Fig. 6

Phase plane trajectories traced out by the responses of the model to two different SEEs (panels a and c) and the SEEs profiles (top) and the corresponding voltage responses (bottom) (panels b and d). Four time points A, B, C, and D are chosen and the corresponding location of the (pseudo-)slow manifolds (dashed lines) $M_{\mathrm{A}}$, $M_{\mathrm{C}}$, and $M_{\mathrm{D}}$ are plotted in a and c. Dotted lines are nullclines when $I=I_{\mathrm{bias}}+I_{\mathrm{ext}}$. Note that the location of the points A–D vary around the location of the slow manifold in Type I (top row), while for Type II (bottom row) these values fluctuate less, thus yielding values of the response well below the (pseudo-)slow manifold as the input signal strength increases for Type II. Note in particular that the value of w for Type II, point D, is well below the values on the pseudo-slow manifold $M_{\mathrm{D}}$. Noise coefficients ${\delta }_1$ and ${\delta }_2$ for Type I and Type II are as in Figs. 3b, d