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. 2009 Jun 24;29(25):7991–8004. doi: 10.1523/JNEUROSCI.0632-09.2009

Figure 1.

Figure 1.

CPX I−/− mice are hearing impaired. A, B, ABR audiograms with average thresholds ± SEM of CPX I−/− (gray) and CPX I+/+ (black) littermate mice. The asterisks denote data points with significant threshold differences (*p < 0.05,**p < 0.001, unpaired t test). A, Three- to 4-week-old CPX I−/− mice showed a significant but mild increase of ABR threshold in the midfrequency range. B, Hearing impairment of CPX I−/− mice was more prominent at 6–10 weeks of age [n (CPX I−/−) = 7; n (CPX I+/+) = 9]. The empty squares in B represent the mean ASSR threshold for a 12 kHz tone that was sinusoidally amplitude modulated using individually chosen modulation frequencies >400 Hz (see F). C, D, Average ABR waveforms of individual mice in response to 80 dB click stimuli in animals aged 3–4 weeks (C) [n (CPX I−/−) = 6; n (CPX I+/+) = 5] or 6–10 weeks (D) [n (CPX I−/−) = 8; n (CPX I+/+) = 11]. The bold overlaid traces represent grand averages. E, ASSR, The mean modulation transfer functions (at 80 dB SPL) of 8-week-old CPX I−/− mice (n = 5) showed reduced ASSR amplitudes for all modulation frequencies when compared with the CPX I+/+ littermates (n = 5). F, Amplitude growth functions of ABR wave I and the ASSR peak (individually chosen modulation frequencies between 200 and 400 Hz) of 8-week-old CPX I−/− mice were shifted toward higher stimulation levels but showed comparable slopes as those of the CPX I+/+ littermates. G, DPOAEs at 2f1-f2 were recorded at different primary tone frequencies at stimulus levels of 60 dB and are displayed relative to the noise floor (n = 8 each). H, Growth functions of DPOAE amplitude (n = 7 each; displayed relative to the noise floor) in response to 10/12 kHz primary tones at varying levels. No significant differences in DPOAE levels across frequencies or amplitudes were observed between CPX I−/− and CPX I+/+ mice.