Effects of a 60 Hz Magnetic Field Exposure Up to 3000 μT on Human Brain Activation as Measured by Functional Magnetic Resonance Imaging

Abstract

Several aspects of the human nervous system and associated motor and cognitive processes have been reported to be modulated by extremely low-frequency (ELF, < 300 Hz) time-varying Magnetic Fields (MF). Due do their worldwide prevalence; power-line frequencies (60 Hz in North America) are of particular interest. Despite intense research efforts over the last few decades, the potential effects of 60 Hz MF still need to be elucidated, and the underlying mechanisms to be understood. In this study, we have used functional Magnetic Resonance Imaging (fMRI) to characterize potential changes in functional brain activation following human exposure to a 60 Hz MF through motor and cognitive tasks. First, pilot results acquired in a first set of subjects (N=9) were used to demonstrate the technical feasibility of using fMRI to detect subtle changes in functional brain activation with 60 Hz MF exposure at 1800 μT. Second, a full study involving a larger cohort of subjects tested brain activation during 1) a finger tapping task (N=20), and 2) a mental rotation task (N=21); before and after a one-hour, 60 Hz, 3000 μT MF exposure. The results indicate significant changes in task-induced functional brain activation as a consequence of MF exposure. However, no impact on task performance was found. These results illustrate the potential of using fMRI to identify MF-induced changes in functional brain activation, suggesting that a one-hour 60 Hz, 3000 μT MF exposure can modulate activity in specific brain regions after the end of the exposure period (i.e., residual effects). We discuss the possibility that MF exposure at 60 Hz, 3000 μT may be capable of modulating cortical excitability via a modulation of synaptic plasticity processes.

Human exposure to power frequency magnetic fields up to 7.6 mT: An integrated EEG/fMRI study

“…Interestingly, EEG data provide a consistent view with BOLD (acquired simultaneously) results, suggesting an absence of EEG effects due to 3 mT 60 Hz MF exposure on brain electrical or functional activity. It is worth mentioning that the level of MF flux density during this sequence was identical to previous research in our group [Legros et al, ], while the exposure duration was different (60 min in previous research, 10 s repeated 12 times in the present study). In terms of accumulated time of exposure, it sums up to 2 min for the current study versus 60 min in previous research where significant effects on brain functional activation were identified [Legros et al, ].…”

“…It is worth mentioning that the level of MF flux density during this sequence was identical to previous research in our group [Legros et al, ], while the exposure duration was different (60 min in previous research, 10 s repeated 12 times in the present study). In terms of accumulated time of exposure, it sums up to 2 min for the current study versus 60 min in previous research where significant effects on brain functional activation were identified [Legros et al, ]. Therefore, participants to the present study have been exposed for a duration 30 times lower, with an identical MF flux density, suggesting that MF exposure duration might be a critical parameter in possible neurophysiological effects.…”

“…The absence of neurophysiological effects in humans, observed in the present study as a result of 60 Hz MF exposures at 3 and 7.6 mT, is informative in terms of possible interaction mechanisms between power‐line frequency MF and the CNS. These results in light of previous research in which effects were observed on brain functional activation with a longer MF exposure period [Legros et al, ] suggest the possibility of a “cumulative effect” of the exposure, which would take a certain time to build up. One possible biological substrate for this effect is the modulation of “synaptic plasticity,” which is one plausible candidate for explaining the persistence of effects after exposure, and also that effects take place after some time [Modolo et al, ,].…”

“…), where the “exposure” condition could be either “MF exposed” (“exp”) or “sham.” We present in Figure the GLM results regarding fMRI group results ( N = 25), and emphasize the left motor cortex and cerebellum. The reason for this emphasis is that, in a previous experiment, these regions were shown to have their activity modulated in a finger tapping task after a 60‐min exposure to a 60 Hz MF of identical MF flux density (3 mT, see Legros et al [, ]). However, since the experimental protocol was different (e.g., a motor task was involved, whereas no task was included in the present study), it was not obvious that these regions could be modulated in the present experiment.…”

Evaluation of the effects of power-frequency magnetic fields on the electrical activity of cardiomyocytes differentiated from human induced pluripotent stem cells

“…Various types of human cells derived from iPS cells could be utilized for assessment of the health risks of various targets, including EMFs. The current international guidelines/standards for low-frequency EMF exposure deserve further investigation on many points, and experimental data on human neural responsiveness to EMFs have attracted much interest in recent years (Legros et al, 2012(Legros et al, , 2015. We propose that data on muscles, in particular CMs, should be similarly collected for evaluation of the risk of exposure to EMFs.…”