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

描述(申请人提供)：本项目的长期目标是研究外周听觉功能在成熟和衰老过程中的变化，并研究这些变化与伴随的听觉感知变化之间的关系。具体地说，我们将：(1)定义失真产物耳声发射(DPOAE)精细结构和组成失真产物的单个组件的成熟和老化的时间进程；(2)定义内侧橄榄耳蜗(MOC)反射的成熟和老化的时间进程；(3)将观察到的外周听觉生理学变化与人类一生中言语感知的变化联系起来。过去的工作已经证实，听觉系统中的外周不成熟在出生后就存在，但成熟的时间进程还没有确定，这种不成熟的来源也没有完全明确。这个项目中的实验将使我们能够完成成熟的时间线，通过研究系统多个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。这些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周围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来源的相对贡献：DPOAE产生区和DP特征频率(CF)区。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。目前还没有发表关于婴儿DPOAE精细结构的研究，尽管这个问题可能与耳蜗成熟问题高度相关。第二个目标将通过实施DPOAE对侧噪声技术来实现，以在三个频率上测量相同八个年龄组的MOC反射。这一范式将考虑每个受试者各自的DPOAE精细结构模式，并仅记录反应峰值(Maxima)的MOC反射，以控制DPOAE成分在成熟和老化期间的关系。第三个目标将通过测量噪声中的言语知觉以及前面描述的两个外围听觉功能指标来实现，在青少年到老年受试者中。这项实验将考察外周的变化和交流能力之间的关系，并确定一生中听觉外周生理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相关，因为它将为听觉外周功能从出生到老年的变化提供一个规范的框架。此外，在儿科人群中确定DPOAE的精细结构将有助于明确在常规DPOAE听力测试中评估哪些耳蜗区，从而有可能提高儿童听力诊断的准确性。最后，这个项目将导致更清楚地了解听觉外周功能的自然变化如何导致晚年言语感知的减弱，并将有助于解析外周和中枢对这种下降的影响。这项工作将为成熟和老化过程中听觉外周功能的自然变化提供一个标准化框架，并将有助于指定在使用耳声发射进行常规儿科听力评估期间实际评估哪些耳蜗区(和频率)。这些信息有可能增加听力评估的复杂性和准确性，从而增加后续干预的复杂性和准确性。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在生命的最后几十年导致言语知觉的减弱，并帮助解析外周和中枢对这种下降的影响。

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.