Adopted from BBC News website, By James Gallagher, Health editor,
The Nobel Prize for physiology or medicine has been awarded to three scientists who discovered the brain's "GPS system".
UK-based researcher Prof John O'Keefe as well asMay-Britt Moser and Edvard Moser share the award.
They discovered how the brain knows where we are andis able to navigate from one place to another.
Their findings may help explain why Alzheimer'sdisease patients cannot recognise their surroundings.
"The discoveries have solved a problem that hasoccupied philosophers and scientists for centuries," the Nobel Assemblysaid.
Prof O'Keefe, from University College London,discovered the first part of the brain's internal positioning system in 1971.
On hearing about winning the prize, he said: "I'mtotally delighted and thrilled, I'm still in a state of shock, it's the highestaccolade you can get."
His work showed that a set of nerve cells becameactivated whenever a rat was in one location in a room.
A different set of cells were active when the rat wasin a different area.
Prof O'Keefe argued these "place cells" -located in the hippocampus - formed a map within the brain.
He will be having a "quiet celebration" thisevening and says the prize money "should be used for the commongood".
In 2005, husband and wife team, May-Britt and Edvard,discovered a different part of the brain which acts more like a nautical chart.
These "grid cells" are akin to lines oflongitude and latitude, helping the brain to judge distance and navigate.
They work at the Norwegian University of Science andTechnology in Trondheim.
Secretary of the Nobel Assembly, Goran K Hansson,announces the winners of the Nobel Prize in medicine
The Nobel committee said the combination of grid andplace cells "constitutes a comprehensive positioning system, an inner GPS,in the brain".
They added: "[This system is] affected in severalbrain disorders, including dementia and Alzheimer's disease.
"A better understanding of neural mechanismsunderlying spatial memory is therefore important and the discoveries of placeand grid cells have been a major leap forward to advance this endeavour."
Dr Colin Lever, from the University of Durham, workedin Prof O'Keefe's laboratory for ten years and has already dreamt on twooccasions that his former mentor had won the award.
He told the BBC: "He absolutely deserves theNobel Prize, he created a cognitive revolution, his research was really forwardthinking in suggesting animals create representations of the external worldinside their brains."
"Place cells help us map our way around theworld, but in humans at least they form part of the spatiotemporal scaffold inour brains that supports our autobiographical memory.
"The world was not ready for his original reportof place cells in 1971, people didn't believe that 'place' was what bestcharacterised these cells, so there was no great fanfare at that time.
"But his work on hippocampal spatial mappingcreated the background for discovering grid cells and with grid cells, theworld was prepared and we all thought wow this is big news.
"Plus John taught the Mosers how to do theserecordings!"
Also commenting on the announcement, Prof John Steinform the University of Oxford, said: "This is great news and welldeserved.
"I remember how great was the scoffing in theearly 1970s when John first described 'place cells'.
"Now, like so many ideas that were at firsthighly controversial, people say 'Well that's obvious!'"