- バイオメカニズム (ISSN:13487116)
- vol.12, pp.173-183, 1994-08-10 (Released:2016-12-05)
Previous studies showed that three reflex EMG responses were recorded from the stretched muscle, when the wrist flexors were stretched by sudden angular displacements of the wrist joint in the extension direction. The first response, with short latency is called the M1 component and is thought to be a monosynaptic spinal reflex. The second and third responses, with long latency, are labelled M2 and M3 components and are assumed to be transcortical reflexes. It has been reported, however, that the M3 component is not reliable in occurrence. The amplitudes of reflex components are known to be modified by voluntary movement. Premotor time (PMT) in the reaction time movement is not studied in relation to aspects of the reflex EMG responses including long latency components. The present study was performed in order to investigate whether the PMT under conditions of stretch stimulus (SS-PMT) differs from that under conditions of light stimulus (LS-PMT) and touch stimulus (TS-PMT), and how the PMTs are related to the aspects of the appearance of the reflex EMG responses. Nineteen healthy males, ranging in age from 21 to 28, participated in this study. The DC torque motor was used to evoke the reflex EMG activities of the wrist flexors. The results are summarized as follows: 1) In all subjects SS-PMT was significantly shorter than TS- and LS-PMT. The results suggest that input from the muscle spindle to cerebral cortex shortened the PMT. 2) The short and long latency reflex components appeared preceding the voluntary EMG burst. The latency of M1, M2, and M3 was 19.1ms, 49.2ms, and 71.7ms, respectively. 3) The subjects were classified into three groups (A, B, C) according to the presence or absence of reflex components (M1, M2, M3) and these EMG amplitudes. SS-, TS- and LS-PMTs in group A were significantly shorter than the PMTs in group B, and each PMT in group B was significantly shorter than in the group C. 4) In group A the amplitude of M2 was significantly higher than the M1 amplitude. The M3 component was not identified, since the M2 component was followed by voluntary EMG burst. In group B the M2 amplitude was significantly higher than the M1, and the M3 amplitude appearing before the voluntary EMG burst was significantly smaller than the M2 amplitude. In group C the amplitudes of M1, M2, and M3 were larger in that order. These results suggest that the PMT is related to the presence or absence of the long latency components and those amplitudes.