Stockholm, Oct 6 (IANS): Three scientists - John O'Keefe, and May-Britt Moser and Edvard Moser - have shared the 2014 Nobel Prize in physiology or medicine, the Nobel Committee announced Monday.

The Nobel assembly at the Karolinska Institute has decided to award one half of the physiology or medicine prize to John O'Keefe and the other half jointly to May-Britt Moser and Edvard Moser for their discovery of cells that constitute a positioning system in the brain, Xinhua reported.

According to a statement of the committee, this year's laureates have discovered an "inner GPS" in the brain that "makes it possible to orient ourselves in space, demonstrating a cellular basis for higher cognitive function".

John O'Keefe discovered in 1971 that certain nerve cells in the rat's brain were activated when it assumed a particular place in the environment, while other nerve cells were activated at other places. He proposed that these "place cells" build up an inner map of the environment. Place cells are located in a part of the brain called the hippocampus.

In 2005, May-Britt and Edvard Moser discovered that other nerve cells in a nearby part of the brain, the entorhinal cortex, were activated when a rat passed certain locations.

Together, these locations formed a hexagonal grid, with each "grid cell" reacting in a unique spatial pattern. Collectively, these grid cells form a coordinate system that allows for spatial navigation.