Allum J H, Honegger F, Schicks H
Department of ORL, University Hospital, Basel, Switzerland.
J Vestib Res. 1994 Spring;4(1):49-70.
The role of vestibular sensory information in the triggering, selection and modulation of postural response synergies was evaluated by comparing the EMG responses of normal subjects to balance perturbations with those of subjects with a bilateral peripheral vestibular deficit. The balance perturbations were a rotation and/or a translation of a support surface on which the test subjects stood with eyes open. Onset latencies and most timing patterns of muscle responses were not altered in vestibular-loss subjects. Major changes were observed, however, in the muscle amplitude synergy. Responses between 120 and 240 ms in tibialis anterior, soleus, and quadriceps muscles were reduced more than 50% with respect to normal amplitudes. In contrast, responses in paraspinal muscles were enhanced nearly 100% with respect to normal values. These changes in muscle amplitudes with accompanying vestibular loss were highest for rotation and lowest for translation perturbations. The identification of a bilateral vestibular loss using EMG amplitudes was always 100% correct for rotation perturbations and between 75 to 85% correct for translation perturbations. Multivariate linear correlations between muscle EMG response areas, and the amplitudes of initial link velocities revealed an increased contribution of afferent signals from the upper leg and a decreased dependence on signals from the trunk and head to postural synergies in vestibular-loss subjects. The afferent modulation of the muscle amplitude synergy correcting a balance disturbance to the stance of normal subjects is, on the basis of these findings, highly dependent on vestibular afferent signals. Our results indicate that vestibular afferent signals are used to enhance the amplitude of responses in tibialis anterior, quadriceps, and soleus muscles; and inhibit the responses of paraspinal muscles, once the response timing has been triggered and selected by proprioceptive signals. Lacking this modulation, bilateral vestibular deficit subjects respond to balance perturbations under eyes-open conditions as if the perturbation were 50% slower. Clinically, our results document that the perturbation of choice, when testing vestibular deficit patients, is a rotation (greater than 3 degrees in amplitude and 15 degrees/s in velocity) and not a translation of the support surface.
通过比较正常受试者与双侧外周前庭功能缺失受试者对平衡扰动的肌电图（EMG）反应，评估前庭感觉信息在姿势反应协同作用的触发、选择和调节中的作用。平衡扰动是测试受试者睁眼站立的支撑面的旋转和/或平移。在前庭功能丧失的受试者中，肌肉反应的起始潜伏期和大多数时间模式没有改变。然而，观察到肌肉幅度协同作用有重大变化。与正常幅度相比，胫前肌、比目鱼肌和股四头肌在120至240毫秒之间的反应减少了50%以上。相比之下，椎旁肌的反应相对于正常值增强了近100%。伴随前庭功能丧失的这些肌肉幅度变化在旋转时最高，在平移扰动时最低。使用EMG幅度识别双侧前庭功能丧失对于旋转扰动总是100%正确，对于平移扰动正确度在75%至85%之间。肌肉EMG反应区域与初始环节速度幅度之间的多元线性相关性表明，在前庭功能丧失的受试者中，来自大腿的传入信号对姿势协同作用的贡献增加，而对来自躯干和头部信号的依赖性降低。基于这些发现，正常受试者在平衡扰动时对姿势进行纠正的肌肉幅度协同作用的传入调节高度依赖于前庭传入信号。我们的结果表明，一旦反应时机由本体感觉信号触发和选择，前庭传入信号就用于增强胫前肌、股四头肌和比目鱼肌的反应幅度，并抑制椎旁肌的反应。由于缺乏这种调节，双侧前庭功能缺失的受试者在睁眼条件下对平衡扰动的反应就好像扰动慢了50%。临床上，我们的结果证明，在测试前庭功能缺失患者时，首选的扰动是旋转（幅度大于3度，速度为15度/秒），而不是支撑面的平移。
