SYNAPTIC ORGANIZATION OF THE AUDITORY SYSTEM

这项研究将确定神经支配模式和突触 组织的双耳和单声道处理的基础， 听觉脑干 本提案将具体侧重于 双耳听觉的基础通路， (CN)经上级橄榄复合体到达下丘 （SOC）。 每个实验将使用细胞内样顺行填充 和/或在脑切片中的经鉴定的神经元的细胞内注射。 每个实验将确定结构/功能关系， 内侧上级橄榄（MSO），在IC中，或在覆盖物升 通往IC的道路 目标1. 为了确定MSO的神经支配和突触组织是如何 创建双耳时间灵敏度。 神经回路从 将可视化MSO的前腹CN（AVCN）。 实验 将：（A）用葡聚糖完全填充AVCN的轴突， 完全重建他们对SOC的投射。（B）用大脑 切片填充MSO中轴突投射到IC的神经元，并研究 它们的神经支配通过用葡聚糖标记的AVCN轴突。 可能存在 在轴突分支，长度，直径， 髓鞘形成和可能构成延迟线机制的地形。 目标2. 为了确定MSO如何传递壁间时间差， (ITD)信息到IC。 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 的IC可以发挥重要作用，在保持ITD的灵敏度。 到 测试：（A）在MSO中注射顺行标记物将 确定到IC的投影的形貌。 IC的记录 体内的神经元将把反应与MSO的终末场联系起来 轴突 (B)细胞内填充将识别特定的神经元类型， IC和它们由MSO传入的神经支配将在 脑切片制备。 MSO的投影可以提供解剖学上的 IC中方位角的空间图的证据。 这一预测可能是 分离成低频IC的一部分，并且它可以不 类似地支配每种细胞类型。 目标3. 为了确定IC的神经支配和突触组织是如何 将MSO输入与双耳和单耳输入进行集成， 其他来源 将注射两种顺行标记物：一种 第二个在另一个脑干核团。 MSO输入可保留 与来自对侧LSO，对侧AVCN， 和对侧DNLL。 这些实验将证明， 传入系统的覆盖范围，并保持隔离的IC。

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.