, only frontal and periventricular LA contributed to the speeded and mental manipulation of executive functioning. This study provides a normative description of LA for non-demented adults to use as a comparison to more disease samples.