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Cited by 45Neuroscience and Neural EngineeringMuscle activation and electromyography studiesVagus Nerve Stimulation Research

Optimization of selective stimulation parameters for multi-contact electrodes

Open access
Fisher, Lee E, Tyler, Dustin J, Triolo, Ronald J·2013·Journal of NeuroEngineering and Rehabilitation
DOI 10.1186/1743-0003-10-25PMC PMC3599334
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Abstract

BACKGROUND: Multi-contact stimulating electrodes are gaining acceptance as a means for interfacing with the peripheral nervous system. These electrodes can potentially activate many independent populations of motor units within a single peripheral nerve, but quantifying their recruitment properties and the overlap in stimulation between contacts is difficult and time consuming. Further, current methods for quantifying overlap between contacts are ambiguous and can lead to suboptimal selective stimulation parameters. This study describes a novel method for optimizing stimulation parameters for multi-contact peripheral stimulating electrodes to produce strong, selective muscle contractions. The method is tested with four-contact spiral nerve-cuff electrodes implanted on bilateral femoral nerves of two individuals with spinal cord injury, but it is designed to be extendable to other electrode technologies with higher densities of contacts. METHODS: To optimize selective stimulation parameters for multi-contact electrodes, first, recruitment and overlap are characterized for all contacts within an electrode. Recruitment is measured with the twitch response to single stimulus pulses, and overlap between pairs of contacts is quantified by the deviation in their combined response from linear addition of individual responses. Simple mathematical models are fit to recruitment and overlap data, and a cost function is defined to maximize recruitment and minimize overlap between all contacts. RESULTS: Results are presented for four-contact nerve-cuff electrodes stimulating bilateral femoral nerves of two human subjects with spinal cord injury. Knee extension moments between 11.6 and 43.2 Nm were achieved with selective stimulation through multiple contacts of each nerve-cuff with less than 10% overlap between pairs of contacts. The overlap in stimulation measured in response to selective stimulation parameters was stable at multiple repeated time points after implantation. CONCLUSIONS: These results suggest that the method described here can provide an automated means of determining stimulus parameters to achieve strong muscle contractions via selective stimulation through multi-contact peripheral nerve electrodes.

AI snapshot

Written from the paper’s full text.

TL;DR

This paper presents an automated method to optimize selective stimulation parameters for multi-contact peripheral nerve electrodes by modeling recruitment and pairwise overlap and minimizing a cost function. In four-contact spiral nerve-cuff electrodes implanted on bilateral femoral nerves of two individuals with spinal cord injury, the method produced knee extension moments of 11.6–43.2 Nm with less than 10% overlap between contact pairs.

Key findings

  • Selective stimulation through multiple contacts of four-contact nerve-cuff electrodes produced knee extension moments between 11.6 and 43.2 Nm with less than 10% overlap between every pairwise combination of contacts.
  • The Gompertz function best modeled recruitment (R² = 0.98 ± 0.01), and a third-order polynomial best modeled overlap (R² = 0.92 ± 0.11).
  • The twitch-to-tetanic scaling factor was linear across all sixteen contacts, with a ratio of 2.56 ± 0.55.
  • Overlap remained stable at repeated post-implantation time points up to 53 weeks for Subject 1 and 37 weeks for Subject 2; no mean pairwise overlap was statistically greater than 10%, and only three pairs had standard deviations greater than 5%.

Methods

  • Four CWRU four-contact spiral nerve-cuff electrodes were implanted around bilateral femoral nerves in two volunteers with motor-complete spinal cord injury (Subject 1: C7, ASIA B; Subject 2: T11, ASIA B). Stimulus amplitudes were 1.4 mA for Subject 1 and 0.8 mA for Subject 2; initial testing occurred at 15 and 14 weeks post-implantation, respectively.
  • Recruitment was characterized from isometric knee extension twitch responses to single pulses, and overlap was quantified from paired pulses separated by a 2 ms delay, with pulse widths varied between 1 and 255 µs. The knee was fixed at 20° flexion.
  • For each contact or contact pair, 48 data points were collected; 32 were used to fit models and 16 to test goodness-of-fit. Models were compared using R² and corrected Akaike Information Criterion. A cost function maximized normalized joint moment and minimized normalized pairwise overlap, with equal weighting and penalties if any contact produced less than 5 Nm or any pair exceeded 10% overlap; optimal pulse widths were found by direct search.

