Human Cochlear Function: A Continuum of Maturation and Aging

 描述（由申请人提供）：在人的整个生命周期中，在成熟和衰老的连续过程中，皮质醇功能发生变化。耳声发射（OAE）提供了一个非侵入性的窗口进入耳蜗和驱动这些变化的机制。在这里，我们应用耳声发射来绘制与年龄相关的耳蜗力学变化，并探索新的听力探头的潜力。在目标1中，我们利用新生儿耳朵产生的强大反射，并记录刺激频率（SF）OAE，反射源发射，在新生儿。SFOAE与耳蜗调谐和增益有关，但从未在新生儿中表征，主要是因为它们需要过长的协议来实现足够的信噪比。这个问题是呈现易于处理的新算法，允许快速呈现的刺激作为扫音。我们将首次在一个大型新生儿耳队列中对SFOAE进行表征，并调整创新的扫音算法，以在该年龄组中获得最佳使用。目的2研究新生儿和成人耳蜗的顶端部分，这一区域代表了我们近一半的可听频率范围，但在成熟过程中了解甚少，完全未被探索。在新生儿的耳朵，非成人一样的DPOAE阶段已被观察到的低频信号，我们假设，微妙的不成熟的顶端频率的位置图可能占这些发现。在这里，从反射源和畸变源OAE中寻找会聚证据，记录和建模DPOAE顶端相位图，并对人类颞骨进行组织学分析，以将发育过程中的顶端解剖结构与OAE特征联系起来。耳蜗力学的变化不会在婴儿期后停止;老化的耳朵经历记录的感觉细胞健康和代谢环境的变化，产生耳蜗效率的改变。以耳蜗为基础的缺陷会导致老年听众常见的感知困难。在目标3中，我们假设这样的缺陷之一是耳蜗非线性在老化耳朵的损失，我们定义了如何从中年到衰老的非线性变化的基于OAE的指标。此外，我们假设耳蜗随着年龄的增长变得更加“粗糙”，这可能是因为尽管耳蜗健康状况下降，但它仍然能够产生反射发射。这三个目标适用于不同的实验和理论工具，并开辟新的天地;他们的特点SFOAE在新生儿作为第一步，探索其潜力作为新生儿听力屏幕，探测经常被忽视的顶端一半的人类耳蜗新生儿不成熟，并定义如何耳蜗非线性和OAE生成的变化在老化的耳朵。

 DESCRIPTION (provided by applicant): Cochlear function changes throughout the human lifespan in a continuum of maturation and aging. Otoacoustic emissions (OAE) provide a non-invasive window into the cochlea and the mechanisms driving these changes. Here, we apply OAEs to map age-related shifts in cochlear mechanics and explore the potential for new probes of hearing. In Aim 1 we exploit the robust reflection generated by neonatal ears and record stimulus frequency (SF) OAEs, a reflection-source emission, in newborns. SFOAEs have been linked to cochlear tuning and gain yet have never been characterized in newborns, mostly because of their need for prohibitively long protocols to achieve adequate signal-to-noise ratios. This problem is rendered tractable by novel algorithms allowing for the rapid presentation of stimuli as sweeping tones. We will characterize the SFOAE for the first time in a large cohort of newborn ears and adapt the innovative swept-tone algorithm for optimal use within this age group. Aim 2 studies the apical portion of the newborn and adult cochlea, a region representing nearly half of our audible frequency range, yet poorly understood and wholly unexplored during maturation. In newborn ears, non-adult-like DPOAE phase has been observed for low-frequency signals; we hypothesize that subtle immaturities in the apical frequency-place map may account for these findings. Here, seek converging evidence from reflection- and distortion-source OAEs, record and model DPOAE apical phase maps, and conduct histological analysis of human temporal bones to link apical anatomy to OAE features during development. Changes in cochlear mechanics do not cease after infancy; the aging ear experiences documented changes in the health of its sensory cells and in its metabolic environment, producing altered cochlear efficiency. Cochlear-based deficits contribute to perceptual difficulties common to older listeners. In Aim 3, we hypothesize that one such deficit is the loss of cochlear nonlinearity in the aging ear, and we define how OAE-based metrics of nonlinearity change from middle-age through senescence. Furthermore, we hypothesize that the cochlea becomes more "rough" with aging, possibly accounting for its ability to generate reflection emissions despite declining cochlear health. These three aims apply diverse experimental and theoretical tools and break new ground; they characterize SFOAEs in newborns as a first step in exploring their potential as a neonatal hearing screen, probe the oft-neglected apical half of the human cochlea where neonatal immaturities have been observed, and define how cochlear nonlinearities and OAE generation change in the aging ear.