Postural sway reduction by weak electrical noise into the wrist median nerve using portable stimulator

Stochastic resonance (SR) is a weak noise stimulation that improves the function of standing balance by increasing sensitivity to somatosensory information. SR implemented in the lower limbs may increase the standing balance function, but the effect of noise stimulation on upper limbs has not been investigated to date. This study aims to investigate the effect of weak electrical noise stimulation of the median nerve at the wrist on the balance control system function using a portable stimulator. Ten healthy individuals participated in the study. Each subject maintained quiet standing with their eyes closed for 40 s while receiving white noise electrical stimulation to the median nerve at the wrist. Center of pressure (COP) displacement and change in the joint position (left and right waist) were measured and compared between a no-stimulus trial (control trial) and a stimulus intensity trial that maximized the effect of SR (optimal trial). Experimental results show that weak electrical noise stimulation of the median nerve at the wrist stabilized the COP and joint position. The anteroposterior (AP) standard deviation of the optimal trial were significantly reduced compared to the control trial in terms of COP and left and right waist, and AP low-frequency range power of the optimal trial were significantly reduced compared to the control trial in terms of COP and left waist. AP mean velocity and AP high-frequency range power at the left waist were significantly reduced in the optimal trial. It was concluded that weak electrical noise stimulation applied to the median nerve can reduce static postural sway.