Chan C W, Kearney R E, Jones G M
Brain Res. 1979 Sep 14;173(2):303-14. doi: 10.1016/0006-8993(79)90630-9.
It is well known that in Parkinsonian subjects with akinesia, reaction times are increased but reflex latencies remain normal. We have attempted to use this knowledge to distinguish between 'reflex' and 'voluntary' components of the electromyographic (EMG) response to ankle displacement. The EMG and torque responses of tibialis anterior (TA) to randomly applied servo-controlled plantar-flexing displacements of the ankle with and without the subject's intentional opposition were examined in 9 Parkinsonian and 9 age-matched normal humans. To obtain a measure of akinesia, the response latency to a visual stimulus was subsequently measured in the same subjects. Three principal findings emerged. (1) The intermediate latency EMG component (PSR) of the response evoked by ankle displacement with the subject instructed to relax was more regularly evoked and of lower threshold in Parkinsonians than in normals. This finding corresponds to the enlarged M2 component in upper limb muscles. However, the facilitation of PSR was not found to be associated with an increase in torque. In fact, the patients did not exhibit more stiffness than normals under our experimental conditions. (2) Mean latency estimate of the PSR was indistinguishable between Parkinsonians and normals. This finding puts the PSR in the nature of a reflex. Indeed, in accordance with reflex behaviour which is proportional to input characteristics, its area increased linearly with increase in the magnitude of displacement velocity. (3) In contrast, the 'late' EMG response (FSR) evoked by opposing sudden ankle displacement exhibited a significantly longer latency in 6 out of 8 Parkinsonians than normals. In the same patients, the EMG response latency to a visual signal was similarly increased. The delay of FSR in akinesia patients thus argued against its being a stereotyped reflex. The result is discussed with reference to the recent finding that preprogrammed responses are delayed in Parkinsonians.
众所周知，在患有运动不能的帕金森病患者中，反应时间会延长，但反射潜伏期仍保持正常。我们试图利用这一知识来区分对踝关节位移的肌电图（EMG）反应中的“反射”和“自主”成分。在9名帕金森病患者和9名年龄匹配的正常人中，研究了胫前肌（TA）在有或没有受试者有意对抗的情况下，对随机施加的伺服控制的踝关节跖屈位移的EMG和扭矩反应。为了获得运动不能的测量值，随后在同一受试者中测量了对视觉刺激的反应潜伏期。出现了三个主要发现。（1）在受试者被指示放松的情况下，踝关节位移诱发的反应的中间潜伏期EMG成分（PSR）在帕金森病患者中比正常人更常被诱发且阈值更低。这一发现与上肢肌肉中增大的M2成分相对应。然而，未发现PSR的易化与扭矩增加有关。事实上，在我们的实验条件下，患者并未表现出比正常人更多的僵硬。（2）帕金森病患者和正常人之间PSR的平均潜伏期估计没有差异。这一发现表明PSR具有反射的性质。实际上，根据与输入特征成比例的反射行为，其面积随位移速度大小的增加而线性增加。（3）相比之下，在8名帕金森病患者中有6名，对抗突然的踝关节位移诱发的“晚期”EMG反应（FSR）的潜伏期明显长于正常人。在同一患者中，对视觉信号的EMG反应潜伏期也同样增加。因此，运动不能患者中FSR的延迟表明它不是一种刻板的反射。结合最近的发现，即帕金森病患者的预编程反应会延迟，对这一结果进行了讨论。
