Age and sex differences in human motor cortex input-output characteristics
Age and sex differences in human motor cortex input-output characteristics
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DOI：
10.1113/jphysiol.2002.029454
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发表时间：
2003-01-15
影响因子：
5.5
通讯作者：
Miles, TS
中科院分区：
文献类型：
--
作者：
Pitcher, JB;Ogston, KM;Miles, TS
刺激-反应曲线运动诱发电位（MEPs）引起的手肌肉经颅磁刺激（TMS）的42名受试者的目的是确定与年龄和性别的差异。年龄对TMS的静息阈值、可诱发的MEP最大振幅（MEPmax）或刺激-反应曲线的最大斜率没有影响。然而，在老年受试者中，需要更高的刺激强度来实现MEP最大值和最大斜率。在老年受试者中，MEP的试验间变异性更大，特别是在阈值附近的强度下。年龄、阈值和MEP振幅的试验间变异性之间存在显著的交互作用。总的来说，MEP变异性下降显着刺激强度增加阈值以上，但在老年人比年轻的受试者迅速。女性往往有较大的MEP变异性比男性，但年龄和阈值比性别更强的调制器。这些差异的输入-输出特性可能是由于脊髓运动神经元的数量减少同步激活老年受试者，或激活相同数量的运动神经元在一个不太同步的方式，导致相位取消的表面肌电图。
Stimulus-response curves for motor evoked potentials (MEPs) induced in a hand muscle by transcranial magnetic stimulation (TMS) were constructed for 42 subjects with the aim of identifying differences related to age and sex. There was no effect of age on the resting threshold to TMS, the maximal amplitude of the MEP that could be evoked (MEPmax) or the maximal slope of the stimulus-response curve. However, higher stimulus intensities were required to achieve both MEPmax and the maximal slope in the older subjects. The trial-to-trial variability of MEPs was greater in the older subjects, particularly at intensities near threshold. There was a significant interaction between age, threshold and trial-to-trial variability of MEP amplitude. Overall, MEP variability fell markedly as stimulus intensity increased above threshold but less rapidly in older than in younger subjects. Females tended to have larger MEP variability than males, but age and threshold were much stronger modulators than sex. These differences in input-output characteristics are likely to be due either to a decreased number of spinal motoneurones being activated synchronously in older subjects, or to the activation of the same number of motoneurones in a less synchronous manner, leading to phase cancellation in the surface electromyogram.