FIG. 9.

Dynamical instability produces non-Poisson-like firing irregularity. The estimate of the Fano factor (A, C) and Lyapunov exponent (B, D) versus the discharge rate for the FN model without and with ongoing noise (RS = 0.07). Gray curves indicate loess trend line fits (A, C). As in Figures 4 and 6, points within the gray region in C and D fall between the 1% and 99% quantiles of the best-fitting dead-time modified Poisson process. Approximately 950 data points are shown for the deterministic and stochastic FN simulations.