Extended Data Figure 2. Characterization of the inter-cell variability of EPSCs, IPSCs, and E/I ratios.

(a, b) The inter-cell variability of EPSCs, IPSCs, and E/I ratios among neighboring pyramidal cells does not correlate with their inter-soma distances. (a) The average relative deviations of EPSCs, IPSCs, and E/I ratios from each experiment in Fig. 1f are plotted against the average inter-soma distance from the same experiment. The average inter-soma distance is the mean of the distances between each pair of pyramidal cells. For the experiments in which only two pyramidal cells were recorded, the inter-soma distance between the two pyramidal cells was used. Lines: linear regression fits. (b) The ratio of the EPSC amplitudes of two simultaneously recorded pyramidal cells was first calculated, and then the logarithm of this ratio was computed. The absolute value of the logarithm was plotted against the inter-soma distance between the two pyramidal cells. Similarly, the data for IPSCs and E/I ratios were plotted against the inter-soma distances. Lines: linear regression fits. (c) The distribution of the E/I ratios across the pyramidal cells varies less than if EPSCs and IPSCs were randomly paired between cells and less than the distributions of EPSC and IPSC amplitudes. To determine whether the precise E/I ratio recorded within each pyramidal cell minimizes the average relative deviation, we computed the E/I ratios from randomly but uniquely paired EPSCs and IPSCs within each of the 20 experiments from Fig. 1f. By randomizing within each experiment we ensure that the average relative deviation is only modified due to the pairing of EPSCs to IPSCs. Note, for an experiment with N pyramidal cells, there are N! possible randomized pairings of EPSCs and IPSCs, and hence N! possible E/I ratio average relative deviations (referred as random-E/I ratio average relative deviation). The distribution of the means of the random-E/I ratio average relative deviations (grey histogram) was constructed from the means of 10,000 samples. Each sample consisted of 20 random-E/I ratio average relative deviations, each of which was randomly chosen from the N! possible random-E/I ratio average relative deviations of each experiment. The grey vertical line represents the mean of the distribution. The distribution of the means of the E/I ratio average relative deviations (black histogram) was generated by bootstrapping (i.e. resampling 10,000 times with replacement). Each resample consisted of 20 randomly chosen E/I ratio average relative deviations from the 20 experiments in Fig. 1f and an E/I ratio average relative deviation was allowed to be repeated within one resample (i.e. sampling with replacement). The black vertical line represents the mean of the experimentally obtained E/I ratio average relative deviations. The E/I ratio average relative deviations are smaller than the random-E/I ratio average relative deviations (P < 0.0001). The distributions of the means of the EPSC average relative deviations (red histogram) and the means of the IPSC average relative deviations (blue histogram) were generated by similar bootstrapping to the E/I ratio average relative deviations. The red and blue vertical lines represent the mean of the experimentally obtained EPSC average relative deviations and IPSC average relative deviations, respectively. The E/I ratio average relative deviations are smaller than the EPSC average relative deviations (P < 0.0001) and the IPSC average relative deviations (P < 0.0001).