The place-cell representation of volumetric space in rats

Place cells are spatially modulated neurons found in the hippocampus that underlie spatial memory and navigation: how these neurons represent 3D space is largely unknown. We wirelessly recorded place cells in rats at they explored a cubic lattice climbing frame which could be aligned or tilted with respect to gravity. Place cells represented the entire volume of the mazes: the activity of these cells tended to be aligned with the maze axes, and when it was more difficult for the animals to move vertically the cells represented space less accurately and less stably. These results demonstrate that surface dwelling animals also represent 3D space and suggests there is a fundamental relationship between environment structure, gravity, movement and spatial memory.