Max Planck Institute for Human Development, Center for Lifespan Psychology, Lentzeallee 94, 14195, Berlin, Germany.
Exp Brain Res. 2011 Apr;210(2):313-24. doi: 10.1007/s00221-011-2636-9. Epub 2011 Mar 26.
Neck muscle vibration (NMV) during upright standing is known to induce forward leaning, which has been explained as a global response to the (illusory) perception of a lengthening of the dorsal neck muscles. However, the effects of NMV both at the level of individual joints and on whole-body postural coordination, and its potential modulation by vision, have not yet been analyzed in detail. Eight healthy young adult participants completed a total of ten trials each, with a 10-s period of unperturbed standing followed by a 10-s period of NMV. Participants were instructed to stand "as still as possible". This postural task was executed under two visual conditions: eyes open (EO) and eyes closed (EC). Postural responses were measured in terms of center of pressure (CoP) and center of mass (CoM) profiles, and whole-body kinematics. Responses to NMV at the level of individual body segments and joints were assessed by decomposing the time series into linear trends and residual fluctuations. Inter-segmental coordination was analyzed using a decorrelation technique, assessing motor-equivalent stabilization of four task-related variables: CoM position, trunk orientation, as well as head position and orientation. NMV induced a general forward leaning response under both visual conditions, visible in CoP, CoM, segment positions and orientations. Locally, NMV induced a pronounced extension of the atlanto-occipital joint. Residual fluctuations were higher with EC and unaffected by NMV. Coordination analysis showed that stabilization of different body parts was differentially affected by NMV. Head orientation was consistently stabilized across all conditions, with weaker coordination in the EC condition. In contrast, motor-equivalent stabilization of CoM and head position, and trunk orientation was only observed during no-vibration periods. Taken together, our results demonstrate specific effects of vision and proprioception on different aspects of local and global postural control. While perturbed neck proprioception seemed to affect the postural "set point" (inducing forward leaning), vision appeared to mainly serve in noise reduction (residual fluctuations) and control of head orientation.
颈部肌肉振动（NMV）在直立位时已知会引起前倾，这被解释为对背部颈部肌肉延长的（虚幻）感知的整体反应。然而，NMV 对个体关节水平和整个身体姿势协调的影响，以及其对视觉的潜在调节作用，尚未得到详细分析。八名健康的年轻成年参与者每人共完成十次试验，其中包括 10 秒无干扰站立期和 10 秒 NMV 期。参与者被指示“尽可能静止地站立”。在两种视觉条件下执行这个姿势任务：睁眼（EO）和闭眼（EC）。姿势反应通过压力中心（CoP）和质心（CoM）轮廓以及整个身体运动学来测量。通过将时间序列分解为线性趋势和剩余波动来评估对 NMV 的个体身体部位和关节的反应。使用去相关技术分析节段间协调，评估与四个任务相关的变量（CoM 位置、躯干方向以及头部位置和方向）的电机等效稳定。NMV 在两种视觉条件下都引起了一般的前倾反应，CoP、CoM、节段位置和方向都可见。局部来看，NMV 引起寰枕关节明显伸展。EC 时剩余波动较高且不受 NMV 影响。协调分析表明，不同身体部位的稳定受到 NMV 的不同影响。头部方向在所有条件下都保持稳定，EC 条件下的协调较弱。相比之下，CoM 和头部位置以及躯干方向的电机等效稳定仅在无振动期间观察到。总的来说，我们的结果表明视觉和本体感觉对局部和全局姿势控制的不同方面有特定的影响。虽然受扰的颈部本体感觉似乎会影响姿势“设定点”（诱导前倾），但视觉似乎主要用于降噪（剩余波动）和头部方向的控制。
