For at least a century London taxi drivers who want the green All London Taxi sticker have had to pass The Knowledge, an oral test demonstrating that the candidate possessed "a thorough knowledge...[of] all of London's ]24,000] streets; housing estates; parks and open spaces; government offices and departments...In fact, anywhere a taxi passenger might ask to be taken." (Rosen, 2014)
Success on The Knowledge requires the implementation of two cognitive functions: remembering--the ability to store and recall memories; and wayfinding--the ability to find your way from place to place.
But, in fact, all humans, and not just London cabbies, possess these particular cognitive functions and implement them with ease.
Forget those terrible associations with school as you were required to remember the states and their capitals and consider instead the myriad facts you easily can recall about your family, friends, acquaintances, your work. Then, whether or not you claim to have a good "sense of direction," reflect on how easily you make your way to work everyday; how easy it is for you to detour around a traffic accident.
While we may take memory and wayfinding for granted, neuroscientists do not. For the neuroscientist the puzzle is how the brain's neural activity creates cognitive functions like memory and wayfinding.
The 2014 Nobel Prize for Physiology or Medicine celebrated a set of discoveries that have opened "our eyes to some of the secrets of the brain...and has put us on track of the neural computations responsible for the perception of space as well as cognitive brain cell functions as well." (Moser, 2014)
These discoveries were indirectly prompted by a 1953 operation gone wrong. An operation that removed a young man's hippocampus in an attempt to relieve his epileptic seizures resulted in his tragic post-operation inability to create long term memories. The young man (known only as H.M. during his lifetime) could not recognize old friends and could not even remember how to find the hospital bathroom. H.M.'s case pointed to the brain's hippocampus as a place to look for memory.
In the early 1960s neuroscientists investigating the hippocampus learned to attach electrodes to specific animal's behavior while at the same time recording the activity of brain cells.
John O'Keefe, a young scientist at the University College London, found that as his lab rats explored a particular maze, brain cells in the hippocampus would fire at specific locations. When the rat ran the maze a second time the same neurons would flash at the same location in the maze. Place the rat in a different maze and a new maze-specific map would be created. O'Keefe named the cells that fired "place cells," because each seemed to define a map-specific landmark; e.g. "turn right here to get to the food."
But whether one is a rat or a human, a landmark is not enough to find your way. To navigate with landmarks, the navigator needs to know the relationship of any given landmark (distance and heading) to the other landmarks. In paper maps this need is filled by a coordinate system like latitude and longitude.
Sure enough, a second discovery showed the brain creating what might be a coordinate system.
Researchers Edvard and May-Britt Moser used O’Keefe’s methods but attached electrodes to their rats’ entrorhinal cortex, one synapse away from the hippocampus. Cells in the entrorhinal cortex also fired but in groups of three forming creating a grid of equilateral triangles that tiled the entire explored space. The Mosers named these “grid cells.”
As the rat explores its environment place cells identify landmarks while the grid created by the grid cells create a way to relate the locations of the landmarks to one another.
Together the grid cells’ “coordinate system” and the place cells’ landmarks make it possible for the rat “to go from where it happened to be in the environment to a particular place” in that environment. (O’Keefe & Dostrovsky, 1971)
View the graphic on from the (Singer, 2014) article here.
Neuroscience has not yet identified what specific data the entrorhinal-cortex or the hippocampus uses to create this map. However, because the entrorhinal cortex and hippocampus sit atop of the brain’s hierarchy of neurons this means that the grid and place cells have large amounts of highly processed data from all over the brain to use as inputs. Indeed, recent experiments show that when rats learn new information about their mazes such as the location of food, the grids are altered to reflect the new information; that is, grid and place cells encode both position and experiences that occurred in a particular place: “each memory stored in the hippocampus contains information about place, expressed in firing locations of place cells, as well as the events that take place in each of those places....” (Moser, 2014)
When H.M lost his hippocampus, both his positioning system was lost but so were both the memories stored there as well as the ability to create new long-term memories. This loss meant that for the fifty-five years of his life, “...each time H.M. met a friend, each time he ate a meal, each time he walked in the woods, it was as if for the first time.” (Moser, 2014)
While much remains to discover, the entrorhinal cortex-hippocampus positioning system suggests why we are good at remembering facts and experiences long-term and getting around in our environment. The positioning system creates a conceptual map of the environment based on landmarks (place cells) and the relationships between them (grid cells). Each landmark is located with positional information, but encodes lots of other information: a statue of Ben Franklin, the first U.S. postmaster; it was hot and cloudy; you heard about 9/11 here...; that is experiences and facts.
We have probably known about the connection between place and memory intuitively.
Temples and churches decorated with beautiful art makes them memorable places and therefore what occurs in them memorable as well.
A school field trip provides a way to make a lesson memorable because it happens in a memorable place—an art museum or a science laboratory.
To make learning memorable a classroom should itself be a memorable place as well so that there is a flood of interesting data to influence the creation of the grid and place cells.
Subsequent research has identified a suite of cells that appear to augment our positioning system: speed cells, head direct cells that indicate the direction the head is facing and boundary cells that seem to demarcate the edges of a space.
The German philosopher Immanual Kant declared that “Space is not something objective...; instead, it...originates from the mind’s nature in accord with a stable law as a scheme, as it were, for coordinating everything sensed externally.” Perhaps he got it right! Quotation from https://plato.stanford.edu/entries/kant-spacetime/
You can find out more about the discovery of place and grid cells here, here, and here. These are the Nobel Prize lectures by the 2014 winners in the Physiology or Medicine, John O’Keefe, Edvard Moser, and May-Britt Moser for their “discoveries of cells that constitute a positioning system in the brain.”
Cepelewicz, Jordana (2019). Goals and Rewards Redraw the Brain’s Map of the World. Quanta Magazine. March 28, 2019.
O’Keefe, John, Dostovsky, J. (971). The hippocampus as a spatial map. Preliminary evidence from unit activity in the freely-moving rat. Brain Research 1971Nov;34(1):171-5
Moser, May-Britt (2014). Nobel Prize Lecture, December 7, 2014.
Rosen, Jody (2014). The Knowledge, London’s Legendary Taxi-Driver Test, Puts Up a Fight in the Age of GPS. New York Times Style Magazine. November 10, 2014.
Singer, Emily (2014). Brain’s Positioning System Linked to Memory. Quanta Magazine October 7, 2014.
Dr. John HOlton
Dr. John Holton joined the S²TEM Centers SC in July of 2013, as a research associate with an emphasis on the STEM literature including state and local STEM plans from around the nation.