Illustration of the US-British neuroscientist John OKeefe (born 1939). OKeefe is best known for the discovery of place cells in the brain. These are neurons (nerve cells) in the hippocampus that fire when an animal visits a specific location in its environment. The cells help build a neural map of the environment and are important for navigation, spatial learning and memory. OKeefe shared the 2014 Nobel Prize in Physiology or Medicine with Edvard and May-Britt Moser for their discoveries of cells that constitute a positioning system in the brain.