Auditory Function at the Base of the Human Cochlea

描述(由申请人提供)：由于老化和其他破坏性暴露造成的听力损失通常从高频发展到低频。因此，要检测这些渐进性和累积性听力损失以及评估预防或干预策略的能力，需要能够探测高达 人类听觉的最高范围。然而，我们对人类耳蜗基底端基础听觉功能的生理学和力学知识是有限的，高频是在那里编码的。此外，耳声发射(OAEs)是耳道中记录的微弱声音，来自耳蜗内活跃的外毛细胞介导的过程，在高于传统听力范围(8 KHz)的频率下，听力功能客观测量的基本特性和潜在用途相对较少被探索。尤其是高频单音诱发的OAEs，称为刺激频率OAEs(SFOAEs)的报道很少。目前尚不清楚SFOAE的产生机制是否延伸到耳蜗基底端，SFOAE特性与8 kHz以上的耳蜗声状态如何相关，以及到达耳道的SFOAE能量在高频时是否尤其受到中耳传输特性的限制。为了解决这些问题，我们建议(1)确定SFOAE幅度如何与8 kHz以上频率下行为纯音听力阈值的水平和结构相关，以及(2)将SFOAE幅度与一种相关听力测量现象的强度进行比较，这种现象被称为“阈值精细结构”，涵盖了广泛的频率范围。这种精细的结构被认为是当测试音调引起的SFOAE的一部分没有传输到耳道，而是在中耳边界反射回来，从而重新刺激耳蜗时出现的。通过对临床听力正常成人的这些现象的详细研究，我们预计SFOAE幅度将与行为听阈显著相关，并且在存在倾斜阈值配置的情况下将显著降低，这表明SFOAEs高度依赖于耳蜗状态。此外，我们预计SFOAE的幅度和阈值精细结构的强度在8 kHz以上和以下都将以类似的方式发生变化，这表明通过中耳的传播在高频下并不是特别有限。这些结果将为耳声发射产生、耳蜗力学和中耳传导的理论提供重要信息，并将有助于开发基于耳声发射的诊断工具，以评估在常规听力范围以上的频率下的耳蜗功能。

DESCRIPTION (provided by applicant): Hearing loss due to aging and other damaging exposures often progresses from high to low frequencies. The ability to detect these progressive and cumulative forms of hearing loss, as well as to evaluate strategies for prevention or intervention, therefore requires diagnostic tools that are capable of probing cochlear status up to the highest range of human hearing. However, our knowledge of the physiology and mechanics underlying auditory function at the basal end of the human cochlea, where high frequencies are encoded, is limited. In addition, the basic properties and potential utility of objective measures f hearing function, such as otoacoustic emissions (OAEs), faint sounds recorded in the ear canal that originate from active, outer hair cell- mediated processes in the cochlea, have been relatively unexplored at frequencies above the conventional audiometric range (> 8 kHz). In particular, there are few reports of OAEs evoked by single tones, termed stimulus-frequency OAEs (SFOAEs), at high frequencies. It is unknown whether SFOAE generation mechanisms extend to the basal end of the cochlea, how SFOAE properties are related to cochlear status above 8 kHz, and whether the amount of SFOAE energy reaching the ear canal is especially limited at high frequencies by characteristics of middle-ear transmission. To address these questions, we propose to (1) determine how SFOAE amplitudes are related to the level and configuration of behavioral pure-tone hearing thresholds at frequencies above 8 kHz, and (2) compare SFOAE amplitudes to the strength of a related audiometric phenomenon, termed "threshold fine structure," across a wide range of frequencies. This fine structure is thought to arise when a portion of the SFOAE evoked by the test tone is not transmitted out to the ear canal, but instead is reflected back at the middle-ear boundary, thus re-stimulating the cochlea. Through detailed investigation of these phenomena in clinically normal-hearing adults, we expect that SFOAE amplitudes will be significantly correlated with behavioral hearing thresholds, and will be markedly reduced in the presence of sloping threshold configurations, suggesting that SFOAEs are highly dependent on cochlear status. In addition, we expect that SFOAE amplitudes and the strength of threshold fine structure will co-vary in a similar fashion both above and below 8 kHz, suggesting that transmission via the middle ear is not especially limiting at high frequencies. The results will critically inform theories of OAE generation, cochlear mechanics and middle-ear transmission, and will aid in the development of OAE-based diagnostic tools for assessing cochlear function at frequencies above the conventional audiometric range.