TASK-DEPENDENT REFLEX RESPONSES AND MOVEMENT ILLUSIONS EVOKED BY GALVANIC VESTIBULAR STIMULATION IN STANDING HUMANS
TASK-DEPENDENT REFLEX RESPONSES AND MOVEMENT ILLUSIONS EVOKED BY GALVANIC VESTIBULAR STIMULATION IN STANDING HUMANS
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DOI：
10.1113/jphysiol.1994.sp020257
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发表时间：
1994-07-15
影响因子：
5.5
通讯作者：
GANDEVIA, SC
中科院分区：
文献类型：
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作者：
FITZPATRICK, R;BURKE, D;GANDEVIA, SC
1.为了确定前庭对人类站立的贡献，研究了前庭电刺激诱发的腿部肌肉的反应。阶跃脉冲的电流之间的乳突正常受试者和比目鱼肌和胫骨前肌肌电图（EMG），踝关节扭矩和身体摇摆的影响进行了鉴定后刺激平均。当受试者站在一个稳定的平台或一个不稳定的平台上时，测量反应，并评估闭眼的影响。反应也记录在自愿收缩的腿部肌肉和当受试者平衡相当于自己的身体在前庭姿势反射将是无用的情况下的负载。在平均刺激后潜伏期为56 ms时，比目鱼肌和胫骨前肌活动出现相互变化，随后在105 ms时出现相反符号的更大反应。这些分别称为短潜伏期反应和中潜伏期反应。这两种反应都随刺激强度的增加而增加，但短潜伏期反应的阈值更高。早期反应有类似的潜伏期，快速姿势扰动诱发的肌电图反应。当眼睛闭上时，两种反应都更大，但眼睛闭上与摇摆和EMG活动增加有关，当缩放到背景EMG水平时，反应的幅度相似。比目鱼肌和胫骨前肌的短潜伏期和中潜伏期EMG反应产生小的短暂姿势摆动。EMG活动的短暂变化之后，是一个更大的长期摇摆，这不是由于在这些肌肉的活动，而是反射或意志的调整，在其他身体部位的运动。当受试者被阻止摇摆时，电流刺激产生了与站立时引起的摇摆相反方向的错觉运动，并且可能长时间的摇摆是对摇摆错觉的反应。短潜伏期和中潜伏期反应在不同的姿势任务根据前庭反射的依赖性进行修改。当支撑平台不稳定时，电流刺激的肌电反应较大。当受试者坐着做腿部肌肉的随意收缩或当他们直立着支撑躯干，用脚踝平衡身体负荷时，没有前庭诱发反应。它的结论是，第一，前庭对下肢肌肉的影响的效力取决于前庭线索是否需要姿势稳定性;第二，这是存在适当的本体感受线索，视觉输入对前庭效力的影响不大;第三，视觉线索本身不能弥补模糊的本体感受线索。
1. To identify the vestibular contribution to human standing, responses in leg muscles evoked by galvanic vestibular stimulation were studied. Step impulses of current were applied between the mastoid processes of normal subjects and the effects on the soleus and tibialis anterior electromyograms (EMGs), ankle torque, and body sway were identified by post-stimulus averaging. The responses were measured when subjects stood on a stable platform or on an unstable platform and the effects of eye closure were also assessed. Responses were also recorded during voluntary contraction of the leg muscles and when subjects balanced a load equivalent to their own body in a situation where vestibular postural reflexes would not be useful.2. At a mean post-stimulus latency of 56 ms, there were reciprocal changes in soleus and tibialis anterior muscle activity followed, at 105 ms, by larger responses of opposite sign. These were termed the short- and middle-latency responses, respectively. Both responses increased with stimulus intensity, but the short-latency response had a higher threshold. The early response had a similar latency to EMG responses evoked by rapid postural perturbations. Both responses mere larger when the eyes were closed, but eye closure was associated with increased sway and EMG activity, and the responses were of similar magnitude when scaled to background EMG level.3. Both short- and middle-latency EMG responses in soleus and tibialis anterior muscles produced small transient postural sways. The transient changes in EMG activity were followed by a larger prolonged sway which was not attributable to the activity in these muscles but rather to reflex or volitional adjustments to movements at other body segments. when subjects were prevented from swaying, the galvanic stimulus produced illusory movements in the opposite direction to the sway evoked when standing, and it is possible that the prolonged sway is a reaction to the illusion of sway.4. The short- and middle-latency responses were modified during different postural tasks according to the dependence on vestibular reflexes. When the support platform was unstable, the EMG responses to galvanic stimulation were larger. There were no vestibular-evoked responses when seated subjects made voluntary contractions of the leg muscles or when they stood upright with the trunk supported, using the ankles to balance a body-like load.5. It is concluded, first, that the potency of vestibular effects on lower-limb muscles depends on whether vestibular cues are required for postural stability; second, that is the presence of appropriate proprioceptive cues, visual inputs have little effect on vestibular potency; and third, that visual cues by themselves cannot compensate for ambiguous proprioceptive cues.