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Mechanism-based modeling of time-varying magnetic fields effects on cortical activity

Background

Understanding how extremely low-frequency (ELF, < 300 Hz) magnetic fields (MF) interact with human brain activity is an important question, especially regarding potential effects of power-lines MF (60 Hz in North America). Such knowledge is critical to 1) contribute to guidelines protecting public and workers from exposure to ELF MFs [1, 2]; and 2) design novel non-invasive brain stimulation techniques using ELF MFs to interfere with pathological brain activity patterns.

Methods

We used an extensively validated neural mass model [3] describing the main neuronal populations forming a cortical column, which we extended by including 1) a time-dependent membrane potential perturbation caused by the induced electric field; 2) a model linking post-synaptic calcium concentration and synaptic plasticity processes [4]. We used increasing levels of MF flux density at 60 Hz to identify the threshold for significant effects on simulated EEG alpha (8-12 Hz) power. A 4x3x2 ANOVA for repeated measured measures was conducted on EEG alpha power before/during/after exposure, with/without 60 Hz MF exposure, with/without synaptic plasticity.

Results

Simulated EEG alpha power decreased with increased 60 Hz MF flux density (significant for 250<dV<500 μV when only pyramidal neurons were modulated), without significant effects from synaptic plasticity processes. If slow inhibitory interneurons [3] were also modulated, EEG alpha power decrease due to MF exposure was significantly diminished (see Figure).

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Figure 1

Conclusions

The model will be used to 1) understand human data currently acquired in our group [5]; and 2) study in silico effects of transcranial alternating current stimulation and magnetic stimulation (tACS/TMS). Future work will include frequency-dependent effects from extracellular medium dielectric properties, and selective modulation of specific neuronal populations.

References

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    ICNIRP: Guidelines for limiting exposure to time-varying electric and magnetic fields (1 Hz to 100 kHz). Health Phys. 2010, 99 (6): 818-836.

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    IEEE: C95.6 – IEEE standard for safety levels with respect to human exposure to electromagnetic fields, 0-3 kHz. IEEE. 2002, New York

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    Wendling F, Bartolomei F, Bellanger JJ, Chauvel P: Epileptic fast activity can be explained by a model of impaired GABAergic dendritic inhibition. Eur J Neurosci. 2005, 22: 343-356. 10.1111/j.1460-9568.2005.04213.x.

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    Shouval HZ, Castellani GC, Blais BS, Yeung LC, Cooper LN: Converging evidence for a simplified biophysical model of synaptic plasticity. Biol Cybern. 2002, 87: 383-391. 10.1007/s00422-002-0362-x.

  5. 5.

    Legros A, Modolo J, Goulet D, Plante M, Souques M, Deschamps F, Ostigui G, Mezei G, Lambrozo J, Thomas AW: Magnetophophene perception and associated neurophysiological responses of the human central nervous system exposed to 50 and 60 Hz magnetic fields of up to 50 mT. CIGRE EMF International colloquium. 2013

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Acknowledgements

Lawson Health Research Institute, Mitacs Elevate Program, Hydro-Québec/Electricité de France/Réseau de Transport d'Electricité, and Canadian Institutes of Health Research.

Author information

Correspondence to Julien Modolo.

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This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

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Keywords

  • Magnetic Field Effect
  • Magnetic Field Exposure
  • Neural Mass Model
  • Specific Neuronal Population
  • Brain Stimulation Technique