Nudo R J, Sutherland D P, Masterton R B
Department of Psychology, Florida State University, Tallahassee 32306, USA.
J Comp Neurol. 1995 Jul 24;358(2):181-205. doi: 10.1002/cne.903580203.
The morphology of the somata originating the corticospinal tract was examined in 24 species of mammals to identify commonalities and major sources of variation among the different species. Horseradish peroxidase was applied to a hemisection of the spinal cord at the C1-C2 junction. After tetramethylbenzidine processing, the labeled somata throughout the cerebral cortex were plotted and counted. Then, 23 morphological characteristics of the corticospinal somata were examined, including their number, size, and density across the cortical surface. The results show that morphological characteristics of corticospinal somata are closely related to an animal's body, brain, and cerebral cortex size. That is, mammals with large neocortical surfaces tend to have larger as well as more corticospinal somata; mammals with large bodies tend to have corticospinal somata that are less densely distributed. Moreover, the probable increase in the ratio of local noncorticospinal somata to corticospinal somata implies that the evolution of the corticospinal tract was accomplished by an increase in "support" or "server" cells as well as an increase in the size of the tract itself. The results also show that several characteristics are reliably related to an animal's taxonomic classification and hence its ancestry. Comparisons among three mammalian lineages indicate that some characteristics may have changed uniquely in the anthropoid primate lineage, and thus, presumably, in the human lineage. The results suggest that if morphological characteristics of the corticospinal tract important in the evolution of the specialized motor abilities in anthropoid primates are sought, then examination of the role of changes in soma diameter, rostral (motor)/caudal (sensory) ratios of density, concentration, surface density, and volume density may be more instructive than examination of the total number of corticospinal neurons alone.
在24种哺乳动物中研究了起源于皮质脊髓束的胞体形态，以确定不同物种之间的共性和主要变异来源。将辣根过氧化物酶应用于C1 - C2交界处的脊髓半切处。经过四甲基联苯胺处理后，绘制并计数整个大脑皮质中标记的胞体。然后，检查了皮质脊髓胞体的23种形态特征，包括它们在皮质表面的数量、大小和密度。结果表明，皮质脊髓胞体的形态特征与动物的身体、大脑和大脑皮质大小密切相关。也就是说，新皮质表面大的哺乳动物往往有更大且更多的皮质脊髓胞体；体型大的哺乳动物往往皮质脊髓胞体分布密度较低。此外，局部非皮质脊髓胞体与皮质脊髓胞体比例可能的增加意味着皮质脊髓束的进化是通过“支持”或“服务”细胞的增加以及束本身大小的增加来实现的。结果还表明，一些特征与动物的分类学分类及其祖先可靠相关。对三个哺乳动物谱系的比较表明，某些特征可能在类人猿灵长类谱系中，因此大概在人类谱系中发生了独特的变化。结果表明，如果要寻找在类人猿灵长类特殊运动能力进化中重要的皮质脊髓束的形态特征，那么检查胞体直径、密度的嘴侧（运动）/尾侧（感觉）比率、浓度、表面密度和体积密度的变化所起的作用可能比仅检查皮质脊髓神经元的总数更具指导意义。
