Figure 4.

Schematic of the interference model of grid cell firing. Left: Grid cell (pale blue) receiving input from three dendritic subunits (red, blue, green). Middle: Spikes, Somatic theta input (black) and dendritic membrane potential oscillations (MPOs, red, blue, green). The rat is shown (upper right) running perpendicular to the preferred direction of one of the subunits (blue), so the MPO of this subunit oscillates at theta frequency. Since the rat is running approximately along the preferred directions of the other two subunits (red and green, i.e. within 30° of their preferred directions), these MPOs oscillate above theta frequency. Spikes are shown at the times of the peaks of the product of the 3 interference patterns each MPO makes with the somatic theta input. The locations of the peaks of the envelopes of the 3 interference patterns are shown on the environment in the corresponding colors (red, green and blue stripes, lower right). The locations of grid cell firing are shown in pale blue and occur in the environment wherever the 3 envelopes all peak together (upper right).