Shipp S, Blanton M, Zeki S
Wellcome Laboratory of Neurobiology, University College, London, UK.
Eur J Neurosci. 1998 Oct;10(10):3171-93. doi: 10.1046/j.1460-9568.1998.00327.x.
This report addresses the connectivity of the cortex occupying middle to dorsal levels of the anterior bank of the parieto-occipital sulcus in the macaque monkey. We have previously referred to this territory, whose perimeter is roughly circumscribed by the distribution of interhemispheric callosal fibres, as area V6, or the 'V6 complex'. Following injections of wheatgerm agglutinin conjugated to horseradish peroxidase (WGA-HRP) into this region, we examined the laminar organization of labelled cells and axonal terminals to attain indications of relative hierarchical status among the network of connected areas. A notable transition in the laminar patterns of the local, intrinsic connections prompted a sub-designation of the V6 complex itself into two separate areas, V6 and V6A, with area V6A lying dorsal, or dorsomedial to V6 proper. V6 receives ascending input from V2 and V3, ranks equal to V3A and V5, and provides an ascending input to V6A at the level above. V6A is not connected to area V2 and in general is less heavily linked to the earliest visual areas; in other respects, the two parts of the V6 complex share similar spheres of connectivity. These include regions of peripheral representation in prestriate areas V3, V3A and V5, parietal visual areas V5A/MST and 7a, other regions of visuo-somatosensory association cortex within the intraparietal sulcus and on the medial surface of the hemisphere, and the premotor cortex. Subcortical connections include the medial and lateral pulvinar, caudate nucleus, claustrum, middle and deep layers of the superior colliculus and pontine nuclei. From this pattern of connections, it is clear that the V6 complex is heavily engaged in sensory-motor integration. The specific somatotopic locations within sensorimotor cortex that receive this input suggest a role in controlling the trunk and limbs, and outward reaching arm movements. There is a secondary contribution to the brain's complex oculomotor circuitry. That the medial region of the cortex is devoted to tightly interconnected representations of the sensory periphery, both visual and somatotopic-which are routinely stimulated in concert-would appear to be an aspect of the global organization of the cortex which must facilitate multimodal integration.
本报告探讨了猕猴顶枕沟前壁中至背侧水平的皮质的连接性。我们之前将这个区域称为V6区或“V6复合体”,其边界大致由半球间胼胝体纤维的分布界定。在将与辣根过氧化物酶结合的小麦胚芽凝集素(WGA-HRP)注射到该区域后,我们检查了标记细胞和轴突终末的分层组织,以了解相连区域网络中相对层级状态的指标。局部内在连接的分层模式发生了显著转变,促使我们将V6复合体本身进一步划分为两个独立区域,即V6区和V6A区,V6A区位于V6区的背侧或背内侧。V6区接受来自V2区和V3区的上行输入,与V3A区和V5区处于同一层级,并在更高水平向V6A区提供上行输入。V6A区与V2区不相连,总体上与最早的视觉区域联系较少;在其他方面,V6复合体的这两个部分具有相似的连接范围。这些区域包括纹前区V3、V3A和V5中的周边表征区域、顶叶视觉区V5A/MST和7a、顶内沟内和半球内侧表面的其他视-体感联合皮质区域以及运动前皮质。皮质下连接包括内侧和外侧丘脑枕、尾状核、屏状核、上丘中层和深层以及脑桥核。从这种连接模式可以清楚地看出,V6复合体大量参与感觉-运动整合。感觉运动皮质内接受这种输入的特定躯体定位表明其在控制躯干和四肢以及向外伸展手臂运动中发挥作用。它对大脑复杂的眼球运动回路也有次要贡献。皮质的内侧区域专门用于紧密连接的视觉和躯体定位感觉周边表征,这些表征通常会同时受到刺激,这似乎是皮质整体组织的一个方面,必然有助于多模态整合。