In 1971, scientist John O'Keefe and his student Jonathan Dostrovsky discovered neurons in the hippocampus which fire in connection to a specific location and called them place cells. In 2005, Edvard Moser and May-Britt Moser discovered another type of spatial cell in the entorhinal cortex which they named grid cells. Grid cells allow the body to know its place in space. Together with the place cells, they allow the brain to maintain an internal map of where your body is in Euclidian space.
Essentially, your brain has its own GPS which maps out the environment around you. The work by these scientists answers the question of how we can successfully move through our environment in all its complexity. Their work has been recognized by the Nobel committee who awarded them the 2014 Nobel Prize for physiology or medicine.
So how is this research connected to Alzheimer's? Individuals with Alzheimer's or other forms of dementia may not recognize where they are even if they are in their normal environment. We see this pretty clearly in Sundowning. The light changes and the environment looks different. The individual doesn't recognize where they are and exhibits increasing anxiety. As the disease progresses, the individual can literally become lost when they don't recognize the space around them. They may wander away because they're looking for home. If we can understand how the brain's GPS is supposed to work, it may help us understand what is happening when it no longer works.