STRUCTURAL ORGANIZATION OF THE SUPERIOR COLLICULUS

许多类型的实验表明，上丘在头、眼和耳朝向感兴趣的物体的定向运动中起着关键作用。关于其结构和功能之间的关系，至少可以区分出三类模型：那些认为上丘各层之间的通路整合了参与启动定向运动的感觉和运动系统的模型；一些人认为各层是独立的，主要用于将信息分发到不同的目的地；而那些提出单个层内隔室之间的连接为感觉和运动系统之间的相互作用提供了基础。这个应用程序的具体目的是测试这些模型。由于技术上的限制，过去的解剖学研究提供了很少的线索，以胞内电路。因此，目前的模型主要基于丘神经元的生理特性，例如它们的反应潜伏期和它们的连接特性，但是这些假设很难用生理方法来测试。拟议的研究将直接通过细胞内注射每层细胞并追踪它们的细胞内连接来测试当前的模型，使用树鼩（Tupaia belangeri）的活脑切片。与其他常见的研究物种相比，这种类似灵长类动物的哺乳动物有一个特别大且分化良好的上丘，这极大地促进了分析各层之间联系的任务。在某些情况下，细胞将通过轴突逆行转运进行预标记，以便除了轴突的位置、形态和胞内连接外，还可以通过轴突的胞外目的地来识别注射细胞。在其他实验中，通往上丘的感觉或运动通路将被预先标记，以确定它们是否会聚在不同类型的丘神经元上。这些实验旨在为基于细胞内电路知识的新模型提供一个框架，并以这种方式有助于我们理解脊椎动物大脑中感觉运动整合的神经机制。接受场和运动场。

Many types of experiments indicate that the superior colliculus plays a key role in initiating orienting movements of the head, eyes and ears toward objects of interest. At least three classes of models of the relationship between its structure and function can be distinguished: those proposing that pathways between the layers of the superior colliculus integrate the sensory and motor systems involved in initiating orienting movements; those arguing that the layers are independent and serve mainly to distribute information to different destinations; and those proposing that connections between compartments within individual layers provide the substrate for interactions between the sensory and motor systems. The specific aims of this application are to test these models. Because of technical limitations, past anatomical studies have provided few clues to intracollicular circuitry. Consequently, current models have been based primarily on physiological properties of collicular neurons, such as the latencies of their responses and properties of their connections, but the postulates are difficult to test with physiological methods. The proposed research will test the current models directly by intracellularly injecting cells of each layer and tracing their intracollicular connections, using living brain slices from the tree shrew, Tupaia belangeri. Relative to other commonly studied species, this primate-like mammal has an especially large and well differentiated superior colliculus, which greatly facilitates the task of analyzing the connections between the layers. In some cases, cells will be prelabeled by retrograde axonal transport so that the injected cells can be identified by the extracollicular destinations of their axons, in addition to their location, morphology and intracollicular connections. In other experiments, sensory or motor pathways to the superior colliculus will be prelabeled to determine whether they converge on collicular neurons of different types. These experiments are designed to provide a framework for new models based on knowledge of intracollicular circuitry and, in this way, will contribute to our understanding of the neural mechanisms underlying sensorimotor integration in the vertebrate brain. receptive and movement fields.