DEVELOPMENT OF PERIPHERAL AUDITORY NONLINEARITIES

尽管人们已经知道了许多关于非线性特性的知识 成体脊椎动物的外周听觉系统，知之甚少 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 发育和成人型特征的获得 快速用于简单形式的刺激(即音调刺激)，同时 伴随着耳蜗分化的最后阶段。耳蜗骨 另一方面，非线性除了在后面的 出生后的生活，需要更长的时间才能成熟，而不是做更简单的反应 功能。我们假设该模型的非线性响应特性 外周听觉系统在出生后第一周接近尾声时出现， 他们的作用机制(S)与频率无关，因为 由双音同时发育的出现来表示的 听神经特征频率以上和以下的抑制 横跨听力测量范围的纤维。我们还假设两个音调 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 响应和失真产物耳声发射)以识别 将原本截然不同的非线性现象联系在一起的共性。非常 人们对水平依赖关系的发展知之甚少 在耳蜗失真产品中，我们假设它们是 复数，反映动态频率和动态频率的发展习得 一般情况下，周围听觉功能的水平属性。失真 将使用产品耳声发射来实现目标 与拟议研究的这一方面相关。我们还假设 这种听觉功能更容易受到能量耗尽和/或 在开发早期阻止操作，并计划进行实验 在不同的阶段操控依赖能量的耳蜗过程 发展，通过全身给药机构速尿 和缺氧。这些药物扰乱了活跃的耳蜗机制，并且 建议实验的目的是确定年龄相关的 通过这些操纵的行为所揭示的差异。最终， 拟议研究的目的是扩大我们对 外周听觉非线性在大鼠耳蜗神经加工中的作用 成年和未成熟的哺乳动物，以及形成未来的基础 针对与先天性耳聋相关的临床问题的研究，以及 在危急时刻暴露于环境危害的后果 发育阶段。

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.