FIG. 3.

Noise broadens the rate-level function to low-rate stimulation. A Firing rate versus pulse amplitude for noise intensities producing typical (black points, black solid line), low (gray points, gray line), and high (open boxes, dashed line) values of the relative spread (see figure legend for details). The stimulus is a low-rate (T = 10t_d) pulse train consisting of 100 pulses. The pulse amplitude A is expressed in the units of Eq. (1) and the firing rate (R) is expressed as the fraction of stimulus pulses eliciting a spike (N_spike/N_pulse). Sigmoidal curves represent two-parameter least-square fits of the cumulative Gaussian function expressed in terms of the error function . The inflection point of the sigmoid is determined by the parameter A_50% and the sigmoid’s width by σ_out. B The relative spread as a function of the input noise level (σ_in). Points represent the mean of five trials and the error bars indicate the standard deviation. A linear least-squares fit constrained to go through the origin is represented by the straight line. The best-fitting slope is 1.2332. The residuals about this fit are shown in the inset panel. The estimate of the uncertainty in the RS is