SYNAPTIC ORGANIZATION OF THE AUDITORY SYSTEM

下丘（IC）是一个重要的结构，它整合来自下脑干的信号，然后将信息投射到听觉丘脑和皮层。我们建议，IC中的功能区可以通过脑干来源的输入的特定组合来创建。目的1将使用解剖学和生理学的方法在猫识别功能区的IC的基础上三个主要的兴奋性输入。我们将检验同侧内侧上级橄榄（MSO）和对侧外侧橄榄（LSO）的投影在解剖学上分离的假设。我们将表明，MSO和MSO和耳蜗核的输入也定义了单独的功能区。此外，我们还将从生理学上确定与MSO、LSO和耳蜗核输入相关的功能区。目标2将根据兴奋性和抑制性输入的整合来识别IC中的功能区。对IC的抑制性输入产生抑制性边带，并将响应转换为耳间时间差（ITD）。抑制性输入的主要来源是外侧丘系背核（DNLL）、同侧LSO投射和局部抑制性IC神经元。我们将检验同侧MSO和对侧DNLL的投射在IC中具有共同靶点的假设。我们还将表明，从对侧DNLL和同侧LSO的输入不收敛。我们将识别IC中的局部回路神经元。最后，我们将测试的假设，在IC的一些ITD反应将被改变抑制DNLL或抑制性本地IC输入。在目标3中，我们将鉴定IC中的功能细胞类型。我们将证明K+通道的组合或其亚细胞定位与IC中的细胞类型和GABA含量有关。最后，我们将证明具有不同放电模式和全细胞电流的神经元与K+通道和/或GABA表达的不同模式有关。

The inferior colliculus (IC) is a critical structure that integrates signals from the lower brainstem before projecting the information towards the auditory thalamus and cortex. We propose that functional zones in the IC may be created by specific combinations of inputs from brainstem sources. Aim 1 will use anatomical and physiological methods in the cat to identify functional zones in the IC based on three major excitatory inputs. We will test the hypothesis that ipsilateral projects from medial superior olive (MSO) and contralateral projects from the lateral SO (LSO) are anatomically segregated. We will show that the inputs from MSO and MSO and cochlear nucleus also define separate functional zones. Moreover, we will physiologically identify the functional zones related to MSO, LSO, and cochlear nucleus inputs. Aim 2 will identify functional zones in the IC based on the integration of excitatory and inhibitory inputs. Inhibitory inputs to the IC create inhibitory side bands and transform the response to interaural time differences (ITD). Major sources of inhibitory inputs are the dorsal nucleus of the lateral lemniscus (DNLL), the ipsilateral project from LSO, and local inhibitory IC neurons. We will test the hypothesis that the projections from the ipsilateral MSO and the contralateral DNLL have a common target in the IC. We will also show that the inputs from the contralateral DNLL and ipsilateral LSO do not converge. We will identify local circuit neurons in the IC. Finally, we will test the hypothesis that some ITD responses in IC will be altered by suppression of DNLL or inhibitory local IC inputs. In aim 3, we will identify functional cell types in the IC. We will show that the combination of K+ channels or their subcellular localization are related to cell type and GABA content in the IC. Finally, we will demonstrate that neurons with different firing patterns and whole-cell currents are related to different patterns of K+ channel and/or GABA expression.