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Finding The Brain's SatNav Ap

This article is more than 9 years old.

Why aren't you always lost? The answer is that we have a SatNav system in our brains, using tags for particular places and a hexagonal grid system.

And figuring this out has led three scientists to Stockholm to receive the Nobel Prize for Physiology or Medicine.

Professor John O'Keefe, a New Yorker now working at University College London, was awarded half the prize by Sweden's Karolinska Institute yesterday (6 October) for his discovery, reported in Brain Research in 1971, that rats had individual cells that were always on when they were in a particular place, and off when they were anywhere else.

Together these cells form a map of the real world known to the animal. Crucially, Professor O'Keefe was able to demonstrate that these cells were not just responding to visual stimuli.

The cells that form this map are in the hippocampus, so named because it looks like a seahorse, a brain structure which is shared by all vertebrates.

The hippocampus is best known for its role in remembering. Damage to it can lead to anterograde amnesia, the inability to form new memories, as depicted in the 2004 Hollywood film 50 First Dates.

The second half of the prize was shared by Norwegian husband-and-wife team Professors Edvard and May-Britt Moser of the Kavli Institute for Systems Neuroscience for their discovery of a grid system that works much like the X-Y co-ordinate Cartesian system.

The couple, who had previously worked with Professor O'Keefe at UCL, were looking at connections to the hippocampus in rats when they found that cells in the adjacent entorhinal cortex were activated in a grid pattern as the animals moved, as they and their colleagues reported in Nature in 2005.

These two systems, interacting with cells that indicate which way the animal's head is facing, form "a comprehensive positioning system, an inner GPS, in the brain," the Nobel committee said.

More recent research using brain scans and studies of neurosurgery patients has shown that grid cells also exist in humans.

It is thought that the early disorientation caused by Alzheimer's disease is a result of damage to these systems in the hippocampus and entorhinal cortex.

"Knowledge about the brain's positioning system may, therefore, help us understand the mechanism underpinning the devastating spatial memory loss that affects people with this disease," said the Nobel committee.

Scientists and philosophers have struggled with our sense of place and ability to navigate for centuries. The German philosopher Emanuel Kant thought that place was innate, but maze experiments in the mid-20th Century by American psychologist Edward Tolman demonstrated that rats could learn to navigate and first proposed that the brain had a "cognitive map".