Neurozentrum, Neurologie der Universität Freiburg, Freiburg, Germany;
J Neurophysiol. 2014 May;111(9):1852-64. doi: 10.1152/jn.00669.2013. Epub 2014 Feb 5.
Healthy humans control balance during stance by using an active feedback mechanism that generates corrective torque based on a combination of movement and orientation cues from visual, vestibular, and proprioceptive systems. Previous studies found that the contribution of each of these sensory systems changes depending on perturbations applied during stance and on environmental conditions. The process of adjusting the sensory contributions to balance control is referred to as sensory reweighting. To investigate the dynamics of reweighting for the sensory modalities of vision and proprioception, 14 healthy young subjects were exposed to six different combinations of continuous visual scene and platform tilt stimuli while sway responses were recorded. Stimuli consisted of two components: 1) a pseudorandom component whose amplitude periodically switched between low and high amplitudes and 2) a low-amplitude sinusoidal component whose amplitude remained constant throughout a trial. These two stimuli were mathematically independent of one another and, thus, permitted separate analyses of sway responses to the two components. For all six stimulus combinations, the sway responses to the constant-amplitude sine were influenced by the changing amplitude of the pseudorandom component in a manner consistent with sensory reweighting. Results show clear evidence of intra- and intermodality reweighting. Reweighting dynamics were asymmetric, with slower reweighting dynamics following a high-to-low transition in the pseudorandom stimulus amplitude compared with low-to-high amplitude shifts, and were also slower for inter- compared with intramodality reweighting.
健康人通过使用基于视觉、前庭和本体感觉系统的运动和方向线索的组合来生成校正扭矩的主动反馈机制来控制站立时的平衡。先前的研究发现，这些感觉系统中的每一个的贡献取决于在站立期间施加的扰动和环境条件而变化。调整平衡控制的感觉贡献的过程称为感觉重新加权。为了研究视觉和本体感觉感觉模式的重新加权的动力学，14 名健康的年轻受试者在记录摇摆反应的同时，暴露于六种不同的连续视觉场景和平台倾斜刺激的组合下。刺激由两个组成部分组成：1）其幅度在低幅度和高幅度之间周期性切换的伪随机分量，和 2）幅度在整个试验中保持恒定的低幅度正弦分量。这两个刺激彼此在数学上是独立的，因此允许对两个分量的摇摆反应进行单独分析。对于所有六种刺激组合，对于恒定幅度正弦的摇摆反应受到伪随机分量的变化幅度的影响，这种影响与感觉重新加权一致。结果清楚地表明了内模式和外模式的重新加权。重新加权动力学是不对称的，与低至高幅度变化相比，在伪随机刺激幅度从高到低的过渡后重新加权动力学较慢，与内模式相比，外模式重新加权动力学也较慢。
