Postnatal development of corticospinal projections from motor cortex to the cervical enlargement in the macaque monkey
Postnatal development of corticospinal projections from motor cortex to the cervical enlargement in the macaque monkey
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DOI：
10.1523/jneurosci.17-01-00251.1997
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发表时间：
1997-01-01
影响因子：
5.3
通讯作者：
Lemon, RN
中科院分区：
文献类型：
--
作者：
Armand, J;Olivier, E;Lemon, RN
本文用麦胚凝集素-辣根过氧化物酶顺行性注射于11只猕猴初级运动皮质手区，观察了皮质脊髓投射的生后发育。虽然皮质脊髓束的纤维在出生时就到达了脊髓白色物质的各个层面，但它们对灰质的穿透还远远没有完成。在出生时，与成人一样，皮质脊髓投射分布在中间带的相同区域，尽管它们在头5个月内显示出明显的密度增加。灵长类皮质脊髓束的独特特征，即直接皮质-运动神经元投射到支配手部肌肉的脊髓运动核，在出生时并不明显，这些皮质运动神经元预测的密度迅速增加，在第一个5个月，随后延长到第二年的生活。1个月时，皮质脊髓终末仅占第一胸段手运动核团的40%，5个月时为73%，3年时为75.5%。在整个发展过程中，持续到成人的手运动核的尾侧梯度的终止密度。因此，颈膨大内的节段越向尾侧，就越早达到成人的投射密度模式。未发现短暂的皮质脊髓投射。出生后灵长类动物皮质运动神经元向手运动核的投射持续扩张，与亚灵长类动物其他感觉和运动通路发育特征的旺盛投射的收缩形成鲜明对比。
The postnatal development of corticospinal projections was investigated in 11 macaques by means of the anterograde transport of wheat germ agglutin-horseradish peroxidase injected into the primary motor cortex hand area. Although the fibers of the corticospinal tract reached all levels of the spinal cord white matter at birth, their penetration into the gray matter was far from complete. At birth, as in the adult, corticospinal projections were distributed to the same regions of the intermediate zone, although they showed marked increases in density during the first 5 months, The unique feature of the primate corticospinal tract, namely direct cortico-motoneuronal projections to the spinal motor nuclei innervating hand muscles, was not present to a significant extent at birth, The density of these cortico-motoneuronal projections increased rapidly during the first 5 months, followed by a protracted period extending into the second year of life. The densest corticospinal terminations occupied only 40% of the hand motor nuclei in the first thoracic segment at 1 month, 73% at 5 months, and 75.5% at 3 years. A caudo-rostral gradient of termination density within the hand motor nuclei was present throughout development and persisted into the adult. As a consequence, the more caudal the segment within the cervical enlargement, the earlier the adult pattern of projection density was reached. No transitory corticospinal projections were found, The continuous postnatal expansion of cortico-motoneuronal projections to hand motor nuclei in primates is in marked contrast to the retraction of exuberant projections that characterizes the development of other sensory and motor pathways in subprimates.