Study type: Medical/biological study (experimental study)

Changes in human EEG alpha activity following exposure to two different pulsed magnetic field sequences. med./bio.

Published in: Bioelectromagnetics 2009; 30 (1): 9-20

Aim of study (acc. to author)

To examine the effects of pulsed extremely low frequency magnetic field sequences upon alpha wave activity (8-13 Hz) of the human EEG over the occipital-parietal regions.

Background/further details

Two previous studies (see publication 11906 and publication 10628) determined that exposure to pulsed extremely low frequency electromagnetic fields can affect the EEG, notably the alpha wave frequency (8-13 Hz). In the present study 22 participants from two previous studies (see publication 11906 [sequence 2 with a refractory period of 5000 ms] and publication 10628 [sequence 1 with a refractory period of 1200 ms]) and 10 additional subjects were randomly assigned to two different pulsed magnetic field sequences, used in the previous studies. Participation consisted of two sessions (exposure and sham exposure), separated by approximately 1 week (7+/-2 days).

Endpoint

Exposure

Exposure Parameters
Exposure 1: 0–500 Hz
Modulation type: pulsed
Exposure duration: continuous for 15 min

General information

two different pulse forms were used a) pulses with a refractory period of 1200 ms b) pulses with a refractory period of 5000 ms

Exposure 1

Main characteristics
Frequency 0–500 Hz
Type
Exposure duration continuous for 15 min
Modulation
Modulation type pulsed
Pulse width 853 ms
Rise time 1 ms
Exposure setup
Exposure source
Setup three orthogonal square Helmholtz coils with 2.0 m, 1.75 m, 1.5 m sides and 10 turns of 8-gauge stranded conductor each
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 200 µT peak value measured - -

Reference articles

  • Cook CM et al. (2005): Resting EEG effects during exposure to a pulsed ELF magnetic field.
  • Cook CM et al. (2004): Resting EEG is affected by exposure to a pulsed ELF magnetic field.
  • Thomas AW et al. (2001): Magnetic field exposure and behavioral monitoring system.
  • Thomas AW et al. (2001): A comparison of rheumatoid arthritis and fibromyalgia patients and healthy controls exposed to a pulsed (200 microT) magnetic field: effects on normal standing balance.
  • Thomas AW et al. (2001): Human subjects exposed to a specific pulsed (200 microT) magnetic field: effects on normal standing balance.
  • Thomas AW et al. (1998): Analgesic effects of a specific pulsed magnetic field in the land snail, Cepaea nemoralis: consequences of repeated exposures, relations to tolerance and cross-tolerance with DPDPE.
  • Thomas AW et al. (1997): Pulsed magnetic field induced "analgesia" in the land snail, Cepaea nemoralis, and the effects of mu, delta, and kappa opioid receptor agonists/antagonists.
  • Thomas AW et al. (1997): Antinociceptive effects of a pulsed magnetic field in the land snail, Cepaea nemoralis.

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)

Compared to sham exposure, alpha wave activity was lowered over the occipital-parietal regions of the brain during exposure to sequence 1, while alpha wave activity over the same regions was higher after sequence 2 exposure. The effects occured after 5 min of exposure and were dependent on the order of exposure (magnetic field followed by sham exposure).
This study supports previous observations of EEG changes after 5 min pulsed extremely low frequency magnetic field exposure. The results also suggest that a previous exposure to the pulsed magnetic field sequence determined subjects´ responses in the present experiment, i.e. subjects previously exposed to sequence 1(and now to sequence 2) displayed higher occipital alpha wave activity after magnetic field exposure. Subjects previously exposed to sequence 2 (and now sequence 1) displayed lower alpha wave activity over posterior scalp regions in the present study.

Study character:

Study funded by

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