Spatial Navigation in Early-Stage Alzheimer\u27s Disease

There is increasingly interest in navigational deficits in Alzheimer’s disease (AD) as components of the neural circuitry that subserve navigation abilities are compromised early in the course of AD and a significant portion of AD individuals engage in wandering behavior. The primary goal of the study is to characterize spatial navigation skills in preclinical AD, early-stage AD, and at-risk populations (cognitively normal APOE e4+ individuals). A second goal was to examine the associations between regional brain volumes (specifically, the hippocampus, caudate, and prefrontal cortex) and navigation performance. Performance on tasks of wayfinding and route learning in a virtual reality environment and the degree to which individuals acquire the environmental knowledge that facilitates navigation and learning new environments and routes were examined. In addition, MRI-based regional brain volumes were obtained. AD individuals performed more poorly than cognitively normal older adults on both wayfinding and route learning tasks. APOE e4+ individuals performed more poorly than APOE e4- individuals, but primarily on wayfinding tasks. There were no significant effects of PIB status on any of the navigation tasks. Volumetric results revealed several interactive effects for the wayfinding condition. Specifically, greater distances traveled during the test phases were associated with smaller hippocampal volumes for CN individuals, but not for AD individuals. Distance traveled during the test phase in the wayfinding condition was more strongly related to both hippocampal and caudate volumes in the APOE e4+ individuals. Finally, distance traveled during the test phase in the wayfinding condition was more strongly related to caudate volume in the PIB-individuals