CEREBELLAR CONTROL OF POSTURAL SCALING AND CENTRAL SET IN STANCE
CEREBELLAR CONTROL OF POSTURAL SCALING AND CENTRAL SET IN STANCE
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DOI：
10.1152/jn.1994.72.2.479
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发表时间：
1994-08-01
影响因子：
2.5
通讯作者：
DIENER, HC
中科院分区：
文献类型：
--
作者：
HORAK, FB;DIENER, HC
1. 研究了人类小脑缺陷对基于感觉反馈和预测中心集的自动姿势反应幅度的影响。对小脑前叶疾病患者和正常健康成年人在站立期间暴露于四种速度和五种表面平移幅度的块的肌电图（EMG）和表面反应扭矩进行了比较。最早的姿势反应（积分肌电图和初始扭矩变化率）与平移速度之间的相关性提供了使用来自当前位移的感觉信息来测量姿势幅度缩放的方法。响应与平移幅度的相关性提供了基于预测中心集的缩放测量，该预测中心集基于先前类似位移的连续经验，因为最早的姿势反应发生在位移完成之前，并且因为当正常受试者中的幅度被随机化时，位移幅度的缩放消失了。 2．小脑患者对向后表面位移引起的向前身体摇摆的反应是超量度的，也就是说，表面反应扭矩反应比正常情况大两到三倍，并且更长的肌肉爆发导致初始姿势的过度调节。尽管存在这种姿势性高度测量，但小脑患者的踝关节、膝关节和髋关节激动肌爆发的绝对和相对潜伏期均正常。3．尽管它们是超测量的，但小脑患者最早的姿势反应通过体感反馈正常缩放到平台位移速度。然而，小脑患者无法根据使用中心设置的先前经验将初始姿势反应幅度调整为预期位移幅度。位移幅度的随机化消除了幅度对正常受试者初始反应的设定影响，但小脑患者对随机和分组试验的反应没有差异。4．小脑患者通过用位移速度和幅度缩放大的、相互激活的胫骨肌和股四头肌拮抗剂活动来补偿超测量反应和最早腓肠肌活动的预期缩放的缺乏。当幅度被随机化时，这些拮抗剂肌电图积分和位移幅度之间的相关性得以保留，这表明反馈依赖性而非设定依赖性机制负责小脑患者对拮抗剂的缩放。当法线对出乎意料的小幅度的表面位移做出过度反应时，也可能会在法线中引起对初始超测量反应的拮抗补偿。5。小脑前叶损伤对人类姿势反应的主要影响涉及基于预测中心集的反应幅度损害，而不是基于速度反馈的使用或多关节姿势协调的时间协同组织。因此，小脑前叶似乎在根据先前的经验调整对预期位移条件的自动姿势反应的幅度方面发挥着关键作用。这项研究表明，小脑中线通过调整自动姿势反应的阈值或偏差，而不是斜率或增益来调整体感环路的大小，以维持站立姿势。
1. The effects of cerebellar deficits in humans on scaling the magnitude of automatic postural responses based on sensory feedback and on predictive central set was investigated. Electromyographic (EMG) and surface reactive torques were compared in patients with anterior lobe cerebellar disorders and in normal healthy adults exposed to blocks of four velocities and five amplitudes of surface translations during stance. Correlations between the earliest postural responses (integrated EMG and initial rate of change of torque) and translation velocity provided a measure of postural magnitude scaling using sensory information from the current displacement. Correlations of responses with translation amplitude provided a measure of scaling dependent on predictive central set based on sequential experience with previous like displacements because the earliest postural responses occurred before completion of the displacements and because scaling to displacement amplitude disappeared when amplitudes were randomized in normal subjects.2. Responses of cerebellar patients to forward body sway induced by backward surface displacements were hypermetric, that is, surface-reactive torque responses were two to three times larger than normal with longer muscle bursts resulting in overshooting of initial posture. Despite this postural hypermetria, the absolute and relative latencies of agonist muscle bursts at the ankle, knee, and hip were normal in cerebellar patients.3. Although they were hypermetric, the earliest postural responses of cerebellar patients were scaled normally to platform displacement velocities using somatosensory feedback. Cerebellar patients, however, were unable to scale initial postural response magnitude to expected displacement amplitudes based on prior experience using central set. Randomization of displacement amplitudes eliminated the set effect of amplitude on initial responses in normal subjects, but responses to randomized and blocked trials were not different in cerebellar patients.4. Cerebellar patients compensated for hypermetric responses and lack of anticipatory scaling of earliest gastrocnemius activity by scaling large, reciprocally activated tibialis and quadriceps antagonist activity with the displacement velocity and amplitude. Correlations between these antagonist EMG integrals and displacement amplitudes were preserved when amplitudes were randomized, suggesting that feedback-dependent and not set-dependent mechanisms were responsible for scaling of antagonists by cerebellar patients. Antagonist compensation for initial hypermetric responses also could be induced in normals when they overresponded to unexpectedly small amplitudes of surface displacements.5. The major effects of anterior lobe cerebellar damage on human postural responses involves impairment of response magnitude based on predictive central set and not on use of velocity feedback or on the temporal synergic organization of multijoint postural coordination. Thus the anterior lobe of the cerebellum appears to play a critical role in modifying the magnitude of automatic postural responses to anticipated displacement conditions based on prior experience. This study suggests that the midline cerebellum tunes the magnitude of somatosensory loops for maintenance of stance posture by adjusting the threshold or bias, and not the slope or gain, of automatic postural responses.