PERIODIC EXTRINSIC CONNECTIONS IN VISUAL CORTEX

外在结构的层流组织和切向组织 来自初级视觉皮质的皮质连接(L7区 或V1)是已知的，但仅通过批量注射 ~3H-氨基酸或HRP。这些正交线传输方法是 相对粗糙，不容易区分轴突 前终末和终末，或以其他方式解析轴突 形态学。因此，我们目前不知道是否像在 膝纹终止的病例，有几种 在形态上不同的纹状传出轴突， 可能在不同的亚层中形成树枝。建议数 实验将分析纹状传出神经的树枝状分布 注射菜豆在纹前区V2和MT的轴突 猕猴V1区的凝集素(PHA)。了解 这些轴突树枝的精确形态是 更好地理解可视信息的前提条件 从V1中分离出来，并且进一步是定义 纹前皮质模块化组织的结构基础。 周期性组织已经被描述为几个 V2和MT的解剖联系；但是，部分原因是 周期间隔在不同的系统中变化很大，它 目前尚不清楚是否存在基本的 纹前皮质的解剖-功能单位可与 V1中的超列。我们将具体研究是否 纹状轴突分支显示反复出现的终末前宽度 或者形成规则周期性的切向斑块。这些 参数可能指向下面的大脑皮层子结构， 或许是其他解剖系统所共有的。详细 我们将对V2中纹状体轴突的分支方式进行比较 和MT，以确定这些纤维是否具有 立体解剖学，或者，交替地，他们的解剖学 反映了特定区域的特定功能特性。 其他实验目标包括：1)调查， 使用PHA和荧光珠，相互连接 纹状体和纹前区之间；2)EM-PHA研究 突触后至第四层横纹终末的神经元靶点 猕猴V2区；3)比较解剖学 注射用PHA治疗纹状体铁中毒的研究 在本种的V2里的网状分枝。除了……之外 与视觉皮质组织相关的问题，这 研究还将为未来的工作提供基线 皮质连接的发育阶段。另外，更多的 有必要建立详细的皮质组织动物模型。 用于解释人类的病理情况，包括 精神发育迟滞。

The laminar and tangential organization of extrinsic corticocortical connection from primary visual cortex (area l7 or Vl) is known, but only as revealed by bulk injections of 3H-amino acids or HRP. These orthograde transport methods are relatively crude and cannot easily distinguish between axon preterminals and terminals, or otherwise resolve axon morphology. Thus, we do not currently know whether, as in the case of geniculostriate terminations, there are several morphologically distinct classes of striate efferent axons, perhaps arborizing in distinct sublaminae. The proposed experiment will analyse the arborization of striate efferent axons in prestriate areas V2 and MT, by injecting kidney bean lectin (PHA) in area Vl of the macaque monkey. Knowing the precise morphology of these axonal arborizationsis a prerequisite to better understanding how visual information is dispersed from Vl, and is further essential for defining the structural basis of modular organization in prestriate cortex. A periodic organization has been described for several anatomical connections in V2 and MT; but, partly because the periodic spacing varies widely among the differnt systems, it is not presently clear whether there is a basic anatomical-functional unit in prestriate cortex comparable to the hypercolumn in V1. We will specifically examine whether striate axon arborizations exhibit recurrent preterminal widths or form tangential patches of regular periodicity. These parameters might point to an underlying cortical substructure, perhaps shared by other anatomical systems. Detailed comparisons will be made of how striate axons arborize in V2 and MT in order to ascertain whether these fibers have a sterotyped anatomy, or whether, alternately, their anatomy relects the particular funtional prpoperties of a given area. Additional experimental goals include: 1) an investigation, using PHA and florescent beads, of reciprocal connections between striate and prestriate area; 2) an EM-PHA study of neuronal targets postsynaptic to striate termnations in layer 4 of area V2 in the macaque; and 3) a comparative anatomical investigation in the ferrent, using PHA injections, of striate effernet arborizations in V2 of this species. In addition to relevance for issues of visual cortical organization, this research will also provide a baseline for future work on developmental stages of cortical connections. Also, a more detailed animal model of cortical organiztion will be necessary for interpreting human pathological conditions, including mental retardation.