Located in the hippocampus and other areas of the brain associated with memory and spatial awareness, the grid cell generates electrical activity that represents an organism’s environment. It is one of three types of neurons that map the environment from within the brain. Discovered in mice brains in 2005, grid cells create triangle-shaped grids that are thought to represent physical locations. They were detected in human brains in 2010 using equipment to detect neurological electrical response in relation to the spatial grids of terrain, and objects in a virtual reality environment.
Grid cells allow the brain to map the location of objects and features in the physical environment as well as remember where things are. The geometric patterns that represent the electrical activity in the cells can be plotted by imaging devices and computers. While they tend to be arranged in triangles, the effect is a latitude and longitude line like analysis of information that is created in the brain. Grid cell activity is complemented by the function of place cells, which is to fire accordingly when a person or animal stays in a certain position, and head cells which sense direction. The brain can process information and remember landmarks even in an unfamiliar environment.
The function of the grid cell is affected by Alzheimer’s disease because it is located in regions of the brain where the disease begins. Alzheimer’s patients often experience disorientation and difficulty recalling spatial details early on, and a disruption in the mapping ability of grid cells may be the reason. These neurons provide a perception of the environment as well as memories. Without the map produced by grid cell activity to serve as a guide, the brain is unable to process information sufficiently for spatial awareness.
Data gathered by mapping the location of grid cells and associated activity is also beneficial for neurosurgeons. By imaging the brain’s electrical activity and analyzing electrical signals, they can measure what areas are affected by diseases such as Alzheimer’s or epilepsy, and use the information as a guide while operating. The electrical activity of a grid cell is symmetrical about a circle, with the triangular segmentation occurring in six distinct regions. Faster motion and changes in the environment cause the cells to fire more frequently; changes in direction and speed are immediately detected so the brain can reformulate an internal picture of the environment.
