STOCKHOLM (AP) — U.S.-British scientist John O’Keefe and Norwegian married couple May-Britt Moser and Edvard Moser won the Nobel Prize in medicine on Monday for discovering the brain’s positioning system.

This “inner GPS” helps explain how the brain creates “a map of the space surrounding us and how we can navigate our way through a complex environment,” the Nobel Assembly said.

O’Keefe, of University College London, discovered the first component of this positioning system in 1971 when he found that a certain type of nerve cell was always activated when a rat was at a certain place in a room.

Thirty-four years later May-Britt and Edvard Moser, of the Norwegian University of Science and Technology in Trondheim, identified another type of nerve cell that generates a coordinate system for precise path-finding, the assembly said.

It said that knowledge about the brain’s positioning system may “help us understand the mechamism underpinning the devastating spatial memory loss” that affects people with Alzheimer’s disease.

The Nobel awards in physics, chemistry, literature and peace will be announced later this week. The economics prize will be announced next Monday.