Herculano-Houzel Suzana, Collins Christine E, Wong Peiyan, Kaas Jon H, Lent Roberto
Instituto de Ciências Biomédicas, Universidade Federal Rio de Janeiro, Brazil.
Proc Natl Acad Sci U S A. 2008 Aug 26;105(34):12593-8. doi: 10.1073/pnas.0805417105. Epub 2008 Aug 8.
Evolutionary changes in the size of the cerebral cortex, a columnar structure, often occur through the addition or subtraction of columnar modules with the same number of neurons underneath a unit area of cortical surface. This view is based on the work of Rockel et al. [Rockel AJ, Hiorns RW, Powell TP (1980) The basic uniformity in structure of the neocortex. Brain 103:221-244], who found a steady number of approximately 110 neurons underneath a surface area of 750 microm(2) (147,000 underneath 1 mm(2)) of the cerebral cortex of five species from different mammalian orders. These results have since been either corroborated or disputed by different groups. Here, we show that the number of neurons underneath 1 mm(2) of the cerebral cortical surface of nine primate species and the closely related Tupaia sp. is not constant and varies by three times across species. We found that cortical thickness is not inversely proportional to neuronal density across species and that total cortical surface area increases more slowly than, rather than linearly with, the number of neurons underneath it. The number of neurons beneath a unit area of cortical surface varies linearly with neuronal density, a parameter that is neither related to cortical size nor total number of neurons. Our finding of a variable number of neurons underneath a unit area of the cerebral cortex across primate species indicates that models of cortical organization cannot assume that cortical columns in different primates consist of invariant numbers of neurons.
大脑皮层是一种柱状结构，其大小的进化变化通常是通过在皮层表面单位面积下增加或减少具有相同神经元数量的柱状模块来实现的。这一观点基于罗克尔等人的研究工作[罗克尔AJ、希orns RW、鲍威尔TP（1980年）新皮层结构的基本一致性。《大脑》103:221 - 244]，他们发现来自不同哺乳纲的五个物种的大脑皮层在750平方微米（1平方毫米下有147,000个）的表面积下神经元数量稳定在约110个左右。此后，不同的研究团队对这些结果有的进行了证实，有的则提出了质疑。在这里，我们表明，九种灵长类物种以及与之亲缘关系较近的树鼩属动物的大脑皮层表面1平方毫米下的神经元数量并非恒定不变，而是在不同物种间相差三倍。我们发现，跨物种来看，皮层厚度与神经元密度并非成反比，而且总的皮层表面积的增加速度比其下方的神经元数量增加速度更慢，并非呈线性关系。皮层表面单位面积下的神经元数量与神经元密度呈线性变化，而神经元密度这一参数既与皮层大小无关，也与神经元总数无关。我们发现灵长类物种间大脑皮层单位面积下的神经元数量存在差异，这表明皮层组织模型不能假定不同灵长类动物的皮层柱由固定数量的神经元组成。
