Reading the neural code for space

The cognitive map for spatial navigation is thought to rely on grid cells. Scientists at LMU and Harvard University have now put forward a mathematical theory that explains key grid-cell features and how these give rise to a neural metric for space. One year ago, the Nobel Prize in Physiology or Medicine went to the discoverers of the mammalian "GPS system" for spatial navigation. Measuring neural activity in cortex, these researchers had found that some cells represent space in a highly surprising manner: As the animal moves through its environment, distinct sets of cells are sequentially activated. Each individual "grid cell" responds to multiple positions in space that form a virtual hexagonal lattice tessellating the environment. This strikingly periodic and beautiful spatial pattern has caught the imagination of experimental and theoretical neuroscientists alike, and has been proposed to constitute the brain's metric for space. Theoretical neuroscientists at LMU Munich and the Bernstein Center for Computational Neuroscience in Munich, and at Harvard University, have now put forward a comprehensive mathematical theory that explains many features of grid cell activity that had remained mysterious, and makes specific predictions that can be tested in neurophysiological and behavioral experiments.