title: White matter microstructure mediates the relationship between cardiorespiratory fitness and spatial working memory in older adults.
abstract: White matter structure declines with advancing age and has been associated with a decline in memory and executive processes in older adulthood. Yet, recent research suggests that higher physical activity and fitness levels may be associated with less white matter degeneration in late life, although the tract-specificity of this relationship is not well understood. In addition, these prior studies infrequently associate measures of white matter microstructure to cognitive outcomes, so the behavioral importance of higher levels of white matter microstructural organization with greater fitness levels remains a matter of speculation. Here we tested whether cardiorespiratory fitness (VO2max) levels were associated with white matter microstructure and whether this relationship constituted an indirect pathway between cardiorespiratory fitness and spatial working memory in two large, cognitively and neurologically healthy older adult samples. Diffusion tensor imaging was used to determine white matter microstructure in two separate groups: Experiment 1, N=113 (mean age=66.61) and Experiment 2, N=154 (mean age=65.66). Using a voxel-based regression approach, we found that higher VO2max was associated with higher fractional anisotropy (FA), a measure of white matter microstructure, in a diverse network of white matter tracts, including the anterior corona radiata, anterior internal capsule, fornix, cingulum, and corpus callosum (PFDR-corrected<.05). This effect was consistent across both samples even after controlling for age, gender, and education. Further, a statistical mediation analysis revealed that white matter microstructure within these regions, among others, constituted a significant indirect path between VO2max and spatial working memory performance. These results suggest that greater aerobic fitness levels are associated with higher levels of white matter microstructural organization, which may, in turn, preserve spatial memory performance in older adulthood.
authors.affiliation: Department of Psychology, University of Pittsburgh, USA; Center for the Neural Basis of Cognition, University of Pittsburgh, USA. Electronic address: leo11@pitt.edu.
authors.forename: Lauren E
authors.initials: LE
authors.lastname: Oberlin
authors.affiliation: Center for the Neural Basis of Cognition, University of Pittsburgh, USA; Department of Psychology, Carnegie Mellon University, USA.
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Verstynen
authors.affiliation: Department of Human Development and Family Studies, Colorado State University - Fort Collins, USA; Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, USA.
authors.forename: Agnieszka Z
authors.initials: AZ
authors.lastname: Burzynska
authors.affiliation: Department of Psychological and Brain Sciences, University of Iowa, USA.
authors.forename: Michelle W
authors.initials: MW
authors.lastname: Voss
authors.affiliation: Department of Psychology, Ohio State University, USA.
authors.forename: Ruchika Shaurya
authors.initials: RS
authors.lastname: Prakash
authors.affiliation: Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, USA.
authors.forename: Laura
authors.initials: L
authors.lastname: Chaddock-Heyman
authors.affiliation: Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, USA.
authors.forename: Chelsea
authors.initials: C
authors.lastname: Wong
authors.affiliation: Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, USA.
authors.forename: Jason
authors.initials: J
authors.lastname: Fanning
authors.affiliation: Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, USA.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Awick
authors.affiliation: Department of Kinesiology, Wayne State University, USA.
authors.forename: Neha
authors.initials: N
authors.lastname: Gothe
authors.affiliation: Department of Preventative Medicine, Northwestern University, USA.
authors.forename: Siobhan M
authors.initials: SM
authors.lastname: Phillips
authors.affiliation: Department of Kinesiology, Kansas State University, USA.
authors.forename: Emily
authors.initials: E
authors.lastname: Mailey
authors.affiliation: Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, USA.
authors.forename: Diane
authors.initials: D
authors.lastname: Ehlers
authors.affiliation: Harvard Medical School, USA.
authors.forename: Erin
authors.initials: E
authors.lastname: Olson
authors.affiliation: Exercise Science Department, Bellarmine University, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Wojcicki
authors.affiliation: Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, USA.
authors.forename: Edward
authors.initials: E
authors.lastname: McAuley
authors.affiliation: Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, USA.
authors.forename: Arthur F
authors.initials: AF
authors.lastname: Kramer
authors.affiliation: Department of Psychology, University of Pittsburgh, USA; Center for the Neural Basis of Cognition, University of Pittsburgh, USA.
authors.forename: Kirk I
authors.initials: KI
authors.lastname: Erickson
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000473:pathology* / Q000502:physiology*; D001921:Brain / Q000166:cytology* / Q000502:physiology; D001931:Brain Mapping; D000072599:Cardiorespiratory Fitness / Q000502:physiology*; D056324:Diffusion Tensor Imaging / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D008875:Middle Aged; D009415:Nerve Net / Q000166:cytology / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology; D010101:Oxygen Consumption / Q000502:physiology; D065852:Spatial Memory / Q000502:physiology*; D066127:White Matter / Q000166:cytology* / Q000502:physiology
keywords: Aging; Fitness; Memory; White matter