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.

By: Carrubba S, Frilot 2nd C, Chesson Jr AL, Marino AA

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

effects on the neurological system: magneto-sensory evoked potentials

Exposure

- 50/60 Hz
- magnetic field

Exposure	Parameters
Exposure 1: 60 Hz Exposure duration: three blocks of 70 trials (see add. information)	magnetic flux density: 1 µT effective value magnetic flux density: 5 µT effective value

Exposure 1

Main characteristics

Frequency	60 Hz
Type	magnetic field
Waveform	sinusoidal
Exposure duration	three blocks of 70 trials (see add. information)

Exposure setup

Exposure source	coil(s)
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:

human
whole body: sagittal plane perpendicular to the field

Methods Endpoint/measurement parameters/methodology

effects on the neurological system: magneto-sensory evoked potentials (latency, duration (EEG; nonlinear recurrence analysis and linear time averaging analysis))

Investigated system:

investigation on living organism

Investigated organ system:

brain/CNS

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:

medical/biological study
experimental study
full/main study
blind study

Davarpanah Jazi S et al. (2017): Effects of A 60 Hz Magnetic Field of Up to 50 milliTesla on Human Tremor and EEG: A Pilot Study
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. (2015): Effects of a 60 Hz magnetic field exposure up to 3000 µT on human brain activation as measured by functional magnetic resonance imaging
Marino AA et al. (2010): Simulated MR magnetic field induces steady-state changes in brain dynamics: Implications for interpretation of functional MR studies
Carrubba S et al. (2009): The electric field is a sufficient physical determinant of the human magnetic sense
Marino AA et al. (2009): Evidence that transduction of electromagnetic field is mediated by a force receptor
Carrubba S et al. (2008): The effects of low-frequency environmental-strength electromagnetic fields on brain electrical activity: a critical review of the literature
Carrubba S et al. (2008): Magnetosensory evoked potentials: consistent nonlinear phenomena
Carrubba S et al. (2007): Nonlinear EEG activation evoked by low-strength low-frequency magnetic fields
Carrubba S et al. (2007): Evidence of a nonlinear human magnetic sense
Carrubba S et al. (2006): Detection of nonlinear event-related potentials
Marino AA et al. (2004): Effect of low-frequency magnetic fields on brain electrical activity in human subjects
Marino AA et al. (2003): Consistent magnetic-field induced dynamical changes in rabbit brain activity detected by recurrence quantification analysis
Marino AA et al. (2003): Localization of electroreceptive function in rabbits
Marino AA et al. (2002): Consistent magnetic-field induced dynamical changes in rabbit brain activity detected by recurrence quantification analysis (Corrected and republished in Brain Res. 2003 Feb 28;964(2):317-26)