Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2025 Oct 15.
doi: 10.1113/EP092659. Online ahead of print.

Temporal summation in human peripheral axons when stimulated transcutaneously with a 10-kHz waveform

Billy L Luu  1 , Harrison T Finn  1   2 , Terry Trinh  1   2 , Simon C Gandevia  1   3   4 , Martin E Héroux  1   2 , Jane E Butler  1   2
Affiliations

Temporal summation in human peripheral axons when stimulated transcutaneously with a 10-kHz waveform

Billy L Luu et al. Exp Physiol. .

Abstract

Transcutaneous spinal cord stimulation, as used for rehabilitation of impaired motor function after spinal cord injury, often involves a 10-kHz waveform modulated to produce repetitive bursts of stimulation. Kilohertz-frequency waveforms may facilitate the summation of subthreshold depolarisations, but the optimal burst duration for nerve stimulation has not been systematically investigated. In 11 adults, the ulnar nerve was stimulated transcutaneously with a 10-kHz waveform that contained 1, 2, 4, 6, 8 or 10 pulses, in random order. Compound muscle action potentials (CMAPs) and sensory nerve action potentials (SNAPs) were measured from motor threshold up to the maximal CMAP (Mmax). The efficacy of each waveform was determined at Mmax as CMAP amplitude divided by total phase charge. For CMAPs and SNAPs, increasing the number of pulses shifted the stimulus-response curves to the left for current and to the right for total charge. Accordingly, an increase in the number of pulses decreased the current but increased the total charge at sensory and motor thresholds and Mmax. Efficacy decreased as the number of pulses increased. Onset latencies were delayed for waveforms with six or more pulses compared to a single pulse. These findings provide evidence of the summation of subthreshold depolarisations in sensory and motor axons in humans. However, the optimal number of pulses for summation remains unclear due to the opposing changes in current and total charge. It is clear, though, that more than six pulses is suboptimal, as there were no further decreases in threshold current while total charge continued to increase.

Keywords: Gildemeister; axonal membrane; burst‐modulated currents; subthreshold depolarisation.

PubMed Disclaimer

References

REFERENCES

    1. Bigland‐Ritchie, B., Jones, D. A., & Woods, J. J. (1979). Excitation frequency and muscle fatigue: Electrical responses during human voluntary and stimulated contractions. Experimental Neurology, 64(2), 414–427.
    1. Bostock, H. (1983). The strength–duration relationship for excitation of myelinated nerve: Computed dependence on membrane parameters. The Journal of Physiology, 341(1), 59–74.
    1. Bostock, H., Lin, C. S., Howells, J., Trevillion, L., Jankelowitz, S., & Burke, D. (2005). After‐effects of near‐threshold stimulation in single human motor axons. The Journal of Physiology, 564(3), 931–940.
    1. Bostock, H., & Rothwell, J. C. (1997). Latent addition in motor and sensory fibres of human peripheral nerve. The Journal of Physiology, 498(1), 277–294.
    1. Dalrymple, A. N., Hooper, C. A., Kuriakose, M. G., Capogrosso, M., & Weber, D. J. (2023). Using a high‐frequency carrier does not improve comfort of transcutaneous spinal cord stimulation. Journal of Neural Engineering, 20(1), 016016.

LinkOut - more resources