Study type: Medical/biological study (experimental study)

The electric field is a sufficient physical determinant of the human magnetic sense. med./bio.

Published in: Int J Radiat Biol 2009; 85 (7): 622-632

Aim of study (acc. to author)

To investigate whether magneto-sensory evoked potentials triggered by magnetic fields could be mediated by a biophysical mechanism actually involving only the electric field component.

Background/further details

Previous studies (Carrubba et al., 2008; Carrubba et al., 2007a; Carrubba et al., 2007b) have shown that weak low frequency magnetic fields trigger magneto-sensory evoked potentials. Because the magnetic fields and their induced electric fields were both present in the brain the distinct influence of the components (magnetic/electric) on brain activity is unclear.
23 subjects (six males) were exposed to electric fields whose strength was capable of producing brain electric fields comparable to those of magnetic fields from the previous studies (see above). To test the sensitivity, the strength of the electric field was systematically reduced and was always below the threshold for awareness. Sham exposure (negative control) was performed randomly before or after exposure.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 60 Hz
Modulation type: pulsed
Exposure duration: 80 pulses

Exposure 1

Main characteristics
Frequency 60 Hz
Type
Waveform
Exposure duration 80 pulses
Modulation
Modulation type pulsed
Pulse width 2 s
Rise time 5 ms
Fall time 15 ms
Additional info

5 s interval between pulses

Exposure setup
Exposure source
  • two 76 cm square parallel metal plates, separated by 15 cm
Setup plates inside an electrically grounded room, test person's head between the plates; field perpendicular to the sagittal plane
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
electric field strength 1 V/m - calculated - -
electric field strength 1,000 V/m peak value calculated - -
electric field strength 1 mV/m - calculated - induced in the brain

Reference articles

  • Carrubba S et al. (2007): Evidence of a nonlinear human magnetic sense.
  • Dawson TW et al. (1997): Influence of human model resolution on computed currents induced in organs by 60-Hz magnetic fields.
  • Hart FX (1992): Numerical and analytical methods to determine the current density distributions produced in human and rat models by electric and magnetic fields.

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)

Evoked potentials were observed in all but one subject in response to electric fields. The evoked potentials had the same latency, duration and distribution of magnitudes as the potentials triggered by magnetic fields in earlier studies (see above). Evoked potentials were not detected based on EEG analysis using time averaging, but only by means of recurrence analysis. No sensitivity threshold could be determined.
It was concluded that the electric field was a sufficient biophysical determinant of the evoked potentials in this study and previous studies. The transduction of an electric field could be explained by biophysical coupling between fields and tissue by processes involving forces on ion channel gates.

Study character:

Study funded by

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