Creath Rob, Kiemel Tim, Horak Fay, Jeka John J
Department of Kinesiology, 2359 HHP Building,University of Maryland, College Park, MD 20742-2611, USA.
Exp Brain Res. 2002 Aug;145(3):323-33. doi: 10.1007/s00221-002-1110-0. Epub 2002 Jun 13.
When subjects stand on an unstable or compliant support surface, rather than a stable one, vestibular information becomes more important for the control of posture. We investigated how subjects with bilateral vestibular loss (BVL) controlled their upright posture, with and without light-touch contact at the fingertip, while standing on a support surface, sinusoidally rotating at different frequencies. Subjects stood with eyes closed on a platform that rotated +/-1.2 degrees around an axis directly beneath the midline of the ankle for frequencies ranging from 0.01 to 0.4 Hz for two sensory conditions: (1) with light, nonsupportive touch (less than 1 N vertical force) on a stationary surface; or (2) with the fingertip held in a position directly above the contact surface (no contact). Gain, phase, and variability of the center of mass (CoM) and the finger were analyzed to compare BVL subjects with healthy controls in the no-touch and light-touch conditions. Three important results were observed: First, CoM gain and variability of BVL subjects was distinctly higher than control subjects with no-touch contact, particularly at the higher platform frequencies. Second, with light-touch contact, BVL and control subjects showed equivalent gain, variability, and phase. Third, multiple relationships between the finger and the CoM were observed in control subjects, whereas BVL subjects implemented a single finger/CoM control scheme. The results are explained in terms of three interacting factors: the transfer function of the vestibular system, a sensory reweighting mechanism, and the inertial properties of the body. Moreover, multiple control strategies observed in control subjects suggest a more flexible control system than that of individuals with severely diminished vestibular function.
当受试者站在不稳定或柔顺的支撑面上而非稳定支撑面上时，前庭信息对于姿势控制变得更加重要。我们研究了双侧前庭丧失（BVL）的受试者在站在以不同频率做正弦旋转的支撑面上时，在有无指尖轻触接触的情况下是如何控制其直立姿势的。受试者闭眼站在一个平台上，该平台围绕踝关节中线正下方的轴以±1.2度旋转，频率范围为0.01至0.4赫兹，共两种感觉条件：（1）在静止表面上有轻微的、无支撑的触摸（垂直力小于1牛）；或（2）指尖保持在接触表面正上方的位置（无接触）。分析了重心（CoM）和手指的增益、相位及变异性，以比较BVL受试者与健康对照在无接触和轻触条件下的情况。观察到三个重要结果：第一，BVL受试者的CoM增益和变异性明显高于无接触的对照受试者，尤其是在较高的平台频率下。第二，有轻触接触时，BVL受试者和对照受试者表现出等效的增益、变异性和相位。第三，在对照受试者中观察到手指与CoM之间存在多种关系，而BVL受试者采用单一的手指/CoM控制方案。这些结果从三个相互作用的因素来解释：前庭系统的传递函数、感觉重新加权机制和身体的惯性特性。此外，在对照受试者中观察到的多种控制策略表明其控制系统比前庭功能严重受损的个体更灵活。
