SYNAPTIC ORGANIZATION IN THE SUPERIOR COLLICULUS

上级的传入和传出连接模式 丘脑提示大脑的这一区域参与了 感觉-运动整合。特别是，丘脑是 参与视觉、听觉和躯体感觉的整合 信息，以及随后的眼睛和头部的生成 动静。尽管有关于这一角色的累积证据， 令人惊讶的是，人们对其内在组织知之甚少 上丘。因此，特别需要 解剖学研究以确定局部的精确形态 丘脑中的回路。如果没有这种知识，它几乎是 不可能开始构建丘脑是如何形成的模型 参与定向运动的控制。 到目前为止，几乎不可能分析 由于技术上的原因，丘脑的内在组织 现有技术的局限性。最近，一个新的 已发现顺行解剖示踪剂： 菜豆-亮氨酸凝集素(PHA-L)。这种植物凝集素是 无细胞毒性，似乎不被传代轴突所吸收， 并且与光学显微镜和电子显微镜兼容。因此，对于 第一次有可能检查内在的联系 上丘的神经元。我们的初步研究 用PHA-L法可见丘脑内轴突分枝 在特定的皮质区进行非常有限的注射后 片层。我们还看到了两国之间的广泛联系 小丘的浅层和深层，这一发现 几十年来一直备受争议。 在提议的实验中，特定模型的本征电路 将进行测试，以确定深层的功能单元 的小丘是有组织的。我们将确定是否有 是从上覆到深层的直接视觉输入 浅层，以及这种视觉输入是如何组织的。 最后，我们将确定深部的传出神经元 层还接收来自横向的直接可视输入 上丘脑视皮质。这些研究将使我们能够 概述感官信息如何传播的模型 在整个丘脑中，视觉和运动图是如何 丘被编织成功能单位，以及它们是如何起作用的 眼睛和头部运动的产生。

The pattern of afferent and efferent connections of the superior colliculus suggests that this area of the brain is involved in sensory-motor integration. In particular, the colliculus is involved in the integration of visual, auditory and somatosensory information, and the subsequent generation of eye and head movements. Despite the accumulated evidence for this role, surprisingly little is known about the intrinsic organization of the superior colliculus. Thus there is a special need for anatomical studies to identify the precise morphology of local circuits in the colliculus. Without this knowledge it is almost impossible to begin to construct a model of how the colliculus is involved in the control of orienting movements. Up to this time it has been almost impossible to analyze the intrinsic organization of the colliculus due to the technical limitations of the techniques available. Recently, a new anterograde anatomical tracer has been discovered: Phaseolus vulgaris-leucoagglutinin (PHA-L). This plant lectin is non-cytotoxic, does not appear to be taken up by axons of passage, and is compatible with light and electron microscopy. Thus, for the first time it is possible to examine the intrinsic connections of neurons in the superior colliculus. Our preliminary studies with PHA-L show axonal arborizations throughout the colliculus following very restricted injections in specific collicular laminae. We have also seen extensive connections between the superficial and deep layers of the colliculus, a finding that has been disputed for several decades. In the proposed experiments specific models of intrinsic circuitry will be tested to establish how functional units in the deep layers of the colliculus are organized. We will determine whether there is direct visual input to the deep layers from the overlying superficial layers, and how this visual input is organized. Finally, we will establish whether efferent neurons in the deep layers also receive direct visual input from the lateral suprasylvian visual cortex. These studies will enable us to outline a model of how sensory information is disseminated throughout the colliculus, how visual and motor maps in the colliculus are woven into functional units, and how they contribute to the generation of eye and head movements.