Cochlear neural output is reduced in homozygote transgenic mice, although outer hair cell function can be nearly normal. A, ABR thresholds for a cohort of mice including six wild-type, five hemizygote, and six homozygote ears. Homozygotes and wild types ranged in age from 31 to 149 d; hemizygotes were tested at 138 d. Arrows at 80 dB indicate that, for several homozygotes, there was no response at the highest sound levels tested. B, Comparison of cochlear neural output (assayed by shift in CAP thresholds) versus OHC function (assayed by shift in DPOAE threshold) for two selected homozygote cases. Threshold shifts were computed by averaging the CAP and DPOAE thresholds in the wild-type animals and then subtracting CAP and DPOAE thresholds in each ear from these mean values.