Investigating Neurometabolite Changes in Response to Median Nerve Stimulation

Houlgreave, Mairi S.; Dyke, Katherine; Berrington, Adam; Jackson, Stephen R.

Abstract

Background
Rhythmic median nerve stimulation (MNS) at 10 Hz has been shown to cause a substantial reduction in tic frequency in individuals with Tourette syndrome. The mechanism of action is currently unknown but is hypothesized to involve entrainment of oscillations within the sensorimotor cortex.

Objective
We used functional magnetic resonance spectroscopy (fMRS) to explore the dynamic effects of MNS on neurometabolite concentrations.

Methods
Here, we investigated the effects of rhythmic and arrhythmic 10 Hz MNS on glutamate (Glu) and GABA concentrations in the contralateral sensorimotor cortex in 15 healthy controls, using a blocked fMRS design. We used a Mescher–Garwood-semi-localized by adiabatic selective refocusing (MEGA-sLASER) sequence at 7 T.

Results
Our results show no difference in the difference-from-baseline measures between the two stimulation conditions. Looking at the effect of MNS over both conditions there is a trend for an initial increase in Glu/tCr (total creatine) followed by a decrease over time, whereas GABA/tCr decreased during each stimulation block.

Conclusions
These results suggest that despite entrainment of oscillations during rhythmic MNS, there are no significant differences in the tonic neuromodulatory effects of rhythmic and arrhythmic stimulation. The reduction in Glu over the course of stimulation may reflect a decrease in the glutamatergic firing due to adaptation. This may make it less likely that an involuntary movement is generated during continuous stimulation.

Citation

Houlgreave, M. S., Dyke, K., Berrington, A., & Jackson, S. R. (2025). Investigating Neurometabolite Changes in Response to Median Nerve Stimulation. Brain and Behavior, 15(1), Article e70250. https://doi.org/10.1002/brb3.70250

• Journal Article Type: Article
• Acceptance Date: Dec 14, 2024
• Online Publication Date: Jan 8, 2025
• Publication Date: 2025-01
• Deposit Date: Jan 6, 2025
• Publicly Available Date: Jan 8, 2025
• Print ISSN: 2162-3279
• Electronic ISSN: 2157-9032
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 15
• Issue: 1
• Article Number: e70250
• DOI: https://doi.org/10.1002/brb3.70250
• Public URL: https://nottingham-repository.worktribe.com/output/43948939
• Publisher URL: https://onlinelibrary.wiley.com/doi/10.1002/brb3.70250