Investigation on the effect of noisy galvanic vestibular stimulation on fine motor skills during a visuomotor task in healthy participants

Abstract

Noisy galvanic vestibular stimulation (nGVS) has been shown to improve dynamic walking stability, affect postural responses, enhance balance in healthy subjects, and influence motor performance in individuals with Parkinson’s disease. Although the studies to fully characterize the effect of nGVS are still ongoing, stochastic resonance theory which states that the addition of noisy signal may enhance a weak sensory input signals transmission in a non-linear system may provide a possible explanation for the observed positive effects of nGVS. This study explores the effect of nGVS on fine tracking behavior in healthy subjects. Ten healthy participants performed a computer-based visuomotor task by controlling an object with a joystick to follow an amplitude-modulated signal path while simultaneously receiving a sham or pink noise nGVS. The stimulation was generated to have a zero-mean, linearly detrended 1/f-type power spectrum, Gaussian distribution within 0.1–10 Hz range, and a standard deviation (SD) set to 90% based on each participant’s cutaneous threshold value. Results show that simultaneous nGVS delivery statistically improved the tracking performance with a decreased root-mean-squared error of 5.71±6.20% (mean±SD), a decreased time delay of 11.88±9.66% (mean±SD), and an increased signal-to-noise ratio of 2.93% (median, interquartile range (IQR) 3.31%). This study showed evidence that nGVS may be beneficial in improving sensorimotor performance during a fine motor tracking task requiring fine wrist movement in healthy subjects. Further research with a more comprehensive subset of tasks is required to fully characterize the effects of nGVS on fine motor skills.

Effects of Noisy Galvanic Vestibular Stimulation During a Bimanual Tracking Robotic Task

“…Exclusion criteria included: allergy to rubbing alcohol and/or conductive paste/gel; history of epilepsy or seizures; metallic implants in the head or neck; concussion or head trauma within the last year; brain or spinal cord surgery; fainting spells or syncope; electric or electronic devices implanted in the body; severe skin condition which requires medical treatment and/or is painful in stimulation area; musculoskeletal injury or condition that affects the upper extremities; neurological, auditory, or vestibular condition; pregnancy or possibility of pregnancy; uncorrected visual impairment; consumption of coffee, alcohol, or other recreational drugs 10 h before the study. Sample size ( n = 12) was determined by conducting a power analysis ( d = 0.92, α = 0.05, β = 0.8, one sample t -test) on the percent improvement of root mean square error (RMSE) of a study that investigated the effects of nGVS on a unimanual tracking task in people without disabilities (Kuatsjah et al, 2019).…”

“…The noisy signal was generated by a laptop computer running a custom MATLAB (MathWorks, MA, United States) script and was sent to the stimulator via the analog output of a USB data acquisition card (USB-6002, National Instruments Corporation, Austin, TX, United States). The noisy zero-mean linearly detrended stimulus had a Gaussian distribution with a 1/f-type power spectrum, which has been employed in people with and without Parkinson’s disease (Yamamoto et al, 2005; Pan et al, 2008; Kim, 2013; Kim et al, 2013; Lee et al, 2015; Kuatsjah et al, 2019). The signal was generated in the range of 0.1–10 Hz and sent to the stimulator at a rate of 60 Hz (Kim, 2013; Lee et al, 2015; Kuatsjah et al, 2019).…”

“…The stimulus was delivered below the cutaneous sensory threshold of each participant (Lee et al, 2015; Wuehr et al, 2016; Kuatsjah et al, 2019). To determine the sensory threshold, at the beginning of the session, we followed a procedure similar to the stair-case method (Wilkinson et al, 2008; Lee et al, 2015; Wuehr et al, 2016).…”

“…Noisy galvanic vestibular stimulation (nGVS) is a non-invasive electrical stimulation technique in which a noise signal is delivered through the mastoids (Pan et al, 2008). nGVS has been shown to have beneficial motor effects in different activities, such as standing balance and walking performance in people with and without bilateral peripheral vestibular dysfunction (Iwasaki et al, 2014, 2018; Wuehr et al, 2016; Inukai et al, 2018) and upper-limb fine motor performance in people with and without Parkinson’s disease (Kim, 2013; Lee et al, 2015; Kuatsjah et al, 2019). In terms of non-motor effects, nGVS has been shown to speed visual memory recall in people without disabilities (Wilkinson et al, 2008).…”

“…Thus, the investigation of effects of nGVS on upper limb motor performance is of particular interest to assess its potential as a clinical tool. Previous studies on upper-limb performance employed visuomotor tasks, as a means to gain insight into human neuromotor response (Ryu and Buchanan, 2012), and focused on the effects of nGVS on unimanual fine motor movements of people with and without Parkinson’s disease (Kim, 2013; Lee et al, 2015; Kuatsjah et al, 2019) reporting positive effects on motor performance. In contrast, it has also been reported that sub-threshold non-noisy GVS deteriorates left arm horizontal position sense in right-handers (Schmidt et al, 2013a, b), and that subthreshold and suprathreshold pseudo-random sinusoidal GVS does not affect unimanual tracking performance (Dilda et al, 2012).…”