Do static magnetic fields of NMR influence biological signals?
When measuring auditory evoked potentials on test persons we found that an early signal, measurable between the mastoid and vertex electrodes and possibly caused by capacitive or/and inductive coupling from the electrodynamic headphone, was phase-shifted when the person was exposed to a static 0.35 T field. This shift only slowly (greater than 15 min) returned to zero after termination of the magnetic exposure. Using a circuit stimulating the EEG measurement we now show that this shift is caused by a change in the total capacity of the electrode impedances. Therefore, the magnetically induced shift may be explained by changes in electric capacities of the magnetically exposed biological system.
D005072:Evoked Potentials, Auditory; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008280:Magnetics