David Shultz in Science:
The way you navigate a virtual maze may predict your chances of getting Alzheimer’s. That’s the conclusion of a new study, which finds that people at risk for Alzheimer’s have lower activity in a newly-discovered network of navigational brain cells known as “grid cells.” The finding could lead to new ways to diagnose this debilitating disorder. The discovery of the grid cell network won the Nobel Prize in Medicine or Physiology last year. The neurons that make up the “grid” are arranged in a triangular lattice in the entorhinal cortex—a region of the brain used in memory and navigation. The “grid” activates in different patterns based on how individuals move, keeping track of our location in the coordinate plane.
Researchers think the cells help create mental maps and allow us to navigate through space even in the absence of visual cues. “If you close your eyes and walk ten feet forward and turn right and walk three feet forward, the grid cells are believed to [track your position],” says neuroscientist Joshua Jacobs at Columbia University. Intriguingly, people withthe so-called e4 variant of a gene known as APOE—the largest genetic risk factor for developing Alzheimer’s later in life—are at a higher risk for developing abnormalities in their entorhinal cortex. Because the grid cells are found in the same region, scientists wondered if the reason Alzheimer’s patients are more likely to get lost and have difficulty navigating could be explained by damage to the network.