Figure 4.

Grid-cell spatial periodicity cannot be maintained in an oscillatory interference model of grid cell firing, when running speed is integrated over >∼200 ms. Grid-cell firing was modeled using the oscillatory interference model (see Materials and Methods). Left, Random trajectory (gray lines) of an animal exploring a rectangular arena (1 × 1 m in size); red dots indicate spiking events of the modeled grid cell. Right, The unsmoothed running speed signal (blue) compared with smoothed running speed signals (green). A, No smoothing; B, 60 ms smoothing; C, 100 ms smoothing; D, 200 ms smoothing; E, 400 ms smoothing; F, 1000 ms smoothing of running speed.