Discussion of jpn's comment: I have two criticisms, one major and one minor. Starting small, the use of rainbow color maps is highly misleading due to the non-uniform sensitivity of human vision across the visible spectrum, the non linear progression of luminescence across colors, and artificial 'bands' that it introduces into data. This document outlines the problem and solutions: http://root.cern.ch/drupal/content/rainbow-color-map). The major criticisms i have is that the the trained moved at a constant velocity regardless of the effort that the rat put forth on the treadmill. I think that coupling the velocity of the treadmill to the velocity of the train (via a direct or inverted mapping) would be a major improvement because it would link the animal's motor commands to its physical location in terms of the 'allocentric' frame of reference. Perhaps hippocampal circuitry is 'disregarding' the allocentric frame of reference because it 'realizes' that the mutual information between motor commands and allocentrially-referenced position is ~0. If the train's movement was coupled to motor output, forward or backward, this would not be the case.