Miles T S, Türker K S, Nordstrom M A
Exp Brain Res. 1987;65(2):331-6. doi: 10.1007/BF00236305.
The reflex responses of single motor units in human masseter muscle to electrical stimulation of the lip were recorded. The subject maintained a content mean level of pre-stimulus excitation of the parent motor neurone by biting in such a way that the unit fired at either 10 or 15 Hz during each trial. When firing at 10 Hz, most units were reflexly inhibited for up to 90 ms by electrical stimuli at intensities that were perceived to be mildly uncomfortable. In many units, the inhibition consisted of 2 phases which were separated from each other by a few spikes occurring about 30 ms after the stimulus. It was occasionally possible to evoke only the latter phase (latency about 40 ms) with stimulus at intensities near the response threshold. In these instances, the inhibitory response became biphasic at higher stimulus intensities with the emergence of a shorter (10-15 ms) component. Still higher intensities caused the 2 phases of inhibition to merge, giving the appearance of a single, prolonged, inhibitory response. When the pre-stimulus firing frequency of the unit was changed from 10 Hz to 15 Hz, the inhibitory responses to the same stimuli were decreased, with the longer-latency component usually surviving beyond the shorter-latency phase. The pattern of reflex responses observed can be explained by a model based on information derived from intracellular recordings in animal experiments.
记录了人类咬肌单个运动单位对唇部电刺激的反射反应。受试者通过以某种方式咬合来维持母运动神经元刺激前兴奋的平均水平，使得在每次试验中该单位以10或15Hz的频率放电。当以10Hz放电时，大多数单位会被强度被认为轻度不适的电刺激反射性抑制长达90毫秒。在许多单位中，抑制包括两个阶段，这两个阶段被刺激后约30毫秒出现的几个尖峰分隔开。偶尔有可能用接近反应阈值的强度刺激仅诱发后一阶段（潜伏期约40毫秒）。在这些情况下，随着较短（10 - 15毫秒）成分的出现，抑制反应在较高刺激强度下变为双相。更高的强度导致抑制的两个阶段合并，呈现出单一、延长的抑制反应的外观。当单位的刺激前放电频率从10Hz变为15Hz时，对相同刺激的抑制反应降低，潜伏期较长的成分通常在潜伏期较短的阶段之后仍然存在。观察到的反射反应模式可以用基于动物实验细胞内记录所获得信息的模型来解释。
