How does the efferent auditory system function in the neural encoding and perception of speech-in-noise?

描述（由申请人提供）：严重的理解噪音中的言语困难会导致社交退缩，抑制学业成就，并限制受影响者的职业机会。令人费解的是，有些人尽管听力正常，但在理解噪音中的言语方面存在严重困难，比如正常的老年人和患有阅读、语言、听觉处理和学习障碍的儿童。这些人的噪音言语缺陷的神经生物学基础目前尚不清楚，这限制了对这种听力障碍的评估和有针对性的治疗。传出听觉系统是听觉神经系统的一个分支，当听觉信息从内耳传到大脑时，传出听觉系统被认为对其进行微调和过滤。这个系统已经在动物身上进行了广泛的研究，但对人类在语音噪声处理过程中如何工作却知之甚少。一些证据表明，传出听觉系统的选择性功能障碍可能导致严重的噪音听力困难，而听觉灵敏度却完好无损。本研究旨在探讨人类传出听觉系统的一种特殊机制——内侧耳蜗束（medial olivocochlear， MOC）在正常听力成人和儿童噪声语音的神经编码和感知中的作用。MOC束是一种传出神经回路，已被证明在动物内耳水平上过滤和抑制背景噪声。这种过滤器可能允许更少的噪声被转录成神经编码，从而提高在竞争背景噪声中听觉信号的感知能力。目前尚不清楚人类MOC反射是否：a)是一种重要的输出机制，可以减少噪音对自下而上的语音神经编码的影响；b)由自上而下的过程（如主动倾听）调节，以增强噪音中的听力。这些问题将在两份研究报告中讨论。第一项研究将包括测量MOC反射激活过程中听神经和脑干的言语诱发神经活动，以确定这种反射是否改善了噪声中言语的神经编码。假设MOC反射的激活会在听神经和脑干水平上改善噪声中言语的神经编码。在第二项研究中，参与者将在进行MOC反射的同时积极地听一个听觉Stroop任务，以确定认知需求是否调节MOC反射。假设听觉Stroop任务中更具挑战性的听力条件对MOC反射强度的影响更大，表明大脑与内耳之间存在调节关系。本研究的结果阐明了传出系统在噪音语音处理中的作用，并可用于为理解噪音语音严重困难的个体创建有针对性的治疗和客观评估。

DESCRIPTION (provided by applicant): Severe difficulty understanding speech-in-noise causes social withdrawal, inhibits academic achievement, and limits vocational opportunities for those affected. Inexplicably, there are individuals who experience severe difficulty understanding speech-in-noise despite having normal hearing sensitivity, such as normally aging adults and children with reading, language, auditory processing, and learning disorders. The neurobiological basis of speech-in-noise deficits in these individuals is currently unknown, which limits evaluation and targeted treatment of this hearing disability. The efferent auditory system is the division of the auditory nervous system that is believed to fine-tune and filter auditory information as it ascends from the inner ears to the brain. This system has been studied extensively in animals, but far less is known about how it works in humans during speech-in-noise processing. Some evidence suggests that selective dysfunction in the efferent auditory system may cause severe difficulty hearing in noise while leaving hearing sensitivity intact. The proposed research investigates the function of one specific mechanism of the human efferent auditory system, the medial olivocochlear (MOC) bundle, in the neural encoding and perception of speech-in-noise in normal hearing adults and children. The MOC bundle is an efferent neural circuit, which has been shown to filter and suppresses background noise at the level of the inner ear in animals. This filter may allow less noise to be transcribed into neural code, which in turn improves perception of auditory signals in competing background noise. It remains unclear if the human MOC reflex is: a) an important efferent mechanism that reduces the effect of noise on the bottom-up neural encoding of speech, and b) modulated by top-down processes, such as active listening, to enhance hearing in noise. These issues will be addressed in two studies. The first study will involve measurements of speech-evoked neural activity from the auditory nerve and brainstem during MOC reflex activation to determine if this reflex improves the neural encoding of speech-in-noise. It is hypothesized that activation of the MOC reflex will improve the neural encoding of speech-in-noise at the level of the auditory nerve and brainstem. In the second study, participants will actively listen to an Auditory Stroop Task while the MOC reflex is engaged to determine if cognitive demands modulate the MOC reflex. It is hypothesized that more challenging listening conditions of the Auditory Stroop Task will have a greater impact on MOC reflex strength, indicating a modulatory relationship between the brain and inner ears. The outcomes of this research clarify the role of the efferent system in speech-in-noise processing and can be used to create targeted treatments and objective assessments for individuals with severe difficulties understanding speech-in-noise.