Fig. 9.

ABR thresholds (A) are a less reliable metric of post-ouabain synaptic survival than suprathreshold ABR amplitudes (B). For 3 control and 12 ouabain-treated ears, ABR data were obtained at 8, 16, and 32 kHz and then the ears were processed to count IHC synapses in the same three cochlear regions. Synaptic counts and ABR data are normalized to the mean data at the same frequency region from the control ears. ABR amplitudes are for wave 1 measured in response to tone pips at 80 dB SPL. Two ouabain-treated cases with near-normal ABR thresholds are indicated by the encircled points in each panel: both of these had 1 month posttreatment survival.