Rakic P
Section of Neurobiology, Yale University School of Medicine, New Haven, CT 06510, USA.
Trends Neurosci. 1995 Sep;18(9):383-8. doi: 10.1016/0166-2236(95)93934-p.
The more than 1000-fold increase in the cortical surface without a comparable increase in its thickness during mammalian evolution is explained in the context of the radial-unit hypothesis of cortical development. According to the proposed model, cortical expansion is the result of changes in proliferation kinetics that increase the number of radial columnar units without changing the number of neurons within each unit significantly. Thus, mutation of a regulatory gene(s) that controls the timing and ratio of symmetric and asymmetric modes of cell divisions in the proliferative zone, coupled with radial constraints in the distribution of migrating neurons, could create an expanded cortical plate with enhanced capacity for establishing new patterns of connectivity that are validated through natural selection.
在哺乳动物进化过程中，皮质表面增加了1000多倍，但其厚度却没有相应增加，这在皮质发育的径向单元假说的背景下得到了解释。根据所提出的模型，皮质扩张是增殖动力学变化的结果，这种变化增加了径向柱状单元的数量，而每个单元内的神经元数量没有显著改变。因此，控制增殖区细胞对称和不对称分裂时间及比例的一个或多个调控基因发生突变，再加上迁移神经元分布的径向限制，可能会产生一个扩展的皮质板，其建立新连接模式的能力增强，并通过自然选择得到验证。
