Sherwood Chet C, Stimpson Cheryl D, Raghanti Mary Ann, Wildman Derek E, Uddin Monica, Grossman Lawrence I, Goodman Morris, Redmond John C, Bonar Christopher J, Erwin Joseph M, Hof Patrick R
Department of Anthropology, The George Washington University, Washington, DC 20052, USA.
Proc Natl Acad Sci U S A. 2006 Sep 12;103(37):13606-11. doi: 10.1073/pnas.0605843103. Epub 2006 Aug 28.
Evidence from comparative studies of gene expression and evolution suggest that human neocortical neurons may be characterized by unusually high levels of energy metabolism. The current study examined whether there is a disproportionate increase in glial cell density in the human frontal cortex in comparison with other anthropoid primate species (New World monkeys, Old World monkeys, and hominoids) to support greater metabolic demands. Among 18 species of anthropoids, humans displayed the greatest departure from allometric scaling expectations for the density of glia relative to neurons in layer II/III of dorsolateral prefrontal cortex (area 9L). However, the human glia-neuron ratio in this prefrontal region did not differ significantly from allometric predictions based on brain size. Further analyses of glia-neuron ratios across frontal areas 4, 9L, 32, and 44 in a sample of humans, chimpanzees, and macaque monkeys showed that regions involved in specialized human cognitive functions, such as "theory of mind" (area 32) and language (area 44) have not evolved differentially higher requirements for metabolic support. Taken together, these findings suggest that greater metabolic consumption of human neocortical neurons relates to the energetic costs of maintaining expansive dendritic arbors and long-range projecting axons in the context of an enlarged brain.
基因表达与进化的比较研究证据表明，人类新皮层神经元的特征可能是能量代谢水平异常高。当前研究调查了与其他类人猿灵长类物种（新大陆猴、旧大陆猴和类人猿）相比，人类额叶皮质中胶质细胞密度是否有不成比例的增加，以支持更高的代谢需求。在18种类人猿物种中，人类背外侧前额叶皮质（9L区）II/III层中胶质细胞相对于神经元密度的异速生长缩放预期偏差最大。然而，该前额叶区域的人类胶质细胞与神经元比例与基于脑容量的异速生长预测并无显著差异。对人类、黑猩猩和猕猴样本中4、9L、32和44区额叶的胶质细胞与神经元比例进行的进一步分析表明，参与人类特殊认知功能的区域，如“心理理论”（32区）和语言（44区），在代谢支持方面并没有进化出更高的差异需求。综上所述，这些发现表明，人类新皮层神经元更高的代谢消耗与在大脑扩大的情况下维持广泛的树突分支和长距离投射轴突的能量成本有关。
