This post has been geo-located to New Delhi in India. My tablet’s inbuilt GPS did that for me. What does that for me (and most of us) every time I move? We become aware of our existence when we can distinct ourselves from and place ourselves in space. How we do this had been a philosophical puzzle since ages. This year’s Nobel prize for Physiology has been awarded to three scientists whose work has explained how we navigate in space. In simple terms, how the inner GPS in the brain functions.
John O’Keefe, who has been awarded one half of the prize, discovered in 1971 that particular neurons are activated in the rat brain when it is at a certain position in a room. He noticed the phenomenon while recording signals from individual neurons in the hippocampus to study how brain affects behaviour. His work proved Edward Tolman’s hypothesis of mapping by the brain.
O’Keefe demonstrated that these neurons, called place cells, were using visual inputs to build up an inner map of the environment the rat was in. The hippocampus generated different maps, memory of each environment being stored as firing off particular combinations of place cells. How the brain works out the latitude and longitude to position us in space was worked out three decades later.
The husband-wife team of May-Britt and Edvard Moser has been awarded the other half of the prize. O’Keefe’s work explained the formation of maps, but how these maps are navigated was explained by the Mosers’ in 2005. It had been established that cells with traits also existed in other region of the brain, the entorhinal cortex. As the Mosers discovered, these cells integrated the space cell maps.
This type was termed the grid cells. In studies on rats, individual grid cells were activated when the rats were at particular locations in a bound area. These locations were observed to be in a hexagonal pattern, suggesting that grid cells assigned distances to spatial maps dawn by place cells. Other neurons embedded in the entorhinal cortical network are head-direction cells and border cells. These act like a compass and a wall respectively in that they guide our direction and define the boundaries of our environment.
Functional MRI has been exploited to confirm the existence of place cells and grid cells in humans. The sense of place gives us position and the ability to navigate gives us direction. When combined, these constitute our internal positioning system. Any anamoly in these cells and you would find it incredibly difficult to find your way back home. That’s what happens in Alzheimer’s as regions of the hippocampus and the entorhinal cortex are damaged.
Other science laureates
The Nobel prize for Physics has been awarded to Isamu Akasaki, Hiroshi Amano and Shuji Nakamura for inventing blue LED. After the development of red and green LEDs, it was the only hurdle in producing white LED light. LEDs are cheaper and environment-friendly when compared to incandescent or fluorescent lights.
The prize for Chemistry has been conferred upon Stefan Hell, Eric Betzig and William Moerner for circumventing the physical limit on optical microscopy resolution. Both stimulated emission depletion microscopy and near-field microscopy have revolutionised science by allowing single molecules to be visualised.