Score one for theoretical neuroscience! Neuroscientists have previously known about three types of cells that help our internal sense of ‘space’: place cells, grid cells, and head direction cells. Place cells fire preferentially when an animal is in a certain location in an environment. For instance, if you put a rat in a circular maze, a place cell may fire every time the rat runs through a small section of the maze. Grid cells, on the other hand, respond to multiple locations in a grid-like fashion. So one grid cell may fire, say, every meter at points on a hexagonal lattice. Head direction cells, obviously, respond to an animal’s head being in a certain direction.
Computational models suggested that there was another type of cell needed to have an accurate cognitive map: border cells. Border cells respond when the animal is near some salient border, such as a wall. And lo and behold, such cells were recently discovered!
So, a win for theory in neuroscience. Theory helps the field make coherent descriptions of what the system is trying to accomplish and how it is doing it. If you can describe something coherently, you can make predictions like for future experiments such as this one. If the experiments turn out negative, maybe you don’t understand the system as well as you think you did.