Organization of hippocampal place cells by enthorinal cortex grid cells. A functional role for the phase precession mechanism.

Thirty years ago, hippocampal cells firing at selective location in the environment were discovered, with a major impact in our understanding of memory formation. Recently, "grid cells", firing when the rat is located at any of the vertices of grid fields covering the environment, have been discovered in the medial enthorinal cortex. These cells are supposed to be responsible for the organization of hippocampal place cells. Computational models have already validated this theory. However, multiple grid scales were assumed which does not follow anatomical evidences. We propose here a model relying on the phase precession dynamics: when the rat crosses a field of a particular grid cell, its spikes shift to earlier phases of the theta rhythm. We demonstrate how this dynamics can reliably explain the organization of place cells without relying on multiple grid scales. Moreover, hippocampal place cell phase precession results from grid cell phase precession.