Study type: Medical/biological study (experimental study)

Resting EEG is affected by exposure to a pulsed ELF magnetic field. med./bio.

Published in: Bioelectromagnetics 2004; 25 (3): 196-203

Aim of study (acc. to editor)

To study the effects of extremely low frequency magnetic fields with most power at frequencies between 0 and 500 Hz on the human EEG.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 0–500 Hz
Modulation type: pulsed
Exposure duration: intermittent for 15 min, see Modulation

Exposure 1

Main characteristics
Frequency 0–500 Hz
Type
Waveform
Exposure duration intermittent for 15 min, see Modulation
Additional info The power content was extremely low above 500 Hz with most of the power content below 300 Hz.
Modulation
Modulation type pulsed
Rise time 1 ms
Pulse type biphasic
Additional info

The (patented) pulsed MF design was made of individual pulses, each of which a doublet, combined in an 853 ms segment including 18 pulses. Each pulse had a maximum rise time of 1 ms resulting in a maximum time changing MF of 0.4 T/s. In between segments were varying refractory periods of 110, 220, 330 ms followed by a longer fourth refractory period of 1200 ms after which another pulse segment of 853 ms began. This pattern was repeated for 15 min.

Exposure setup
Exposure source
Chamber The MF exposure system [Thomas et al., 2001] consisted of three orthogonal square Helmholtz-like coil pairs with 2, 1.75, and 1.5 m sides (10 turns of 8-gauge stranded conductor per coil with an incorporated high temperature, non-conductive cooling/heating tube wound on Lexan® frames). During exposure, only the vertical coil pair was driven by a constant current amplifier via a digital to analog converter; all other coils were unpowered. During sham exposure, the amplifiers were on but there was no signal.
Setup Subjects were fitted with the EEG recording apparatus (cap) and seated within the exposure system. They were instructed to relax, but to not fall asleep.
Sham exposure A sham exposure was conducted.
Additional info Twenty subjects received both an MF and a sham session approx. 1 week apart, in a random, counterbalanced, cross-over design. The experiment consisted of 5 min of pre-exposure baseline EEG followed by either 15 min of MF or sham exposure. Due to the interference of the pulsed MF with the recording, EEG was sampled approximately 7 s after the end of the MF or sham condition.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 200 µT peak value measured - biphasic

Reference articles

Exposed system:

Methods Endpoint/measurement parameters/methodology

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

Main outcome of study (acc. to author)

Exposure to a specific pulsed extremely low frequency magnetic field was revealed to result in higher resting EEG alpha wave activity (8-13 Hz) compared to sham exposure.
The authors suggest that this result may be a nonspecific physiological response to the pulsed magnetic fields.

Study character:

Study funded by

Replication studies

Related articles