Krishnamoorthy Vijaya, Slijper Harm, Latash Mark L
Department of Kinesiology, Rec. Hall - 267L, The Pennsylvania State University, University Park, PA 16802, USA.
Exp Brain Res. 2002 Nov;147(1):71-9. doi: 10.1007/s00221-002-1206-6. Epub 2002 Sep 13.
When a standing person applies a light finger touch to an external stable object, postural sway is reduced. We tested a hypothesis that two factors related to touch can induce this effect, the presence of a stable reference point and the modulation of contact forces leading to tissue deformation. Force platform signals were analyzed while subjects stood quietly with or without additional light touch to an external object (contact forces under 1 N). The point of touch on the body was manipulated. We also investigated the effects of active touch vs fixation of a finger at a point in external space. The results show that touch to the head or neck can be more effective in reducing body sway than a finger touch. A larger reduction in sway was observed when the finger was fixed in a clip (the net forces between the clip and the point of its fixation to the stand were under 1 N) as compared to a free light touch to a pad. The subjects showed a reduction in postural sway while holding a load suspended using a pulley system; in this situation, contact with the load via the pulley provided modulation of contact forces but not a fixed reference point. This finding emphasizes the importance of such factors as stability of the contact point and modulation of contact forces, as compared to active touch or to an implicit task of stabilizing the kinematic chain. The system of postural stabilization can reduce postural sway, making use of either of two sources of sensory information associated with touch, one related to providing a fixed reference point in space, and the other related to transient force changes at the point of contact related to the sway.
当站立的人用手指轻轻触碰一个外部稳定物体时，姿势摆动会减少。我们测试了一个假设，即与触摸相关的两个因素可诱发这种效应，一个是存在稳定的参考点，另一个是接触力的调制导致组织变形。在受试者安静站立且有无额外轻轻触碰外部物体（接触力低于1牛顿）的情况下，分析了力平台信号。对身体上的触摸点进行了操控。我们还研究了主动触摸与手指固定在外部空间某一点的效果。结果表明，触摸头部或颈部在减少身体摆动方面可能比手指触摸更有效。与自由轻轻触摸垫子相比，当手指固定在夹子中（夹子与其固定在支架上的点之间的净力低于1牛顿）时，观察到摆动有更大程度的减少。受试者在握住通过滑轮系统悬挂的负载时，姿势摆动减少；在这种情况下，通过滑轮与负载的接触提供了接触力的调制，但没有固定的参考点。这一发现强调了接触点稳定性和接触力调制等因素的重要性，与主动触摸或稳定运动链的隐性任务相比。姿势稳定系统可以利用与触摸相关的两种感官信息来源中的任何一种来减少姿势摆动，一种与在空间中提供固定参考点有关，另一种与与摆动相关的接触点处的瞬态力变化有关。
