Neuroscience Program and Biomedical Engineering Laboratory, Universidade de São Paulo, EPUSP, PTC, Avenida Professor Luciano Gualberto, Travessa 3, n.158, São Paulo, SP, Brazil.
Exp Brain Res. 2012 Mar;217(2):175-86. doi: 10.1007/s00221-011-2983-6. Epub 2011 Dec 24.
Optimal levels of noise stimulation have been shown to enhance the detection and transmission of neural signals thereby improving the performance of sensory and motor systems. The first series of experiments in the present study aimed to investigate whether subsensory electrical noise stimulation applied over the triceps surae (TS) in seated subjects decreases torque variability during a force-matching task of isometric plantar flexion and whether the same electrical noise stimulation decreases postural sway during quiet stance. Correlation tests were applied to investigate whether the noise-induced postural sway decrease is linearly predicted by the noise-induced torque variability decrease. A second series of experiments was conducted to investigate whether there are differences in torque variability between conditions in which the subsensory electrical noise is applied only to the TS, only to the tibialis anterior (TA) and to both TS and TA, during the force-matching task with seated subjects. Noise stimulation applied over the TS muscles caused a significant reduction in force variability during the maintained isometric force paradigm and also decreased postural oscillations during quiet stance. Moreover, there was a significant correlation between the reduction in force fluctuation and the decrease in postural sway with the electrical noise stimulation. This last result indicates that changes in plantar flexion force variability in response to a given subsensory random stimulation of the TS may provide an estimate of the variations in postural sway caused by the same subsensory stimulation of the TS. We suggest that the decreases in force variability and postural sway found here are due to stochastic resonance that causes an improved transmission of proprioceptive information. In the second series of experiments, the reduction in force variability found when noise was applied to the TA muscle alone did not reach statistical significance, suggesting that TS proprioception gives a better feedback to reduce force fluctuation in isometric plantar flexion conditions.
已证实，最佳的噪声刺激水平可以增强神经信号的检测和传输，从而提高感觉和运动系统的性能。本研究的第一个系列实验旨在研究在坐姿受试者中，对三头肌（TS）施加亚阈电噪声刺激是否会降低等长跖屈力匹配任务中的扭矩变异性，以及相同的电噪声刺激是否会降低安静站立时的姿势摆动。相关测试用于研究噪声引起的姿势摆动减小是否可以通过噪声引起的扭矩变异性减小来线性预测。第二个系列实验旨在研究在坐姿受试者的力匹配任务中，仅对 TS、仅对胫骨前肌（TA）以及对 TS 和 TA 施加亚阈电噪声刺激时，在哪些条件下 TS 处的扭矩变异性存在差异。在保持等长力范式期间，TS 肌肉上的噪声刺激会导致力变异性显著降低，并且在安静站立时会降低姿势摆动。此外，噪声刺激引起的力波动减小与姿势摆动减小之间存在显著相关性。这一最后结果表明，对 TS 的给定亚阈随机刺激的响应中跖屈力变异性的变化可以提供由 TS 的相同亚阈刺激引起的姿势摆动变化的估计。我们认为，这里发现的力变异性和姿势摆动减小是由于随机共振引起的，这导致本体感觉信息的传输得到改善。在第二个系列实验中，当仅将噪声施加到 TA 肌肉时，发现力变异性的减小未达到统计学意义，这表明 TS 本体感觉在等长跖屈条件下提供了更好的反馈以减小力波动。
