Using Low Levels of Stochastic Vestibular Stimulation to Improve Balance Function

Abstract

Low-level stochastic vestibular stimulation (SVS) has been associated with improved postural responses in the medio-lateral (ML) direction, but its effect in improving balance function in both the ML and anterior-posterior (AP) directions has not been studied. In this series of studies, the efficacy of applying low amplitude SVS in 0–30 Hz range between the mastoids in the ML direction on improving cross-planar balance function was investigated. Forty-five (45) subjects stood on a compliant surface with their eyes closed and were instructed to maintain a stable upright stance. Measures of stability of the head, trunk, and whole body were quantified in ML, AP and combined APML directions. Results show that binaural bipolar SVS given in the ML direction significantly improved balance performance with the peak of optimal stimulus amplitude predominantly in the range of 100–500 μA for all the three directions, exhibiting stochastic resonance (SR) phenomenon. Objective perceptual and body motion thresholds as estimates of internal noise while subjects sat on a chair with their eyes closed and were given 1 Hz bipolar binaural sinusoidal electrical stimuli were also measured. In general, there was no significant difference between estimates of perceptual and body motion thresholds. The average optimal SVS amplitude that improved balance performance (peak SVS amplitude normalized to perceptual threshold) was estimated to be 46% in ML, 53% in AP, and 50% in APML directions. A miniature patch-type SVS device may be useful to improve balance function in people with disabilities due to aging, Parkinson’s disease or in astronauts returning from long-duration space flight.

Improving postural control by applying mechanical noise to ankle muscle tendons

“…An improvement in static postural control via stochastic resonance is consistent with previous reports of the enhancement of plantar cutaneous information by mechanical noise (Priplata et al 2003(Priplata et al , 2006 and by noisy electrical stimulation of the vestibular system (Mulavara et al 2011;Goel et al 2015). More particularly, the present results agree with the studies of Kohn (2012, 2014) and Gravelle and collaborators (2002), which investigated the effect of electrical noise stimulation of the ankle and knee muscles, respectively.…”

“…Stochastic resonance has been described in a variety of physiological functions (reviews: Moss et al 2004;McDonnell and Ward 2011). With respect to postural control, in healthy subjects, improved balance performance was reported for vestibular optimization that was achieved through vestibular stimulation with subthreshold electrical noise (Mulavara et al 2011;Goel et al 2015). When plantar skin information was optimized by applying vibrations to the soles of the feet, decreased body sway was also reported in healthy young and elderly individuals (Priplata et al 2003;Lipsitz et al 2015), patients with diabetes, and stroke patients (Priplata et al 2006).…”

Subthreshold stochastic vestibular stimulation affects balance-challenged standing and walking

“…Additionally, we applied sports pre-wrap around the head of the participant to secure the electrodes and ensure a uniform current distribution. We developed the SVS signal, which consisted of zero mean, Gaussian-distributed white noise within a frequency range of 0-30 Hz [19][20][21][22]24], using a custom LabVIEW program (National Instruments, Austin, TX). An example of the stimulus is shown in Fig 1C. Electrical vestibular stimulation activates the afferents of both semicircular canals and otolith organs [30][31][32].…”

“…Subthreshold SVS may indeed facilitate upright posture when balance is challenged. For example, some healthy adults show improved balance function in response to SVS while standing with their eyes closed on a compliant surface [21,22]. In contrast, Pal et al [23] studied the effect of SVS on postural sway, with and without vision, while healthy adults and patients with Parkinson's disease stood on foam.…”

“…Two threshold techniques are commonly used in SVS studies: sinusoidal and cutaneous. For the sinusoidal technique, a 1 Hz sinusoidal waveform with currents ranging from 0-1500 μA is applied to determine a motion threshold [21,24]; that is, the lowest stimulation intensity that elicits perceived or observable sway of the head or body. Alternatively, for the cutaneous technique, varying stimulation intensities using a 0-30 Hz stochastic signal are applied in a stepwise manner until a sensation is felt on the skin under the electrode site [17][18][19][20].…”