Influence of an alternating 3 Hz magnetic field with an induction of 0.1 millitesla on chosen parameters of the human occipital EEG.

Neuroscience letters · 1997 · Harm · Moderate evidence

← Research stream

HarmModerate evidencePaper 4134

Study snapshot

PublicationNeuroscience letters · 1997

Study typerandomized_trial

Reported directionHarm

Evidence ratingModerate

Abstract

In 62 volunteers it was studied, whether an alternating 3 Hz magnetic field (induction 0.1 mT) vertically applied to the head over a period of 20 min causes changes in EEG parameters. The study's design was a random crossover controlled, blind one. The field was generated by a Helmholtz coils arrangement. The occipital surface EEGs (O1 and O2) were derived against the left earlobe. Significant differences (two-tailed P < 0.05) between sham and real exposure were found for the relative spectral amplitudes of the theta (3.5-7.5 Hz) and beta band (12.5-25.0 Hz) and the theta/beta ratio. These observations can be interpreted as a more pronounced reduction of alertness under the real field condition compared with the control.

Machine Enhanced Logic

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 typerandomized_trial

Effect directionharm

Population62 volunteers

Sample size62

ExposureELF · 20 min

Evidence strengthModerateConfidence: 74% · Peer reviewed: yes

Main findings

In a randomized, blind, crossover, sham-controlled study of 62 volunteers, a vertically applied alternating 3 Hz magnetic field (0.1 mT) for 20 minutes produced statistically significant differences versus sham in occipital EEG relative spectral amplitudes in the theta and beta bands and in the theta/beta ratio (two-tailed P < 0.05). The authors interpret these EEG changes as indicating a more pronounced reduction of alertness during real-field exposure compared with control.

Outcomes measured

Occipital EEG spectral parameters (relative spectral amplitudes)
Theta band (3.5–7.5 Hz) relative spectral amplitude
Beta band (12.5–25.0 Hz) relative spectral amplitude
Theta/beta ratio
Alertness (interpretation based on EEG changes)

Limitations

Only occipital surface EEG (O1, O2) reported; other brain regions not described
Short exposure duration (20 min)
Details on randomization procedure, blinding assessment, and effect sizes are not provided in the abstract
Alertness outcome is inferred from EEG parameters rather than directly measured (per abstract interpretation)

View raw extracted JSON

{
  "study_type": "randomized_trial",
  "exposure": {
    "band": "ELF",
    "source": "experimental (Helmholtz coils; head exposure)",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": "20 min"
  },
  "population": "62 volunteers",
  "sample_size": 62,
  "outcomes": [
    "Occipital EEG spectral parameters (relative spectral amplitudes)",
    "Theta band (3.5–7.5 Hz) relative spectral amplitude",
    "Beta band (12.5–25.0 Hz) relative spectral amplitude",
    "Theta/beta ratio",
    "Alertness (interpretation based on EEG changes)"
  ],
  "main_findings": "In a randomized, blind, crossover, sham-controlled study of 62 volunteers, a vertically applied alternating 3 Hz magnetic field (0.1 mT) for 20 minutes produced statistically significant differences versus sham in occipital EEG relative spectral amplitudes in the theta and beta bands and in the theta/beta ratio (two-tailed P < 0.05). The authors interpret these EEG changes as indicating a more pronounced reduction of alertness during real-field exposure compared with control.",
  "effect_direction": "harm",
  "limitations": [
    "Only occipital surface EEG (O1, O2) reported; other brain regions not described",
    "Short exposure duration (20 min)",
    "Details on randomization procedure, blinding assessment, and effect sizes are not provided in the abstract",
    "Alertness outcome is inferred from EEG parameters rather than directly measured (per abstract interpretation)"
  ],
  "evidence_strength": "moderate",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "ELF magnetic field",
    "3 Hz",
    "0.1 mT",
    "Helmholtz coils",
    "randomized crossover",
    "sham-controlled",
    "blind",
    "EEG",
    "occipital",
    "theta",
    "beta",
    "theta/beta ratio",
    "alertness"
  ],
  "suggested_hubs": [
    {
      "slug": "occupational-exposure",
      "weight": 0.2,
      "reason": "ELF magnetic-field exposure study; however exposure appears experimental rather than workplace-based."
    }
  ]
}

AI can be wrong. Always verify against the paper.

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/s0304-3940(97)00881-1
PubMed: 9469655

Read the original paper →

Related papers

← Back to the Research Library