Figure 1: (a) Example of persistent firing in layer II pyramidal cell showing alternating cycles of spiking and nonspiking in data from Klink and Alonso [5]. (b) Simulation of grid cell firing dependent upon cyclical persistent spiking gated by random movement in a two-meter square environment. Spiking shown as black dots on trajectory in gray. (c) Simulation from same model using rat trajectory from experimental data in an 85 cm square environment.