Annual Review of Neuroscience

Science has solved a centuries-old question: How does the mind process space?

Kant got it right. "Space is not something object and real, nor a substance, nor an accident, nor a relation," he wrote in his 1770 Inaugural Dissertation. "[I]nstead, it is subjective and ideal, and originates from the mind's nature in accord with a stable law as a scheme, as it were, for coordinating everything sensed externally."

That's the best explanation I've heard yet for the 2014 Nobel Prize in Physiology or Medicine, which was awarded early this week to three scientists for a key discovery in epistemology. Almost 250 years after Kant described the concept of space as "pure intuition," neuroscientists John O'Keefe and May-Britt and Edvard Moser jointly took the award for discovering the brain's internal positioning center.  

Back in 1971, O'Keefe discovered a type of nerve cell in the hippocampus called "place cells." The American British scientist found that, in a rat's brain, specific place cells fired whenever the rat found itself in a specific location. Neighboring place cells fired as the rat moved around the local environment. Place cells fired in different patterns to represent distinct places, providing an internal spatial map of a location inside the hippocampus.

John O'Keefe, one of three scientist honored with the 2014 Nobel Prize for medicine. (Suzanne Plunkett/Reuters)

That's the first part of the brain's GPS. The second part was discovered decades later. In 2005, the Norwegian Mosers identified a class of "grid cells" in the entorhinal cortex that make navigation possible. Together, these parts of the brain provide the mind with two different kinds of mapping: "allocentric" (object-to-object relations) and "egocentric" (self-to-object relations).

Place cells in the hippocampus help animals (rats and humans alike) to remember features of maps and to distinguish between maps. Indeed, the hippocampus loads different maps, as it were, depending on a rat's location. Grid cells in the entorhinal cortex, on the other hand, help animals to navigate these maps. A rat can determine its relation to a location even in darkness thanks to this function.

So the structure of the brain prefigures our conception of space: interesting! And as the Nobel committee observed, these discoveries may help us to understand how and why cognitive disorders such as Alzheimer's disease and dementia affect our ability to navigate through the world.

The discoveries will also undergird our efforts to build computers and robots that can simulate mechanical calculations that we perform intuitively. Now, even as we are coming closer to self-driving cars that can navigate through the world, we have a basic understanding of how we do that ourselves.

May-Britt and Edvard Moser (TT News Agency/Reuters)

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