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)：在噪音中理解语音的严重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，有些人尽管有正常的听力敏感度，但在噪音中理解语音却遇到了严重的困难，例如正常年龄的成年人和儿童，他们有阅读、语言、听觉处理和学习障碍。这些人在噪声中言语障碍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部分，被认为在听觉信息从内耳上升到大脑时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，但人们对它在人类噪声中语音处理过程中是如何工作的知之甚少。一些证据表明，传出听觉系统的选择性功能障碍可能会导致在噪声中严重听力困难，同时保持听力敏感度不变。该研究旨在研究人类传出听觉系统的一种特殊机制--内侧橄榄耳蜗束(MOC)在正常听力成人和儿童对噪声中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较少的噪声被转录成神经代码，这反过来又提高了对竞争背景噪声中听觉信号的感知。目前尚不清楚人类的MOC反射是否是：a)减少噪声对语音自下而上神经编码的影响的重要传出机制，以及b)受自上而下的过程(如主动倾听)调制，以增强在噪声中的听力。这些问题将在两项研究中得到解决。第一项研究将涉及在MOC反射激活过程中测量听神经和脑干的语音诱发神经活动，以确定这种反射是否改善了噪声中语音的神经编码。据推测，MOC反射的激活将在听神经和脑干水平改善噪声中语音的神经编码。在第二项研究中，参与者将主动听一项听觉Stroop任务，同时参与MOC反射，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将对MOC反射强度产生更大的影响，这表明大脑和内耳之间存在调制关系。这项研究的结果阐明了传出系统在噪声中语音处理中的作用，并可用于为理解噪声中语音有严重困难的个人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.