[Investigation of resonance effect caused by local exposure of extremely low frequency magnetic field on brain signals: a randomize clinical trial]

ABSTRACT

Some studies have investigated the effects of extremely low frequency magnetic fields [ELF-MFs] on brain signals, but only few of them have reported that humans exposed to magnetic fields exhibit changes in brain signals at the frequency of stimulation, i.e. resonance effect. In most investigations, researchers usually take advantage of a uniform field which encompasses the head. The aim of present study was to expose different parts of the brain to ELF-MFs locally and to investigate variation of brain signal and resonance effect. The subjects consisting of 19 male-students with the mean age of 25.6 +/- 1.6 years participated in this study. Local ELF-MFs with 3, 5, 10, 17 and 45Hz frequencies and 240 microT intensity was applied on five points [T3, T4, Cz, F3 and F4] of participants scalp Separately in 10-20 system. In the end, relative power over this points in common frequency bands and at the frequency of magnetic fields was evaluated by paired t-test. Exposure of Central area by local magnetic field caused significant change [p<0.05] in the forehead alpha band. Reduction in the alpha band over central area was observed when temporal area was exposed to ELF MF. The results showed that resonance effect in the brain signals caused by local magnetic field exposure was not observed and change in every part of the relative power spectrum might occur. The changes in the EEG bands were not limited necessarily to the exposure point