AREAS AND LAYERS OF CORTICOCORTICAL TERMINATIONS IN VISUAL CORTEX OF VIRGINIA OPOSSUM
AREAS AND LAYERS OF CORTICOCORTICAL TERMINATIONS IN VISUAL CORTEX OF VIRGINIA OPOSSUM
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DOI：
10.1002/cne.901410203
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发表时间：
1971-01-01
影响因子：
2.5
通讯作者：
EBNER, FF
中科院分区：
文献类型：
--
作者：
BENEVENTO, LA;EBNER, FF
负鼠的视皮层在操作上被定义为纹状皮层和接受同侧纹状皮层投射的皮层总面积。这个区域包括所有的格雷（'24）纹周皮质。在这项研究中，几个领域被确定在灰色的纹状体和纹状体周围地区的细胞结构的变化和丘脑皮质纤维终止模式的平行变化的基础上。通过Fink-Heimer染色确定这些皮质区域内同侧联合纤维、连合纤维和来自半丘脑的丘脑皮质纤维的终止层。(1)连合纤维终端出现在个别致密的“带”在某些地区的不同细胞结构领域的视觉皮层。这些连合纤维末端的带被仅接受稀疏连合纤维末端的皮质区分开。第一条连合终止带位于过渡皮质区，占据外侧纹状皮质和邻近的纹周皮质。这条带的特征是在所有皮层层的外周纹侧和终端外接的侧边缘的第IV层的纹状体侧的终端。第二连合带的终端位于前和中央周纹区与终端在所有层中，除了V的细胞结构描绘是存在于中央周纹皮质之间的这两个乐队的连合终端。第三条带与第二条带相似，其连合终止的层状模式位于沿着鼻裂和颞叶皮质的其他纹周区的更外侧。这三条带在中点处变宽，相互融合。在大脑半球内侧表面的条纹状皮质带中也发现了连合末梢。层I中所有连合末端的特征是其限制在该层的内部四分之三。视皮质次全损害显示了同位和异位连合连接。中央纹状皮质很少有连合连接。这个区域的大部分接受一些连合纤维终端从外侧部分的纹状皮质，也从周纹状皮质。来自纹状体皮质外侧区的纤维产生末端，其形成围绕纹状体边界的带，如邻近外侧纹状体皮质边界的周纹皮质。内侧周纹皮层有同伦互连，而其他周纹区既有异位和同伦互连。(2)同侧纹状皮质的联合投射主要终止于周纹状皮质的I ~ IV层。这些终端重叠的区域的纹周皮质接收稀疏和密集的连合终端。病变半球的变性显示，I层的切向纤维存在于大范围的视觉皮层。只有第一层和第二层的纹状皮质的热损伤表明，至少有一部分的同侧关联终止模式来自第二层。(3)在每一个细胞构筑区中，将皮质终末与丘脑皮质终末以及高尔基和电镜研究所描述的其他哺乳动物的轴突分布进行了比较，得出结论：负鼠视皮层具有细胞构筑亚区，和连接基底，用于视野的至少两个皮质表示，并且负鼠视觉系统的纤维连接包含存在于其他物种中的基本组织。
Visual cortex in the opossum was defined operationally as striate cortex and the total cortical area receiving ipsilateral projections from striate cortex. This area included all of Gray's ('24) peristriate cortex. In this study several areas were identified within Gray's striate and peristriate areas on the basis of changes in cytoarchitecture and parallel changes in thalamocortical fiber termination patterns. The layers of termination within these cortical areas, of the ipsilateral associational fibers, the commissural fibers and the thalamocortical fibers from the hemithalamus were determined by means of the Fink‐Heimer stain. (1) Commissural fiber terminations occur in individual dense “bands” in certain regions of the different cytoarchitectural areas of visual cortex. These bands of commissural fiber terminations are separated by zones of cortex which receive only sparse commissural fiber terminations. The first band of commissural terminations is found in a zone of transitional cortex occupying lateral striate cortex and adjacent peristriate cortex. This band is characterized by terminations in all layers of cortex on the peristriate side and terminations circumscribing the lateral edge of layer IV on the striate side. A second commissural band of terminations lies in anterior and central peristriate areas with terminations in all layers except V. A cytoarchitectural delineation is present in central peristriate cortex between these two bands of commissural terminations. A third band with a laminar pattern of commissural terminations similar to the second band lies more laterally in other peristriate areas along the rhinal fissure and temporal cortex. These three bands broaden at their midpoints to fuse with one another. Commissural terminations are also found in a strip of peristriate cortex on the medial surface of the hemisphere. Characteristic of all commissural terminations in layer I is their restriction to the inner three‐fourths of this layer. Subtotal lesions of visual cortex reveal homotopic and heterotopic commissural connections. Central striate cortex has few commissural interconnections. Most of this area receives a few commissural fiber terminations from the lateral portion of striate cortex and also from peristriate cortex. Fibers from the lateral region of striate cortex give rise to terminations which form the band about the striate border as may peristriate cortex adjacent to the lateral striate cortex border. Medial peristriate cortex has homotopic interconnections while the other peristriate areas have both heterotopic and homotopic interconnections. (2) the ipsilateral associational projections from striate cortex terminate mainly in layers I to IV in peristriate cortex. These terminations overlap the zones of peristriate cortex which receive sparse and dense commissural terminations. Degeneration in the lesioned hemisphere revealed tangential fibers in layer I that are present over a large extent of visual cortex. Thermal lesions of only layers I and II of striate cortex show that at least part of the ipsilateral association termination pattern arises from layer II. (3) In each cytoarchitectural area the corticocortical terminations are compared with the thalamocortical terminations and also with such axonal distributions described by Golgi and EM studies in other mammals.It is concluded that the visual cortex of the opossum has the cytoarchitectural subdivisions, and connectional substrate for at least two cortical representations of the visual field and that the fiber connections of the visual system of the opossum contain a basic organization present in other species.