2020 Feb 07 – In 2011, Kate Jeffery and her group at the University College London, UK, investigated for the first time how hippocampal place cells operate in three dimensions (3D) in the rat. Since then, two relevant studies have characterized 3D place fields in the rat and the flying bat, respectively. Jeffery’s group has now released the most recent data on the subject. The activity of place cells in rats implanted with an Axona microdrive were wirelessly recorded as they explored a cubic climbing frame, which was either aligned or tilted with respect to gravity, or a third shallower apparatus (arena). Place cells representations tended to be aligned with the maze axes more than would be expected by chance, and were significantly less accurate and stable when greater movement constraints occurred for vertical travel, slowing down motor activity (spatial information was lowest along the Z dimension of the aligned cube). In addition, place fields were elongated parallel to the maze axes and only a minority in each maze was more spherical (isotropic: of equal resolution in all dimensions) than expected by chance. The study suggests that internal representation of 3D space is not fixed and may imply a fundamental relationship between environment structure, gravity, movement and spatial memory. “The spatial map may form the framework for other types of cognition in which information dimensionality is higher than in real space”.