How does our brain know where we are? How do we navigate from place to place? These are questions that have plagued the minds of philosophers and scientists for hundreds of years. So much so, in fact, that the three scientists who helped unravel these mysteries have just won one of the world’s most prestigious awards for intellectual achievement: the Nobel Prize for physiology and medicine.
British-American neuroscientist John O’Keefe, based at University College London, was the first of the three to begin identifying components of our brain’s internal GPS system. Back in 1971, after examining the brains of rats, he discovered a set of cells located in a region called the hippocampus that always became activated when the animal was in a particular place. He then found that another bunch of neurons started firing when the rat entered a different area. He was then able to demonstrate that these cells, which he dubbed “place cells,” were not merely registering visual information, but were actually building up a map of the area. This idea was initially poorly received by the scientific community, and many believed he was neglecting other important senses such as smell.
“I remember how great was the scoffing in the early 1970s when John first described these ‘place cells’” recalls Oxford University physiologist John Stein. “Now, like so many ideas that were first highly controversial, people say: ‘Well, that’s obvious!’”
The next pieces of the puzzle were revealed more than three decades later by a Norwegian husband and wife team, May-Britt and Edvard Moser, who have been working at the Norwegian University of Science and Technology, Trondheim. The pair actually completed a short research stint with O’Keefe back in 1995 shortly after they graduated, where they learned how to take electrical recordings of place cells.
The duo later identified a different set of brain cells located in the entorhinal cortex, which they coined “grid cells,” that generate a coordinate system, somewhat like lines of longitude and latitude. Just like place cells, these cells became activated every time a rat went to a particular location, but each cell was found to have multiple firing locations which formed a bizarrely precise hexagonal grid. These particular cells allowed the animal to navigate and achieve precise positioning.
More recent work has provided evidence that these two types of brain cells are not exclusive to rats and exist in humans also. For example, the brains of Alzheimer’s patients show a loss of cells in both the hippocampus and the entorhinal cortex fairly early on, and it is common for sufferers to lose their way and fail to recognize familiar environments. These discoveries will therefore hopefully help scientists understand more about diseases such as this.
“The discovery of the brain’s positioning system represents a paradigm shift in our understanding of how ensembles of specialized cells work together to execute higher cognitive functions,” said the Nobel committee. “It has opened new avenues for understanding other cognitive processes, such as memory, thinking and planning.”
[Via Nobel Prize, BBC News, AFP, Nature and Moser Group]
