color. In the next Section, we consider three different regimes of synchronization: moderately, weakly, and strongly synchronized systems as marked by black dots in Fig. \[fig2\](c).\
Other measures for stochastic synchronization are given by the phase synchronization index [@HAU06], or the mean phase synchronization intervals [@HOE08], but they exhibit qualitatively similar behaviour.

![\[fig2\] Frequency synchronization: Average interspike intervals of each subsystem (black solid curve: $\langle T_1\rangle$, red dashed: $\langle T_2\rangle$) and their ratio (green dotted: $\langle
T_1\rangle /\langle T_2\rangle $) (a) vs. noise intensity $D_1$ (for fixed $C=0.07$), (b) vs. coupling strength $C$ (for fixed $D_1=0.25$). (c): Ratio of the average interspike intervals in the ($D_1,C$) plane. The black dots mark the parameter choices for different synchronization regimes used in Fig. \[fig:isi\_tau\]. Other parameters: $a=1.05$, $\epsilon_1=0.005$, $\epsilon_2=0.1$, $\tau=0$, and $D_2=0.09$.](fig04a "fig:"){width="0.4\linewidth"} ![\[fig2\] Frequency synchronization: Average interspike intervals of each subsystem (black solid curve: $\langle T_1\rangle$, red dashed: $\langle T_2\rangle$) and their ratio (green dotted: $\langle
T_1\rangle /\langle T_2\rangle $) (a) vs. noise intensity $D_1$ (for fixed $C=0.07$), (b) vs. coupling strength $C$ (for fixed $D_1=0.25$). (c): Ratio of the average interspike intervals in the ($D_1,C$) plane. The black dots mark the parameter choices for different synchronization regimes used in Fig. 