SYNCHRONIZATION OF MOTOR-UNIT FIRINGS IN SEVERAL HUMAN MUSCLES
SYNCHRONIZATION OF MOTOR-UNIT FIRINGS IN SEVERAL HUMAN MUSCLES
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DOI：
10.1152/jn.1993.70.5.2010
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发表时间：
1993-11-01
影响因子：
2.5
通讯作者：
ERIM, Z
中科院分区：
文献类型：
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作者：
DE LUCA, CJ;ROY, AM;ERIM, Z
1.同步同时积极的运动单位发射进行了研究，在六个人的肌肉进行等长恒力收缩在30%的最大水平。采用四股针电极检测肌电信号，并采用精确分解技术将其分解为运动单元动作电位序列，其准确性已得到验证.同步被认为是两个运动单元相对于彼此以固定的时间间隔发射的趋势，比如果运动单元独立发射时预期的更频繁。一个严格的统计技术被用来衡量的存在下，在跨区间直方图的运动单元动作电位列车对的峰值。测量了各峰的峰中心位置、峰宽和峰幅。开发了同步指数来测量同步击发的百分比。测量包含同步放电的同时活动的运动单位对的百分比。同步的电机单元发射观察到发生在两种模式。在以零时间延迟为中心的跨间期直方图中，短期模态被视为峰值（0.5 +/- 2.9 ms，平均值+/- SD），平均宽度为4.5 +/- 2.5 ms。长期模态被视为以8 - 76 ms范围内的lapril为中心的峰值。平均而言，长期同步化的峰值低36%，但具有与短期同步化的峰值大致相同的宽度。60%的运动单位对出现短期同步，而10%的运动单位对出现长期同步。短时间同步化发生在连续放电的爆发中，数量从1到10不等，其中91%的同步放电发生在1或2组中;在收缩过程中，爆发性放电出现在零星的时间。在电机单元对同步量被认为是低的。在测试的六块肌肉中，平均8.0%的放电是短期同步的，平均1.0%是长期同步的。同步指数在不同肌肉之间和11名受试者中的9名之间无统计学差异（P = 0.07-0.89）。60%的同时活动的运动单元对显示短期同步，10%的对显示长期同步，8%的显示两种模式。运动单位的同步水平显着降低较大的肌肉[胫骨前肌（54%的短期，13%的长期）。和三角肌（45%短期，12%长期）]比小肌肉[第一骨间背侧肌（71%短期，15%长期），尺侧腕伸肌（74%短期，11%长期），桡侧腕长伸肌（69%短期，9%长期）]，以及11名受试者中的2名.同步的量不依赖于运动单位的募集阈值或任何两个显示同步的运动单位的募集阈值之间的差异。我们的研究结果反驳了以前用来解释同步发生的共同突触前纤维分支假说和肌肉传入反馈假说。我们认为，运动单元放电之间的同步可能没有重要的生理目的;相反，它可能是其他生理机制活动的副产品。我们引入一个新的假设来解释同步。中枢神经系统内的振荡器偶尔会驱动运动神经元同步放电。这个假说不需要直接的共同身体连接来驱动运动神经元，并且能够解释我们所有的观察结果。
1. Synchronization of concurrently active motor-unit firings was studied in six human muscles performing isometric constant-force contractions at 30% of the maximal level. The myoelectric signal was detected with a quadrifilar needle electrode and was decomposed into its constituent motor-unit action-potential trains with the Precision Decomposition technique, whose accuracy has been proven previously.2. Synchronization was considered as the tendency of two motor units to fire at fixed time intervals with respect to each other more often than would be expected if the motor units fired independently. A rigorous statistical technique was used to measure the presence of peaks in the cross-interval histogram of pairs of motor-unit action-potential trains. The location of the center of peak as well as their width and amplitude were measured. A synch index was developed to measure the percentage of firings that were synchronized. The percentage of concurrently active motor-unit pairs that contained synchronized firings was measured.3. Synchronization of motor-unit firings was observed to occur in two modalities. The short-term modality was seen as a peak in the cross-interval histogram centered about zero-time delay (0.5 +/- 2.9 ms, mean +/- SD) and with an average width of 4.5 +/- 2.5 ms. The long-term modality was seen as a peak centered at latencies ranging from 8 to 76 ms. On the average, the peaks of the long-term synchronization were 36% lower but had approximately the same width as the peaks for the short-term synchronization. Short-term synchronization was seen in 60% of the motor-unit pairs, whereas long-term synchronization was seen in 10% of the pairs.4. Short-term synchronization occurred in bursts of consecutive firings, ranging in number from 1 to 10, with 91% of all synchronized firings occurring in groups of 1 or 2; and the bursts of discharges appeared at sporadic times during the contraction.5. The amount of synchronization in motor-unit pairs was found to be low. In the six muscles that were tested, an average of 8.0% of all the firings were short-term synchronized, and an average of 1.0% were long-term synchronized. The synch index was statistically indistinguishable (P = 0.07-0.89) among the different muscles and among 9 of the 11 subjects tested.6. Sixty percent of concurrently active motor-unit pairs displayed short-term synchronization, 10% of the pairs displayed long-term synchronization, and 8% displayed both modalities. Motor-unit synchronization level was significantly lower in the larger muscles [tibialis anterior (54% short-term, 13% long-term). and deltoid (45% short-term, 12% long-term)] than in the smaller muscles [first dorsal interosseous (71% short-term, 15% long-term), extensor carpi ulnaris (74% short term, 11% long-term), and the extensor carpi radialis longus (69% short-term, 9% long-term)], and in 2 of the 11 subjects.7. The amount of synchronization was not found to be dependent on the recruitment threshold of the motor units or on the difference between the recruitment thresholds of any two motor units that displayed synchronization.8. Our results argue against the common presynaptic fiber-branches hypothesis and the muscle afferent feedback hypothesis that have previously been used to explain the occurrence of synchronization.9. We suggest that synchronization among motor-unit firings may not have a significant physiological purpose; instead, it may be a by-product of the activity of other physiological mechanisms.10. We introduce a new hypothesis for explaining synchronization. Oscillators within the CNS drive motoneurons to fire in synchrony occasionally. This hypothesis requires no direct common physical connection to drive the motoneurons and is capable of explaining all our observations.