Their findings in rats represent a “paradigm shift” in our knowledge of how cells work together to perform cognitive functions, the Nobel Assembly said.

Research suggests humans have the same system in their brains and the trio’s work could help scientists understand the mechanisms behind Alzheimer’s disease, it added.

“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.

Mr O’Keefe, 75, of University College London, discovered the first component of this system in 1971 when he found 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.

Mr O’Keefe’s father was from Scarteen Lower, New market, and his mother was from Co Mayo. He is to receive an honorary doctorate from University College Cork (UCC) on December 5 in recognition of his enormous contributions to neuroscience.

Some 34 years later the Mosers, of 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.

“I’m still in shock. This is so great,” May-Britt Moser, 51, said.

A spokeswoman at the university in Trondheim, said May-Britt Moser was at the university when she found out she had won.

“She needed a minute to cry and speak with her team,” she said. Her 52-year-old husband was on a plane and did not immediately learn the news.

The Nobel Assembly said that knowledge 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.

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

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

The winners of each Nobel category split prize money of €880,000. Each winner also receives a diploma and a gold medal.

“This is crazy,’ an excited May-Britt added. “This is such a great honour for all of us and all the people who have worked with us and supported us.

“We are going to continue and hopefully do even more groundbreaking work in the future.”

Mr Moser was flying to the Max Planck Institute in Germany to demonstrate their research when the news broke.

He told the Norwegian news agency NTB that he discovered he was a Nobel Prize winner when he landed in Munich, turned on his phone and saw a flood of emails, texts 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.