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 specialized 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 labor 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.
‘In 1971, John O’Keefe discovered the first component of this positioning system. He found that a type of nerve cell in an area of the brain called the hippo campus that was always activated when a rat was at a certain place in a room. Other nerve cells were activated when the rat was at other places. O’Keefe concluded that these ‘place cells’ formed a map of the room. ‘More than three decades later, in 2005, May-Britt and Edward Moser discovered another key component of the brain’s positioning system. They identified another type of nerve cell, which they called ‘grid cells that generate a coordinate system and allow for precise positioning and path finding. Their subsequent research showed how place and grid cells make it possible to determine position and to navigate.’
May Britt and Edward Moser watched rats but looked at cells in the Entorhinal cortex of rat brains, a region close and very well connected to the hippocampus. Here, they found nerve-cells werent active in only one location but fired when the rats passed multiple locations. Each of these cells was activated in a unique spatial pattern and collectively these grid cells constitute a coordinate system that allows for spatial navigation, a system arranged in a hexagonal grid. This coordinate system divides the environment into latitudes and longitudes that basically keeps track of how far we are from a turning and/or starting point.
It was during this time that the Norwegian couple May-Britt and Edward Moser finished their PhD degrees from the University of Oslo and went first to the University of Edinburgh and then to the OKeefe lab at London as postdoctoral fellows to be mentored by him. Here they decided to take further neurophysiology of the inner GPS in rats. Finally, the work also highlights how important working with animals as models is. The recent banning of animal experiments in schools and colleges has been a bad move, and needs to be rescinded.