CLINICAL MEASURES OF AUDITORY LINEAR/NONLINEAR PROCESSES

临床听力学的一个普遍发现是，听力图相似的听力受损听者在言语感知方面的表现不同，他们从放大中获得的好处也不同。听力受损的听者缺乏同质性的一个原因是，听力图只能提供对耳蜗病理的粗略估计。有可能听力受损的听者在其潜在的耳蜗病理上有所不同，纯音阈值缺乏区分个体的敏感性。耳蜗病理改变了耳蜗的传导过程。机械-电转导过程的改变，要么直接通过毛细胞结构的改变，要么间接通过毛细胞转导所依赖的结构。表征这些过程的客观测量将描述耳蜗障碍的生理后果，并提供比目前可用的更准确的感觉神经性听力损失描述。本研究的长期目标是开发耳蜗转导的临床测量方法，为基于潜在病理生理学的感觉神经性听力损失提供一种新的分类方案。随着毛细胞再生和基因治疗的未来发展，这些信息将有助于将治疗药物靶向生理部位，以及为助听器和人工耳蜗开发新的信号处理算法。描述耳蜗传导过程的指标是通过应用于耳蜗电位的基于工程的非线性系统识别程序和应用于畸变产物耳声发射的建模方法来估计的。本研究的一个具体目的是确定最佳信号参数，以获得人类耳蜗转导的指标。在动物模型中，目的是确定中耳传递功能对耳蜗转导过程的影响，并确定耳蜗转导指标的敏感性和特异性，以区分永久性听力损失耳的耳蜗病理。

A common finding in clinical audiology is that hearing-impaired listeners with similar audiograms perform differently on measures of speech perception and differ in the benefits they receive from amplification. One reason for the lack of homogeneity among hearing-impaired listeners is that the audiogram provides only a rough estimate of cochlear pathology. It is possible that hearing-impaired listeners differ in their underlying cochlear pathology and pure-tone thresholds lack the sensitivity to distinguish individuals. Cochlear pathology alters cochlear transduction processes. Mechano-electric transduction processes are modified, either directly through changes in hair cell structure, or indirectly through structures on which hair cell transduction relies. An objective measure that characterizes these processes will describe the physiologic consequences of cochlear disorders and supply a more accurate description of sensorineural hearing loss then presently available. The long term goal of this research is to develop clinical measures of cochlear transduction to provide a new categorization scheme of sensorineural hearing loss based on the underlying pathophysiology. With future developments in hair cell regeneration and gene therapy, this information will be useful for targeting therapeutic agents towards physiologic sites as well as for developing new signal processing algorithms for hearing aids and cochlear implants. Indices describing cochlear transduction processes are estimated from an engineering-based nonlinear systems identification procedure applied to cochlear potentials and from a modeling approach applied to distortion product otoacoustic emissions. One specific aim of this research is to determine the optimal signal parameters to obtain indices of cochlear transduction in humans. In an animal model, the aims are to determine the influence of the middle ear transfer function on cochlear transduction processes, and to determine the sensitivity and specificity of cochlear transduction indices to distinguish cochlear pathology in ears with permanent hearing loss.