Improving balance function using vestibular stochastic resonance: optimizing stimulus characteristics

Abstract

Stochastic resonance (SR) is a phenomenon whereby the response of a non-linear system to a weak periodic input signal is optimized by the presence of a particular non-zero level of noise. Stochastic resonance using imperceptible stochastic vestibular electrical stimulation, when applied to normal young and elderly subjects, has been shown to significantly improve ocular stabilization reflexes in response to whole-body tilt; improved balance performance during postural disturbances and optimize covariance between the weak input periodic signals introduced via venous blood pressure receptors and the heart rate responses. In our study, 15 subjects stood on a compliant surface with their eyes closed. They were given low-amplitude binaural bipolar stochastic electrical stimulation of the vestibular organs in two frequency ranges of 1-2 and 0-30 Hz over the amplitude range of 0 to ±700 μA. Subjects were instructed to maintain an upright stance during 43-s trials, which consisted of baseline (zero amplitude) and stimulation (non-zero amplitude) periods. Measures of stability of the head and trunk using inertial motion unit sensors attached to these segments and the whole body using a force plate were measured and quantified in the mediolateral plane. Using a multivariate optimization criterion, our results show that the low levels of vestibular stimulation given to the vestibular organs improved balance performance in normal healthy subjects in the range of 5-26% consistent with the stochastic resonance phenomenon. In our study, 8 of 15 and 10 of 15 subjects were responsive for the 1-2- and 0-30-Hz stimulus signals, respectively. The improvement in balance performance did not differ significantly between the stimulations in the two frequency ranges. The amplitude of optimal stimulus for improving balance performance was predominantly in the range of ±100 to ±400 μA. A device based on SR stimulation of the vestibular system might be useful as either a training modality to enhance adaptability or skill acquisition, or as a miniature patch-type stimulator that may be worn by people with disabilities due to aging or disease to improve posture and locomotion function.

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).…”

Effect of mechanical tactile noise on amplitude of visual evoked potentials: multisensory stochastic resonance

“…Such is the case for the vestibular system involved in the balance control in humans, in which tactile noise can improve the balance (Magalhães and Kohn 2011;Mulavara et al 2011;Priplata et al 2002; see also Johannsen et al 2015). For example, Keshner et al (2014) and Dettmer et al (2015) demonstrated that balance improvements by tactile noise are more pronounced with no vision available.…”

Noise-Enhanced Vestibular Input Improves Dynamic Walking Stability in Healthy Subjects

“…Stochastic resonance has further been used to improve sensory feedback involved in postural control. Accordingly, it was shown that a subthreshold noise input to the somatosensory as well as the vestibular system is able to improve static postural equilibrium in healthy subjects standing with eyes closed as well as in patients with sensory deficits [8][9][10].…”