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Effects of Stochastic Resonance on Perception and Cutaneous Reflexes in the Lower Limb

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Title: Effects of Stochastic Resonance on Perception and Cutaneous Reflexes in the Lower Limb
Author: Plater, Emma Beth
Department: Department of Human Health and Nutritional Sciences
Program: Human Health and Nutritional Sciences
Advisor: Bent, Leah R.
Abstract: The glabrous, or non-hairy skin of the soles of the feet act as the interface between humans and their environment. After lower extremity amputation (LEA), the skin at the residual limb acts as the interface; this hairy skin is not optimized for this function. Improving skin sensation in individuals with LEA is important because decreased sensation can lead to multiple health sequelae including poor balance and skin breakdown. Stochastic resonance (SR), where adding a noisy input to a subthreshold stimulus improves the strength of the stimulus, can be used to enhance skin sensitivity. The aim of this thesis was to evaluate the effectiveness of SR in the hairy skin of the calf in non-LEA individuals. Specifically, we looked to determine 1) if SR is effective in this hairy skin region, and 2) whether there is an optimal noise level, relative to baseline level, that leads to the greatest enhancement in sensory function. This is an important first step towards the application of SR in a LEA population. Study 1 found that remote electrotactile noise at the thigh may enhance perception of a vibrotactile stimulus at the calf, but there was no consistent optimal level of noise. There was also evidence of threshold drift in approximately one third of participants. This led to Study 2, which compared various SR testing methods and found that all the methods lead to threshold drift, and none showed a consistent optimal level of noise. These two studies highlighted the limitations inherent to perceptual testing. Study 3 found that vibrotactile noise may enhance cutaneous reflexes at the leg, but despite this more objective measure there was again no consistent optimal level of noise. Overall, SR may be effective in the hairy skin of the leg but there does not appear to be an optimal level of noise. These findings highlight the limitations of SR for sensory enhancement; the variability, threshold drift and lack of an optimal level make SR challenging from an application standpoint. Further research should be done in an LEA population to determine whether a consistent optimal level can in found in this population where leg skin is used as the interface with the ground.
Date: 2022-05
Rights: Attribution 4.0 International
Related Publications: Plater EB, Seto VS, Peters RM, Bent LR. Remote Subthreshold Stimulation Enhances Skin Sensitivity in the Lower Extremity. Front Hum Neurosci. 2021 Dec 22;15:789271. doi: 10.3389/fnhum.2021.789271.
Embargoed Until: 2023-05-01

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Attribution 4.0 International Except where otherwise noted, this item's license is described as Attribution 4.0 International