Manzoni T, Conti F, Fabri M
J Comp Neurol. 1986 Oct 8;252(2):245-63. doi: 10.1002/cne.902520208.
The present research was aimed at ascertaining in the macaque monkey the reciprocity of the heterotopical callosal connections between SI and SII, with particular regard to the connectivity of the hand representation, and at comparing the topographical and laminar pattern of these callosal connections with those of association connections entertained by these areas. Horseradish peroxidase (HRP) was unilaterally injected into area SI in five monkeys. The sites of HRP delivery included the trunk and the hand zones preliminarily identified by recording multi-unit responses to peripheral stimulation by means of microelectrodes. Anterograde and retrograde labelling was studied in SII of both sides. The results showed the complete reciprocity of the heterotopical callosal connections between SI and SII. In the latter area both callosal axon terminals and neurones were found, which were labelled from either the trunk or the hand zone of contralateral SI. Labelling of callosal axon terminals occurred mainly in layer IV and in the lowermost part of layer III. Labelled callosal neurones were mainly in the lower half of layer III, whereas few occurred in infragranular layers. Topographically, the distribution of callosal terminals and cell bodies duplicated the distribution of association terminals and cell bodies labelled in SII on the side ipsilateral to HRP injection. The laminar pattern of termination of association fibres from SI was similar to that of callosal fibres. However, the distribution of association-projecting neurones in SII showed a striking difference from that of callosal-projecting neurones. Unlike the latter neurones, which were mainly located in supragranular layers, association cell bodies overwhelmingly dwelt in layers V and VI and were less numerous in layers II and III. This laminar pattern of association SII-SI cells corresponds to the "feed-backward" model and fits the laminar pattern of their axon terminations (Friedman: Brain Res. 273: 147-151, '83). The association and callosal inputs and outputs of area SII are discussed in relation to the function of the forward and backward type of reciprocal connections entertained with SI in the ipsilateral hemisphere and to the function of SII in the interhemispheric exchange of somatosensory information.
本研究旨在确定猕猴大脑体感皮层I区（SI）和体感皮层II区（SII）之间异位胼胝体连接的相互关系，尤其关注手部代表区的连接情况，并将这些胼胝体连接的拓扑和分层模式与这些区域的联合连接模式进行比较。对五只猕猴单侧注射辣根过氧化物酶（HRP）至SI区。HRP注射部位包括通过微电极记录对周围刺激的多单位反应初步确定的躯干和手部区域。研究双侧SII区的顺行和逆行标记。结果显示SI和SII之间异位胼胝体连接完全相互对应。在SII区发现了胼胝体轴突终末和神经元，它们由对侧SI区的躯干或手部区域标记。胼胝体轴突终末标记主要出现在IV层和III层最下部。标记的胼胝体神经元主要位于III层下半部，而颗粒下层中很少见。在拓扑学上，胼胝体终末和细胞体的分布与HRP注射同侧SII区标记的联合终末和细胞体分布一致。来自SI区的联合纤维终末分层模式与胼胝体纤维相似。然而，SII区联合投射神经元的分布与胼胝体投射神经元有显著差异。与主要位于颗粒上层的胼胝体投射神经元不同，联合细胞体绝大多数位于V层和VI层，II层和III层中数量较少。SII - SI联合细胞的这种分层模式符合“反馈”模型，与其轴突终末的分层模式相符（弗里德曼：《脑研究》273: 147 - 151, '83）。结合同侧半球SII与SI之间正向和反向相互连接的功能以及SII在体感信息半球间交换中的功能，讨论了SII区的联合和胼胝体输入及输出。