Limitations

  • The paper states that the method was tested only with four-contact nerve-cuff electrodes, although it was designed to scale to higher-density electrodes; it also relies on pulse width modulation because of implanted stimulator limitations.
  • The paper states that the twitch/tetanic characterization method was chosen for simplicity rather than efficiency, and that it would account for nearly 70% of the estimated 13 hours needed to optimize a 100-contact Utah array; alternative methods could reduce this to approximately six hours.
  • Evident from the text: the sample is very small (two subjects, four nerve-cuffs), and the optimization excluded one or two contacts per electrode; in Subject 2, one contact never produced a measurable motor response, suggesting it was over sensory axons or connective tissue rather than motor fascicles.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1186/1743-0003-10-25

Cites

Statistics

Nothing to recompute.

Claims the paper makes

0 of 22 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    Overlap in stimulation measured in response to selective stimulation parameters was stable at multiple repeated time points after implantation.

    “The overlap in stimulation measured in response to selective stimulation parameters was stable at multiple repeated time points after implantation.”
    • Also stated in: § Stability of overlap · plain
      “Overlap between most pairs of contacts remained low and constant over time, with only three pairs demonstrating standard deviations greater than 5%.”
    • Also stated in: § Conclusions · plain
      “Overlap in stimulation was also found to be stable over months after implantation, with little variation in overlap in response to the same stimulus parameters applied at multiple time points after implantation.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: If the interface between the electrode and nerve is stable, overlap is less likely to change over time.
  • Findingown data

    Every pairwise combination of contacts within each electrode had less than 10% overlap.

    “Every pairwise combination of contacts within each electrode had less than 10% overlap.”
    Quote in the paperSubstantial claim
  • Findingcitation

    If non-adjacent pairwise combinations of contacts were ignored and a limited data set was used to fit the Gompertz and third-order polynomial models, the method would require approximately 13 hours to completely optimize selective stimulation for a 100-contact Utah slant electrode array, as compared to 11.6 days otherwise.

    “If non-adjacent pairwise combinations of contacts were ignored and a limited data set was used to fit the Gompertz and third-order polynomial models, which have three and ten parameters, respectively, the method described above would require approximately 13 hours to completely optimize selective stimulation for a 100-contact Utah slant electrode array, as compared to 11.6 days otherwise [3].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [3] source

      Not checked in the free run.

    • Rests on an assumption: Elimination of overlap between adjacent contacts will also eliminate overlap between non-adjacent contacts.
  • Findingown data

    Knee extension moments between 11.6 and 43.2 Nm were achieved with selective stimulation through multiple contacts of each nerve-cuff with less than 10% overlap between pairs of contacts.

    “Knee extension moments between 11.6 and 43.2 Nm were achieved with selective stimulation through multiple contacts of each nerve-cuff with less than 10% overlap between pairs of contacts.”
    • Also stated in: § Discussion · hedged
      “In the case of these four nerve-cuff electrodes examined in this study, the optimization determined that it is possible for two or three contacts to produce at least 11.6 Nm, but possibly as much as 43.2 Nm of knee extension moment with less than 10% overlap between pairs of contacts.”
    Quote in the paperSubstantial claim
  • Findingown data

    For contact 3 of the left nerve-cuff electrode in Subject 2, there was never any measurable motor response to stimulation.

    “For contact 3 of the left nerve-cuff electrode in Subject 2, there was never any measurable motor response to stimulation”
    Quote in the paperSubstantial claim
  • May combine two claims. 11
  • Classified as probably not a substantial claim. 5

  • May combine two claims.

    Findingown data

    The Gompertz function achieves the best goodness-of-fit (R2 = 0.98 ± 0.01) and is the most appropriate model of the response to stimulation.

    “achieves the best GOF (R2 = 0.98 ± 0.01) and is the most appropriate model of the response to stimulation.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In Subject 1, only two of four contacts, and in Subject 2, only three of four contacts for either electrode have non-zero stimulus parameters.

    “Note that, in Subject 1, only two of four contacts, and in Subject 2, only three of four contacts for either electrode have non-zero stimulus parameters.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    For all sixteen contacts within the four nerve-cuff electrodes, the shape of the twitch recruitment curve was similar to the tetanic curve, and a linear scaling factor was calculated as the ratio of the maxima of the two curves (ratio = 2.56 ± 0.55).

    “For all sixteen contacts within the four nerve-cuff electrodes, the shape of the twitch recruitment curve was similar to the tetanic curve, and a linear scaling factor was calculated as the ratio of the maxima of the two curves (ratio = 2.56 ± 0.55).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The third-order polynomial is the most appropriate model of the overlap in stimulation between two contacts (R2 = 0.92 ± 0.11) with the highest average AICc ranking.

