DEVELOPMENT OF PERIPHERAL AUDITORY NONLINEARITIES

尽管关于非线性特性已经知道很多， 对于成年脊椎动物的外周听觉系统， 关于他们的发展。 最近的实验结果表明， 在哺乳动物的早期阶段，转导动力学是线性的， 发展和成人特征的获得发生 对于简单形式的刺激（即，音调刺激），同时 耳蜗分化的最后阶段。 耳蜗 非线性，另一方面，除了后来出现在 出生后的生活，需要更长的时间来成熟，比做简单的反应 功能. 我们假设，非线性响应特性的 外周听觉系统在出生后第一周末出现， 其作用机制与频率无关， 由双音同时发展的出现表明 听神经特征频率上下抑制 跨越听力范围的纤维 我们还假设双音 抑制和互调失真产品协同发展 与其他耳蜗现象，如调谐，并建议使用收敛 方法（即，个体听神经纤维的傅里叶分析 反应和畸变产物耳声发射）来识别 将不同的非线性现象联系起来的共性。 非常 人们对水平依赖关系的发展知之甚少 在耳蜗失真产物中，我们假设它们是 复杂，反映了动态频率的发展收购， 水平特性的周边听觉功能一般。 失真 产品耳声发射将用于实现目标 与这方面的研究有关。 我们还假设 听觉功能更容易受到能量消耗和/或 在开发早期阻止操作，并计划实验性地 在不同阶段操纵能量依赖性耳蜗过程， 通过全身呋塞米给药机构， 和缺氧。 这些药剂破坏主动耳蜗力学， 建议实验的目的是识别年龄依赖性 这些操纵行为所揭示的差异。 最后， 拟议研究的目的是扩大我们对 外周听觉非线性在耳蜗处理中的作用 成年和未成年的哺乳动物，以及形成一个基础， 针对先天性耳聋相关临床问题的研究， 关键期间暴露于环境危害的后果 发展时期。

Although a great deal is known about the nonlinear characteristics of the peripheral auditory systems of adult vertebrates, very little is known about their development. Results from recent experiments indicate that transduction dynamics are linear during the early stages of mammalian development and that the acquisition of adultlike characteristics occurs rapidly for simple forms of stimulation (i.e., tonal stimuli), coinciding with the final stages of cochlear differentiation. Cochlear nonlinearities, on the other hand, in addition to appearing later in postnatal life, require longer to mature than do more simple response features. We hypothesize that nonlinear response properties of the peripheral auditory system arise near the end of the first postnatal week, and that their mechanism(s) of action is independent of frequency, as indicated by the simultaneous developmental appearance of two-tone suppression above and below the characteristic frequency of auditory nerve fibers spanning the audiometric range. We also hypothesize that two-tone suppression and intermodulation distortion products develop in concert with other cochlear phenomena, like tuning, and propose to use converging methods (i.e., Fourier analysis of individual auditory nerve fiber responses and distortion product otoacoustic emissions) to identify commonalities linking otherwise disparate nonlinear phenomena. Very little is known about the development of level-dependent relationships among cochlear distortion products and we hypothesize that they are complex, reflecting the developmental acquisition of dynamic frequency and level properties of peripheral auditory function in general. Distortion product otoacoustic emissions will be employed to accomplish objectives associated with this aspect of proposed research. We also hypothesize that auditory function is more susceptible to energy-depleting and/or blocking actions early in development and plan to experimentally manipulate energy-dependent cochlear processes at various stages of development, through the agencies of systemic furosemide administration and hypoxia. These agents disrupt active cochlear mechanics, and the purpose of proposed experiments is the identification of age-dependent differences revealed by the actions of these manipulations. Ultimately, the purpose of the proposed research is to extend our understanding of the role of peripheral auditory nonlinearities in cochlear processing in adults and immature mammals, as well as to form a basis for future research targeting clinical issues related to congenital deafness, and the consequences of exposure to environmental hazards during critical developmental periods.