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Decrease of motor cortex excitability following exposure to a 20 Hz magnetic field as generated by a rotating permanent magnet.

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Gallasch E, Rafolt D, Postruznik M, Fresnoza S, Christova M. · 2018

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Just 15 minutes of 20 Hz magnetic field exposure measurably reduced brain excitability in healthy volunteers.

Plain English Summary

Summary written for general audiences

Researchers exposed 14 healthy volunteers to 20 Hz magnetic fields generated by rotating permanent magnets for 15 minutes, then measured brain activity in the motor cortex (the brain region controlling movement). They found that this magnetic field exposure significantly reduced motor cortex excitability, meaning the brain region became less responsive to stimulation. This demonstrates that even brief exposure to rotating magnetic fields can measurably alter brain function.

Why This Matters

This study provides direct evidence that magnetic fields can alter brain function in measurable ways. The researchers used a 20 Hz frequency, which falls within the extremely low frequency (ELF) range commonly emitted by household appliances, power lines, and some electronic devices. What makes this research particularly significant is that it shows brain changes occurring after just 15 minutes of exposure using a relatively simple device - a rotating permanent magnet. The science demonstrates that our brains are not immune to magnetic field influences, contrary to what industry advocates often claim. While this was a controlled laboratory study using healthy volunteers, the findings add to a growing body of evidence showing that EMF exposure can produce biological effects in the nervous system. The reality is that we're exposed to similar frequencies daily from our electrical environment, though typically at lower intensities and for longer durations.

Exposure Information

A logarithmic frequency spectrum from 10 Hz to 100 GHz showing where this study's 20 Hz exposure sits relative to common EMF sources.Where This Frequency Sits on the EMF SpectrumELFVLFLF / MFHF / VHFUHFSHFmm10 Hz100 GHzThis study: 20 HzCell phones~1 GHzWiFi2.4 GHz5G mm28 GHzLogarithmic scale

Specific exposure levels were not quantified in this study. The study examined exposure from: 20 Hz Duration: 15 min

Study Details

The aim of this transcranial magnetic stimulation (TMS) study is to investigate whether such fields are able to influence MC excitability, and whether there are parallels to tACS induced effects.

Fourteen healthy volunteers received 20 Hz tAMF stimulation over the MC, over the vertex, and 20 Hz ...

The tACS and the tAMF stimulation over the MC affected cortical excitability in a different way. Aft...

The recorded single and paired pulse MEPs indicate a general decrease of MC excitability following 15 min of tAMF stimulation.

Cite This Study
Gallasch E, Rafolt D, Postruznik M, Fresnoza S, Christova M. (2018). Decrease of motor cortex excitability following exposure to a 20 Hz magnetic field as generated by a rotating permanent magnet. Clin Neurophysiol. 129(7):1397-1402, 2018.
Show BibTeX
@article{e_2018_decrease_of_motor_cortex_1744,
  author = {Gallasch E and Rafolt D and Postruznik M and Fresnoza S and Christova M.},
  title = {Decrease of motor cortex excitability following exposure to a 20 Hz magnetic field as generated by a rotating permanent magnet.},
  year = {2018},
  
  url = {https://pubmed.ncbi.nlm.nih.gov/29729595/},
}
PubMed: 29729595

Cited By (10 papers)

Quick Questions About This Study

Yes, a 2018 study found that 15-minute exposure to 20 Hz rotating magnetic fields significantly reduced motor cortex excitability in healthy volunteers. This means the brain region controlling movement became less responsive to stimulation, demonstrating that brief magnetic field exposure can measurably alter brain function.
Research shows that just 15 minutes of exposure to rotating permanent magnets generating 20 Hz magnetic fields can significantly decrease motor cortex excitability. This study on 14 healthy volunteers demonstrates that relatively brief magnetic field exposure produces measurable changes in brain function.
Yes, rotating magnetic field stimulation (tAMF) and electrical stimulation (tACS) affect the motor cortex differently. While electrical stimulation increased brain response amplitudes, rotating 20 Hz magnetic fields decreased motor cortex excitability and altered inhibitory brain circuits, showing distinct biological mechanisms.
Exposure to 20 Hz rotating magnetic fields decreases motor cortex excitability, making this brain region less responsive to stimulation. The 2018 study found reduced motor evoked potential amplitudes and changes in cortical facilitation, indicating altered neural communication in movement control areas.
Yes, researchers found that 15-minute exposure to rotating permanent magnets producing 20 Hz magnetic fields significantly altered brain responses in healthy volunteers. The study measured decreased motor cortex excitability and changes in paired-pulse responses, demonstrating that brief exposures can modify neural function.