Supplementary Figure 4: Rates of click trains used in click rate discrimination task.

Four ferrets were trained in the click rate discrimination task (CLR-D). Two ferrets were trained to discriminate high rate Warning click trains (16–48 Hz) from low Safe click trains (4–24 Hz), and two ferrets in the opposite rate discrimination direction (low rate Warning and high rate Safe click trains). The slightly overlapping distribution of click rates for the two classes of high and low rates is shown in Panel A. The minimum rate difference between Safe and Warning click trains was 7 Hz, while the maximum was 32 Hz. The distribution of high-to-low click rate ratios used in every behavioral block is shown in Panel B. The mean (± SD) ratio used was 3.2 ± 1.09. Panel C: In the passive condition, we measured best click rates for neurons in A1 (N=92), dorsal PEG (N=182), and VPr (N=478) that were presented with click trains with rates of 4–60 Hz. These data include responses from neurons in both naïve and trained animals, and clearly indicate that neurons at multiple levels of auditory cortex (A1, dorsal PEG and VPr) respond to a wide range of click rates.