Fig 4. Response of the mean-field network to an oscillatory input.

a: Schematic representation of the random network driven by an external input, with phase randomization. For g > g_c, the chaotic activity can be seen as internally-generated noise. b: Effect of an oscillatory external input on the power spectral density S_x(f). In the example, γ = 0.25, β = 1, g = 2g_c(γ, β), f_I = 0.12, while A_I = 0.5 (blue) and A_I = 0 (gray). Simulations (solid blue) and theory (dashed blue) are superimposed. c: Top: Schematic representation of the separation of the power spectral density into its oscillatory (A_osc) and chaotic (A_bkg) components. Note that these quantities depend on the size of the frequency discretization bin. Bottom: Graphical interpretation of P_bkg, i.e. the total variance of the network activity due to chaotic activity (shaded gray area).