Nudo R J, Masterton R B
Department of Psychology, Florida State University, Tallahassee 32306-1051.
J Comp Neurol. 1990 Jun 22;296(4):559-83. doi: 10.1002/cne.902960405.
The somata of corticospinal neurons were labeled with horseradish peroxidase that had been applied to a hemisection of the spinal cord at the C1-C2 junction in 22 species of mammals. After tetramethylbenzidine processing, with and without counterstaining with cresyl violet or neutral red, the labeled cells in systematic sets of sections throughout the cerebral cortex were plotted and counted. Several morphological features of the corticospinal cells were examined including their cell type, number, density, concentration, laminar distribution, and their distribution across the cortical surface. The results show that the labeled corticospinal neurons were invariably layer V pyramidal cells. However, in many mammals they were found to be stacked one above the other within layer V, sometimes many neurons deep. Despite the concentration of corticospinal neurons within layer V, many unlabeled neurons were also present within the layer throughout the extent of the labeled region. The results also indicate that at least two spatially distinct regions of neocortex originate corticospinal fibers in each of the animals in the sample. In addition to these two regions, a third segregated region is present in the cortex of primates and an apparently different third region is present in the cortex of Glires (Rodentia and Lagomorpha). The third region of corticospinal cortex in primates is located on the lateral surface of the cortex in prosimians and New World monkeys and is buried in the caudal bank of the inferior arcuate sulcus in Old World monkeys. The results also show a predominantly contralateral corticospinal tract in all but 4 of the 22 mammals in the sample. Although these 4 mammals are each members of the order Insectivora, a less modified member of the same order possessed the predominantly contralateral projection of most mammals, hence denying the notion that a predominantly ipsilateral tract is a characteristic of Insectivora.
在22种哺乳动物中，将辣根过氧化物酶应用于C1 - C2交界处的脊髓半切面上，对皮质脊髓神经元的胞体进行标记。经过四甲基联苯胺处理后，无论是否用甲酚紫或中性红进行复染，对整个大脑皮质的一系列切片中的标记细胞进行绘图和计数。研究了皮质脊髓细胞的几个形态学特征，包括它们的细胞类型、数量、密度、浓度、层状分布以及在皮质表面的分布。结果表明，标记的皮质脊髓神经元始终是V层锥体细胞。然而，在许多哺乳动物中，它们在V层内一个叠在另一个之上，有时深入到许多神经元深处。尽管皮质脊髓神经元集中在V层内，但在标记区域的整个范围内，该层内也存在许多未标记的神经元。结果还表明，在样本中的每只动物中，至少有两个空间上不同的新皮质区域产生皮质脊髓纤维。除了这两个区域外，灵长类动物的皮质中存在第三个分离区域，而啮齿目（啮齿动物和兔形目）的皮质中存在一个明显不同的第三个区域。灵长类动物皮质脊髓皮质的第三个区域位于原猴亚目和新大陆猴皮质的外侧表面，在旧大陆猴中则埋在弓状沟下沟的尾侧。结果还表明，在样本中的22种哺乳动物中，除了4种外，其余的都主要是对侧皮质脊髓束。尽管这4种哺乳动物都是食虫目成员，但同一目中一个较少进化的成员具有大多数哺乳动物的主要对侧投射，因此否定了主要同侧束是食虫目的特征这一观点。
