Date of Award

8-2021

Degree Type

Creative Project

Degree Name

Master of Science (MS)

Department

Kinesiology and Health Science

Committee Chair(s)

Chris Dakin (Committee Chair)

Committee

Chris Dakin

Committee

David Bolton

Committee

Talin Louder

Abstract

The transcutaneous application of a sub-sensory electrical stimulation to the vestibular afferents, known as noisy galvanic vestibular stimulation (nGVS), is thought to cause a reduction in postural sway at optimal amplitude intensities due to a mechanism known as stochastic resonance (SR). SR is a phenomenon whereby the addition of low amplitude noise to a non-linear system can be beneficial rather than detrimental. In humans, behavioral markers of SR in postural sway have been inconsistent, potentially due to insufficient power or false positives. Therefore, the main purpose of this study was to determine whether the frequency of observing SR-like effects improves with recording duration and if not, whether SR-like effects can emerge as a result of chance (false positives). To test this, sixteen healthy participants stood on a force plate and on foam with eyes closed and feet together while they were provided 300-second trials of nGVS (ten times longer than what is commonly used) at six stimulation amplitudes (100 µA, 200 µA, 300 µA, 500 µA, 700 µA and a sham of 0 µA). To identify SR-like effects, the center of pressure (COP) area and COP path length were recorded. To quantify the presence of SR-like behavior, COP measures were fit with an SR model and a linear model, then the fit of the two models were compared using the Akaike information criterion (AIC) and the Bayesian information criterion (BIC). Less than 25% of the data fit the SR model better than the linear model. In addition, by randomly extracting 30-second data segments from the 0 µA sham trials, in which no SR-like behavior should be present, the SR model was found to be the best fit model up to 44% of the time in the COP area and up to 38% of the time in the COP path length data. These data support recent findings that suggest SR-like behavior may have been observed by chance in previous studies and true SR may be limited, or absent, in measures of postural sway in healthy young adults.

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