INFLUENCE OF VOLUNTARY INTENT ON THE HUMAN LONG-LATENCY STRETCH REFLEX
INFLUENCE OF VOLUNTARY INTENT ON THE HUMAN LONG-LATENCY STRETCH REFLEX
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DOI：
10.1038/286496a0
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发表时间：
1980-01-01
期刊：
影响因子：
64.8
通讯作者：
MARSDEN, CD
中科院分区：
文献类型：
--
作者：
ROTHWELL, JC;TRAUB, MM;MARSDEN, CD
在人类，主动收缩的肌肉突然伸展会引发经典的单突触脊髓反射，然后是自动的长潜伏期反应，这两种反应都明显表现为肌电(EMG)1的活动爆发。这种长潜伏期反应在人类拇长屈肌中得到了广泛的研究，但也存在于许多其他肌肉2中，它出现得太早，不是自愿的，许多间接证据表明，它代表着一种‘长环’的操作，可能是跨皮质的牵拉反射机制3。一些研究人员发现，长潜伏期反应可能会因受试者的意图而大幅改变。这可能是通过预先设定中枢神经系统内的兴奋性水平，从而影响“长环”机制5-9。然而，其他人几乎没有观察到自愿设定对自动长潜伏期伸展反应10、11的影响。值得注意的是，这些研究在不同的实验条件下涉及不同的肌肉，产生了相互矛盾的结果。在一些研究中，肌肉伸展之前会有警告信号，而在另一些对照试验中，则穿插着伸展运动。为了解决这一困境，我们考察了这些变量的影响，发现在自愿反应时间最短的条件下，自动长潜伏期反应可以被最强烈地修改，例如，当刺激的时间可以被准确预测时。我们认为，长环路拉伸反应的改变不是由于某种中央预先设定的过程，而只是代表了长潜伏期的反射与随后的非常迅速的自愿事件之间的相互作用，由于刺激的可预测性，事件发生得很早。
In man, sudden stretch of an actively contracting muscle evokes a classical monosynaptic spinal reflex followed by an automatic ‘long-latency’ response, both evident as bursts of activity in the electromyogram (EMG)1. This long-latency response, extensively investigated in the human long thumb flexor, but present in many other muscles2, occurs too early to be voluntary and much indirect evidence suggests it represents the operation of a ‘long-loop’, perhaps transcortical, stretch reflex mechanism3,4. Some investigators have found that the long-latency responses may be modified substantially by the subject's intent, possibly by pre-setting of excitability levels within the central nervous system thereby influencing the ‘long-loop’ mechanism5–9. However, others have observed little effect of voluntary set on the automatic long-latency stretch response10,11. It is notable that these studies, which have yielded conflicting results, have involved different muscles in a variety of experimental conditions. In some studies a warning signal preceded muscular stretch, while in others control trials were interspersed with stretches. To resolve the dilemma we have examined the influence of these variables, and found that the automatic long-latency response can be modified most strongly in conditions when the voluntary reaction time is shortest, for example, when the timing of the stimulus can be predicted accurately. We suggest that modification of a long-loop stretch response is not due to some central pre-setting process, but merely represents interaction between a reflex of long latency and a subsequent very rapid voluntary event, occurring early because of predictability of the stimulus.