Goffinet A M
J Comp Neurol. 1983 Apr 20;215(4):437-52. doi: 10.1002/cne.902150408.
From the earliest stage of its ontogenesis, the mammalian cerebral cortex displays a remarkable cytoarchitectonic organization, with its neurons oriented radially within the cortical plate (CP). It is not known whether this radial organization of cortical neurons is characteristic of every cerebral cortex or whether it reflects a progressive phylogenetic acquisition. In order to study this question, the embryonic development of the cortex has been examined in reptiles, where it is the most primitive. Two species, Emys orbicularis and Lacerta agilis, representative of the two principal reptilian orders (chelonians and squamates), have been studied with histological methods. Golgi impregnation, and electron microscopy. Very similar patterns of cell proliferation, migration, maturation, and synaptogenesis have been observed. However, important species differences are present in the cellular organization of the cortical plate. Whereas in Emys the structure of the cortical plate is rudimentary, in Lacerta it appears well developed and quite reminiscent of its mammalian counterpart. Preliminary comparisons with embryological preparations of Sphenodon and Crocodilus niloticus show that the organization of the cortical plate displays significant variations among the different reptilian groups. The present results suggest that the radial organization of cortical neurons is not an all or nothing phenomenon but has been acquired independently and is thus a case of homoplasy, probably due to convergence (Northcutt, 81). Several possible implications of these findings are discussed and a working hypothesis based on the role of radial glial cells in the formation of cytoarchitectonic patterns (Rakic, '80) is presented.
从其个体发生的最早阶段开始，哺乳动物的大脑皮层就呈现出显著的细胞结构组织，其神经元在皮层板（CP）内呈放射状排列。目前尚不清楚皮层神经元的这种放射状组织是所有大脑皮层的特征，还是反映了一种逐步的系统发育获得。为了研究这个问题，已经在最原始的爬行动物中研究了皮层的胚胎发育。使用组织学方法、高尔基氏染色法和电子显微镜，对代表两个主要爬行动物目（龟鳖目和有鳞目）的两种物种——圆斑龟和捷蜥蜴进行了研究。观察到了非常相似的细胞增殖、迁移、成熟和突触形成模式。然而，在皮层板的细胞组织中存在重要的物种差异。在圆斑龟中，皮层板的结构是初步的，而在捷蜥蜴中，它看起来发育良好，并且与哺乳动物的对应物非常相似。与楔齿蜥和尼罗鳄的胚胎标本的初步比较表明，皮层板的组织在不同的爬行动物群体中显示出显著差异。目前的结果表明，皮层神经元的放射状组织不是一种全有或全无的现象，而是独立获得的，因此是一种趋同演化的情况，可能是由于趋同（诺思卡特，81）。讨论了这些发现的几个可能含义，并提出了一个基于放射状胶质细胞在细胞结构模式形成中的作用的工作假设（拉基奇，80）。
