Fig. 2

In vivo physiology of WT and NPC1-KO mice. a-b DP-grams (f2/f1 = 1.2) for mean 2f1–f2 at high (L1 = L2 = 70 dB, a) and moderate (L1 = 50 dB; L2 = 35 dB, b) stimulus levels for WT and NPC1-KO mice at P21–25 (black lines) and P48–54 (red lines). Numbers (n) and sexes of the mice (M, male; F, female) are also indicated. Thin black and red lines are individual traces. In 2B, responses at f2 = 40,910 and 35,625 Hz for older (48–54) mice were significantly reduced (p = 0.03 and 0.0063, respectively) as compared to younger (P21–25) animals. c-f DPOAE input-output functions collected when the level for f1 is 10 dB higher than that for f2 at f2 = 12 kHz (c-d), and f2 = 27 kHz (e-f). DPOAE thresholds for 12 kHz (d) and 27 kHz (f) are also plotted based on the input-output functions in (c) and (e), respectively. Threshold is defined as the level of f1 that generates a DPOAE at 2f1-f2 of 0 dB. The black color indicates data points from P21–25 mice while the red color designates P48–54 mice. At f2 = 27 kHz, DPOAE thresholds of NPC1-KO mice are significantly elevated compared to WT