title: Aerobic fitness, hippocampal viscoelasticity, and relational memory performance.
abstract: The positive relationship between hippocampal structure, aerobic fitness, and memory performance is often observed among children and older adults; but evidence of this relationship among young adults, for whom the hippocampus is neither developing nor atrophying, is less consistent. Studies have typically relied on hippocampal volumetry (a gross proxy of tissue composition) to assess individual differences in hippocampal structure. While volume is not specific to microstructural tissue characteristics, microstructural differences in hippocampal integrity may exist even among healthy young adults when volumetric differences are not diagnostic of tissue health or cognitive function. Magnetic resonance elastography (MRE) is an emerging noninvasive imaging technique for measuring viscoelastic tissue properties and provides quantitative measures of tissue integrity. We have previously demonstrated that individual differences in hippocampal viscoelasticity are related to performance on a relational memory task; however, little is known about health correlates to this novel measure. In the current study, we investigated the relationship between hippocampal viscoelasticity and cardiovascular health, and their mutual effect on relational memory in a group of healthy young adults (N=51). We replicated our previous finding that hippocampal viscoelasticity correlates with relational memory performance. We extend this work by demonstrating that better aerobic fitness, as measured by VO2max, was associated with hippocampal viscoelasticity that mediated the benefits of fitness on memory function. Hippocampal volume, however, did not account for individual differences in memory. Therefore, these data suggest that hippocampal viscoelasticity may provide a more sensitive measure to microstructural tissue organization and its consequences to cognition among healthy young adults.
authors.affiliation: Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, 405 N. Mathews Ave, Urbana, IL 61081, USA. Electronic address: schwarb2@illinois.edu.
authors.forename: Hillary
authors.initials: H
authors.lastname: Schwarb
authors.affiliation: Department of Biomedical Engineering, University of Delaware, 150 Academy Street, 161 Colburn Lab, Newark, DE 19716, USA.
authors.forename: Curtis L
authors.initials: CL
authors.lastname: Johnson
authors.affiliation: Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, 405 N. Mathews Ave, Urbana, IL 61081, USA.
authors.forename: Ana M
authors.initials: AM
authors.lastname: Daugherty
authors.affiliation: Department of Psychology, Northeastern University, 125 Nightingale Hall, 360 Huntington Ave., Boston, MA 02115, USA.
authors.forename: Charles H
authors.initials: CH
authors.lastname: Hillman
authors.affiliation: Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, 405 N. Mathews Ave, Urbana, IL 61081, USA; Department of Psychology, Northeastern University, 125 Nightingale Hall, 360 Huntington Ave., Boston, MA 02115, USA.
authors.forename: Arthur F
authors.initials: AF
authors.lastname: Kramer
authors.affiliation: Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, 405 N. Mathews Ave, Urbana, IL 61081, USA.
authors.forename: Neal J
authors.initials: NJ
authors.lastname: Cohen
authors.affiliation: Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, 405 N. Mathews Ave, Urbana, IL 61081, USA; Department of Psychology, University of Illinois at Urbana-Champaign, 603 E. Daniel St, Champaign, IL 61820, USA; Neuroscience Program, University of Illinois at Urbana-Champaign, 405 N. Mathews Ave, Urbana, IL 61081, USA; Department of Internal Medicine, University of Illinois at Urbana-Champaign, 506 S. Mathews Ave, Urbana, IL 61801, USA; Department of Bioengineering, University of Illinois at Urbana-Champaign, 1304 W. Springfield Ave, Urbana, IL 61801, USA; Carle R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 W. Gregory Dr, Urbana, IL 61801, USA. Electronic address: barbey@illinois.edu.
authors.forename: Aron K
authors.initials: AK
authors.lastname: Barbey
mesh_terms: D000293:Adolescent; D000328:Adult; D000072599:Cardiorespiratory Fitness; D054459:Elasticity Imaging Techniques; D015444:Exercise; D005260:Female; D006624:Hippocampus / Q000502:physiology*; D006801:Humans; D007206:Individuality; D008279:Magnetic Resonance Imaging; D008297:Male; D008959:Models, Neurological; D010101:Oxygen Consumption; D065852:Spatial Memory / Q000502:physiology*; D055815:Young Adult
keywords: Aerobic fitness; Elastography; Hippocampus; Memory; Viscoelasticity