Effects of A 60 Hz Magnetic Field of Up to 50 milliTesla on Human Tremor and EEG: A Pilot Study

Abstract

Humans are surrounded by sources of daily exposure to power-frequency (60 Hz in North America) magnetic fields (MFs). Such time-varying MFs induce electric fields and currents in living structures which possibly lead to biological effects. The present pilot study examined possible extremely low frequency (ELF) MF effects on human neuromotor control in general, and physiological postural tremor and electroencephalography (EEG) in particular. Since the EEG cortical mu-rhythm (8–12 Hz) from the primary motor cortex and physiological tremor are related, it was hypothesized that a 60 Hz MF exposure focused on this cortical region could acutely modulate human physiological tremor. Ten healthy volunteers (age: 23.8 ± 4 SD) were fitted with a MRI-compatible EEG cap while exposed to 11 MF conditions (60 Hz, 0 to 50 mTrms, 5 mTrms increments). Simultaneously, physiological tremor (recorded from the contralateral index finger) and EEG (from associated motor and somatosensory brain regions) were measured. Results showed no significant main effect of MF exposure conditions on any of the analyzed physiological tremor characteristics. In terms of EEG, no significant effects of the MF were observed for C1, C3, C5 and CP1 electrodes. However, a significant main effect was found for CP3 and CP5 electrodes, both suggesting a decreased mu-rhythm spectral power with increasing MF flux density. This is however not confirmed by Bonferroni corrected pairwise comparisons. Considering both EEG and tremor findings, no effect of the MF exposure on human motor control was observed. However, MF exposure had a subtle effect on the mu-rhythm amplitude in the brain region involved in tactile perception. Current findings are to be considered with caution due to the small size of this pilot work, but they provide preliminary insights to international agencies establishing guidelines regarding electromagnetic field exposure with new experimental data acquired in humans exposed to high mT-range MFs.

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A 50 Hz magnetic field affects hemodynamics, ECG and vascular endothelial function in healthy adults: A pilot randomized controlled trial

“…When mainly focusing on Japan, non-thermal noninvasive 50/60 Hz sinusoidal MF therapy has been used to relieve chronic pain, muscle stiffness, muscle fatigue and so on, for over 40 years, since approved by Japanese Ministry of Health, Labour and Welfare for improvement of muscle stiffness and blood circulation in the MF-exposed region, in which the peak magnetic flux density B max at the surface area of the approved therapeutic MF exposure devices should range between 35 and 180 mT. In some studies, head exposure to 50/60 Hz MFs in 3–50 mT range altered electroencephalogram (EEG) signals in several brain regions, indicating the presence of magnetosensory evoked potentials [ 22 , 23 ]. In heart exposure, 50 Hz MFs of 150–200 μT for 30 min significantly reduced low-frequency parameters of heart rate variability (HRV) through known mechanisms [ 24 ].…”