Figure 7.

Dependence of frequency and amplitude of limit cycle oscillations on the background state. System connection weights are fixed as (w_EI, w_IE, w_II, w_EE) = (50,15,0, 20) (dashed line) or (w_EI, w_IE, w_II, w_EE) = (50,15,0, 25) (solid line). Input is a step function of magnitude 0.1. Frequency and amplitude estimated using a Hilbert Transform of the period from of 100τ_E–200τ_E. Normalized frequency is fτ_E. If τ_E = 20 ms, normalized frequency of 1 corresponds to a 50 Hz oscillation. Outside the range of background states shown there are no limit cycle oscillation for each level of w_EE and the oscillations damp out. The main point is that the amplitude of the limit cycle oscillations depend strongly on the background state. Compared to the damped oscillations (Figure 6) the limit cycle frequency does not depend strongly on the background state. (A) Normalized frequency (B) Amplitude.