People who have difficulty finding their way around may be showing the earliest signs of Alzheimer’s disease, according to new research published in the April issue of the Journal of Alzheimer’s Disease.
The finding provides hope that one day a navigation skill test could be able to diagnose brain changes long before memory fails, said senior author Denise Head, Ph.D., associate professor of psychological and brain sciences at Washington University in St. Louis.
Previous research has shown that navigation problems crop up early in individuals with Alzheimer’s disease, Head said, but they have not been studied thoroughly in people with preclinical Alzheimer’s, when disease-related changes occur in the brain but symptoms that lead to diagnosis are not apparent.
For this study, Head and colleagues wanted to see whether they could detect specific problems with route-learning and cognitive map-building in people with preclinical Alzheimer’s. Participants in the study used a joystick to navigate a virtual maze and locate landmarks, such as a bookcase (pictured). The experiment’s design played on the fact that humans generally find their way in life using two distinct forms of spatial representation and navigation.
With egocentric navigation, people rely on past knowledge to follow well-worn routes, moving sequentially from one landmark to another until they reach their target destination. In allocentric navigation, people become familiar with their big-picture surroundings and create a mental map of existing landmarks, allowing them to plot best-available routes and find shortcuts to new destinations.
The researchers found that, when compared with cognitively normal study participants who lacked the cerebrospinal fluid markers of Alzheimer’s, those with preclinical Alzheimer’s disease scored lower on their ability to learn the locations of objects in the virtual environment in relation to each other during the initial study phase. Although these results suggest deficits in the ability to form a cognitive map, the participants eventually managed to overcome the map-learning deficits, performing almost as well as cognitively normal participants during a subsequent wayfinding navigation task.
“These findings suggest that the wayfinding difficulties experienced by people with preclinical Alzheimer’s disease are in part related to trouble acquiring the environmental information,” Head said. “While they may require additional training to learn new environments, the good news here is that they seem to retain sufficient information to use a cognitive map almost as well as their cognitively normal counterparts.”
