EMF-Portal | Resting EEG is affected by exposure to a pulsed ELF magnetic field

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

Aim of study (acc. to editor)

Endpoint

effects on the neurological system: EEG

Exposure

Exposure	Parameters
Exposure 1: 0–500 Hz Modulation type: pulsed Exposure duration: intermittent for 15 min, see Modulation	magnetic flux density: 200 µT peak value (biphasic)

Exposure 1

Main characteristics

Frequency	0–500 Hz
Type	magnetic field
Waveform	pulsed
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	Helmholtz coils
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

Additional parameter details

Ambient sham values were 14.7 µT horizontal, 43.3 µT vertical with 60 Hz < 0.2 µT rms.

Measurement and calculation details

The specific pulsed MF was monitored with a 3-D fluxgate magnetometer through an analog to digital converter.

Reference articles

Thomas AW et al. (2001): Magnetic field exposure and behavioral monitoring system

Exposed system:

human
whole body

Methods Endpoint/measurement parameters/methodology

effects on the neurological system: resting EEG

EOG

Investigated system:

investigation on living organism

Investigated organ system:

brain/CNS

Time of investigation:

before exposure
after exposure

Main outcome of study (acc. to author)

Study character:

medical/biological study
experimental study
full/main study

Study funded by

Canadian Institutes of Health Research (CIHR)

Replication studies

Cook CM et al. (2009): Changes in human EEG alpha activity following exposure to two different pulsed magnetic field sequences

Modolo J et al. (2017): Human exposure to power frequency magnetic fields up to 7.6 mT: An integrated EEG/fMRI study

Legros A et al. (2012): Neurophysiological and behavioral effects of a 60 Hz, 1,800 µT magnetic field in humans

Cvetkovic D et al. (2009): Alterations of human electroencephalographic activity caused by multiple extremely low frequency magnetic field exposures