Placefield

Placefield, or place field, in neuroscience refers to the region of an environment in which a hippocampal place cell increases its firing rate, signaling the animal’s location. Place fields were first described in the hippocampus of rats by John O’Keefe and Lynn Dostrovsky in 1971 and are most closely associated with pyramidal neurons in the CA1 and CA3 subregions, though cells in the dentate gyrus and subiculum can also display spatially selective firing.

Each place cell tends to fire when the animal is in a particular location, creating a sparse, distributed map of space known as a cognitive map. Place fields are relatively stable within a given environment, but the population can undergo remapping when the context changes, such as in a different environment, lighting, or odor cues. Field size and shape scale with environmental size and complexity, and fields are anchored by multisensory landmarks and may be supported by path integration. The firing is modulated by ongoing rhythmic activity in the theta band and can exhibit phase precession, where spikes occur at progressively earlier phases of the theta cycle as the animal traverses the field.

In experiments, researchers record single-unit activity in freely moving animals to construct rate maps, plotting firing rate as a function of position. Place fields are fundamental to spatial navigation and episodic memory, and disruptions to hippocampal place field formation or stability are observed in aging and Alzheimer’s disease. In humans, place-cell–like activity has been observed during navigation tasks in the hippocampus and surrounding cortex.