What happens when the brain's inner GPS gets dismantled

When its inner GPS is dismantled, the brain's ability to remember places gets affected but it retains a host of other memory and navigation-related skills, a new research says.

Grid cells and other specialised nerve cells in the brain, known as "place cells," comprise the brain's inner GPS, the discovery of which earned British-American and Norwegian scientists this year's Nobel Prize for medicine.

"Our work shows a crisp division of labour within memory circuits of the brain," said Robert Clark, senior co-author and professor of psychiatry at the University of California - San Diego in the US.

"Removing the grid-cell network removes memory for places but leaves completely intact a whole host of other important memory abilities like recognition memory and memory of fearful events," Clark added.

The researchers developed a micro-surgical procedure that makes it possible to remove the area of the rat's brain that contains grid cells.

One effect, not surprisingly, is that the rats become very poor at tasks requiring internal map-making skills, such as remembering the location of a resting platform in a water maze test.

"The surprise is the discovery of the type of memory formation that was not disrupted by the removal of the grid cell area," Clark said.

Even without grid cells, the rats could still mark spatial changes in their environment.

They could, for example, notice when an object in a familiar environment was moved a few inches and they could also recognise objects, such as a coffee mug or flower vase, and remember later that they had seen these objects before.

Entorhinal cortex that houses the inner GPS is the first brain region to break down in Alzheimer's disease.

The findings were published online in the journal Cell Reports.