Professor Ole Kiehn presents the winners of the Nobel Prize in Medicine US-British scientist John O'Keefe and Norwegian husband and wife Edvard Moser and May-Britt Moser for their discoveries of cells that constitute a positioning system in the brain, at the Karolinska Institute in Stockholm October 6, 2014. O'Keefe and May-Britt and Edvard Moser won the 2014 Nobel prize for medicine or physiology for discoveries of cells that constitute a positioning system in the brain, the award-giving body said on Monday. [Photo/Agencies]

STOCKHOLM - US-British scientist John O'Keefe and Norwegian scientists May-Britt Moser and Edvard Moser won the Nobel Prize in medicine on Monday for discovering the "inner GPS" in the brain that helps us navigate through the world.

Their findings in rats and research suggests that humans have the same system in their brains represented a "paradigm shift" in the knowledge of how cells work together to perform cognitive functions, the Nobel Assembly said, adding that knowing about the brain's positioning system may "help us understand the mechanism underpinning the devastating spatial memory loss" that affects people with Alzheimer's disease.

"This year's Nobel Laureates have discovered a positioning system, an 'inner GPS' in the brain, that makes it possible to orient ourselves in space," the assembly said.

O'Keefe, 75, of University College London, discovered the first component of this 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. He demonstrated that these "place cells" were building up a map of the environment, not just registering visual input.

Thirty-four years later, in 2005, May-Britt Moser and Edvard Moser, a married couple at the Norwegian University of Science and Technology in Trondheim, identified another type of nerve cell the "grid cell that generates a coordinate system for precise positioning and path-finding, the assembly said.

"This is crazy," an excited May-Britt Moser, 51, told The Associated Press by telephone from Trondheim.

She said her 52-year-old husband didn't immediately find out about the prize because he was flying Monday morning to the Max Planck Institute in Munich, Germany, to demonstrate their research.

"This is such a great honor for all of us and all the people who have worked with us and supported us," she said, adding they had been together for 30 years. "We are going to continue and hopefully do even more groundbreaking work in the future."

Hege Tunstad, a spokeswoman at the university in Trondheim, said May-Britt Moser "needed a minute to cry and speak with her team" when she first heard the news.

Edvard Moser told the Norwegian news agency NTB that he discovered he was a Nobel Prize winner when he landed in Munich, turned on his cellphone and saw a flood of emails, text messages and missed calls.

"I didn't know anything. When I got off the plane there was a representative there with a bouquet of flowers who said `congratulations on the prize," he was quoted as saying.

The Nobel discoveries have also opened new avenues for understanding cognitive functions such as memory, thinking and planning, the assembly said.

"Thanks to our grid and place cells, we don't have to walk around with a map to find our way each time we visit a city because we have that map in our head," said Juleen Zierath, chair of the medicine prize committee. "I think, without these cells, we would have a really hard time to survive."

All three Nobel laureates won Columbia University's Louisa Gross Horwitz Prize last year for their discoveries. They will split the Nobel prize money of 8 million Swedish kronor (about $1.1 million).

The Nobel awards in physics, chemistry, literature and peace will be announced later this week. The economics prize will be announced next Monday. Created by Swedish industrialist Alfred Nobel, the Nobel Prizes were first awarded in 1901. The winners always collect their awards on Dec. 10, the anniversary of Nobel's death in 1896.

Last year's medicine award went to researchers who discovered how substances are transported within cells, a process involved in such important activities as brain cell communication and the release of insulin.