Figure 4.

Analysis of network factors contributing to E/I balance at the first crossing of the E=I balanced state. (a) Schematic of alternate method to change E/I ratio. Synaptic weights are fixed near the E=I balanced state and frequency of noisy external stimuli to the excitatory (E) cells is varied (see text for details). (b) Relationship between E/I ratio values and mean firing rates of the excitatory (E, blue curve) and inhibitory (I, red curve) cell populations as noise event frequency to the E cells is increased. (c) Difference between blue and red curves in (b). (d) Relationship between E/I ratio values and the difference between the mean membrane potentials of the excitatory (${\overline{\mathit{V}}}_{\mathit{E}}$) and inhibitory (${\overline{\mathit{V}}}_{\mathit{I}}$) cell populations, and the reversal potentials of the excitatory (${\mathit{E}}_{\mathit{E}}^{\mathit{syn}}$) and inhibitory (${\mathit{E}}_{\mathit{I}}^{\mathit{syn}}$) synaptic currents as noisy event frequency to the E cells is increased. Blue (red) curves show distances from ${\mathit{E}}_{\mathit{E}}^{\mathit{syn}}({\mathit{E}}_{\mathit{I}}^{\mathit{syn}})$. (e) Difference of distance curves shown in (d).