Perceptual and functional role of medial olivocochlear efferents in humans

项目总结 人们普遍认为，激活内侧橄榄耳蜗区(MOC)传出系统可导致 人类和实验动物的耳蜗增益。在人类中，传出诱导的耳蜗增益减少是 通过测量耳声发射幅度的变化来衡量。因为报告的更改 已经很小，并且由于刺激引起的增益降低的知觉效果被推定为引出 激活一直是难以捉摸的，普遍的观点是，MOC的传出在 日常的听觉处理。这项提议应该会推翻这一观点。这项提议的动机是 在我们的初步实验中观察到MOC传出激活的巨大稳健效应，这利用了 耳声发射测量技术的最新进展以及我们对 刺激频率耳声发射的产生机制。大的生理学 效果将与在相同听众中获得的新的心理物理测量相结合。 在目标1中，我们将探讨最近和高度意想不到的 在我们的实验室中发现了对SFOAE的基于传出的大而持久的影响(大约几秒钟) 这似乎是高频所独有的。我们还将探索对时间的大规模感知揭开 在我们的初步研究中观察到的嵌入在噪声中的音调的幅度调制，时间过程 它表现出类似于对SFOAE的长期传出效应的频率依赖性。这 先前未报告的去掩蔽效应可能具有特殊的功能重要性，因为 最近，噪声中的幅度调制被证明是理解语音的关键。目标2 将刺激频率耳声发射(SFOAE)的新实现与心理声学相结合 提供严格测试耳蜗调优和SFOAE延迟之间的联系的范例，并评估 MOC系统对生理和行为调节的影响。结果应该提供一个明确的 对目前有争议的说法的评估，即人类耳蜗的调谐可能比 这是典型的实验动物。在目标3中，我们将实现一种新的方法来研究调制 注意对MOC传出效应的影响--选择性操纵知觉负荷 以及行为、听觉和视觉任务的认知负荷。 这项研究的结果应该会使我们更好、更完整地了解脑脊液中 人类听觉加工中的MOC传出。通过显示传出激活的相当大的影响 在听力正常的听众中，该提案将强调恢复这些好处的重要性 在听力受损的听众中，包括人工耳蜗者。拟议的实验将提供 关于传出控制耳蜗增益的影响的重要新数据将有助于这种努力并导致新的 在助听器中重建传出驱动的耳蜗增益调制和调谐的算法。

PROJECT SUMMARY It is well accepted that activation of the medial olivocochlear (MOC) efferent system can result in a reduction of cochlear gain in humans and laboratory animals. In humans, efferent-induced cochlear gain reduction is measured by measuring changes in the magnitude of otoacoustic emissions. Because the reported changes have been small and the perceptual effects of gain reduction due to stimuli presumed to elicit efferent activation have been elusive, the general view has been that MOC efferents play a minor (if any) role in everyday auditory processing. This proposal should overturn that view. The proposal has been motivated by large robust effects of MOC efferent activation observed in our preliminary experiments that took advantage of recent improvements in otoacoustic-emission measurement techniques and in our understanding of the mechanisms of the generation of stimulus frequency otoacoustic emissions (SFOAEs). The large physiological effects will be combined with novel psychophysical measures obtained in the same listeners. In Aim 1 we will pursue the phenomenon and functional relevance of a recent and highly unexpected finding in our lab of large and very long lasting (on the order of seconds) efferent-based effects on SFOAEs that seem to be exclusive to high frequencies. We will also explore sizeable perceptual unmasking of temporal amplitude modulation of a tone embedded in noise observed in our preliminary studies, the time course of which exhibits frequency dependence similar to that of the long-lasting efferent effects on SFOAEs. This previously unreported unmasking effect may have particular functional importance, as the processing of amplitude modulation in noise has recently been shown to be crucial for the understanding of speech. Aim 2 combines novel implementations of stimulus-frequency otoacoustic emissions (SFOAEs) with psychoacoustic paradigms to provide rigorous tests of the link between cochlear tuning and SFOAE delay, and to assess the effects of MOC system on physiological and behavioral tuning. The outcomes should provide a definitive assessment of the currently controversial claim that human cochlear tuning may be considerably sharper than that of typical laboratory animals. In Aim 3 we will implement a novel approach to investigating the modulating effect of attention on MOC efferent effects on cochlear responses by selectively manipulating perceptual load and cognitive load of behavioral auditory and visual tasks. The outcomes of the research should result in a refined more complete view of the functional role of MOC efferents in human auditory processing. By showing sizeable effects of efferent activation that benefit perception in normal-hearing listeners, the proposal will underscore the importance of restoring these benefits in hearing-impaired listeners, including cochlear-implant users. The proposed experiments will provide important new data on the effects of efferent control of cochlear gain that will aid such efforts and lead to new algorithms to recreate the efferent-driven modulation of cochlear gain and tuning in hearing-assisting devices.