Kasai T, Komiyama T
Laboratory of Motor Behavior, Faculty of Physical Education, Kokushikan University, Tokyo, Japan.
Brain Res. 1988 May 3;447(2):389-92. doi: 10.1016/0006-8993(88)91146-8.
Experiments were conducted to investigate whether or not reciprocal descending commands occur simultaneously in the brain as well as the phasic changes in the agonist facilitation and the antagonist inhibition involved in the initiation of varying forces of ankle dorsiflexion. The H-reflex and reaction time method were combined. Results showed that: (1) the agonist and the antagonist motoneurones via Ia inhibitory interneurones simultaneously receive a subliminal facilitation and inhibition from the brain before the EMG onset; and (2) the onset of the agonist facilitation and the antagonist inhibition were not modified by different contraction forces; however, the extent of facilitation and inhibition just after the EMG onset were closely related to the amount of contraction forces. These findings suggest that the descending motor command activates parallel agonist alpha-motoneurones and Ia inhibitory interneurones. However, direct action of the descending command prior to the EMG onset may not be strong enough to drive the Ia interneurone for suppressing the antagonist motoneurones, and the agonist facilitation and the antagonist inhibition just after the EMG onset increase as the voluntary effort is strengthened.
进行了实验，以研究在大脑中是否同时出现相互的下行指令，以及在启动不同力量的踝关节背屈时，主动肌易化和拮抗肌抑制的相位变化情况。采用了H反射和反应时间方法相结合的方式。结果表明：（1）在肌电图（EMG）开始之前，主动肌和拮抗肌运动神经元通过Ia抑制性中间神经元同时接受来自大脑的阈下易化和抑制；（2）主动肌易化和拮抗肌抑制的起始不受不同收缩力的影响；然而，EMG开始后易化和抑制的程度与收缩力的大小密切相关。这些发现表明，下行运动指令激活了平行的主动肌α运动神经元和Ia抑制性中间神经元。然而，在EMG开始之前下行指令的直接作用可能不够强大，不足以驱动Ia中间神经元抑制拮抗肌运动神经元，并且随着自主努力的增强，EMG开始后主动肌易化和拮抗肌抑制会增加。
