STRUCTURAL BASIS OF CENTRAL HEARING MECHANISMS

(改编自申请人的摘要。)这项提议的目标是 确定中枢听觉通路的结构组织 处理双耳信息。传入神经的功能类型 投射到下丘中央核的投射相当 不同的，单个IC神经元整合信息是可能的 从许多传入来源。目前没有足够的信息。 关于这些传入的组织，以确定他们的贡献 的接受场属性和其他响应特征 双耳细胞。一种假设是轴突的分布和形态 在等频率平面内是不同的。因此，许多不同的 传入神经的组合将汇聚在突触区域并做出贡献 以响应那些区域中的细胞的属性。第二个假设是 传入同频区域的相对空间关系 核是通过组织投射到 下丘。该拓扑图将提供以下位置代码 双耳功能。 为了解决关于这两个假设的问题，一系列实验 详细说明了到下层的传入连接的组织 本文提出了成年猫的丘状核。具体目标是：1)定义 内侧上叶传入板和单个轴突的几何构型 使用整体和单个轴突顺行向IC投射橄榄核 追踪方法；2)比较汇聚轴突系统的几何结构 MSO轴突的组织和共同标记的方法 来自同一断面的多个来源的预测；以及3)至 轴突内标记轴突的分布和形态与 电生理鉴定细胞的响应特性 正在向IC发送轴突。这些结果将导致进一步的假设 轴突相互作用的组织及其与双耳的关系 在IC中进行处理。双耳处理对于声音来说很重要 语音的复杂特征的本地化、编码和 掩蔽和信号检测等现象。改进对 在听力受损的人中，这些功能需要进行以下实验 因为有人提议增加我们对解剖学和 神经处理声音的生理学基础。

(Adapted from the Applicant's Abstract.) The goal of this proposal is to determine the structural organization of central auditory pathways that process binaural information. The functional types of afferents that project to the central nucleus of the inferior colliculus are quite diverse and it is possible that single IC neurons integrate information from many afferent sources. At present there is insufficient information about the organization of these afferents to determine their contribution to receptive field properties and other response characteristics of binaural cells. One hypothesis is that axonal distribution and morphology are heterogeneous within iso-frequency planes. Thus, many different combinations of afferents would converge in synaptic zones and contribute to response properties of cells in those zones. A second hypothesis is that relative spatial relationships in iso-frequency regions of afferent nuclei are preserved by the organization of the projections to the inferior colliculus. The topology would provide a place code for binaural features. To address questions regarding the two hypotheses, a series of experiments detailing the organization of the afferent connections to the inferior colliculus in the adult cat are proposed. Specific aims are: 1) to define the geometry of the afferent sheets and single axons of medial superior olivary projections to the IC using bulk and single axonal anterograde tracing methods; 2) to compare the geometry of converging axonal systems with the organization of the MSO axons with methods to co-label projections from more than one source in the same sections; and 3) to relate the distribution and morphology of intra-axonally labeled axons to response characteristics of electrophysiologically identified cells sending axons to IC. The results will lead to further hypotheses about the organization of axonal interactions and their relationship to binaural processing in the IC. Binaural processing is important for sound localization, coding of complex features of speech sounds and for phenomena such as masking and signal detection. Improving assessment of these functions in hearing impaired individuals requires experiments such as the one proposed to increase our knowledge about the anatomical and physiological basis for neural processing of sound.