STRUCTURAL ORGANIZATION OF THE SUPERIOR COLLICULUS

许多类型的实验表明，上级丘在启动头部、眼睛和耳朵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：一类认为上级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;一类认为各层是独立的，主要用于将信息分发到不同的目的地;而另一些人则认为，各个层之间的连接为感觉系统和运动系统之间的相互作用提供了基础。本应用程序的具体目的是测试这些模型。由于技术的限制，过去的解剖学研究提供了一些线索，内丘电路。因此，目前的模型主要是基于丘神经元的生理特性，如它们的反应和它们的连接的特性，但这些假设很难用生理学方法进行测试。这项拟议中的研究将通过细胞内注射每层细胞并追踪它们的细胞内连接来直接测试当前的模型，使用来自树鼩 Tupaia belangeri的活脑切片。相对于其他常见的研究物种，这种灵长类哺乳动物有一个特别大的和分化良好的上级丘，这大大有助于分析层之间的连接。在某些情况下，细胞将通过逆行轴突运输进行预标记，使得除了它们的位置、形态和丘内连接之外，还可以通过它们的轴突的丘外目的地来识别注射的细胞。在其他实验中，通往上级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。这些实验的目的是提供一个新的模型框架的基础上的知识，内丘电路，并以这种方式，将有助于我们了解的神经机制的脊椎动物大脑中的感觉运动整合。感受野和运动野。

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.