rats’ brains, and presumably ours, tessellate the plane surface we walk on with multiple overlapping triangular grids (is there a mathematical reason triangles are optimal? euler characteristic, perhaps?) “path” neurons in the hippocampus fire as we cross these grids to reconstruct our previous paths “boundary” neurons in the hippocampus fire as we approach the boundaries of a space (what about agoramaniacs? or ancient people who hunted buffalo on the plain?)
