STRUCTURE AND FUNCTION OF PARALLEL AUDITORY PATHWAYS

该项目将解决神经元的平行组织问题 中枢听觉系统内的通路。而解剖学上的 听觉系统中存在平行电路的证据令人信服， 这种电路的功能后果尚不清楚。这项研究将 阐明这一回路在中枢听觉处理中的作用。 听觉系统中的神经元可以根据它们的 双耳响应特性。单耳神经元只对声音作出反应 出现在一只耳朵里。双耳神经元可以受到声音的影响 两只耳朵都能听到。这两种类型的神经元都可能参与了 各种听觉功能，但有些行为，如声音 本地化，可能强调一类神经元而不是另一类神经元。单声道 双耳神经元可以在听觉系统的所有层面上找到， 但是，与这些反应相关的解剖细胞类型和回路 都不确定。我们假设那些只对 单耳刺激通过突触连接形成一个或多个 单声道电路。这些单声道电路将有别于 与双耳处理有关的电路。 在本提案中，我们将重点介绍具有单耳的神经元 低位脑干的反应特征。耳蜗核(CN)和 外侧丘脑腹侧核(VNLL)是主要中枢 单耳神经元，两者均投射到下丘(IC)。 尽管这些结构对于理解单声道 在IC和更高中心的响应中，关键数据仍然 缺乏参与这些投射的细胞。因此，目标1是 确定哪些细胞类型参与CN-VNLL-IC电路和 将它们与CN-IC电路中涉及的单元进行比较。轴突 体内转运标记和固定脑内细胞内注射 将使用切片。我们预测不同类型的细胞将 参加每一场巡回赛。双标记实验将确定 如果CN中的相同神经元同时投射到VNLL和IC。最后， 顺行转运和细胞内实验将确定 来自CN的轴突在VNLL内建立的突触连接的性质。 我们预计，特定的突触安排将成为 VNLL的神经纤维膜。 VNLL中的单声道反应归因于来自 对侧丘脑核和上橄榄核的输入缺乏 很复杂。几乎没有关于VNLL的生理数据来证实它 陆生哺乳动物的单耳特性。因此，AIM 2是为了 描述觉醒的VNLL中的单元的响应特性 兔子。我们预计VNLL中的大多数细胞将是单耳的；然而， 他们的反应可能与CN中的不同。

This project will address the organization of neurons into parallel pathways within the central auditory system. While the anatomical evidence for parallel circuitry in the auditory system is compelling, the functional consequences of this circuitry are not known. This study will elucidate the role of this circuitry in central auditory processing. Neurons in the auditory system can be classified according to their binaural response properties. Monaural neurons respond only to sounds presented in one ear. Binaural neurons can be effected by sounds delivered to both ears. Both types of neuron may be involved in a variety of auditory functions, but some behaviors, like sound localization, may emphasize one class of neuron over another. Monaural and binaural neurons can be found at all levels of the auditory system, but, the anatomical cell types and circuits related to these responses are not certain. We hypothesize that cells which respond only to monaural stimulation are synaptically connected to form one or more monaural circuits. These monaural circuits would be distinct from circuits concerned with binaural processing. In the present proposal, we will focus on the neurons with monaural response features in the lower brain stem. The cochlear nucleus (CN) and ventral nucleus of the lateral lemniscus (VNLL) are major centers with monaural neurons, and both project to the inferior colliculus (IC). Despite the importance of these structures for understanding monaural responses in the IC and in higher centers, critical data are still lacking on the cells involved in these projections. Therefore, AIM 1 is to determine which cell types participate in the CN-VNLL-IC circuit and compare them to the cells involved in the CN-IC circuit. Axonal transport labeling in vivo and intracellular injections in fixed brain slices will be used. We predict that different cell types will participate in each circuit. Double-labeling experiments will determine if the same neurons in the CN project to both the VNLL and IC. Finally, anterograde transport and intracellular experiments will determine the nature of the synaptic connections made in the VNLL by axons from the CN. We anticipate that specific synaptic arrangements will characterize the neuropil of the VNLL. The monaural responses in VNLL are attributed to strong inputs from the contralateral CN and a dearth of inputs from the superior olivary complex. There is little physiological data on the VNLL to confirm its monaural properties in terrestrial mammals. Therefore, AIM 2 is to characterize the response properties of units in the VNLL of the awake rabbit. We anticipate that most cells in VNLL will be monaural; however, their responses may be different from those in the CN.