STRUCTURAL ORGANIZATION OF THE SUPERIOR COLLICULUS

许多类型的实验表明，上丘起着重要的作用 在启动头部、眼睛和耳朵的定向运动中起关键作用 朝向感兴趣的对象。至少有三类模型 它的结构和功能之间的关系可以区分开来： 那些提出上层之间的通道的人 丘脑整合与启动有关的感觉和运动系统 定向运动；那些认为各层是独立的和 主要用于向不同的目的地分发信息；以及 那些提出个人内部隔间之间联系的人 各层为感官和大脑之间的相互作用提供了底物 马达系统。此应用程序的具体目标是测试以下各项 模特们。由于技术上的限制，过去的解剖学研究 几乎没有提供小球内回路的线索。因此，当前 已有的模型主要基于丘脑的生理特性 神经元，如它们反应的潜伏期和它们的特性 接受区和运动区。这些模型假定特定的模式 联系，但这些假设很难用生理学测试 方法：研究方法。拟议的研究将通过以下方式直接测试当前的模型 细胞内注射每一层的细胞并追踪其 使用树上的活脑片进行的小球内连接 Shrew，Tupaia belangeri。相对于其他被普遍研究的物种，这 类似灵长类的哺乳动物有一个特别大和分化良好的 上丘，这极大地方便了分析 各层之间的连接。在某些情况下，单元格的前缀为 逆行轴突运输以便识别注入的细胞 通过轴突的胞外目的地，除了它们的 位置、形态和囊泡内连接。在其他 上丘的实验、感觉或运动通路将是 预先标记以确定它们是否会聚在丘脑神经元上 不同的类型。这些实验旨在提供一个框架，以 基于对小球内回路的知识的新模型，在这方面 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.