A place cell is a type of neuron in the hippocampus which shows activity in response to an animal's being in a certain area in space. They were first described by O'Keefe and Dostrovsky in 1971, having been identified in rats. O'Keefe and Dostrovsky hypothesized that these cells in collection form a cognitive map of the rat's environment. The cells are the CA1 cells of the hippocampus, the output cells of the trisynaptic pathway. Place cells show increased frequency of firing when an animal is in a specific area, which is referred to as the cell's place field. Each place cell may code for a different place in a different context, such as a different experimental box or maze. The cells appear to take some time to develop their particular place field when an animal encounters a new location.