Viscoelastic and volumetric contributions to age-related cognitive decline

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PROJECT SUMMARY/ABSTRACT It is well understood that typical aging is accompanied by characteristic declines in fluid cognitive abilities as well as declines in the structural integrity of the brain. Structural integrity has typically been inferred from measures of brain volume. Volume, however, is a gross measure that cannot account for smaller-scale changes that may be contributing to diminished cognitive outcomes. Magnetic resonance elastography (MRE) is an emerging tool for acquiring noninvasive measures of the mechanical properties of biological tissue. As such, MRE provides a measure of the microstructural health of the tissue. The proposed work seeks (1) to assess the utility of MRE as a complementary tool to volumetric analysis in the study of human learning and memory and also (2) to establish MRE as a critically sensitive method for mapping degeneration in the aging brain, particularly when volumetric outcomes are equivocal. Volumetric, MRE, and cognitive data will be collected from 80 participants between the ages of 45 and 85. The cognitive assessment will measure both relational memory abilities (dependent on hippocampal function) and implicit sequence learning abilities (dependent on striatal function). Volumetric and MRE analyses will focus on the hippocampus and striatum specifically. These data will be used to examine the relationship between relational memory performance and both hippocampal volume and MRE-derived hippocampal viscoelasticity, as well as implicit sequence learning and both striatal volume and viscoelasticity, to explore the unique contribution of each to behavior. It is expected that, compared to volumetric measures alone, viscoelasticity measures will provide additional explanatory power when investigating the impact of tissue integrity on cognitive outcomes. This work will establish MRE as a useful tool for the study of cognitive neuroscience of aging and highlight the importance of choosing appropriate neuroimaging tools when assessing structural integrity. The resulting data will have important implications for tracking structural changes that impact cognitive abilities in typical aging as well as the diagnosis and tracking of treatment outcomes for patients with hippocampal (e.g., Alzheimer’s disease) and striatal (e.g., Parkinson’s disease) impairments.