Shielding effects of myelin sheath on axolemma depolarization under transverse electric field stimulation

2018 · Mixed · Low evidence

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MixedLow evidencePaper 1942

Study snapshot

Publicationmanual · 2018

Study typeengineering

Reported directionMixed

Evidence ratingLow

Abstract

Shielding effects of myelin sheath on axolemma depolarization under transverse electric field stimulation Ye H, Ng J. Shielding effects of myelin sheath on axolemma depolarization under transverse electric field stimulation. PeerJ. 2018 Dec 3;6:e6020. doi: 10.7717/peerj.6020. Abstract Axonal stimulation with electric currents is an effective method for controlling neural activity. An electric field parallel to the axon is widely accepted as the predominant component in the activation of an axon. However, recent studies indicate that the transverse component to the axolemma is also effective in depolarizing the axon. To quantitatively investigate the amount of axolemma polarization induced by a transverse electric field, we computed the transmembrane potential (Vm) for a conductive body that represents an unmyelinated axon (or the bare axon between the myelin sheath in a myelinated axon). We also computed the transmembrane potential of the sheath-covered axonal segment in a myelinated axon. We then systematically analyzed the biophysical factors that affect axonal polarization under transverse electric stimulation for both the bare and sheath-covered axons. Geometrical patterns of polarization of both axon types were dependent on field properties (magnitude and field orientation to the axon). Polarization of both axons was also dependent on their axolemma radii and electrical conductivities. The myelin provided a significant "shielding effect" against the transverse electric fields, preventing excessive axolemma depolarization. Demyelination could allow for prominent axolemma depolarization in the transverse electric field, via a significant increase in myelin conductivity. This shifts the voltage drop of the myelin sheath to the axolemma. Pathological changes at a cellular level should be considered when electric fields are used for the treatment of demyelination diseases. The calculated term for membrane polarization (Vm) could be used to modify the current cable equation that describes axon excitation by an external electric field to account for the activating effects of both parallel and transverse fields surrounding the target axon. Open access paper: peerj.com

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AI evidence extraction

Structured fields below were generated from the paper’s abstract and metadata to make the evidence easier to inspect. Automated extraction may be incomplete or incorrect; verify important details against the original paper.

Study typeengineering

Effect directionmixed

PopulationNot supplied

Sample sizeNot supplied

ExposureNot supplied

Evidence strengthLowConfidence: 74% · Peer reviewed: yes

Main findings

Computational modeling showed that transverse electric fields can induce axolemma polarization in both bare (unmyelinated or exposed) and myelin sheath-covered axons, with patterns dependent on field magnitude/orientation and axon radius/conductivity. The myelin sheath provided a significant shielding effect against transverse fields, while increased myelin conductivity (as in demyelination) could allow more prominent axolemma depolarization by shifting voltage drop from myelin to axolemma.

Outcomes measured

transmembrane potential (Vm)
axolemma polarization/depolarization
shielding effect of myelin sheath

Limitations

Computational/modeling study; no experimental or clinical validation described in the abstract
No specific exposure frequencies, dosimetry metrics (e.g., SAR), or stimulation durations reported in the abstract

View raw extracted JSON

{
  "study_type": "engineering",
  "exposure": {
    "band": null,
    "source": "transverse electric field stimulation",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": null
  },
  "population": null,
  "sample_size": null,
  "outcomes": [
    "transmembrane potential (Vm)",
    "axolemma polarization/depolarization",
    "shielding effect of myelin sheath"
  ],
  "main_findings": "Computational modeling showed that transverse electric fields can induce axolemma polarization in both bare (unmyelinated or exposed) and myelin sheath-covered axons, with patterns dependent on field magnitude/orientation and axon radius/conductivity. The myelin sheath provided a significant shielding effect against transverse fields, while increased myelin conductivity (as in demyelination) could allow more prominent axolemma depolarization by shifting voltage drop from myelin to axolemma.",
  "effect_direction": "mixed",
  "limitations": [
    "Computational/modeling study; no experimental or clinical validation described in the abstract",
    "No specific exposure frequencies, dosimetry metrics (e.g., SAR), or stimulation durations reported in the abstract"
  ],
  "evidence_strength": "low",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "axon",
    "myelin sheath",
    "axolemma",
    "transverse electric field",
    "neural stimulation",
    "transmembrane potential",
    "demyelination",
    "computational modeling"
  ],
  "suggested_hubs": []
}

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AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: 10.7717/peerj.6020
PubMed: Not supplied

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