Fig 4. f_res and f_{φ = 0} of the optimal models are nearly identical.

a. Z(f) (top) and φ(f) (bottom) for a representative optimal model. Green dots indicate f_res (top) and f_{φ = 0} (bottom). b. Histogram showing the difference between f_res and f_{φ = 0} for 500 randomly selected models. A comparison of f_res and f_{φ = 0} of the experimental data of the PD neuron shows a similar distribution (inset, N = 18). (c) Plots of steady-state responses of I_Ca, I_L, and I_total to sinusoidal voltage inputs at the frequencies marked in panel a shown as a function of normalized time (cycle phase). Dotted vertical line indicates cycle phase 0.5 where the passive currents peak. Solid lines connect the minimum of I_Ca to the peak of I_total. The two lines nearly align at f_{φ = 0}.