Figure 1

The phase diagram for typical HH model parameters [2]in the limit of small synaptic conductivity. There is a well-pronounced minimum at T _i = 17.5 ms. The resonant nature of the response can be seen also at multiples of this value, at T _i ≈ 34 ms and T _i ≈ 50 ms. Near the resonance the system has the tendency to mode locking with high values of k, where k = T _o /T _i is the ratio of the output ISI to the input ISI. For example near the main resonance frequency we find narrow regions with k = 5, 6 or 9. Areas with bistable solutions are shown in grey. We expect the resonance at T _i = 17.5 ms to survive in the presence of noise.