Hippocampal acidity and volume are differentially associated with spatial navigation in older adults

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. T1 p 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 T1 p in the anterior and posterior hippocampus. Regression analyses revealed hippocampal volume was bilaterally related to learning, while right lateralized T1 p was related to delayed landmark location memory and bilateral T1 p was related to the delayed use of a cognitive map. Overall, results suggest hippocampal volume and T1 p 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.

Automated summary

The study found that hippocampal volume and T1 p relaxation rate tap into distinct mechanisms related to preclinical cognitive decline in elderly individuals. Different effects were observed in terms of learning and delayed memory based on the laterality of hippocampal characteristics, rather than the anterior-posterior axis of the hippocampus.