The level of noise-induced ABR threshold shifts is correlated with the level of pre-noise cochlear dysfunction in Prestin-CreER^T2 homozygous mice.

<p><b>A</b> A scatter plot shows significant individual variation in the levels of the threshold shifts of ABRs examined at 2 h post-noise exposure in the ears of Prestin-CreER^T2 homozygous mice. The three horizontal lines in each frequency indicate the mean and ± standard deviation. The curve line represents the distribution curve of the data. One dot represents the averaged threshold of one ear from the thresholds of the four tested frequencies (5, 10, 30 and 40 kHz). <b>B</b> Correlation between the average pre-noise thresholds and post-noise threshold shifts of ABRs in the Prestin-CreER^T2 homozygous mice. There is a negative correlation between the two variables (Pearson's correlation analysis, <i>r</i> = −0.92, <i>p</i><0.001), indicating that, with the increase in the level of pre-noise hearing dysfunction, the noise-induced threshold shift decreases. <b>C</b> Comparison of the magnitude of individual variation in ABR thresholds, measured before and after the acoustic overstimulation in the Prestin-CreER^T2 homozygous mice. One dot represents the threshold of one ear, as averaged from the thresholds of the four tested frequencies. The horizontal lines represent the means of the average ABR thresholds. Notice that the level of individual variation became smaller after the noise exposure. <b>D</b> Comparison of the levels of the two-ear difference in the ABR thresholds examined before and after the acoustic overstimulation. The levels of difference are significantly reduced after the acoustic trauma (two-way ANOVA, <i>F_{1, 120}</i> = 41.47, <i>P</i><0.001; *** indicates <i>P</i><0.001 and ** indicates <i>P</i><0.01 tested by Tukey test). n: the number of ears used for each condition.