Objective: Our aim is to develop a non-invasive treatment for Parkinson’s Disease gait symptoms by applying peripheral stimulation to the feet using coordinated reset stimulation (CRS).

Background: CRS applied to the fingertips is showing promise as a non-invasive treatment for some Parkinson’s Disease symptoms[1]. For CRS to work effectively the stimulation sites must be sufficiently “unique” from each other [2]. To target the gait symptoms of Parkinson’s Disease which are currently not well treated, we plan apply CRS to the feet. To identify appropriate “unique” sites we used an oddball paradigm where a “primary” site is stimulated frequently, and a second “deviant” site is randomly stimulated. Typically, the “deviant” site results in a higher amplitude event related potential (ERP) called a mismatch negativity (MMN) We hypothesized that sites could be deemed independent if mismatch negativity was found.

Method: Twenty healthy participants aged 18-60 years (M=34y, SD =12y) received electrical and vibrotactile stimulation with the order counterbalanced. Six stimulation sites, the big toe, little toe, dorsum, 5^th metatarsal, arch and ankle were examined with each participant receiving stimulation on the right foot to four of these six sites. These sites were chosen as they are involved in gait. We applied an oddball paradigm to each pair of sites (80% to primary, 20% deviant). EEG was recorded at F3, Fz, F4, C3, Cz, C4, P3, Pz and P4 to record ERPs.

Results: ERPs were observed with a negative response at ~150ms and a positive response at ~350ms. A students t-test was used to compare the group average amplitude ERP of primary and deviant sites. The electrical stimulation oddball protocol resulted in nine out of eleven significantly different pairs. The vibrotactile stimulation oddball protocol resulted in six out of eleven significantly different pairs.

Conclusion: Electrical stimulation results in more consistent MMN responses regardless of the region of the foot stimulated compared to vibrotactile stimulation. The oddball tests have informed stimulation sites for future CRS studies.

References: 1. Pfeifer, K.J., et al., Coordinated Reset Vibrotactile Stimulation Induces Sustained Cumulative Benefits in Parkinson’s Disease. Frontiers in Physiology, 2021. 12.
2. Lysyansky, B., O. Popovych, and P. Tass, Optimal number of stimulation contacts for coordinated reset neuromodulation. Frontiers in Neuroengineering, 2013. Volume 6 – 2013.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/identifying-peripheral-stimulation-sites-to-treat-parkinsons-disease-gait-impairments/