Mildren Robyn L, Peters Ryan M, Hill Aimee J, Blouin Jean-Sébastien, Carpenter Mark G, Inglis J Timothy
School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada;
School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada.
J Appl Physiol (1985). 2017 May 1;122(5):1134-1144. doi: 10.1152/japplphysiol.00908.2016. Epub 2017 Feb 16.
Noisy stimuli, along with linear systems analysis, have proven to be effective for mapping functional neural connections. We explored the use of noisy (10-115 Hz) Achilles tendon vibration to examine somatosensory reflexes in the triceps surae muscles in standing healthy young adults ( = 8). We also examined the association between noisy vibration and electrical activity recorded over the sensorimotor cortex using electroencephalography. We applied 2 min of vibration and recorded ongoing muscle activity of the soleus and gastrocnemii using surface electromyography (EMG). Vibration amplitude was varied to characterize reflex scaling and to examine how different stimulus levels affected postural sway. Muscle activity from the soleus and gastrocnemii was significantly correlated with the tendon vibration across a broad frequency range (~10-80 Hz), with a peak located at ~40 Hz. Vibration-EMG coherence positively scaled with stimulus amplitude in all three muscles, with soleus displaying the strongest coupling and steepest scaling. EMG responses lagged the vibration by ~38 ms, a delay that paralleled observed response latencies to tendon taps. Vibration-evoked cortical oscillations were observed at frequencies ~40-70 Hz (peak ~54 Hz) in most subjects, a finding in line with previous reports of sensory-evoked γ-band oscillations. Further examination of the method revealed ) accurate reflex estimates could be obtained with <60 s of low-level (root mean square = 10 m/s) vibration; ) responses did not habituate over 2 min of exposure; and importantly, ) noisy vibration had a minimal influence on standing balance. Our findings suggest noisy tendon vibration is an effective novel approach to characterize somatosensory reflexes during standing. We applied noisy (10-115 Hz) vibration to the Achilles tendon to examine the frequency characteristics of lower limb somatosensory reflexes during standing. Ongoing muscle activity was coherent with the noisy vibration (peak coherence ~40 Hz), and coherence positively scaled with increases in stimulus amplitude. Our findings suggest that noisy tendon vibration, along with linear systems analysis, is an effective novel approach to study somatosensory reflex actions in active muscles.
事实证明，噪声刺激与线性系统分析相结合，对于绘制功能性神经连接十分有效。我们探索了使用噪声（10 - 115赫兹）刺激跟腱振动，来检测健康年轻成年人（ = 8）站立时小腿三头肌的体感反射。我们还使用脑电图检查了噪声振动与感觉运动皮层记录的电活动之间的关联。我们施加了2分钟的振动，并使用表面肌电图（EMG）记录比目鱼肌和腓肠肌的持续肌肉活动。改变振动幅度以表征反射缩放，并研究不同刺激水平如何影响姿势摆动。比目鱼肌和腓肠肌的肌肉活动在很宽的频率范围（约10 - 80赫兹）内与肌腱振动显著相关，峰值位于约40赫兹处。振动 - EMG相干性在所有三块肌肉中均与刺激幅度呈正相关，比目鱼肌显示出最强的耦合和最陡的缩放。EMG反应比振动滞后约38毫秒，这一延迟与观察到的对肌腱轻敲的反应潜伏期相似。在大多数受试者中，在约40 - 70赫兹（峰值约54赫兹）的频率下观察到振动诱发的皮层振荡，这一发现与先前关于感觉诱发γ波段振荡的报道一致。对该方法的进一步研究表明：）使用<60秒的低水平（均方根 = 10米/秒）振动即可获得准确的反射估计；）在2分钟的暴露过程中反应不会产生习惯化；重要的是，）噪声振动对站立平衡的影响极小。我们的研究结果表明，噪声肌腱振动是一种在站立时表征体感反射的有效新方法。我们对跟腱施加噪声（10 - 115赫兹）振动，以检查站立时下肢体感反射的频率特征。持续的肌肉活动与噪声振动相干（峰值相干约40赫兹），并且相干性随刺激幅度的增加而呈正相关。我们的研究结果表明，噪声肌腱振动与线性系统分析相结合，是研究活跃肌肉中体感反射动作的一种有效新方法。
