Investigating the neural odometer function of entorhinal grid cells in rats navigating a multi-planar environment. (360G-Wellcome-202595_Z_16_Z)

It has been proposed that the grid cell system in the medial entorhinal cortex acts as a ‘neural odometer’, encoding both distance travelled and an animal's position in space. These features may be necessary for spatial computations such as path integration, but the relationship of grid cell firing patterns to behaviour remains speculative. In not-yet-published work, it has been shown that for a rat climbing a wall with its body plane aligned vertically the grid fields are expanded, as if the cells underestimate distance travelled. If grid cells support spatial computations then rats should also underestimate distances in this plane. To test this hypothesis rats will learn a distance match-to-sample task leading to triangle completion while both sample and choice phases are in the same plane (both horizontal or both vertical). In probe trials, the sample will be horizontal but the choice vertical. Distance underestimation in the probe trials (walking too far on the vertical wall to achieve a match to the horizontal sample) will link grid cells to behaviour, while the basic distance-matching task will serve as a springboard for neurobiological studies investigating the role of grid cells in odometry generally.