Peripheral Auditory System Function in Humans: Continuum of Maturation and Aging

描述（由申请人提供）：本项目的长期目标是研究成熟和衰老过程中外周听觉功能的变化，以及这些变化与听觉感知变化之间的关系。具体而言，我们将：(1)确定畸变产物耳声发射（DPOAE）精细结构及其组成畸变产物的各个组成部分成熟和老化的时间过程；(2)确定内侧耳蜗（MOC）反射成熟和老化的时间过程；(3)将观察到的外周听觉生理变化与人类一生中语言感知的变化联系起来。过去的工作已经确定，听觉系统的外周不成熟存在于出生后，但成熟的时间过程尚未确定，也没有完全指定这种不成熟的来源。本项目的实验将使我们完成成熟时间线，通过研究系统多层次的听觉功能来检查不成熟的来源，并考虑这些外围功能的变化如何影响交际能力。该目标将通过实施一种新的方法来实现，该方法将整个人类生命周期中外周听觉功能的变化视为一个连续体，包括成熟和衰老过程。第一个目标将通过测量DPOAE精细结构来解析两个基底膜源的相对贡献：DPOAE发生器区域和DP特征频率（CF）区域。最先进的扫音方法将在从早产儿到老年人的八个年龄组中使用。虽然这一问题可能与耳蜗成熟问题高度相关，但婴儿DPOAE精细结构的研究目前尚未发表。第二个目标将通过实施DPOAE对侧噪声技术来实现，以三个频率测量相同八个年龄组的MOC反射。该范式将考虑每个受试者个体的DPOAE精细结构模式，并仅记录响应峰（最大值）处的MOC反射，以控制成熟和衰老过程中DPOAE成分之间的关系。第三个目标将通过测量青少年到老年受试者在噪声中的语音感知以及前面描述的两种外周听觉功能指标来实现。本实验将研究外周生理学的变化与交际能力之间的关系，并确定听觉外周生理学的变化在多大程度上可以解释感知的变化。这项工作与听力健康和临床实践有关，因为它将为从出生到老年的听觉周围功能变化提供一个规范框架。此外，确定儿童人群的DPOAE精细结构将有助于确定在常规DPOAE听力测试中评估哪些耳蜗区域，从而有可能提高儿童听力诊断的准确性。最后，该项目将使人们更清楚地了解听觉外周功能的自然变化如何导致后期语音感知能力的下降，并将有助于分析外周功能与中枢功能对这种下降的贡献。这项工作将为成熟和衰老过程中听觉周围功能的自然变化提供一个规范的框架，并将有助于确定在常规的儿童听力评估中使用耳声发射实际评估哪些耳蜗区域（和频率）。这些信息有可能提高听力评估的复杂性和准确性，从而提高后续干预的准确性。这项工作还将有助于理解听觉外周功能的自然、终生变化如何导致生命后期几十年的语言感知能力下降，并有助于分析外周功能和中枢功能对这种下降的贡献。

DESCRIPTION (provided by applicant): The long-term goals of this project are to investigate changes in peripheral auditory function during maturation and aging and to investigate the relationship between these changes and concomitant changes in auditory perception. Specifically, we will: (1) define the time course for maturation and aging of distortion product otoacoustic emission (DPOAE) fine structure and the individual components comprising the distortion product, (2) define the time course for maturation and aging of the medial olivocochlear (MOC) reflex and (3) relate the observed changes in peripheral auditory physiology to changes in speech perception throughout the human lifespan. Past work has established that peripheral immaturities in the auditory system exist postnatally but the time course for maturation has not been defined, nor have the sources of this immaturity been fully specified. Experiments in this project will allow us to complete the maturational time line, examine the sources of immaturity by studying auditory function at multiple levels of the system, and consider how these changes in peripheral function impact communicative ability. The objectives will be achieved by implementing a novel approach that considers change in peripheral auditory function throughout the human lifespan as a continuum, including both maturational and aging processes. The first aim will be addressed by measuring DPOAE fine structure to parse out the relative contribution from two basilar membrane sources: the DPOAE generator region and the DP characteristic frequency (CF) region. State-of-the-art swept-tone methodology will be used in eight age groups ranging from premature infants to elderly adults. There are currently no published studies of DPOAE fine structure in infants although this issue may be highly relevant to questions of cochlear maturation. The second aim will be accomplished by implementing a DPOAE contralateral noise technique to measure MOC reflexes in the same eight age groups at three frequencies. This paradigm will take into account each subject's individual DPOAE fine structure pattern and record the MOC reflex at response peaks (maxima) only, to control for the relationship between DPOAE components during maturation and aging. The third aim will be accomplished by measuring speech perception in noise along with the two previously described metrics of peripheral auditory function, in adolescent through elderly subjects. This experiment will examine the relationship between changes in the periphery and communicative ability and define the extent to which changes in auditory peripheral physiology throughout life can account for changes in perception. This work is relevant to hearing health and clinical practice because it will provide a normative framework for changes in auditory peripheral function from birth through old age. Furthermore, defining DPOAE fine structure in the pediatric population will help specify which cochlear regions are evaluated during routine DPOAE hearing tests and, thus, have the potential to increase accuracy of hearing diagnoses in children. Finally, this project will lead to a clearer understanding of how natural changes in auditory peripheral function contribute to diminishing speech perception in latter years and will help parse out peripheral versus central contributions to this decline. This work will provide a normative framework for natural changes in auditory peripheral function during maturation and aging and will help specify which cochlear regions (and frequencies) are actually assessed during a routine pediatric hearing evaluation using otoacoustic emissions. This information has the potential to increase the sophistication and accuracy of hearing evaluations and thus, of subsequent intervention. This work will also lead to an understanding of how natural, lifetime changes in auditory peripheral function contribute to diminishing speech perception during the latter decades of life and help parse out peripheral versus central contributions to this decline.