Stochastic Resonance can enhance cutaneous reflex responses in the lower limb
Bent LR, Sharma T, Peters RM
1. Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
2. Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
Location specific stimulation of plantar foot skin has been shown to reflexively modulate lower limb muscles to effect balance and gait strategies1,2. Decreased cutaneous reflex generation has been proposed to contribute to increased fall risk in aging and pathological populations3. One solution is to augment the skin signal with stochastic resonance (SR), a phenomenon whereby the addition of noise to an undetectable stimulus, can make the stimulus detectable4. SR mediated enhancements have been shown in tactile detection but have not been explored in cutaneous reflexes. Here we ask whether enhancing natural skin input through SR could improve cutaneous reflex responses in the lower limb. Eleven young, healthy subjects (mean age 20.9 years) were recruited. To evoke cutaneous reflex responses, we used a mechanical vibrotactile input over the heel at 10 times perceptual threshold (PT). SR noise was elicited with an electrotactile stimulus applied at various intensities between 0 and 100% of noise PT. Electromyography was recorded from soleus (SOL), tibialis anterior (TA) and medial (MG) and lateral gastrocnemius (LG). Cutaneous reflexes were quantified with peak to peak amplitude (PTP) of the cumulant density plot at each noise intensity. Subjects were separated based on their directional response to noise-mediated enhancements of SOL reflex (responders: n=6, non-responders: n=5). SR effects were observed at 20% of noise threshold in responders. We conclude that SR can be elicited in reflex responses in a subset of the population. This information may help inform the design of biomedical aids to improve balance in clinical populations.
- Nakajima T, Sakamoto M, Tazoe T, Endoh T, Komiyama T (2006) Location specificity of plantar cutaneous reflexes involving lower limb muscles in humans. Exp Brain Res 175:514-525.
- Zehr EP, Nakajima T, Barss T, Klarner T, Miklosovic S, Mezzarane RA, Komiyama T (2014). Cutaneous stimulation of discrete regions of the sole during locomotion produces “sensory steering” of the foot. BMC Sports Science, Medicine and Rehabilitation, 6(1), 33.
- Peters RM, McKeown MD, Carpenter MG, Inglis JT (2016) Losing touch: age-related changes in plantar skin sensitivity, lower limb cutaneous reflex strength, and postural stability in older adults. J Neurophys 116:1848-1858.
- Wiesenfeld K, Jaramillo F (1998) Minireview of stochastic resonance. Chaos 8:539-548.