In a previous study (Carrubba et al. 2007) the authors reported that exposure to magnetic fields greater than those typically found in the environment can trigger onset and offset evoked potentials. The authors interpret the evoked potentials as evidence for sensory transduction, which could be the earliest step in the stress response.
22 healthy subjects (10 males) were exposed and sham exposed.
|Setup||two sets of coils; coil set consisting of a circular coil with a radius of 21.6 cm and 21 turns, a square coil with 48.3 cm side lenght and 85 turns and a square coil with a side lenght of 66 cm and 120 turns; coils were shielded with grounded aluminum foil; field in the test person's head region uniform within 5%; test person sitting in a dark isolation chamber|
|Sham exposure||A sham exposure was conducted.|
|Additional info||each trial consisted of 2 min acclimation, 2 s EMF expsoure (1µT or 5 µT) or sham exposure, 5 s inter-stimulus interval; magnetic fields were applied in the first and third block; the middle block served as negative control (sham exposure)|
Onset potentials were seen in all but 3 subjects and offset potentials were seen in all but 4 subjects. Every subject exhibited an onset and/or offset evoked potential. Only by means of recurrence-plot analysis evoked potentials were detected. Time averaging of the EEG (only linear determinism) did not provide any evidence of evoked potentials.
Taken together, exposure to the magnetic field produced changes in brain electrical activity indicative of a detection process based on sensory transduction.