Department of Neurology, Oregon Health and Science University, Portland, OR, USA.
Neuroscience. 2011 Feb 3;174:216-23. doi: 10.1016/j.neuroscience.2010.11.017. Epub 2010 Nov 16.
It is unclear how haptic touch with a stable surface reduces postural sway. We hypothesized that haptic input enhances postural stability due to alterations in axial postural tone. We measured the influence of heavy and light touch (LT) of the hands on a stable bar on axial postural tone and postural sway during stance in 14 healthy adults. A unique "Twister" device measured hip torque by fixing the upper body in space while oscillating the surface in yaw ±10 at 1 deg/s. Subjects were tested while: (1) standing quietly with their arms at their sides, (2) lightly touching a rigid bar in front of them and (3) firmly gripping the bar. Horizontal and vertical sway was not restricted by the device's yaw fixation, therefore, the subjects remained in a state of active postural control during the three touch conditions. Haptic touch significantly increased hip postural tone by 44% during light touch, from 2.5±0.9 to 3.6±1.0 Nm (P=0.005), and by 40% during firm grip to 3.5±0.8 Nm (P=0.005). Increases in hip postural tone were associated with a reduction in postural sway (r=-0.55, P=0.001). This is the first study showing that axial postural tone can be modified by remote somatosensory input and provides a potential explanation for how light touch improves postural stability. Changes in subjects' perception from trunk to surface rotation when changing from no touch (NT) to haptic touch, suggests that the CNS changes from using a global, to a local, trunk reference frame for control of posture during touch. The increase of hip postural tone during touching and gripping can be explained as a suppression of hip muscle shortening reactions that normally assist axial rotation.
触觉触摸稳定表面如何减少姿势摆动尚不清楚。我们假设触觉输入通过改变轴向姿势张力来增强姿势稳定性。我们测量了 14 名健康成年人在稳定杆上进行手部重触和轻触（LT）对轴向姿势张力和站立时姿势摆动的影响。独特的“Twister”装置通过将上半身固定在空间中，同时以 1 度/秒的速度在偏航±10 处振荡表面，来测量臀部扭矩。在以下三种情况下测试了受试者：（1）手臂放在身体两侧安静站立，（2）轻轻触摸面前的刚性杆，（3）紧紧握住杆。该设备的偏航固定不限制水平和垂直摆动，因此，在这三种触摸条件下，受试者仍处于主动姿势控制状态。轻触时，触觉触摸使臀部姿势张力显著增加 44%，从 2.5±0.9 增加到 3.6±1.0 Nm（P=0.005），在紧握时增加 40%至 3.5±0.8 Nm（P=0.005）。臀部姿势张力的增加与姿势摆动的减少相关（r=-0.55，P=0.001）。这是第一项表明可以通过远程躯体感觉输入来改变轴向姿势张力的研究，并为轻触如何改善姿势稳定性提供了潜在的解释。当从无触摸（NT）变为触觉触摸时，受试者从躯干到表面旋转的感知变化表明，中枢神经系统从使用全局、局部躯干参考框架来控制触摸期间的姿势。在触摸和握持时臀部姿势张力的增加可以解释为抑制了通常有助于轴向旋转的臀部肌肉缩短反应。
