Hippocampal acidity and volume are differentially associated with spatial navigation in older adults
Matthew J. Sodoma,
Rachel C. Cole,
Taylor J. Sloan,
Chase M. Hamilton,
James D. Kent,
Vincent A. Magnotta,
Michelle W. Voss
Affiliations
Matthew J. Sodoma
Department of Psychological and Brain Sciences, University of Iowa, Iowa City, IA 52242, USA; Corresponding author.
Rachel C. Cole
Interdisciplinary Graduate Program in Neuroscience, University of Iowa, Iowa City, IA 52242, USA; Department of Neurology, University of Iowa, Iowa City, IA, 52242, USA
Taylor J. Sloan
Department of Psychological and Brain Sciences, University of Iowa, Iowa City, IA 52242, USA
Chase M. Hamilton
Department of Psychological and Brain Sciences, University of Iowa, Iowa City, IA 52242, USA
James D. Kent
Interdisciplinary Graduate Program in Neuroscience, University of Iowa, Iowa City, IA 52242, USA; Department of Psychology, University of Texas at Austin, Austin, TX, 78712 USA
Vincent A. Magnotta
Iowa Neuroscience Institute, University of Iowa, Iowa City, IA 52242, USA; Department of Radiology, University of Iowa, Iowa City, IA 52242, UCA; Department of Biomedical Engineering, University of Iowa, Iowa City, IA 52242, USA; Department of Psychiatry, University of Iowa, Iowa City, IA 52242, USA; Pappajohn Biomedical Institute, University of Iowa, Iowa City, IA 52242, USA
Michelle W. Voss
Department of Psychological and Brain Sciences, University of Iowa, Iowa City, IA 52242, USA; Interdisciplinary Graduate Program in Neuroscience, University of Iowa, Iowa City, IA 52242, USA; Iowa Neuroscience Institute, University of Iowa, Iowa City, IA 52242, USA
The hippocampus is negatively affected by aging and is critical for spatial navigation. While there is evidence that wayfinding navigation tasks are especially sensitive to preclinical hippocampal deterioration, these studies have primarily used volumetric hippocampal imaging without considering microstructural properties or anatomical variation within the hippocampus. T1ρ is an MRI measure sensitive to regional pH, with longer relaxation rates reflecting acidosis as a marker of metabolic dysfunction and neuropathological burden. For the first time, we investigate how measures of wayfinding including landmark location learning and delayed memory in cognitively normal older adults (N = 84) relate to both hippocampal volume and T1ρ in the anterior and posterior hippocampus. Regression analyses revealed hippocampal volume was bilaterally related to learning, while right lateralized T1ρ was related to delayed landmark location memory and bilateral T1ρ was related to the delayed use of a cognitive map. Overall, results suggest hippocampal volume and T1ρ relaxation rate tap into distinct mechanisms involved in preclinical cognitive decline as assessed by wayfinding navigation, and laterality influenced these relationships more than the anterior-posterior longitudinal axis of the hippocampus.
