SYNAPTIC ORGANIZATION IN THE SUPERIOR COLLICULUS

上级的传入和传出联系模式 丘表明大脑的这一区域参与了 感觉运动整合 特别是丘， 参与视觉、听觉和躯体感觉的整合 信息，以及随后产生的眼睛和头部 动作 尽管有越来越多的证据证明这一作用， 令人惊讶的是，人们对生物的内在组织知之甚少。 上级丘。 因此，特别需要 解剖学研究，以确定局部的精确形态， 神经回路 如果没有这些知识， 我们不可能开始构建一个模型来解释丘是如何 参与定向运动的控制。 到目前为止，几乎不可能分析 由于技术性的，丘的内在组织 现有技术的局限性。 最近，一个新的 发现了顺行解剖示踪剂： 菜豆-白细胞凝集素（PHA-L）。 这种植物凝集素是 无细胞毒性，似乎不被通道轴突吸收， 并且与光学和电子显微镜兼容。 因此 这是第一次有可能检查内在联系 上级丘的神经元。 我们的初步研究 与PHA-L显示轴突分支整个丘 在特定的丘状核中进行非常有限的注射后， 纹层 我们还看到了 丘的表层和深层，这一发现 争论了几十年。 在所提出的实验中， 将进行测试，以确定深层的功能单元如何 都是有组织的 我们将确定是否有 是直接的视觉输入到深层从覆盖 表面层，以及这些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是否 层还从侧面接收直接的视觉输入， 上外侧裂视皮层 这些研究将使我们能够 概述了感官信息如何传播的模型 在整个丘，视觉和运动地图如何在 丘被编织成功能单位， 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.