    “is the most appropriate model of the overlap in stimulation between two contacts (R2 = 0.92 ± 0.11) with the highest average AICc ranking.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Alternating stimulation of multiple agonist motor unit populations may reduce stimulation duty cycle and prolong the time of muscle contractions before the onset of fatigue.

    “Further, by alternating stimulation of multiple agonist motor unit populations, it may be possible to reduce stimulation duty cycle and prolong the time of muscle contractions before the onset of fatigue [6].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [6] source

      Not checked in the free run.

    • Rests on an assumption: Multi-contact stimulating electrodes can independently activate multiple fascicles and motor units within a peripheral nerve.

  • May combine two claims.

    Premisecitation

    EMG recordings are commonly used to infer selectivity, but their strong dependence on the spatial relationship between recording electrodes and activated motor units limits practical utility and can lead to over- or underestimation of selectivity.

    “Electromyogram recordings are commonly used to infer selectivity, but the strong dependence on the spatial relationship between the recording electrodes and the activated motor units limits the practical utility of this method and can lead to over- or underestimation of selectivity [4,10].”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [4] source

      Not checked in the free run.

    • cites [10] source

      Not checked in the free run.

    • Rests on an assumption: It is difficult or impossible to separate populations of agonist motor units based on their lines of action or resultant joint moments.

  • May combine two claims.

    Premisecitation

    Peripheral nerves have a highly branched structure and high person-to-person variability in anatomy, both in branching structure and in the location of fascicles that innervate specific muscles.

    “Peripheral nerves, however, have a highly branched structure, and there is a high degree of person-to-person variability in the anatomy of those nerves, both in branching structure and in the location of fascicles that innervate specific muscles [7,8].”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [7] source

      Not checked in the free run.

    • cites [8] source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Other methods described by Durfee et al. require significantly less time to characterize the relationship between twitch and tetanic responses, and could reduce the worst-case scenario time to completely optimize a 100-contact electrode to approximately six hours.

    “Other methods described by Durfee, et al. [23], require significantly less time to characterize the relationship between twitch and tetanic responses, and could reduce the worst-case scenario time to completely optimize a 100-contact electrode to approximately six hours.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [23]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationreasoning

    In Subject 1, the two contacts used in the optimization sit opposite one another around the circumference of the nerve, so it is reasonable to expect that they would have less overlap with one another than contacts that are directly adjacent.

    “In the case of Subject 1, the two contacts used in the optimization sit opposite one another around the circumference of the nerve, so it is reasonable to expect that they would have less overlap with one another than contacts that are directly adjacent.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    The nerve-cuff electrode provides a stable interface with the nerve, and only occasional retuning of stimulation parameters would be required to account for changes in muscle strength during clinical implementation of selective stimulation.

    “This suggests that the nerve-cuff electrode provides a stable interface with the nerve, and that only occasional retuning of stimulation parameters would be required to account for changes in muscle strength during clinical implementation of selective stimulation.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: If the interface between the electrode and nerve is stable, overlap is less likely to change over time.

  • Probably not a substantial claim: may not pass S2 (checkable).

    Interpretationreasoning

    It may be possible to use the selectivity achieved here to produce finer control of motor output by recruiting motor units from a small set of contacts for low-force tasks and recruiting from additional contacts for high-force tasks.

    “Based on these results, it may be possible to use the selectivity achieved here to produce finer control of motor output by recruiting motor units from a small set of contacts for low-force tasks and recruiting from additional contacts for high-force tasks.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing), S4 (based).

    Interpretationnone given

    The methodology can readily be adapted to any electrode technology including high density penetrating arrays or multiple muscle-based or even surface electrodes.

    “The methodology can readily be adapted to any electrode technology including high density penetrating arrays or multiple muscle-based or even surface electrodes.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing), S4 (based).

    Interpretationnone given

    The technique can be applied to any number of real-world situations utilizing multi-contact or multiple single-contact electrodes activating synergistic muscle fiber populations, such as diaphragmatic pacing, hand grasping, or stepping.

    “The technique can be applied to any number of real-world situations utilizing multi-contact or multiple single-contact electrodes activating synergistic muscle fiber populations, such as diaphragmatic pacing, hand grasping, or stepping.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based). May combine two claims.

    Interpretationnone given

    By alternating stimulation between multiple independent populations, it may be possible to reduce the duty cycle of stimulation while maintaining a constant joint moment, and thereby delay the onset of fatigue.

