Extremely Low Frequency Magnetic Fields Do Not Affect LTP-Like Plasticity in Healthy Humans

Fioravante Capone,Francesco Motolese,Mariagrazia Rossi,Giovanni Pellegrino,Gabriella Musumeci,Vincenzo Di Lazzaro

doi:10.3389/fnhum.2020.00014

Abstract

IntroductionSeveral studies explored the biological effects of extremely low-frequency magnetic fields (ELF-MFs) in vitro, reporting the induction of functional changes in neuronal activity. In particular, ELF-MFs can influence synaptic plasticity both in vitro and in animal models but some studies reported an increase in long-term potentiation (LTP) whereas others suggested its reduction. However, no specific study has investigated such effect on humans.AimsTo evaluate whether ELF-MFs affect the propensity of the human cortex to undergo LTP-like plasticity.MethodsWe designed a randomized, single-blind, sham-controlled, cross-over study on 10 healthy subjects. Cortical plasticity was induced by intermittent theta burst stimulation (iTBS) before and after 45-min ELF-MFs (75 Hz; 1.8 mT) or sham exposure and was estimated by measuring the changes of motor evoked potentials (MEP) amplitude before and after each iTBS.ResultsNo adverse events were reported. No significant effects of ELF-MFs on cortical plasticity were found.ConclusionWhole-brain exposure to ELF-MFs (75 Hz; 1.8 mT) is safe and does not seem to significantly affect LTP-like plasticity in human motor cortex.

Highlights

Several studies explored the biological effects of extremely low-frequency magnetic fields (ELF-MFs) in vitro, reporting the induction of functional changes in neuronal activity
Since intracortical facilitation (ICF) mainly reflects excitatory neurotransmission mediated by the N-methyl-D-aspartic acid (NMDA) receptors (Di Lazzaro et al, 2008), we hypothesized that ELF-MFs may produce a selective enhancement of glutamatergic activity in human brain
In the present study we evaluated the effect of ELF-MFs on cortical plasticity, in terms of changes induced by intermittent theta burst stimulation (iTBS) on TMS measures of cortical excitability

Summary

Introduction

Several studies explored the biological effects of extremely low-frequency magnetic fields (ELF-MFs) in vitro, reporting the induction of functional changes in neuronal activity. ELF-MFs can influence synaptic plasticity both in vitro and in animal models but some studies reported an increase in long-term potentiation (LTP) whereas others suggested its reduction. Several studies explored the biological effects of extremely low-frequency (0–300 Hz) magnetic fields (ELF-MFs) in vitro, reporting the induction of functional changes in neuronal activity (Di Lazzaro et al, 2013). ELF-MFs can produce measurable changes in brain electrical activity and can influence cerebral functions such as motor control, sensory perception, cognitive activities, sleep, and mood (Bagheri Hosseinabadi et al, 2019). Other studies have reported, after chronic ELF-MFs exposure, a positive effect in social recognition memory (Varró et al, 2009) and spatial learning (Liu et al, 2015)

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Discussion

Conclusion