Fig 4. Intrinsic noise changes average patterning time along the tissue.

Patterning time, measured as the time to observe a response x_A > 0.9, for the deterministic case (solid line) indicates that the time it takes for a response increases substantially as M approaches the deterministic steady state boundary at M = M_A = 1. The patterning times of stochastic simulations with different values of Ω (circles) are shown and illustrate that change of cellular expression state can occur within the bistable region, 0.1 < M < 1.0. Smaller values of Ω (higher levels of noise) result in decreased patterning times. Each point corresponds to the average mean first passage time of 100 CLE realisations with initial conditions x_A = 0 and x_B = 1.0. Error bars correspond to standard error of the mean. Stochastic parameters are ν_A = ν_B = 1 and Ω = 100, the rest of parameters are those of Fig 2. Inset) Coefficient of variation of the patterning time.