Porter R
John Curtin School of Medical Research, Australian National University, Canberra.
Proc R Soc Lond B Biol Sci. 1987 Jul 22;231(1263):147-68. doi: 10.1098/rspb.1987.0039.
During infancy, children develop an expanding repertoire of movement skills in parallel with the maturation in their brains of direct nerve-fibre connections between the cerebral cortex and motoneurons in the spinal cord. These corticomotoneuronal connections are characteristic of primates and can be studied in monkeys; in these animals, refinement in the control of movements of the hand is also associated with increasing development of corticomotoneuronal connections. In monkeys, motoneurons innervating distally acting muscles are preferentially excited by convergent activities in corticomotoneuronal fibres. This excitation has been demonstrated to be effective in natural functional states when a conscious monkey is performing learned movement tasks. Extensive intraspinal arborizations of individual corticomotoneuronal fibres could permit the engagement of large numbers of local motoneurons and related interneurons by each of these fibres. Abolition of corticomotoneuronal influences, after section of the pyramidal tracts, causes a permanent deficit in fractionation of use of muscles of the forelimb and an inability to carry out independent movements of the fingers.
在婴儿期，儿童运动技能储备不断扩展，与此同时，其大脑中大脑皮层与脊髓运动神经元之间的直接神经纤维连接也在成熟。这些皮质脊髓运动神经元连接是灵长类动物的特征，可在猴子身上进行研究；在这些动物中，手部运动控制的精细化也与皮质脊髓运动神经元连接的不断发展有关。在猴子身上，支配远端肌肉的运动神经元优先受到皮质脊髓运动神经元纤维的汇聚活动的兴奋。当有意识的猴子执行学习到的运动任务时，这种兴奋在自然功能状态下已被证明是有效的。单个皮质脊髓运动神经元纤维广泛的脊髓内分支可能使这些纤维中的每一根都能激活大量的局部运动神经元和相关的中间神经元。切断锥体束后，皮质脊髓运动神经元影响的消除会导致前肢肌肉使用细分的永久性缺陷以及无法进行手指的独立运动。
