CHANGES OF H-REFLEX PRIOR TO VOLUNTARY MOVEMENT IN NORMAL MAN / 体力科学

ABSTRACT

It has been shown that there were the changes of H-reflex prior to the rapid voluntary movement. The present paper is designed to examine the changes of H-reflex about the time course prior to the rapid voluntary movement (dorsiflexion and plantarflexion), and premotor silent period in detail.<BR>H-reflexes were elicited from subjects' right foot at varying intervals after the response signal (sound stimulus) of reaction time task when the response involved the rapid dorsiflexion or plantarflexion of the foot. In plantarflexion, H-reflexes were elicited from two response situations ; one was the situation which subjects were not given the preparatory stimulus (without warning = W -), the other was given the preparatory stimulus (with warning= W+) .<BR>The following results were obtained ;<BR>1) Dorsiflexion and plantarflexion<BR>In case of dorsiflexion, although there were no obvious changes of H-reflex prior to EMG onset, in case of plantarflexion the damping phenomenon of H-reflex prior to EMG onset was observed and this phenomenon was the inhibitory one. Especially, under w-situation, it was obviously and it was about 70-80msec prior to EMG onset.<BR>2) Silent period<BR>The damping phenomenon of H-reflex was observed in accordance with silent period but this value was much the same of control level. This value of the damping of H-reflex was smaller than that of premotor silent period (about 30-40msec) . The time when the damping of H-reflex was observed was in accordance with that of prior to EMG onset of simple plantarflexion and this damping of H-reflex was the inhibitory phenomenon.<BR>These results suggest that the upper center sents some inhibitory motor commands to cotralateral agonist motorneurons in advance of the voluntary movement in spite of the peripheral motor set, and those from the upper center precede the voluntary movement by ahnnt 70-80msec.