title: Age related differences in reaction time components and diffusion properties of normal-appearing white matter in healthy adults.
abstract: Deterioration of the white matter (WM) is viewed as the neural substrate of age differences in speed of information processing (reaction time, RT). However, the relationship between WM and RT components is rarely examined in healthy aging. We assessed the relationship between RT components derived from the Ratcliff diffusion model and micro-structural properties of normal-appearing WM (NAWM) in 90 healthy adults (age 18-82 years). We replicated all major extant findings pertaining to age differences in RT components and WM: lower drift rate, greater response conservativeness, longer non-decision time, lower fractional anisotropy (FA), greater mean (MD), axial (AD) and radial (RD) diffusivity were associated with advanced age. Age differences in anterior regions of the cerebral WM exceeded those in posterior regions. However, the only relationship between RT components and WM was the positive association between DR in the body of the corpus callosum and non-decision time. Thus, in healthy adults, age differences in NAWM diffusion properties are not a major contributor to age differences in RT components. Longitudinal studies with more precise and specific estimates of regional myelin content and evaluation of the contribution of age-related vascular risk factors are necessary to understand cerebral substrates of age-related cognitive slowing.
authors.affiliation: Institute of Gerontology, Wayne State University, USA; Department of Psychology, Wayne State University, USA.
authors.forename: Yiqin
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Institute of Gerontology, Wayne State University, USA; Department of Psychology, Wayne State University, USA.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Bender
authors.affiliation: Institute of Gerontology, Wayne State University, USA; Department of Psychology, Wayne State University, USA. Electronic address: nraz@wayne.edu.
authors.forename: Naftali
authors.initials: N
authors.lastname: Raz
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D016880:Anisotropy; D001921:Brain / Q000033:anatomy & histology* / Q000502:physiology*; D003657:Decision Making / Q000502:physiology*; D056324:Diffusion Tensor Imaging; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008959:Models, Neurological; D011930:Reaction Time; D066127:White Matter / Q000033:anatomy & histology* / Q000502:physiology*; D055815:Young Adult
keywords: Aging; Brain; DTI; MRI; Ratcliff diffusion model