Projections of Characterized Trapezoid Body Axons

听觉信息首先在脑干中由包含几种细胞类型的耳蜗核复合体中的神经元处理。其中许多细胞的输出轴突在一条主要路径上向前投射，形成一种被称为梯形小体的结构(从它的形状来看)。然后，这些轴突终止于下一个更高水平的神经元，称为上橄榄复合体。我们还不清楚来自耳蜗核的信号如何与听觉功能的更高方面有关，例如声音定位或惊吓反应，这些功能是由上橄榄神经元处理的。这个项目将确定这些梯形体轴突的信号和目标目的地。细胞内的记录将被用来对延伸到梯形体内的单个轴突的反应特性进行生理学表征，然后细胞内的染料填充将被用来追踪猫脑干内从起源细胞到靶细胞的路径。光学显微镜和电子显微镜将提供每个细胞的终末位置的细节，以及突触末梢的详细形态，以从形态上表征细胞类型。然后，这种分类将与观察到的这些细胞的功能反应相关联。这项工作将在中枢听觉通路中提供独特的信息整合；它将阐明在连接耳蜗核和上橄榄复合体的重要水平上发生了什么样的信号处理，并将阐明耳蜗核中形态细胞分类的功能意义。

Auditory information is first processed in the brainstem by neurons in the cochlear nuclear complex, containing several cell types. Output axons of many of these cells project forward in a major pathway forming a structure called the trapezoid body (from its shape). These axons then terminate on neurons at the next higher level called the superior olivary complex. We do not yet understand how the signals from the cochlear nuclei are related to higher aspects of auditory function, such as sound localization or startle responses, which are handled by neurons in the superior olive. This project will determine the signalling and target destinations of the these trapezoid body axons. Intracellular recordings will be used to physiologically characterize the response properties of single axons that extend into the trapezoid body, and intracellular dye filling then will be used to trace the pathways, from cells of origin to target cells, within the cat brainstem. Light and electron microscopy will provide details of location of terminals for each cell, and of detailed morphology of the synaptic endings, to morphologically characterize cell types. This classification then will be correlated to the observed functional responses of these cells. This work will provide a unique integration of information in the central auditory pathway; it will clarify what kinds of signal processing occur at the important level connecting the cochlear nuclei to the superior olivary complex, and will clarify the functional significance of morphological cell classification in the cochlear nucleus.