An electrophysiological study of the postnatal development of the corticospinal system in the macaque monkey
An electrophysiological study of the postnatal development of the corticospinal system in the macaque monkey
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DOI：
10.1523/jneurosci.17-01-00267.1997
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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：
Olivier, E;Edgley, SA;Lemon, RN
采用无创经颅磁刺激（TMS）和直接电刺激髓锥体和脊髓的皮质脊髓轴突，研究了13只猕猴出生后皮质脊髓系统的发育情况。在出生后的头几个月里，由锥体诱发并由运动皮层记录的反节律皮质脊髓抽射潜伏期显著下降。我们的数据预测，最快的皮质脊髓神经元在颅脑过程中的传导速度（CV）将在大约11个月时达到成人的水平。脊髓皮质脊髓神经元的CV随年龄的增长而增加，但时间过程较慢。在新生儿中，最快的脊髓CV估计为7.8 m/sec，与成人（平均80.0 m/sec）相比慢了10倍。我们的数据预测，脊髓皮质脊髓轴突的完全髓鞘形成要到36个月左右才会发生。在3月龄之前，经颅磁刺激没有引起手臂和手部肌肉的短潜伏期肌电反应；TMS阈值初始较高，随年龄增长逐渐下降。当校正体型时，肌电反应的相对潜伏期在出生后的头几个月呈指数下降。我们的数据与假设一致，即在功能性CM连接建立良好之前，精细手指运动未被观察到，皮质脊髓系统生理特性的快速变化与精确握力成熟的时期（3-6个月）一致。然而，在灵巧性的简单测量表明功能成熟后，皮质脊髓的发育仍会持续很长时间，这些变化可能有助于提高熟练手任务的速度和协调性。
Postnatal development of the corticospinal system was investigated in 13 macaques using noninvasive transcranial magnetic stimulation (TMS) of the motor cortex and direct electrical stimulation of corticospinal axons in the medullary pyramid and spinal cord. The latency of antidromic corticospinal volleys evoked from the pyramid and recorded from the motor cortex decreased dramatically during the first postnatal months. Our data predict that conduction velocity (CV) of the fastest corticospinal neurons over their cranial course would reach adult values at similar to 11 months. The CV of corticospinal neurons in the spinal cord increased with age but with a slower time course. In the neonate, the fastest spinal CV was estimated at 7.8 m/sec, similar to 10 times slower than in adults (mean 80.0 m/sec). Our data predict that full myelination of corticospinal axons in the spinal cord would not occur until similar to 36 months. No short-latency EMG responses were elicited in arm and hand muscles by TMS until 3 months of age; TMS thresholds were high initially and then fell progressively with age. When corrected for body size, relative latencies of EMG responses showed an exponential decrease during the first postnatal months. Our data are consistent with the hypothesis that fine finger movements are not observed before functional CM connections are well established and that rapid changes in the physiological properties of the corticospinal system coincide with the period in which precision grip is known to mature (3-6 months). However, corticospinal development continues long after simple measures of dexterity indicate functional maturity, and these changes may contribute to the improved speed and coordination of skilled hand tasks.