Even if you don’t have an amazing sense of direction, you aren’t lost all the time. You have some idea of where you are and of the important locations around you.
Figuring out the system behind this “internal GPS” won three researchers the Nobel Prize in Medicine on Oct. 6.
Your sense of place is more than reading maps and navigating road trips: It helps you know where the closest bathroom from your desk is right now. In your home, you know where the kitchen sink is. Outside your apartment, you can always find your way to the corner store or late-night deli — even those times you’d be better off if you couldn’t.
More than that, you have a sense of the space around you — one that constantly updates and takes into account where you are in reference to specific locations. You know when you are moving past the front door and closer to the kitchen.
The brain keeps track of these things using a combination of cells that researchers commonly refer to as place cells and grid cells. Together, they tell you where you are in space, where you are going, and what landmarks you are near.
Your Personal GPS
Place cells, which are associated with one specific location, are found in a part of the brain called the hippocampus, which is largely responsible for memory. Grid cells, which help us understand the general space around us, are found in a nearby brain region, called the entorhinal cortex. Together, these create a sort of internal GPS.
The discoverers of these special components of the brain were jointly awarded the Nobel Prize — James O’Keefe won half for his discovery of place cells in 1971, and Edvard and May-Britt Moser, married former students of O’Keefe from Norway, share the other half for discovering grid cells in 2005.
Finding these specific parts of the brain and the ways they interact reveals all sorts of amazing information about how we process the world.
This information tells us how we find our way around; it helps illustrate the connection between memory and location; and it may help us understand why people with brain disorders like Alzheimer’s get lost and end up confused about where their home is.
The brain is processing a ton of potential information whenever we journey anywhere. “Just to walk [somewhere], we have to understand where we are now, where we want to go, when to turn and when to stop,” May-Britt told Nature. “It’s incredible that we are not permanently lost.”
How It Works
In 1971, O’Keefe found that specific neurons — brain cells — inside rats’ brains were activated when the rats were in a specific location but stayed inactive at all other times. Associating specific locations with particular cells in the hippocampus, where neuroscientists think most memory is stored, was an amazing discovery. It was the beginning of our understanding of how we know where anything is in the world.
The same findings were later demonstrated in humans and other mammals, but the map was still incomplete.
Knowing that cells represented particular locations was one thing, but it didn’t explain how we made sense of the space in between landmarks or of other new space in the world.
The Mosers, who had briefly worked with O’Keefe during post-graduate research in the 1990s, were investigating the same question, but couldn’t find an answer in the hippocampus. Another brain region seemed promising however, located next to the hippocampus — the entorhinal cortex.
After implanting electrodes that could watch individual cells in rat brains, they saw something incredible. Perfectly spaced grids of cells lit up as rats moved through space — any space. Whenever a rat reached a certain point, not only would the cell representing that location light up, but so would the cells in a hexagon around it.
As the rat moved to another point represented on this brain grid, a hexagon of other cells would light up around it. These newly named “grid cells” were the ones that showed how we move through any space, as if we were navigating through a constant matrix-like structure of space around us.
The Mosers realised that the grid cells in the entorhinal cortex communicated with the place cells in the hippocampus.
This connects the grid with the landmarks, the place cells that are connected to specific locations.
What This Means
During the ceremony, Nobel Committee members described this as “a fundamental discovery of how the brain works,” but though it transforms what we know about the brain, it has not yet reached the point where it can be used for disease therapies.
However, in a video, Edvard Moser explains that the area of the brain where the grid cells are located is one of the first to become damaged in Alzheimer’s patients. This may help explain why disorientation is a common feature of certain degenerative brain diseases.
Another fascinating connection is that with memory. Since the ancient Greeks, memory champions have used an approach to memorization that involves storing information in something imagined as a place in the brain, a sort of “memory palace” where each room can contain something new. Current competitive memorizers say this strategy can help you remember anything.
Clarifying this connection between place and memory is a huge step in understanding not just where we are in the world, but also in how we recall everything in it.
More information on how the Mosers discovered grid cells is included in the video below.
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