Figure 2
Mean current, largest Lyapunov exponent and Fourier spectrum in terms of voltage. (a) Mean current and largest Lyapunov exponent vs voltage, and (b) Fourier spectrum vs voltage for the second oscillatory interval. The inset in panel (a) shows the mean current for a larger voltage interval and the vertical arrows mark supercritical Hopf bifurcation points bounding the second oscillatory voltage interval. Without noise, the voltage interval of spontaneous chaos is very narrow (3 mV width) and the LLE is only 0.25. Internal noise increases the LLE up to 0.76 and widens to 30 mV the voltage range for spontaneous chaos.