Fig. 4.

Spectral response of the mean-field model. (A) Left: Spectral phase-diagram illustrating the maximal frequency band over the u and γ₃₁^E dimensions. Right: phase-diagram illustrating the maximum frequency with 1 Hz resolution. This mean-field formulation produces high frequency gamma oscillations, with the highest maximum frequency of 89 Hz. (B) Bifurcation diagram illustrating maximum and minimum pyramidal cell membrane potential along parameter u for γ₃₁^E = 1.5. For this particular value of γ₃₁^E, the system remains at fixed points. (C) Time domain and phase domain portraits for a region of parameter space exhibiting a low frequency quasiperiodic attractor. (D) For high input current and high levels of forward excitatory connectivity (i.e. from the stellate cell input layer to the pyramidal cells) the system exhibits gamma resonance (u = 100 mA; γ₃₁^E = 5).