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Updated: Jun 12, 2026

Electrophysiological Methods to Assess Peripheral Pain Block in an Anesthetized Rat
Published on: November 21, 2025
Peripheral nerve sensory fibers are recruited with less current and greater selectivity by conventional waveforms
Janie Provencher1,2, Harrison T Finn1,3, Janet L Taylor1,3,4,5
1Spinal Cord Injury Research Centre, Neuroscience Research Australia, Randwick, New South Wales, Australia.
High-frequency burst-modulated waveforms are less effective for recruiting sensory fibres during transcutaneous spinal stimulation compared to conventional waveforms. Conventional waveforms achieve sensory recruitment at lower intensities, making them more suitable for therapeutic applications.
Area of Science:
- Neuroscience
- Biomedical Engineering
- Rehabilitation Technology
Background:
- Transcutaneous spinal stimulation (TSS) aims to modulate neural activity by targeting dorsal spinal roots.
- Identifying optimal stimulation waveforms is crucial for effective sensory fibre recruitment in TSS.
- Current understanding lacks a clear comparison of conventional versus high-frequency burst-modulated waveforms for sensory fibre activation.
Purpose of the Study:
- To compare the efficacy of conventional and high-frequency burst-modulated stimulation waveforms in recruiting sensory fibres.
- To assess H-reflex threshold, recruitment characteristics, and motor fibre activation across different waveforms.
- To determine the optimal waveform for eliciting sensory responses at the lowest stimulation intensity.
Main Methods:
- H-reflex recruitment curves were recorded in participants with intact neurological function (n=12).
- Ten stimulation waveforms were tested: a reference 400 μs conventional waveform, 2, 5, and 10 kHz high-frequency burst-modulated waveforms, and a 1000 μs conventional waveform.
- Waveforms were delivered as both biphasic and monophasic pulses, with comparisons based on H-reflex threshold and recruitment slope.
Main Results:
- High-frequency waveforms (2-10 kHz) demonstrated significantly higher H-reflex thresholds compared to conventional waveforms.
- Recruitment curve peak slopes were less steep for high-frequency waveforms, indicating reduced efficiency.
- Increased motor fibre activation (M-wave amplitude) was observed with high-frequency waveforms near H-reflex threshold intensities.
Conclusions:
- Conventional stimulation waveforms are more effective than high-frequency burst-modulated waveforms for eliciting H-reflexes at lower intensities.
- High-frequency waveforms showed greater motor fibre activation, suggesting less selective sensory fibre recruitment.
- Further research into waveform optimization is needed for enhanced efficacy in transcutaneous spinal stimulation applications.
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