Aging/ Psychophysical Estimates of Cochlear Nonlinearity

老年听众的言语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度下降可能是这一发现的原因，但最近的科学研究表明，即使在没有临床上显著听力损失的情况下，也可能存在年龄诱导的阈值上听觉处理缺陷。具体地说，老化可能会导致耳蜗非线性度的降低，这反过来可能会对阈值上的加工产生不利影响。耳蜗非线性度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而增强的光谱对比度的原因。因此，非线性程度的任何降低都可能导致一个或多个功能缺陷，可能包括语音清晰度受损。这项拟议研究的长期目标是加深我们对老年听者听觉处理的理解。特别是，该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者对耳蜗非线性度的多种心理物理估计。对于所有建议的实验，将检查两种不同的信号频率，一个相对较低，一个相对较高；这些频率区域通常可能在非线性处理的强度上有所不同，因此年轻人和老年听者之间的差异可能在较高的频率上更大。因此，这项研究的目的是在同一组受试者中检验多项测量的耳蜗非线性度，以确定是否存在与年龄相关的非线性度的下降。最终目的是为了更好地了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.