Fig. 6

a–c The Green’s functions $G_{m^{-}}(x,y,t)$, $G_{m^{+}}(x,y,t)$, and $G_{n^{\pm }}(x,y,t)$ for a model in Fig. 2 when $x=10\text{ μm}$ and $y=100\text{ μm}$. Parameters: $a=2\text{ μm}$, $D=50000{\text{ μm}}^2\text{/ms}$, $\tau =2\text{ ms}$, $C=1{\text{ μF/cm}}^2$, $R_a=100\mathrm{\Omega }\text{\hspace{0.17em}cm}$, $r=100\mathrm{\Omega }{\text{\hspace{0.17em}cm}}^2$, $L=5{\text{ H\hspace{0.17em}cm}}^2$, $R_{\mathrm{GJ}}=100\text{ M}\mathrm{\Omega }$ (black curves, as in Figs. 4a–c), $R_{\mathrm{GJ}}=1\text{ M}\mathrm{\Omega }$ (red curves), $R_{\mathrm{GJ}}=1000\text{ M}\mathrm{\Omega }$ (green curves). Note that different y-axis limits are used in c