Logan David, Kiemel Tim, Jeka John J
Department of Kinesiology, University of Maryland, College Park, Maryland, United States of America; Neuroscience and Cognitive Science Program, University of Maryland, College Park, Maryland, United States of America.
Department of Kinesiology, University of Maryland, College Park, Maryland, United States of America.
PLoS One. 2014 Jun 24;9(6):e100418. doi: 10.1371/journal.pone.0100418. eCollection 2014.
To investigate sensory reweighting as a fundamental property of sensor fusion during standing, we probed postural control with simultaneous rotations of the visual scene and surface of support. Nineteen subjects were presented with pseudo-random pitch rotations of visual scene and platform at the ankle to test for amplitude dependencies in the following conditions: low amplitude vision: high amplitude platform, low amplitude vision: low amplitude platform, and high amplitude vision: low amplitude platform. Gain and phase of frequency response functions (FRFs) to each stimulus were computed for two body sway angles and a single weighted EMG signal recorded from seven muscles. When platform stimulus amplitude was increased while visual stimulus amplitude remained constant, gain to vision increased, providing strong evidence for inter-modal reweighting between vision and somatosensation during standing. Intra-modal reweighting of vision was also observed as gains to vision decreased as visual stimulus amplitude increased. Such intra-modal and inter-modal amplitude dependent changes in gain were also observed in muscular activity. Gains of leg segment angle and muscular activity relative to the platform, on the other hand, showed only intra-modal reweighting. That is, changing platform motion amplitude altered the responses to both visual and support surface motion whereas changing visual scene motion amplitude did not significantly affect responses to support surface motion, indicating that the sensory integration scheme between somatosensation (at the support surface) and vision is asymmetric.
为了研究感觉重新加权作为站立过程中传感器融合的基本特性，我们通过视觉场景和支撑表面的同时旋转来探究姿势控制。19名受试者在以下条件下接受视觉场景和踝关节处平台的伪随机俯仰旋转，以测试幅度依赖性：低幅度视觉：高幅度平台、低幅度视觉：低幅度平台、高幅度视觉：低幅度平台。针对两个身体摇摆角度以及从七块肌肉记录的单个加权肌电信号，计算对每种刺激的频率响应函数（FRF）的增益和相位。当视觉刺激幅度保持恒定时增加平台刺激幅度，对视觉的增益增加，这为站立过程中视觉与躯体感觉之间的跨模态重新加权提供了有力证据。随着视觉刺激幅度增加，对视觉的增益降低，也观察到了视觉的模态内重新加权。在肌肉活动中也观察到了这种模态内和跨模态幅度依赖性的增益变化。另一方面，腿部节段角度和肌肉活动相对于平台的增益仅表现出模态内重新加权。也就是说，改变平台运动幅度会改变对视觉和支撑表面运动的反应，而改变视觉场景运动幅度不会显著影响对支撑表面运动的反应，这表明躯体感觉（在支撑表面）和视觉之间的感觉整合方案是不对称的。
