Figure 9.

A. Effect of different head direction inputs with different intervals between direction preference angles on simulated grid cell firing fields for a neuron with intrinsic frequency of 7 Hz. A1. Input from three head direction cells (3 HD) at 120 degree intervals of selectivity (top) gives grid patterns of tessellated equilateral triangles (hexagons). A2. Four head direction cells with 90 degree selectivity intervals create a square grid. A3. 5 HD cells at 72 degree intervals create a complex pattern with radial symmetry but no translational equivalence. A4. Six HD cells at 60 degree intervals create a grid pattern similar to that for 120 degree intervals. A5 and A6. 8 HD cells at 45 degrees and 12 HD cells at 30 degree intervals create complex patterns with radial symmetry but no translational equivalence. B. Simulated grid cells with different numbers of head direction inputs show a less consistent grid pattern with two HD cells, but similar properties with 3 HD and 6 HD cell inputs. The simulated grid cell has an intrinsic frequency of 4 Hz in B.