Central auditory pathway of the middle ear reflex

中耳反射的中枢听觉通路

• 批准号: 7068004
• 负责人: DANIEL J. LEE
• 金额: $ 19万
• 依托单位: UNIV OF MASSACHUSETTS MED SCH WORCESTER
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-07-15 至 2008-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7068004
• 关键词: auditory pathways; auditory reflex; brain stem; cochlea; cochlear lesion; ear muscle; electromyography; electron microscopy; electrostimulus; guinea pigs; interneurons; middle ear; motor neurons; neuronal transport; neurotoxins; sensory signal detection; sound

DESCRIPTION (provided by applicant): The goal of this project is to understand the anatomic and physiologic features of interneurons of the mammalian middle ear muscle (MEM) reflex pathway. The neurons of this reflex coordinate the activity of the MEMs to protect the inner ear from intense acoustic stimuli as well as reduce masking. This reflex arc is composed of primary auditory afferents originating in the cochlea, a single or series of interneurons originating in the cochlear nucleus and ultimately synapsing on MEM motoneurons, and efferent fibers of the facial and trigeminal nerves that terminate on the stapedius and tensor tympani muscles, respectively. Although features of primary auditory afferents and the motoneuron efferents have been well characterized, little is known about the reflex interneurons. Which subdivision of the cochlear nucleus contains the reflex interneurons? Is there a single or a series of interneurons from the cochlear nucleus to the facial and trigeminal nuclei? For Aim 1, we will perform focal lesioning studies of the cochlear nucleus using kainic acid, an excitatory neurotoxin. We will correlate focal lesioning of the cochlear nucleus with loss of the MEM electromyography (EMG) response, to determine which division of the cochlear nucleus is involved in the MEM reflex pathway. Since the anatomical cell types of the cochlear nucleus subdivisions are well known, these studies will narrow down the identity of the cochlear nucleus interneurons. For Aim 2, we will examine the cochlear nucleus interneurons by double-injection experiments. We will inject retrograde tracer into either the stapedius or tensor tympani muscles to label their respective motoneurons, and, at the same time, inject an anterograde tracer into the cochlear nucleus to label the interneurons of the MEM reflex. Injections of the cochlear nucleus will be guided by our lesion studies described in Aim 1. Labeled projections from the cochlear nucleus will be identified as interneurons of the MEM reflex if they terminate on labeled MEM motoneurons. Such terminations would reveal a direct connection between the cochlear nucleus and the MEM motoneurons. Overall, the proposed project will improve our understanding of the brainstem connections that comprise the MEM reflex pathway. These findings may provide a basis for refining and extending our interpretation of clinical tests of MEM reflex integrity and brainstem auditory processing in humans.

描述（由申请人提供）：本项目的目标是了解哺乳动物中耳肌（MEM）反射通路中间神经元的解剖和生理特征。这种反射的神经元协调MEM的活动，以保护内耳免受强烈的声学刺激，并减少掩蔽。该反射弧由源自耳蜗的初级听觉传入、源自耳蜗核并最终在MEM运动神经元上突触的单个或一系列中间神经元、以及分别终止于镫骨肌和鼓膜张肌的面神经和三叉神经的传出纤维组成。虽然初级听觉传入和运动神经元传出的特点已经得到很好的表征，反射中间神经元知之甚少。耳蜗核的哪一部分含有反射中间神经元？从耳蜗核到面神经核和三叉神经核是否存在单个或一系列中间神经元？对于目标1，我们将使用海人酸（一种兴奋性神经毒素）对耳蜗核进行局灶性损伤研究。我们将把耳蜗核的局灶性损伤与MEM肌电图（EMG）反应的丧失相关联，以确定耳蜗核的哪一部分参与MEM反射通路。由于耳蜗核亚部的解剖细胞类型是众所周知的，这些研究将缩小耳蜗核中间神经元的身份。目的2：我们将通过双注射实验来研究耳蜗核中间神经元。我们将逆行示踪剂注入镫骨肌或鼓膜张肌，以标记各自的运动神经元，并在同一时间，将顺行示踪剂注入耳蜗核标记MEM反射的中间神经元。耳蜗核的注射将由我们在目标1中描述的损伤研究指导。如果耳蜗核的标记投射终止于标记的MEM运动神经元，则它们将被鉴定为MEM反射的中间神经元。这种终止将揭示耳蜗核和MEM运动神经元之间的直接联系。总的来说，拟议的项目将提高我们对脑干连接的理解，包括MEM反射通路。这些发现可能为我们对人类MEM反射完整性和脑干听觉处理的临床试验的解释提供了基础。