Navigation strategies predict spatial memory and hippocampal recruitment

Navigation in the real world may rely on a multitude of strategies with distinct advantages and disadvantages; however, the characterization of spontaneous strategy use is scarce. We explore data across three groups engaged in virtual navigation: patients with epilepsy undergoing invasive electrophysiological recordings, two groups undergoing fMRI scanning: young adults at genetic risk for Alzheimer's disease (APOE-ε4 carriers), and healthy controls. We establish metrics to quantitatively characterize participants' trajectories, reflecting putative strategies: straightness, deviation to boundary, and overlap of paths. We find that strategy use is variable within participant, changes across the experiment, and is adaptive in a group-dependent manner. While hippocampal blood-oxygen dependent (BOLD) activity and theta power are generally inversely related, hippocampal recruitment is both group- and strategy specific. Our results underscore the idiosyncratic nature of spatial navigation by revealing how these behaviors are altered by disease, the subsequent compensatory neural dynamics, and the link between mesoscopic and macroscopic neural signals.