    “Additionally, by alternating stimulation between multiple independent populations, it may be possible to reduce the duty cycle of stimulation while maintaining a constant joint moment, and thereby delay the onset of fatigue.”
    Quote in the paperNot a substantial claim
14 of 14

  • The paper relies on this without support.

    Multi-contact stimulating electrodes can independently activate multiple fascicles and motor units within a peripheral nerve.

    “These electrodes allow for a high density of contacts to be placed around or in peripheral nerves to independently activate multiple fascicles and motor units.”

  • The paper relies on this without support.

    It is difficult or impossible to separate populations of agonist motor units based on their lines of action or resultant joint moments.

    “It is difficult or impossible to separate populations of agonist motor units based on their lines of action or resultant joint moments.”

  • The paper relies on this without support.

    Current state-of-the-art imaging technology is insufficient to accurately visualize the fascicular structure of nerves in vivo.

    “Because current state-of-the-art imaging technology is insufficient to accurately visualize the fascicular structure of nerves in vivo”

  • The paper relies on this without support.

    Elimination of overlap between adjacent contacts will also eliminate overlap between non-adjacent contacts.

    “since elimination of overlap between adjacent contacts will also eliminate overlap between non-adjacent contacts”

  • The paper relies on this without support.

    If the interface between the electrode and nerve is stable, overlap is less likely to change over time.

    “if the interface between the electrode and nerve is stable, overlap is less likely to change over time”

  • The paper relies on this without support.

    Overlap in recruitment may limit the options available to control the response to stimulation.

    “Overlap in recruitment may limit the options available to control the response to stimulation.”

  • The paper relies on this without support.

    Repeated activation of the same motor units by multiple contacts may contribute to rapid fatigue.

    “Repeated activation of the same motor units by multiple contacts may also contribute to rapid fatigue.”
7 of 7

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Overlap sum counts seven terms for a four-contact cuff

    Minor

    With four contacts and the stated condition i≠j, the displayed summation includes seven terms: three for i=1, two for i=2, and two for i=3. The paper says there are six pairwise combinations, so the formula double-counts one pair and does not normalize six pairs as stated.

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References 25 · Cited by 45

Authors
Fisher, L. E., Tyler, D. J., & Triolo, R. J.
Affiliations
  • Case Western Reserve University (US)
  • United States Department of Veterans Affairs (US)
Corresponding author
Fisher, Lee E
ORCID
Venue
Journal of NeuroEngineering and Rehabilitation
Publisher
Springer Science and Business Media LLC
Published
2013
Volume
10
Issue
1
Pages
25
ISSN
1743-0003 (ISSN-L)
DOI
10.1186/1743-0003-10-25
PMC
PMC3599334
OpenAlex
W2097331723
Semantic Scholar
48d3e75e40bb9a6b5419247b01a424d7d8da595d
Cited by
45
References
25
Citations by year
2025: 3 · 2024: 1 · 2022: 3 · 2021: 5 · 2020: 4 · 2019: 6 · 2018: 5 · 2017: 6 · 2016: 3 · 2015: 3 · 2014: 4 · 2013: 2
FWCI
1.96
Type
journal article
Language
en
Open access
Licence
cc-by
Locations
  • Journal of NeuroEngineering and Rehabilitation (publishedVersion, cc-by)
  • Europe PMC (PubMed Central) (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
Funders
  • Deutsches Krebsforschungszentrum
  • National Institutes of Health (5-R01-, T32-EB04314)
  • National Institute of Biomedical Imaging and Bioengineering (R01EB001889, 5-R01-EB001889, T32-EB04314-08, T32EB004314)
  • National Center for Research Resources (M01RR000080)
Topics
  • Life Sciences › Neuroscience › Cellular and Molecular Neuroscience › Neuroscience and Neural Engineering
  • Physical Sciences › Engineering › Biomedical Engineering › Muscle activation and electromyography studies
  • Life Sciences › Neuroscience › Neurology › Vagus Nerve Stimulation Research
Keywords
selective stimulation, cuff electrodes, motor unit recruitment, spinal cord injury, femoral nerve stimulation, knee extension moment, peripheral nerve stimulation, twitch response
MeSH terms
Algorithms, Electric Stimulation, Electrodes, Implanted, Femoral Nerve, Humans, Joints, Knee, Motor Neurons, Movement, Muscle Contraction, Recruitment, Neurophysiological, Spinal Cord Injuries, Models, Statistical, Peripheral Nervous System, Muscle Fibers, Skeletal

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