Importantly, the grid scores of I cells in all network configurations are less than the corresponding E cells and in many network configurations are <0.4, which is below the cut off applied by Buetfering et al. to identify grid firing.
To assess whether grid scores of I cells can be reduced further in E-I networks while maintaining grid firing by E cells, we investigated networks in which uncorrelated spatial input is applied to each I cell.
In these simulations E cells had grid scores of 0.57 ± 0.25, spatial sparsity of 0.78 ± 0.03 and spatial information of 1.69 ± 0.18 bits/spike, whereas I cells had grid scores of 0.16 ± 0.2 (p < 10−16, paired t-test), spatial sparsity of 0.21 ± 0.01 (p < 10−16, paired t-test) and spatial information of 0.2 ± 0.01 bits/spike (p < 10−16, paired t-test; range of all data sets is mean ± SD).
This resulted in a Chalkley grid score for each hotspot; the sum of the Chalkey scores for each of the five hotspots was termed the cumulative Chalkley score (CCS).
In noisy networks the presence of low grid scores for networks with high bump scores is explained by sensitivity of these network configurations to noise-induced drift.
The thermodynamically stable binding of ligand GSH was revealed by calculation of grid score (Supplementary Table S6).
This method provides us with an equivalent of the traditional grid score used to judge the quality of planar grid cells.
Consistent with this, when we plotted grid score as a function of PE-rate > 300, we found that PE-rate > 300 was relatively informative about the gridness score in networks without noise (MIC = 0.624) and a low value of PE-rate > 300 was necessary for grid firing.
This does occur in the Buetfering paper Figure 4A, but there are also a few with a weak periodic pattern (lower right panel of Figure 4A, grid score 0.18).
From this, we first identify the best plane, the one which yields the highest grid score, measured here as the value of the planar autocorrelogram at the origin, that is, the planar autocorrelation over all the slices passing through the origin.
