DEVELOPMENT AND PLASTICITY OF VISUAL CONNECTIONS

最近的研究已经确定了发育中的视觉系统的途径 随着发展，它们要么完全消失，要么成为 在其起源或终止的区域减少。 在本提案中，我们 将研究这些瞬态投影是如何发展的， 它们被保留或丢失的机制。 请注意 部分与老鼠和树的胼胝体的发育有关。 我们很想知道投影是如何聚焦在 17/18（a）边界的发展以及为什么在操纵之后， 视神经或视束切面，通路呈异常分布。 此外，还希望通过集中精力发展 17/18边境地区，将有可能接近的重要问题， 成熟皮层的异质性特征是如何决定的 参与发展. 最后我们希望通过将移植的组织沿着 通常消失以维持它们的途径的过程， 相信存在适当的目标区域是 这是保存投影的一个重要条件。 从这些实验中，我们希望能够深入了解 如何影响精确的连接，形成正常的基板， 视觉功能已建立。 此外，我们还希望确定某些 正常发育过程可能受到干扰的条件。

Recent studies have identified pathways in the developing visual system which, as development proceeds, either disappear completely or become diminished in their area of origin or termination. In this proposal, we will investigate how some of these transient projections develop and the mechanisms whereby they are maintained or lost. Attention will be directed in part to the development of the corpus callosum of rats and tree shrews. We are interested to know how the projection becomes focussed in development at the 17/18(a) border and why after manipulations such as optic nerve or tract section, the pathway shows an abnormal distribution. It is hoped furthermore that by concentrating on the development of the 17/18 border region, it will be possible to approach the important issue of how the heterogeneities characteristic of the mature cortex are determined in development. Finally we hope by placing transplanted tissue along the course of pathways which normally disappear to maintain them, addiding credence to the view that the presence of an appropriate target region is an important requirement for preserving a projection. From these experiments, we hope to gain insight into factors which influence how the precise connections, forming the substrates of normal visual function, are established. In addition we hope to define certain conditions under which the normal developmental process may be disturbed.