(color online) The space–time plots of u for time delay τ = 1.0 with different diversities σ in EHRNs. (a) σ = 0.0 (R = 0.001, asynchronous state); (b) σ = 0.1 (R = 0.002, asynchronous state); and (c) σ = 0.4 (R = 0.004, asynchronous state). The figures are plotted in greyscale from black (lowest value at 0.0) to white (highest value at 1.0), and this greyscale will be used throughout this paper. Time passes from left to right.