RT Journal Article SR Electronic T1 Grid cell firing fields in a volumetric space JF bioRxiv FD Cold Spring Harbor Laboratory SP 2020.12.06.413542 DO 10.1101/2020.12.06.413542 A1 Roddy M. Grieves A1 Selim Jedidi-Ayoub A1 Karyna Mishchanchuk A1 Anyi Liu A1 Sophie Renaudineau A1 Éléonore Duvelle A1 Kate J. Jeffery YR 2020 UL http://biorxiv.org/content/early/2020/12/07/2020.12.06.413542.abstract AB We investigated how entorhinal grid cells represent volumetric (three-dimensional) space. On a flat surface, grid cell firing fields are circular and arranged in a close-packed hexagonal array. In three dimensions, theoretical and computational work suggests that the most efficient configuration would be a regular close packing of spherical fields. We report that in rats exploring a cubic lattice, grid cells were spatially stable and maintained normal directional modulation, theta modulation and spike dynamics. However, while the majority of grid fields were spherical, they were irregularly arranged, even when only fields abutting the lower surface (equivalent to the floor) were considered. Thus, grid organization is shaped by the environment’s movement affordances, and may not need to be regular to support spatial computations.One Sentence Summary In rats exploring a volumetric space, grid cells are spatially modulated but their firing fields are irregularly arranged.Competing Interest StatementThe Authors declare the following competing interests: K.J. is a non-shareholding director of Axona Ltd.