Functional Split between Parietal and Entorhinal Cortices in the Rat

Posterior parietal cortex (PPC) and medial entorhinal cortex (MEC) are important elements of the neural circuit for space, but whether representations in these areas are controlled by the same factors is unknown. We recorded single units simultaneously in PPC and MEC of freely foraging rats and found that a subset of PPC cells are tuned to specific modes of movement irrespective of the animals' location or heading, whereas grid cells in MEC expressed static spatial maps. The behavioral correlates of PPC cells switched completely when the same animals ran in a spatially structured maze or when they ran similar stereotypic sequences in an open arena. Representations in PPC were similar in identical mazes in different rooms where grid cells completely realigned their firing fields. The data suggest that representations in PPC are determined by the organization of actions while cells in MEC are driven by spatial inputs.