Figure 2: (a) Example of graded persistent firing in a layer V pyramidal cell from Egorov et al. [8]. (b) Simulation of grid cell firing based on persistent firing in cells from deep layers of medial entorhinal cortex. The spiking activity shown as black dots arises from convergent input from three neurons with the same baseline persistent firing frequency, with phase of input neurons influenced by input from different speed modulated head direction cells during movement (trajectory shown in gray). (c) Simulation of grid cell firing based on membrane potential oscillations in dorsal layer II stellate cells in medial entorhinal cortex.