The impact of region-specific leukoaraiosis on working memory deficits in dementia.

MRI leukoaraiosis (LA) is less likely to interfere with simple compared to more complex working memory (WM) skills. We hypothesize that LA within the left hemisphere negatively impacts higher-level WM processes in dementia. Participants with dementia (n=64; MMSE=22.0+/-3.4) performed a Backward Digit Task measuring simple storage/rehearsal (ANY-ORDER) and complex disengagement/temporal re-ordering (SERIAL-ORDER) recall. A visual rating scale categorized MRI-LA in five regions per hemisphere: frontal and parietal centrum semiovale, white matter around the frontal horns, body of the lateral ventricles and posterior horns. Amidst equivalent hemispheric LA scores [t(62)=-1.12, p>0.05], correlations revealed an association between left-sided LA and SERIAL-ORDER recall (r=-0.31, p=0.007) with LA around the posterior horn (rho=-0.30, p=0.008) and frontal centrum semiovale (rho=-0.29, p=0.01) showing the greatest association. Regression modeling confirmed the left posterior horn contribution to SERIAL-ORDER performance variance. Results suggest involvement of anterior (fronto-striatal) and more posterior (inferior parietal) white matter tracts in higher order WM deficits in dementia.