Figure 4.

The cell system changes due to a decrease in the conductances $G_1$ and $G_2$ to the new values $G_1^{’}$ (fixed decrease) and $G_2^{’}$ (three different decreases) shown in the figure (left). The community effect within the depolarized patch can still resist the polarization by the surrounding bulk region if the $G_2$ decrease is small (left, top). Thus, a minimum decrease of $G_2$ is needed to weaken the community effect within the patch enough to be polarized (left, intermediate). Further decreases in $G_2$ (left, bottom) only cause faster patch polarizations, as shown by the electrical potential changes in three cells located at the patch, the surrounding bulk, and the interfacial region (right). The single-cell maximum conductances assumed in Equations (1) and (2) are $G_{\mathrm{pol}}^{\mathrm{o}}=G_{\mathrm{ref}}^{\mathrm{o}}$ and $G_{\mathrm{dep}}^{\mathrm{o}}=1.4G_{\mathrm{ref}}^{\mathrm{o}}$, with $G_{\mathrm{ref}}^{\mathrm{o}}=1_{}^{} \mathrm{nS}$. For the case of isolated cells, these conductances give the stable polarized and depolarized potentials $V_{\mathrm{pol}}\simeq -{50}_{}^{} \mathrm{mV}$ and $V_{\mathrm{dep}}\simeq -{10}_{}^{} \mathrm{mV}$, respectively [39,47]. The ratio between the initially depolarized patch area and the whole system area is 0.16.