White Matter in Aging and Cognition: A Cross-Sectional Study of Microstructure in Adults Aged Eighteen to Eighty-Three

Abstract

Structural brain change and concomitant cognitive decline are the seemingly unavoidable escorts of aging. Despite accumulating studies detailing the effects of age on the brain and cognition, the relationship between white matter features and cognitive function in aging have only recently received attention and remain incompletely understood. White matter microstructure can be measured with diffusion tensor imaging (DTI), but whether DTI can provide unique information on brain aging that is not explained by white matter volume is not known. In the current study, the relationship between white matter microstructure, age and neuropsychological function was assessed using DTI in a statistical framework that employed white matter volume as a voxel-wise covariate in a sample of 120 healthy adults across a broad age range (18-83). Memory function and executive function were modestly correlated with the DTI measures while processing speed showed the greatest extent of correlation. The results suggest that age-related white matter alterations underlie age-related declines in cognitive function. Mean diffusivity and fractional anisotropy in several white matter brain regions exhibited a non-linear relationship with age, while white matter volume showed a primarily linear relationship with age. The complex relationships between cognition, white matter microstructure, and white matter volume still require further investigation.

Superficial White Matter: Effects of Age, Sex, and Hemisphere

“…aging (Bendlin et al, 2010;Birren et al, 2006;Craik and Salthouse, 2007;Sullivan et al, 2010). Although SWM effects of age for FA, RD, and AD showed a more-prominent linear than nonlinear pattern, these results likely reflect the age range of the adult sample investigated.…”

Partial volume effect as a hidden covariate in DTI analyses

“…Shrinkage of the WM causes thinning of several fiber bundles and, as we have shown in this work for the CC, the MD depends on the thickness of this fiber bundle. Although changes in diffusion measures are observed even when correcting for volume (Bendlin et al, 2010), atrophy could still explain part of the observed variance of diffusion measures with age.…”

Verbal working and long-term episodic memory associations with white matter microstructure in normal aging investigated using tract-based spatial statistics.

“…Although our group and others have reported significant associations between MD and age using TBSS Bendlin et al, 2010), few studies have applied MD-TBSS measures to cognitive analyses. Using regions of interest or voxel based analyses DTI studies have identified significant correlations between mnemonic function and MD (Charlton et al, 2006;Kantarci et al, 2011).…”