Year in review: ‘Speed cells’ help make navigation possible

Tucked away in the brain, cellular speedometers clock a rat’s swiftness. These “speed cells,” reported in Nature this year, were a missing piece in science’s understanding of how the brain creates an internal map of the world.

Two of the authors, Edvard and May-Britt Moser of the Norwegian University of Science and Technology in Trondheim, are well-acquainted with these maps; the Mosers shared a Nobel Prize for discovering specialized mental navigators called grid cells that help orient an animal in space. To be precise, that orientation also requires information about how fast the animal is moving.

In the study, a population of nerve cells fired off signals at rates corresponding to the paces of a moving rat, from a slow walk to a run (SN: 8/8/15, p. 8). These speed cells are found along with grid cells in a brain area important for navigation.

As it turns out, grid cells themselves have several talents. Beyond detecting spatial locations, grid cells can map time and distance, scientists found in rats (SN: 12/12/15, p. 12). Because mammals have similar navigation systems, scientists wouldn’t be surprised if grid cells and speed cells also help people get around.