Development & Connections of Cochlear Spiral Ganglion

这项拟议的研究解决了关于耳蜗和 螺旋神经节向耳蜗核(CN)投射的定位组织的建立。 神经元束示踪结合电生理的细胞化学标记技术(NB和DIL) 将使用记录和大量的定量光学和电子显微镜分析。我们最近 研究表明，从螺旋神经节的基底区到CN的每个亚区的投射 在出生后早期发育过程中经历显著的精炼。前腹侧的投射 当对细分(AVCN)大小进行标准化时，新生儿的AVCN比成年人宽50%以上， 这些神经元的下行侧支投射到背侧(DCN)和腹后部 室旁核(PVCN)的亚群比其成年对应的亚群宽30%。拟议实验的目标包括： 1)进一步研究妊娠晚期地形细化的时机和顺序 和出生后早期向CN各亚区的投射发展。2)检查投影 以确定其CN投射的成熟是否平行于基底部至顶端 科尔蒂器官的成熟。3)完成新生儿耳聋效应的定量研究 在经历了一生严重的听力剥夺后，成年后对CN投射的特异性进行了检查。 4)确定CN预测是否正常发展，或者是否发生重大重组 在发育早期造成螺旋神经节局限性损害的后果。5)确定 CN投射的解剖重构是否是频率选择性明显丧失的基础 由慢性电刺激引起的。6)探索支撑正常的机制 自发性活动(如果有的话)对听神经投射的影响 螺旋神经节。7)研究猫生后发育的超微结构特征 在特定频率位置的科尔蒂器官。拟议中的实验将增加我们对 发育中听觉系统的信息处理机制的解剖学框架和意志 解决有关关键期和可塑性的重要问题。此外，将在以下地点进行的研究 聋人动物对儿童人工耳蜗术的应用具有实际意义。

This proposed research addresses specific questions regarding the development of the cochlea and the establishment of the topographic organization of spiral ganglion projections to the cochlear nuclei (CN). Cytochemical labeling techniques (NB and Dil) for neuronal tract tracing combined with electrophysiological recording and extensive quantitative light and electron microscopic analyses will be employed. Our recent studies have shown that projections from basal sectors of the spiral ganglion to each subdivision of the CN undergo significant refinement during early postnatal development. Projections to the anteroventral subdivision (AVCN) are more than 50% broader in neonates than in adults when normalized for CN size, and the descending collaterals of these same neurons projecting to the dorsal (DCN) and posteroventral (PVCN) subdivisions are 30% broader than their adult counterparts. Goals of proposed experiments include: 1) To further investigate the details of timing and sequence of topographic refinement during late gestation and early postnatal development of the projections to each subdivision of the CN. 2) To examine projections from the apical cochlea to determine if maturation of its CN projections parallels the basal-to-apical maturation of the organ of Corti. 3) To complete quantitative studies of the effects of neonatal deafening upon the specificity of CN projections examined in adulthood after a lifetime of severe auditory deprivation. 4) To determine whether CN projections develop normally or if significant reorganization occurs as a consequence of restricted lesions of the spiral ganglion created during early development. 5) To determine whether anatomical remodeling of CN projections underlies the apparent loss of frequency selectivity induced by chronic intracochlear electrical stimulation. 6) To explore the mechanisms which underlie normal development of the auditory nerve projections by examining the nature of spontaneous activity (if any) in spiral ganglion. 7) To characterize selected ultrastructural features of postnatal development of the cat organ of Corti at specific frequency locations. The proposed experiments will increase our understanding of the anatomical framework for information processing mechanisms in the developing auditory system and will address important questions regarding critical periods and plasticity. In addition, studies to be conducted in deafened animals have practical implications regarding application of cochlear implants in children.