Electrotonic measurements by electric field-induced polarization in neurons: theory and experimental estimation.

Biophysical journal · 1997 · Unclear · Insufficient evidence

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UnclearInsufficient evidencePaper 4161

Study snapshot

PublicationBiophysical journal · 1997

Study typeother

Reported directionUnclear

Evidence ratingInsufficient

Abstract

We present a theory for estimation of the dendritic electrotonic length constant and the membrane time constant from the transmembrane potential (TMP) induced by an applied electric field. The theory is adapted to morphologically defined neurons with homogeneous passive electric properties. Frequency characteristics and transients at the onset and offset of the DC field are considered. Two relations are useful for estimating the electrotonic parameters: 1) steady-state polarization versus the dendritic electrotonic length constant; 2) membrane time constant versus length constant. These relations are monotonic and may provide a unique estimate of the electrotonic parameters for 3D-reconstructed neurons. Equivalent tip-to-tip electrotonic length of the dendritic tree was estimated by measuring the equalization time of the field-induced TMP. For 11 turtle spinal motoneurons, the electrotonic length from tip to tip of the dendrites was in the range of 1-2.5 lambda, whereas classical estimation using injection of current pulses gave an average dendrite length of 0.9-1.1 lambda. For seven ventral horn interneurons, the estimates were 0.7-2.6 lambda and 0.6-0.9 lambda, respectively. The measurements of the field-induced polarization promise to be a useful addition to the conventional methods using microelectrode stimulation.

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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 typeother

Effect directionunclear

Populationturtle spinal neurons (motoneurons and ventral horn interneurons)

Sample size18

ExposureNot supplied

Evidence strengthInsufficientConfidence: 74% · Peer reviewed: yes

Main findings

Presents a theory to estimate dendritic electrotonic length constant and membrane time constant from transmembrane potential induced by an applied DC electric field in morphologically defined neurons. In 11 turtle spinal motoneurons, field-based tip-to-tip electrotonic length estimates were 1–2.5 lambda versus 0.9–1.1 lambda from classical current-pulse injection; in seven ventral horn interneurons, estimates were 0.7–2.6 lambda versus 0.6–0.9 lambda, respectively. The authors suggest field-induced polarization measurements could complement conventional microelectrode stimulation methods.

Outcomes measured

dendritic electrotonic length constant (lambda)
membrane time constant
field-induced transmembrane potential (TMP) polarization/equalization time

Limitations

Exposure characteristics (field strength) not provided in abstract
Assumes homogeneous passive electric properties in morphologically defined neurons
Animal preparation (turtle spinal neurons) limits generalizability to humans
Primarily methodological/theoretical; not designed to assess health effects

View raw extracted JSON

{
  "study_type": "other",
  "exposure": {
    "band": null,
    "source": "applied electric field (DC)",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": null
  },
  "population": "turtle spinal neurons (motoneurons and ventral horn interneurons)",
  "sample_size": 18,
  "outcomes": [
    "dendritic electrotonic length constant (lambda)",
    "membrane time constant",
    "field-induced transmembrane potential (TMP) polarization/equalization time"
  ],
  "main_findings": "Presents a theory to estimate dendritic electrotonic length constant and membrane time constant from transmembrane potential induced by an applied DC electric field in morphologically defined neurons. In 11 turtle spinal motoneurons, field-based tip-to-tip electrotonic length estimates were 1–2.5 lambda versus 0.9–1.1 lambda from classical current-pulse injection; in seven ventral horn interneurons, estimates were 0.7–2.6 lambda versus 0.6–0.9 lambda, respectively. The authors suggest field-induced polarization measurements could complement conventional microelectrode stimulation methods.",
  "effect_direction": "unclear",
  "limitations": [
    "Exposure characteristics (field strength) not provided in abstract",
    "Assumes homogeneous passive electric properties in morphologically defined neurons",
    "Animal preparation (turtle spinal neurons) limits generalizability to humans",
    "Primarily methodological/theoretical; not designed to assess health effects"
  ],
  "evidence_strength": "insufficient",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "electric field",
    "DC field",
    "neurons",
    "transmembrane potential",
    "polarization",
    "electrotonic length constant",
    "membrane time constant",
    "motoneuron",
    "interneuron",
    "turtle spinal cord"
  ],
  "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: 10.1016/s0006-3495(97)78329-2
PubMed: 9414215

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