STRUCTURAL ORGANIZATION OF THE SUPERIOR COLLICULUS

许多类型的实验表明，上级丘起着 在启动头部、眼睛和耳朵的定向运动中起关键作用 对感兴趣的对象。至少有三类模型， 它的结构和功能之间的关系可以区分： 那些提出上级层之间的通路 丘整合感觉和运动系统，参与启动 定向运动;那些认为层是独立的， 主要用作向不同目的地分发资料;及 这些人认为， 层为感觉和感觉之间的相互作用提供了基底， 运动系统此应用程序的具体目标是测试这些 模型由于技术上的限制，过去的解剖学研究 提供了一些关于耳蜗内回路的线索。因此，目前 模型主要基于丘状体的生理特性， 神经元，如他们的反应和他们的属性的延迟， 感受野和运动野。这些模型假设了特定的模式， 连接，但这些假设很难用生理学来测试。 方法.拟议的研究将直接测试当前的模型， 细胞内注射每层细胞并追踪它们的 利用树上的活脑切片， 鼩 鼱属Tupaia belangeri.相对于其他常见的研究物种， 类灵长类哺乳动物有一个特别大的和分化良好的 上级丘，这极大地促进了分析的任务， 层之间的连接。在某些情况下，细胞将被预先标记， 逆行轴突运输，以便可以识别注射的细胞 除了他们的轴突外， 位置、形态和丘内连接。换句 实验中，感觉或运动通路的上级丘将 预先标记，以确定它们是否聚集在 不同的类型。这些实验旨在提供一个框架， 新模型基于对耳蜗内电路的了解， 这将有助于我们理解神经机制 脊椎动物大脑中潜在的感觉运动整合。

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 receptive and movement fields. These models postulate specific patterns of 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.