People With Increased Risk of Alzheimer's Have Deficits in Navigating

A study in Science Advances indicates that problems in spatial navigation are detectable in people with a genetic risk for Alzheimer's disease, reports Technology Networks . Animals and humans are able to follow their own position in space through self-motion cues, even when other sensory information is lacking — a skill called path integration; scientists assume that this ability is governed by the activity of grid cells in the entorhinal cortex. When navigating a spatial environment, these cells exhibit a unique activity pattern, and the entorhinal cortex is one of the first brain regions affected by Alzheimer's. An earlier study showed grid cells' function changes in people at genetic risk for Alzheimer's, although test subjects had no obvious navigation problems. "We assume that they used compensatory mechanisms to find their way, presumably via external cues in their surroundings," said Professor Nikolai Axmacher at Ruhr-Universität Bochum and Universitätsklinikum Freiburg. The new study involved a computerized navigation task in which participants could not use external landmarks. The team compared the navigation performance of 202 volunteers without genetic Alzheimer's risk and 65 volunteers with increased genetic risk who had a specific expression of the gene for apolipoprotein E, the APOE-e4 allele. Participants with a genetic risk of Alzheimer's performed less well than the controls, and further analysis with magnetic resonance imaging found grid cell representations in the entorhinal cortex were associated with navigation without external cues.