MORPHOLOGY AND CONNECTIONS OF THE SPIRAL GANGLION

本申请中提出的实验解决了特定的问题 与婴儿出生后听觉外周成熟有关的 猫。这些研究将提供关于 Corti发育器官的形态及有关解剖细节 耳蜗螺旋神经节细胞投射的发育 正常和耳聋动物的耳蜗核。细胞化学 神经束追踪和单纤维标记(BRP)技术 结合生理记录和广泛光照的标记 在这些研究中将使用电子显微镜分析。其中 目标如下：1)绘制儿童出生后发育图 用HRP微量注射法将螺旋神经节投射至中央核团 螺旋神经节，并确定精炼等频板是否 出生时和/或在成人听觉发育之前就存在 阈值。2)确定耳蜗核投射模式 保持静止，或经历深刻的地形重塑 耳毒性药物所致耳聋的感觉剥夺。3)审查 慢性电刺激对组织的影响 CN投影，从而确定解剖重塑是否 预测是频率选择性显著丧失的根本原因 新生儿电刺激产生听觉中脑的研究 耳聋的猫。4)确定老年人自发活动的性质 新生儿耳聋猫的听神经，从而评估它是如何 可能有助于建立正常的立体声 CN的组织。5)探索罢工背后的机制 神经节细胞与Corti器官形态的差异 耳毒性药物致新生儿耳聋后观察到的变性。6) 特异生后胚胎超微结构特征的研究 猫耳蜗体的发育位置由成体决定 基底膜的频率图。7)关联功能 个体、生理特征的听神经发育 具有Corti器官发育形态特征的纤维 单个标记神经元支配的耳蜗区。 这项拟议的工作将增加我们对解剖学 开发中的信息处理机制框架 外周听觉系统，应该是许多人非常感兴趣的 调查人员。对耳聋动物的研究解决了重要的问题 关于听觉系统的敏感期和可塑性，以及 具有实际意义的有效性和最优化 儿童人工耳蜗植入术。

The experiments proposed in this application address specific questions relating to the postnatal maturation of the auditory periphery in the cat. These studies will provide fundamental new information about the morphology of the developing organ of Corti and about anatomical details of the development of cochlear spiral ganglion cell projections to the cochlear nuclei (CN) in normal and deafened animals. Cytochemical labeling (BRP) techniques for neuronal tract tracing and single fiber labeling combined with physiological recording and extensive light and electron microscopic analyses will be employed in these studies. Among the objectives are the following: 1) To map the postnatal development of spiral ganglion projections to the CN utilizing HRP microinjections into the spiral ganglion, and to determine if refined isofrequency laminae are present at birth and/or prior to the development of adult auditory thresholds. 2) To determine if cochlear nucleus projection patterns remain static, or undergo topographic remodeling following profound sensory deprivation from ototoxic drug-induced deafness. 3) To examine the consequences of chronic electrical stimulation upon the organization of CN projections, and thus to determine if anatomical remodeling of projections underlies the striking loss of frequency selectivity in the auditory midbrain produced by electrical stimulation in neonatally deafened cats. 4) To determine the nature of spontaneous activity in the auditory nerve of neonatally deafened cats, and thus to assess how it might contribute to the establishment of the normal tonotopic organization of the CN. 5) To explore mechanisms underlying the striking disparity between patterns of ganglion cell and organ of Corti degeneration observed following neonatal deafening by ototoxic drugs. 6) To characterize specific ultrastructural features of postnatal development of the cat cochlea at locations defined by the adult frequency map of the basilar membrane. 7) To correlate the functional development of individual, physiologically-characterized auditory nerve fibers with the morphologic features of organ of Corti development at cochlear locations innervated by individual labeled neurons. This proposed work will increase our understanding of the anatomical framework for information processing mechanisms in the developing peripheral auditory system and should be of critical interest to many investigators. Studies in deafened animals address important questions regarding sensitive periods and plasticity in the auditory system, and have practical implications regarding the efficacy and optimization of cochlear implants in children.