Co-ordination of the upper and lower limbs for vestibular control of balance.
Co-ordination of the upper and lower limbs for vestibular control of balance.
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DOI：
10.1113/jp274272
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发表时间：
2017-11-01
期刊：
影响因子：
--
通讯作者：
Reynolds RF
中科院分区：
文献类型：
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作者：
Smith CP;Allsop JE;Mistry M;Reynolds RF
当站立并握住固定在地面上的物体时，前庭电刺激（GVS）可以引起上肢反应以保持平衡。在目前的研究中，我们确定了这些反应是如何受到握力环境（无接触、轻握力和握力）的影响，以及它们如何与下肢协调以保持平衡。当GVS应用在牢固的抓地力，手和地面反作用力产生。这些力向量的方向是协调一致的，这样整体的身体摇摆响应总是与耳间轴（即以颅为中心）对齐。当轻握力（< 1 N）时施加GVS时，手部力量次于身体运动，这表明手臂的作用主要是被动的。这些结果表明，在上肢主动控制平衡之前，需要最低水平的抓地力，并且上肢和下肢协调以实现适当的全身摇摆响应。当前庭刺激用于平衡时，可以引起手臂的反应。在目前的研究中，我们确定了这些反应是如何受到握力环境的影响，以及它们是如何与身体的其他部分协调的。前庭电刺激（GVS）用于在三种情况下唤起手接触地面固定物体的平衡反应：无接触、轻握（< 1 N） （LG）和紧握（FG）。随着抓地力的增加，我们观察到GVS诱发的手部力增加，同时脚部的地面反作用力（GRF）减少。在LG实验中，手的力量次于GVS诱发的身体摇摆反应，这表明手臂的作用主要是被动的。相比之下，在FG期间，手臂变得积极参与驱动身体摇摆，正如在LG中看到的相反方向的早期力脉冲所揭示的那样。然后，我们检查了这个活动手矢量的方向如何与下肢协调。与之前关于摇摆各向异性的研究结果一致，FG使GVS诱发的GRF矢量向基线姿势不稳定轴线倾斜。然而，这被手的力向量有效地抵消了，这样整个身体的摇摆响应仍然与耳间轴对齐，保持了颅中心的原则。这些结果表明，上肢在前庭诱发的平衡反应中发挥积极作用之前，必须达到最低的握力水平。此外，他们证明了上肢和下肢的力是协调的，以产生适当的全身摇摆响应。当站立并握住固定在地面上的物体时，前庭电刺激（GVS）可以引起上肢反应以保持平衡。在目前的研究中，我们确定了这些反应是如何受到握力环境（无接触、轻握力和握力）的影响，以及它们如何与下肢协调以保持平衡。当GVS应用在牢固的抓地力，手和地面反作用力产生。这些力向量的方向是协调一致的，这样整体的身体摇摆响应总是与耳间轴（即以颅为中心）对齐。当轻握力（< 1 N）时施加GVS时，手部力量次于身体运动，这表明手臂的作用主要是被动的。这些结果表明，在上肢主动控制平衡之前，需要最低水平的抓地力，并且上肢和下肢协调以实现适当的全身摇摆响应。
When standing and holding an earth‐fixed object, galvanic vestibular stimulation (GVS) can evoke upper limb responses to maintain balance. In the present study, we determined how these responses are affected by grip context (no contact, light grip and firm grip), as well as how they are co‐ordinated with the lower limbs to maintain balance. When GVS was applied during firm grip, hand and ground reaction forces were generated. The directions of these force vectors were co‐ordinated such that the overall body sway response was always aligned with the inter‐aural axis (i.e. craniocentric). When GVS was applied during light grip (< 1 N), hand forces were secondary to body movement, suggesting that the arm performed a mostly passive role. These results demonstrate that a minimum level of grip is required before the upper limb becomes active in balance control and also that the upper and lower limbs co‐ordinate for an appropriate whole‐body sway response. Vestibular stimulation can evoke responses in the arm when it is used for balance. In the present study, we determined how these responses are affected by grip context, as well as how they are co‐ordinated with the rest of the body. Galvanic vestibular stimulation (GVS) was used to evoke balance responses under three conditions of manual contact with an earth‐fixed object: no contact, light grip (< 1 N) (LG) and firm grip (FG). As grip progressed along this continuum, we observed an increase in GVS‐evoked hand force, with a simultaneous reduction in ground reaction force (GRF) through the feet. During LG, hand force was secondary to the GVS‐evoked body sway response, indicating that the arm performed a mostly passive role. By contrast, during FG, the arm became actively involved in driving body sway, as revealed by an early force impulse in the opposite direction to that seen in LG. We then examined how the direction of this active hand vector was co‐ordinated with the lower limbs. Consistent with previous findings on sway anisotropy, FG skewed the direction of the GVS‐evoked GRF vector towards the axis of baseline postural instability. However, this was effectively cancelled by the hand force vector, such that the whole‐body sway response remained aligned with the inter‐aural axis, maintaining the craniocentric principle. These results show that a minimum level of grip is necessary before the upper limb plays an active role in vestibular‐evoked balance responses. Furthermore, they demonstrate that upper and lower‐limb forces are co‐ordinated to produce an appropriate whole‐body sway response. When standing and holding an earth‐fixed object, galvanic vestibular stimulation (GVS) can evoke upper limb responses to maintain balance. In the present study, we determined how these responses are affected by grip context (no contact, light grip and firm grip), as well as how they are co‐ordinated with the lower limbs to maintain balance. When GVS was applied during firm grip, hand and ground reaction forces were generated. The directions of these force vectors were co‐ordinated such that the overall body sway response was always aligned with the inter‐aural axis (i.e. craniocentric). When GVS was applied during light grip (< 1 N), hand forces were secondary to body movement, suggesting that the arm performed a mostly passive role. These results demonstrate that a minimum level of grip is required before the upper limb becomes active in balance control and also that the upper and lower limbs co‐ordinate for an appropriate whole‐body sway response.