While Google is intent on mapping everything in your universe, it just so happens that your brain may have its own internal GPS system.
Neuroscientists studying this belief have won the 2014 Nobel Prize in Physiology or Medicine. The prize (jointly awarded to John O´Keefe, a neuroscientist at University College London, and May-Britt and Edvard Moser, a married couple and neuroscience team at the Norwegian University of Science and Technology) recognizes their identification of grid cells in the human brain.
Though first discovered in rats, the cells are widespread in mammalian brains, including those of humans.
A remarkable feature of the system of grid and place cells is that it seems to encode abstract properties.
“The big breakthrough is that these cells are not just responding to sensory cues, like an odor on the ground,” said David Redish, a neuroscientist at the University of Minnesota in Minneapolis.
Instead, grid cells form an internal positioning system, and place cells use that information along with other cues to create a sense of place. They combine to create a very rich map.
“Understanding how we build those maps is part of a larger framework of cognitive science — how do we build inner models?” said Matthew Wilson, a neuroscientist at the Massachusetts Institute of Technology.
Place cells are found in the hippocampus, which has long been considered the brain’s memory hub. Removing it, as happened with the famous patient H.M., wipes out the brain’s ability to form new memories. But O’Keefe’s discovery showed that the hippocampus is also essential for navigation.
“O’Keefe recorded the impulses from neurons in a specific part of the hippocampus in rats as they explored an open space,” notes Quanta Magazine. “He discovered that individual neurons would fire only when the rat was in a certain spot. By altering the surrounding environment, he showed that the animal wasn’t simply responding to sensory cues. Rather, the neurons were responding to a more sophisticated sense of location.”
Interestingly, the cell activity has a hexagonal characteristic. Hexagonal patterns of grid cell activity are repeated all over nature, from honeycombs to the benzene ring to a tightly packed crate of oranges. It’s a highly efficient arrangement; bees use hexagons in their combs to minimize their use of wax. In the grid-cell system, the hexagon isn’t a physical object. Rather, it’s the organization of space that encodes information most efficiently.
“It’s the most efficient way to compress data,” said Marianne Hafting Fyhn, a neuroscientist at the University of Oslo in Norway and a former student of the Mosers.
Researchers aren’t sure why grid cells use hexagons, but the hexagonal organizing principle has attracted attention from computational biologists, who are trying to figure out how the grid is generated.
Scientists don’t yet know exactly how the mind constructs its spatial maps or how they are used for navigation. But the work of O’Keefe and the Mosers might ultimately illuminate much more than the brain’s navigational system.
Now researchers want to know more about how the brain encodes information about the world in electrical signals, and how it integrates new information as those signals move from region to region in the brain.
“If we want to understand brain processing, we need to know what transformation occurs from one part of the brain to the next,” Knierim said. “What rules transform information from area A into information in area B?” The process by which grid cells send information to place cells in the hippocampus allows researchers to explore this question.