Figure 7. Impaired sound encoding at afferent IHC synapses.

• A
  All SGNs of Wrb ^fl/fl:Cre ^A mice had spontaneous firing rates (SR) below 20 Hz (P > 0.05, Kolmogorov–Smirnov test).
• B
  Representative tuning curves from Wrb ^fl/fl:Cre ^A and Wrb ^+/+:Cre ^A SGNs indicating preserved active cochlear amplification despite disruption of Wrb in IHCs.
• C
  Normal thresholds at the characteristic frequency (CF) in Wrb ^fl/fl:Cre ^A SGNs.
• D–D″
  Mean poststimulus time histograms (PSTH) ± SEM of Wrb ^fl/fl:Cre ^A and Wrb ^+/+:Cre ^A SGNs in response to 50 ms tone bursts presented at CF, 30 dB above threshold at stimulus rates of 2 Hz (D), 5 Hz (D′), or 10 Hz (D″). While the general response pattern was preserved, spike rates were drastically reduced in Wrb ^fl/fl:Cre ^A SGNs, especially at higher stimulus rates. Data from auditory neurons (SGN and cochlear nucleus) of Otof ^Pga/Pga animals from Pangrsic et al (2010) were replotted for direct comparison.
• E
  Spike rates in response to sound onset (maximum rate in PSTH with 0.5 ms binwidth) and adapted rates (averaged between 35 and 45 ms after stimulus onset) were significantly lower in Wrb ^fl/fl:Cre ^A SGNs (stimulus rate 5 Hz, P < 0.001).
• F
  In line with the reduction in spike rates, first spike latency (FSL) following stimulus onset was greatly increased in Wrb ^fl/fl:Cre ^A SGNs compared to Wrb ^+/+:Cre ^A (stimulus rate 5 Hz, P < 0.001).
• G
  Illustration of the stimulus paradigm for forward masking experiments: a 100‐ms masker tone presented at CF, 30 dB above threshold was followed by a silent interval of variable duration and a 15‐ms probe tone (CF, 30 dB above threshold). Bottom: in Wrb ^fl/fl:Cre ^A SGNs, the response to the first 5 ms of the masker probe tone (shown as a fraction of the response to the first 5 ms of the masker) was strongly reduced, and the half time of recovery (from normalized curves) was increased from 39.2 ± 12.2 ms in Wrb ^+/+:Cre ^A to 215.7 ± 51.2 ms in Wrb ^fl/fl:Cre ^A SGNs (P < 0.001, Mann–Whitney U‐test). Data represent means ± SEM.