Grid cell

A grid cell is a type of neuron within the entorhinal cortex that fires at regular intervals as an animal navigates an open area, allowing it to understand its position in space by storing and integrating information about location, distance, and direction.

They were awarded the 2014 Nobel Prize in Physiology or Medicine together with John O'Keefe for their discoveries of cells that constitute a positioning system in the brain.

The arrangement of spatial firing fields, all at equal distances from their neighbors, led to a hypothesis that these cells encode a neural representation of Euclidean space.

[1] The discovery also suggested a mechanism for dynamic computation of self-position based on continuously updated information about position and direction.

The resulting data can be visualized by marking the rat's position on a map of the arena every time that neuron fires an action potential.

[7] This discovery, although controversial at first, led to a series of investigations that culminated in the 1978 publication of a book by O'Keefe and his colleague Lynn Nadel called The Hippocampus as a Cognitive Map (a phrase that also appeared in the title of the 1971 paper)[8]—the book argued that the hippocampal neural network instantiates cognitive maps as hypothesized by the psychologist Edward C. Tolman.

The earliest studies, such as Quirk et al. (1992), described neurons in the entorhinal cortex as having relatively large and fuzzy place fields.

Accordingly, together with Marianne Fyhn, Sturla Molden, and Menno Witter, the Mosers set out to examine spatial firing from the different dorsal-to-ventral levels of the entorhinal cortex.

[12] The arrangement of the firing fields showed hints of regularity, but the size of the environment was too small for spatial periodicity to be visible in this study.

The next set of experiments, reported in 2005, made use of a larger environment, which led to the recognition that the cells were actually firing in a hexagonal grid pattern.

The entorhinal cortex is no exception: like the hippocampus, it receives cholinergic and GABAergic input from the medial septal area, the central controller of theta.

[22] Burak and Fiete (2009) showed that a computational simulation of the grid cell system was capable of performing path integration to a high level of accuracy.

A convergent evolution analogy has been argued to exist between grid cells and the decomposition of images in JPEG compression into superimposed discrete cosine basis functions.