Figure 3.

Simulation of 'grid cell' firing as the product of three linear interference patterns with different combinations of preferred directions (see equation 5). Simulated cells with regular grid firing patterns achieve high firing rates more often than those with irregular patterns, so long as collinear patterns are excluded. A) The most frequently high-firing grid cell (firing at 90% of maximum firing rate, 8Hz, 1310 times in the 28125 locations sampled by a rat in 10mins, same trajectory as Figure 2). B) The median frequency high-firing cell is shown in the middle (433 times). C) The least often high-firing cell on the right (228 times). Cell firing rate was simulated as the product of the firing envelopes of the three inputs to each cell, to facilitate speed and reliability. All unique combinations of preferred directions (ø₁, ø₂, ø₃) selected from (0°, 10°, .. ,350°) such that all angles differ by at least 20° were simulated. These firing rate maps are shown with 5cm boxcar smoothing for better comparison with experimental data.