OBJECTIVE Understanding of maturational properties of sensory and motor axons is of central importance for determining the impact of nerve changes in health and in disease in children and young adults. METHODS This study investigated maturation of sensory axons using axonal excitability parameters of the median nerve in 47 children, adolescents and young adults (25 males, 22 females; age range 1-25 years) and compared them to concurrent motor studies. RESULTS The overall pattern of sensory maturation was similar to motor maturation demonstrating prolongation of the strength duration time constant (P < 0.001), reduction of hyperpolarising threshold electrotonus (P = 0.002), prolongation of accommodation half-time (P = 0.005), reduction in hyperpolarising current-threshold slope (P = 0.03), and a shift to the right of the refractory cycle curve (P < 0.001), reflecting changes in passive membrane properties and fast potassium channel conductances. Sensory axons, however, had a greater increase in strength duration time constant and more attenuated changes in depolarising threshold electrotonus and current-threshold parameters, attributable to a more depolarised resting membrane potential evident from early childhood and maintained in adults. Peak amplitude was established early in sensory axons whereas motor amplitude increased with age (P < 0.001), reflecting non-axonal motor unit changes. CONCLUSIONS Maturational trajectories of sensory and motor axons were broadly parallel in children and young adults, but sensory-motor differences were initiated early in maturation. SIGNIFICANCE Identifying the evolution of biophysical changes within and between sensory and motor axons through childhood and adolescence is fundamental to understanding developmental physiology and interpreting disease-related changes in immature nerves.

中文翻译：

---

儿童早期周围神经的成熟和兴奋特性：运动神经和感觉神经的比较

目的了解感觉和运动轴突的成熟特性对于确定神经变化对儿童和年轻人健康和疾病的影响至关重要。方法 本研究使用 47 名儿童、青少年和年轻成人（25 名男性，22 名女性；年龄范围 1-25 岁）的正中神经的轴突兴奋性参数调查了感觉轴突的成熟，并将其与同时进行的运动研究进行了比较。结果 感觉成熟的总体模式与运动成熟相似，表明力量持续时间常数延长（P < 0.001），超极化阈值电紧张降低（P = 0.002），适应半时间延长（P = 0.005），减少在超极化电流阈值斜率（P = 0.03）中，以及向难治循环曲线右侧移动（P < 0.001），反映了被动膜特性和快速钾通道电导的变化。然而，感觉轴突的强度持续时间常数增加更大，去极化阈值electrotonus和电流阈值参数的变化更减弱，这归因于儿童早期明显的去极化静息膜电位并在成人中保持。峰值振幅在感觉轴突的早期建立，而运动振幅随着年龄的增长而增加（P < 0.001），反映了非轴突运动单位的变化。结论 感觉和运动轴突的成熟轨迹在儿童和年轻人中大致平行，但感觉运动差异在成熟早期就开始了。