r r The Influence of Aerobic Fitness on Cerebral White Matter Integrity and Cognitive Function in Older Adults: Results of a One-Year Exercise Intervention Michelle W. Voss, 1 * Susie Heo, 2,3 Ruchika S. Prakash, 4 Kirk I. Erickson, 5 Heloisa Alves, 2,3 Laura Chaddock, 2,3 Amanda N. Szabo, 6 Emily L. Mailey, 6 Thomas R. Wo ´ jcicki, 6 Siobhan M. White, 6 Neha Gothe, 6 Edward McAuley, 6 Bradley P. Sutton, 3,7 and Arthur F. Kramer 2,3 1 Department of Psychology, The University of Iowa, Iowa 2 Department of Psychology, University of Illinois at Urbana-Champaign, Illinois 3 Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Illinois 4 Department of Psychology, The Ohio State University, Columbus, Ohio 5 Department of Psychology, University of Pittsburgh, Pennsylvania 6 Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Illinois 7 Department of Bioengineering, University of Illinois at Urbana-Champaign, Illinois r r Abstract: Cerebral white matter (WM) degeneration occurs with increasing age and is associated with declin- ing cognitive function. Research has shown that cardiorespiratory fitness and exercise are effective as protec- tive, even restorative, agents against cognitive and neurobiological impairments in older adults. In this study, we investigated whether the beneficial impact of aerobic fitness would extend to WM integrity in the context of a one-year exercise intervention. Further, we examined the pattern of diffusivity changes to better under- stand the underlying biological mechanisms. Finally, we assessed whether training-induced changes in WM integrity would be associated with improvements in cognitive performance independent of aerobic fitness gains. Results showed that aerobic fitness training did not affect group-level change in WM integrity, executive function, or short-term memory, but that greater aerobic fitness derived from the walking program was associ- ated with greater change in WM integrity in the frontal and temporal lobes, and greater improvement in short- term memory. Increases in WM integrity, however, were not associated with short-term memory improve- ment, independent of fitness improvements. Therefore, while not all findings are consistent with previous research, we provide novel evidence for correlated change in training-induced aerobic fitness, WM integrity, and cognition among healthy older adults. Hum Brain Mapp 00:000–000, 2012. V C 2012 Wiley-Periodicals, Inc. Key words: diffusion tensor imaging; anisotropy; cerebrum; cognition; physical fitness; aging r r Additional Supporting Information may be found in the online version of this article. Contract grant sponsor: National Institute on Aging at the National Institutes of Health; Contract grant number: RO1 AG25667 and RO1 AG25032. *Correspondence to: Michelle W. Voss, Department of Psychol- ogy, The University of Iowa, 11 Seashore Hall E, Iowa City, IA 52242. E-mail: michelle-voss@uiowa.edu Received for publication 21 December 2010; Revised 13 February 2012; Accepted 5 April 2012 DOI: 10.1002/hbm.22119 Published online in Wiley Online Library (wileyonlinelibrary. com). V C 2012 Wiley-Periodicals, Inc. Human Brain Mapping 000:000–000 (2012)