Study type: Medical/biological study (experimental study)

Numerical analysis of recurrence plots to detect effect of environmental-strength magnetic fields on human brain electrical activity. med./bio.

Published in: Med Eng Phys 2010; 32 (8): 898-907

Aim of study (acc. to author)

To determine whether magnetic fields having strengths comparable to those typically found in the environment (60 Hz, 1 and 5 µT) elicit evoked potentials.

Background/further details

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.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 60 Hz
Exposure duration: three blocks of 70 trials (see add. information)

Exposure 1

Main characteristics
Frequency 60 Hz
Type
Waveform
Exposure duration three blocks of 70 trials (see add. information)
Exposure setup
Exposure source
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)
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 1 µT effective value measured - -
magnetic flux density 5 µT effective value measured - -

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Investigated organ system:
Time of investigation:
  • before exposure
  • during exposure
  • after exposure

Main outcome of study (acc. to author)

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.

Study character:

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