PL is supported by an increasing separation of the warn and safe FR distributions. (A) Warn (−9-dB AM) and safe (unmodulated) FR distributions from one representative multiunit show increasing separation during training. sp, spikes. (B) Perceptual training increases FR ratios across the population (−12 dB: H = 59.2, P < 0.0001; −9 dB: H = 65.8, P < 0.0001). (C) Perceptual training does not affect CV [unmodulated: H = 3.61, P = 0.73; −12 dB: H = 5.12, P = 0.53; −9 dB: H = 7.25, P = 0.30]. In B and C, n = 231 (range: 29 to 39 sites per d; SI Appendix, Table S1).