Martin John H
Center for Neurology and Behavior, Columbia University, 1051 Riverside Drive, New York, NY 10032, USA.
Neuroscientist. 2005 Apr;11(2):161-73. doi: 10.1177/1073858404270843.
The corticospinal system is the principal motor system for controlling movements that require the greatest skill and flexibility. It is the last motor system to develop. The pattern of termination of corticospinal axons, as they grow into the spinal gray matter, bears little resemblance to the pattern later in development and in maturity. Refinement of corticospinal terminations occurs during a protracted postnatal period and includes both elimination of transient terminations and growth to new targets. This refinement is driven by neural activity in the motor cortical areas and by limb motor experience. Developing corticospinal terminals compete with each other for synaptic space on spinal neurons. More active terminals are more competitive and are able to secure more synaptic space than their less active counterparts. Corticospinal terminals can activate spinal neurons from very early in development. The importance of this early synaptic activity appears to be more for refining corticospinal connections than for transmitting signals to spinal motor circuits for movement control. The motor control functions of the corticospinal system are not expressed until development of connectional specificity with spinal cord neurons, a strong capacity for corticospinal synapses to facilitate spinal motor circuits, and the formation of the cortical motor map.
皮质脊髓系统是控制需要最高技能和灵活性运动的主要运动系统。它是最后发育的运动系统。皮质脊髓轴突在向脊髓灰质生长时的终止模式，与发育后期和成熟时的模式几乎没有相似之处。皮质脊髓终止的精细化在出生后的一段较长时期内发生，包括消除短暂的终止和向新靶点生长。这种精细化由运动皮质区域的神经活动和肢体运动经验驱动。发育中的皮质脊髓终末相互竞争脊髓神经元上的突触空间。更活跃的终末更具竞争力，比不太活跃的终末能获得更多的突触空间。皮质脊髓终末在发育早期就能激活脊髓神经元。这种早期突触活动的重要性似乎更多在于完善皮质脊髓连接，而非向脊髓运动回路传递信号以控制运动。皮质脊髓系统的运动控制功能直到与脊髓神经元建立连接特异性、皮质脊髓突触促进脊髓运动回路的强大能力以及皮质运动图谱形成后才得以表达。
