Frequency peaks of tremor, muscle vibration and electromyographic activity at 10 Hz, 20 Hz and 40 Hz during human finger muscle contraction may reflect rhythmicities of central neural firing
Frequency peaks of tremor, muscle vibration and electromyographic activity at 10 Hz, 20 Hz and 40 Hz during human finger muscle contraction may reflect rhythmicities of central neural firing
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DOI：
10.1007/pl00005662
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发表时间：
1997-05-01
影响因子：
2
通讯作者：
Marsden, CD
中科院分区：
文献类型：
--
作者：
McAuley, JH;Rothwell, JC;Marsden, CD
从中枢神经系统到肌肉的输出本质上可以是有节奏的。先前研究这种节律活动的外周表现的记录是相互矛盾的。本研究试图解决这些冲突，采用一种新的安排，以测量和相关的节律，震颤，肌电图（EMG）活动和肌肉振动的声音稳定食指外展。食指与应变计的弹性连接允许第一背侧骨间肌（1DI）发生强有力但相对不固定的外展收缩。一个加速度计连接到手指的末端记录震颤，表面电极超过1DI记录EMG信号和心音监测器放置在1DI记录振动。这种布置使得能够维持恒定的总体肌肉收缩强度，同时仍然允许测量手指的颤抖运动的发生。10名正常受试者进行了研究，首先在休息时伸出食指，然后收缩1DI，以对抗三种不同的稳定力，达到最大随意收缩（MVC）的50%。对震颤、EMG活动和肌肉振动信号的功率谱分析各自揭示了在10 Hz、20 Hz和40 Hz附近一起发生的三个频率峰值。相干分析表明，在三个信号中存在相同的三个峰。相位分析表明一个固定的时间滞后的震颤背后的肌电图约6.5毫秒。这是比较与以前的测量机电延迟。其他实验表明，这三个峰起源于中枢神经。引入机械扰动或额外的负载的手指，并在部分麻醉的手和前臂下进行记录，证明了所有的峰的保存，这表明它们并不源自机械共振或外周反馈回路共振。它的结论是，至少对于一个小的手肌肉，存在不是一个，而是一些独立的峰值频率的振荡在主动收缩，这些振荡反映了同步的运动单位在中枢神经系统内确定的频率。有人提出，多个振荡可能是一种手段的频率编码的电机命令。
The output from the central nervous system to muscles may be rhythmic in nature. Previous recordings investigating peripheral manifestations of such rhythmic activity are conflicting. This study attempts to resolve these conflicts by employing a novel arrangement to measure and correlate rhythms in tremor, electromyographic (EMG) activity and muscle vibration sounds during steady index finger abduction. An elastic attachment of the index finger to a strain gauge allowed a strong but relatively unfixed abducting contraction of the first dorsal interosseous (1DI). An accelerometer attached to the end of the finger recorded tremor, surface electrodes over 1DI recorded EMG signals and a heart-sounds monitor placed over 1DI recorded vibration. This arrangement enabled maintenance of a constant overall muscle contraction strength while still allowing measurement of the occurrence of tremulous movements of the finger. Ten normal subjects were studied with the index finger first extended at rest and then contracting 1DI to abduct the index finger against three different steady forces up to 50% of maximal voluntary contraction (MVC). Power spectral analysis of tremor, EMG activity and muscle vibration signals each revealed three frequency peaks occurring together at around 10 Hz, 20 Hz and 40 Hz. Coherence analysis showed that the same three peaks were present in the three signals. Phase analysis indicated a fixed time lag of tremor behind EMG of around 6.5 ms. This is compared with previous measurements of electromechanical delay. Other experiments indicated that the three peaks were of central nervous origin. Introducing mechanical perturbations or extra loading to the finger and making recordings under partial anaesthesia of the hand and forearm demonstrated preservation of all the peaks, suggesting that they did not originate from mechanical resonances or peripheral feedback loop resonances. It is concluded that, at least for a small hand muscle, there exist not one but a number of separate peak frequencies of oscillation during active contraction, and that these oscillations reflect synchronization of motor units at frequencies determined within the central nervous system. It is proposed that the multiple oscillations may be a means of frequency coding of motor commands.