Spinally targeted paired associative stimulation with high-frequency peripheral component induces spinal level plasticity in healthy subjects

Scientific Reports, 2024 · DOI: https://doi.org/10.1038/s41598-024-82271-4 · Published: December 4, 2024

Spinal Cord Injury Neurology Rehabilitation

Simple Explanation

This study explores a novel method called high-PAS, a variation of paired associative stimulation (PAS), which combines transcranial magnetic stimulation (TMS) and peripheral nerve stimulation (PNS). The goal was to see if it could induce changes at the spinal cord level in healthy individuals. The researchers compared two approaches: one where the stimulation was timed to target the spinal cord (SPINAL) and another aimed at the cortex (CORTICAL). They measured motor-evoked potentials (MEPs) and Hoffmann (H)-reflexes to assess changes in excitability. The results showed that spinally targeted high-PAS led to an increase in spinal excitability, as indicated by enhanced H-reflex amplitudes, suggesting that this method can indeed influence spinal cord activity.

Study Duration

Not specified

Participants

10 healthy subjects (8 females, 2 males)

Evidence Level

Level 3: Experimental study

Key Findings

1
MEPs were significantly enhanced in both spinally and cortically targeted interventions, indicating increased corticospinal excitability.
2
Maximal H-reflex amplitudes significantly increased in the SPINAL session at two timepoints, but not in the CORTICAL session, suggesting an increase in spinal excitability.
3
The H/M ratio showed a significant increase from PRE to POST30 timepoint in the SPINAL session when compared with the CORTICAL equivalent.

Research Summary

This study investigates the effects of spinally and cortically targeted high-frequency paired associative stimulation (high-PAS) on spinal level plasticity in healthy subjects. The results indicate that spinally targeted high-PAS enhances spinal excitability, as evidenced by increased Hmax amplitudes and H/M ratio, more significantly than cortically targeted high-PAS. These findings support the potential of high-PAS as a clinical tool for targeting plasticity at different levels of the corticospinal tract, particularly in the context of spinal cord injury rehabilitation.

Practical Implications

Clinical Rehabilitation

High-PAS can be used as a tool for motor rehabilitation of individuals with spinal cord injuries, potentially improving motor performance and functional independence.

Targeted Plasticity

The ability to target plasticity at different levels of the corticospinal tract opens new avenues for tailored therapeutic interventions.

Understanding Mechanisms

Further research into the mechanisms of action of high-PAS can lead to optimized protocols and more effective clinical applications.

Study Limitations

1
Small sample size of ten healthy subjects limits the generalizability of the results.
2
The change in subject position from sitting to prone between MEP and H-reflex assessments may introduce variability.
3
The study only examined acute effects, and long-term studies are needed to understand the sustained impact of high-PAS.

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