Aging/ Psychophysical Estimates of Cochlear Nonlinearity

老年听众的语音清晰度往往比年轻听众差，尤其是在有噪音的情况下。尽管与年龄相关的听力敏感性降低可能有助于这一发现，但最近的科学研究表明，即使在没有临床上显着的听力损失的情况下，也可能存在年龄引起的阈上听觉处理缺陷。具体来说，衰老可能导致耳蜗非线性的减少，这反过来可能对阈上处理产生不利影响。耳蜗非线性被认为反映了耳蜗外毛细胞的功能，是高灵敏度、尖锐的频率调谐和通过抑制增强的频谱对比的原因。因此，任何非线性程度的降低都可能导致一种或多种功能缺陷，可能包括言语可理解性受损。本研究的长期目标是进一步了解老年听众的听觉加工过程。特别地，本项目将评估听力正常和轻度至中度听力损失的年轻和老年听众耳蜗非线性的多种心理物理估计。对于所有提议的实验，将检查两个不同的信号频率，一个相对较低，一个相对较高；这些频率区域的非线性处理强度通常不同，因此年轻听众和老年听众之间的差异可能在更高的频率上更大。因此，本研究的目的是在同一组受试者中检查耳蜗非线性的多种测量方法，以确定是否存在与年龄相关的非线性下降。最终目的是为了更好地理解老年听众所经历的听力困难。

Elderly listeners often experience poorer speech intelligibility than younger listeners, particularly in the presence of noise. Although an age- related reduction in hearing sensitivity likely contributes to this finding, recent scientific research suggests that an age-induced deficit in suprathreshold auditory processing may be present even in the absence of clinically significant hearing loss. Specifically, aging may result in a reduction in the cochlear nonlinearity which in turn may adversely affect suprathreshold processing. The cochlear nonlinearity, which is thought to reflect the functioning of the outer hair cells in the cochlea, is responsible for high sensitivity, sharp frequency tuning, and enhanced spectral contrasts via suppression. Thus, any reduction in the magnitude of the nonlinearity may result in one or more functional deficits, possibly including impaired speech intelligibility. The long-term goal of the proposed research is to further our understanding of the auditory processing of elderly listeners. In particular, this project will evaluate multiple psychophysical estimates of cochlear nonlinearity in young and aged listeners both with normal hearing and with mild- to-moderate hearing loss. For all proposed experiments, two different signal frequencies will be examined, one relatively low and one relatively high; these frequency regions may normally differ in their strength of nonlinear processing and thus differences between young and elderly listeners may be greater at the higher frequency. Thus, the purpose of this study is to examine multiple measures of cochlear nonlinearity in the same group of subjects to determine whether or not an age-related decline in the nonlinearity exists. The ultimate goal is to provide a better understanding of the listening difficulties experienced by elderly listeners.