FIG. 10.

The critical signal duration Δτ_min as a function of the step stimulus amplitude S_max. We compare the results of a numerical calculation (solid line) with the linear approximation (10). For weak supercritical stimuli the approximation differs from the numerical result because of the underestimated positive feedback contribution in the production rate of the response component. For higher levels of stimulus, the approximation agrees with the numerical solution.