SYNAPTIC ORGANIZATION OF THE AUDITORY SYSTEM

这项研究将确定神经支配模式和突触 作为双声道和单声道处理基础的组织 听觉脑干。目前的提案将特别侧重于 双耳听力的基础通路，来自耳蜗核的通路 (CN)经上橄榄复合体至下丘(IC) (SoC)。每个实验都将使用细胞内类顺行填充 和/或对脑片中已识别的神经元进行细胞内注射。 每个实验将确定结构/功能关系在 内侧上橄榄(MSO)，在IC中，或在盖层上升 通向IC的路径。 目的1.确定MSO的神经支配和突触组织 创建双耳时间灵敏度。神经回路来自于 MSO的前腹侧核(AVCN)将被可视化。这些实验 将：(A)向动静脉核的轴突完全填充葡聚糖和 完全重建他们对SOC的预测。(B)动动脑筋 脑片填充轴突投射至中脑内侧核的神经元并进行研究 用右旋糖苷标记的AVCN轴突对它们进行神经支配。可能会有 嘴-尾轴突的分支、长度、直径、 髓鞘形成，以及可能构成延迟线机制的地形。 目的2.确定MSO如何转移校际时差 (ITD)向IC提供信息。从MSO到MSO的地形投影 IC是假设的。在这个目标区域内，突触组织 IC在维持ITD敏感性方面可能起重要作用。至 测试这个：(A)在MSO中注入顺行标记将 确定到IC的投影的地形。IC的录音 活体神经元将把对MSO终末区域的反应联系起来 轴突。(B)细胞内充盈将识别特定类型的神经元 由MSO传入的IC及其神经支配将在 脑片准备。来自MSO的投影可以提供解剖结构 IC中方位角空间地图的证据。这一预测可能是 只隔离到低频IC的一部分，它可能不会 对每种细胞类型进行相似的神经支配。 目的3.建立IC的神经支配和突触组织 将MSO输入与来自的双声道和单声道输入集成 其他消息来源。将进行两个顺行标记的注射：一个 在MSO，第二个在另一个脑干核团。MSO输入可能会保留 与来自对侧LSO、对侧AVCN的其他输入分开， 对侧DNLL。这些实验将证明 输入系统覆盖范围，并在IC中保持隔离。

This research will identify the innervation patterns and synaptic organization that underlie binaural and monaural processing in the auditory brainstem. The present proposal will focus specifically on the pathways that underlie binaural hearing, those from the cochlear nucleus (CN) to the inferior colliculus (IC) via the superior olivary complex (SOC). Each experiment will use intracellular-like anterograde filling and/or intracellular injections of identified neurons in a brain slice. Each experiment will identify structure/function relationships in the medial superior olive (MSO), in the IC, or in the covering ascending pathways to the IC. Aim 1. To determine how the innervation and synaptic organization of MSO create binaural time sensitivity. The neural circuity from the anteroventral CN (AVCN) to the MSO will be visualized. The experiments will: (A) Completely fill the axons from the AVCN with dextran and completely reconstruct their projections to the SOC. (B) Use a brain slice to fill neurons in MSO whose axons project to the IC and study their innervation by AVCN axons labeled with dextran. There may be rostra-caudal differences in axon branching, length, diameter, myelination, and topography that may underlie the delay-line mechanism. Aim 2. To determine how the MSO transfer intermural time differences (ITD) information to the IC. A topographical projection from MSO to the IC is hypothesized. Within this target zone, the synaptic organization of the IC may play an important role in maintaining ITD sensitivity. To test this: (A) Injections of anterograde markers in the MSO will determine the topography of the projection to the IC. Recordings of IC neurons in vivo will relate the responses to the terminal fields of MSO axons. (B) Intracellular filling will identify specific neuron types in the IC and their innervation by MSO afferent will be determined in a brain slice preparation. The projection from MSO may provide anatomical evidence for a spatial map of azimuth in the IC. This projection may be segregated into only part of the low-frequency IC, and it may not innervate each cell type similarly. Aim 3. To establish how the innervation and synaptic organization of IC integrates the MSO inputs with the binaural and monaural inputs from other sources. Injections of two anterograde markers will be made: one in MSO and a second in another brainstem nucleus. MSO inputs may remain separate from other inputs from contralateral LSO, contralateral AVCN, and contralateral DNLL. These experiments will demonstrate which afferent systems coverage and which remain segregated in the IC.