Miles T S, Türker K S
Exp Brain Res. 1987;65(2):337-42. doi: 10.1007/BF00236306.
The activity of up to 4 motor units was recorded simultaneously with electrodes placed in the masseter muscle in human subjects. Mildly noxious electrical shocks were applied to the ipsilateral lip while one of the units was kept firing at a steady frequency by voluntary control. The pattern of reflex responses of each of the units was determined, and spike-triggered averaging was used to measure the potential that each action potential contributed to the rectified surface electromyogramme (EMG). Finally, the average contribution made to the surface EMG by each unit throughout the whole course of the reflex was determined. The contribution of each unit to the reflex response in the surface EMG was found to depend on its firing frequency throughout the course of the response, and on its amplitude measured at the surface. The timing of the various phases of inhibition and activation of different units depended on their pre-stimulus firing frequency. In a given bite, the lowest-threshold units were more likely to be firing most rapidly, and these were least susceptible to the inhibitory stimulus. Higher-threshold units tended to produce larger potentials at the muscle surface but, because they fired more slowly in a given bite, they were more powerfully inhibited by the stimulus. Most units showed the same general pattern of inhibitory and excitatory activity that can be seen in the surface EMG. However, the timing of these various phases in the surface EMG did not necessarily correspond with the timing of inhibition and activation in the records of individual units.(ABSTRACT TRUNCATED AT 250 WORDS)
在人类受试者的咬肌中放置电极，同时记录多达4个运动单位的活动。对同侧唇部施加轻度有害的电击，同时通过自主控制使其中一个单位以稳定频率持续放电。确定每个单位的反射反应模式，并使用触发尖峰平均法测量每个动作电位对整流后的表面肌电图（EMG）的贡献。最后，确定每个单位在整个反射过程中对表面EMG的平均贡献。发现每个单位对表面EMG反射反应的贡献取决于其在反应过程中的放电频率以及在表面测量的幅度。不同单位抑制和激活的各个阶段的时间取决于其刺激前的放电频率。在给定的咬合中，阈值最低的单位最有可能放电最快，并且这些单位对抑制性刺激最不敏感。阈值较高的单位往往在肌肉表面产生较大的电位，但是，由于它们在给定的咬合中放电较慢，因此它们受到刺激的抑制作用更强。大多数单位表现出与表面EMG中可见的相同的抑制和兴奋活动的一般模式。然而，表面EMG中这些不同阶段的时间不一定与单个单位记录中的抑制和激活时间相对应。（摘要截断于250字）
