Population properties of the three groups of A1 neurons. A–C, Mean PSTHs of sustained-, On–Off-, and On-response units, respectively. PSTHs of 10, 20, 40, 80, 160, and 320 ms are superimposed to show the effect of stimulus duration on each unit group. Shaded area shows SE. D–F, Mean duration tuning function averaged over each group. Shaded area shows SE. Dotted line is the mean level of 2 SDs of background firing. G–I, Mean neurometric function averaged over each group. Dots show SD. Horizontal line is the level of 0.75.