Noise Stimuli Improve the Accuracy of Target Aiming: Possible Involvement of Noise-Enhanced Balance Control

Balance stability is important for human beings. Previous studies have shown that mechanical noise applied to the soles of the feet via vibrating insoles can improve human balance control. In this study we designed an experimental procedure called standard aiming target test to quantitatively evaluate the effect of vibrating insole on specific task of aiming during standing. Ten subjects were asked to aim at a target sheet using laser gun, and the traces of their aimed light spots and the center of pressure (COP) were recorded simultaneously. The same test was repeated twice for each individual with vibrating insole off and on, respectively. To assess dynamic patterns in aiming spot and COP signals, we calculated the entropies in the magnitude increments of both signals at different time scales, i.e., multiscale entropies (MSE).We found that the vibrating insole significantly improved the aiming performance and led to increased entropy in the fluctuations of aiming spot displacement over a range of time scales from 0.001 to 0.05 s. In addition, subjects with larger entropies in the aiming spot fluctuations had better aiming performances. Furthermore, we found that the entropy of the light spot signal was positively correlated with the entropy of the magnitude time series of COP fluctuations. These results suggest that vibrating insoles is beneficial for the complex postural control process during target aiming, possibly via their dynamic influences on the balance regulatory system.