Knowles Hearing Center.
Roxelyn and Richard Pepper Department of Communication Sciences and Disorders, Northwestern University, Evanston IL 60208.
eNeuro. 2018 Dec 26;5(6). doi: 10.1523/ENEURO.0314-18.2018. eCollection 2018 Nov-Dec.
Spontaneous otoacoustic emissions (SOAEs) recorded from the ear canal in the absence of sound reflect cochlear amplification, an outer hair cell (OHC) process required for the extraordinary sensitivity and frequency selectivity of mammalian hearing. Although wild-type mice rarely emit, those with mutations that influence the tectorial membrane (TM) show an incidence of SOAEs similar to that in humans. In this report, we characterized mice with a missense mutation in a gene required for the formation of the striated-sheet matrix within the core of the TM. Mice heterozygous for the Y1870C mutation ( ) are prolific emitters, despite a moderate hearing loss. Additionally, Kimura's membrane, into which the OHC stereocilia insert, separates from the main body of the TM, except at apical cochlear locations. Multimodal SOAEs are also observed in mice where energy is present at frequencies that are integer multiples of a lower-frequency SOAE (the primary). Second-harmonic SOAEs, at twice the frequency of a lower-frequency primary, are the most frequently observed. These secondary SOAEs are found in spatial regions where stimulus-evoked OAEs are small or in the noise floor. Introduction of high-level suppressors just above the primary SOAE frequency reduce or eliminate both primary and second-harmonic SOAEs. In contrast, second-harmonic SOAEs are not affected by suppressors, either above or below the second-harmonic SOAE frequency, even when they are much larger in amplitude. Hence, second-harmonic SOAEs do not appear to be spatially separated from their primaries, a finding that has implications for cochlear mechanics and the consequences of changes to TM structure.
自发性耳声发射（SOAEs）是在没有声音反射的情况下从耳道记录到的，这反映了耳蜗放大的外毛细胞（OHC）过程，这是哺乳动物听觉的非凡灵敏度和频率选择性所必需的。尽管野生型小鼠很少发出 SOAEs，但那些影响到听骨膜（TM）的突变小鼠则显示出与人类相似的 SOAEs 发生率。在本报告中，我们描述了一种在 TM 核心条纹状基质形成所需的基因中出现错义突变的小鼠。杂合 Y1870C 突变（）的小鼠是丰富的发射器，尽管有中度听力损失。此外，Kimura 膜，OHC 纤毛插入其中，与 TM 的主体分离，除了在耳蜗顶端位置。在 小鼠中也观察到多模态 SOAEs，其中能量存在于比低频 SOAE（基频）整数倍的频率处。二次谐波 SOAEs 的频率是基频的两倍，是最常观察到的。这些二次 SOAEs 存在于刺激诱发的 OAEs 较小或在噪声基底的空间区域。在基频 SOAE 频率上方引入高水平的抑制剂会降低或消除基频和二次谐波 SOAEs。相比之下，二次谐波 SOAEs 不受抑制剂的影响，无论是在基频上方还是下方，即使它们的幅度大得多。因此，二次谐波 SOAEs 似乎没有与它们的基频在空间上分离，这一发现对耳蜗力学和 TM 结构变化的后果具有重要意义。
