Electronic Thesis and Dissertation Repository


Master of Science




Legros, Alexandre


Background: Magnetophosphenes are among the most reliably reported effects resulting from magnetic induction. The frequency dependence of the perception threshold is crucial, as guideline agencies use this information to set exposure limits whose purpose is to protect public and workers.

Objective:Establish the magnetophosphene perception thresholds throughout the extremely low frequency range (0-300 Hz) and evaluate the use of EEG as a biomarker.

Hypothesis:Perception thresholds will be lowest at ~30 Hz. EEG occipital alpha power will decrease upon perception.

Methods:60 participants were exposed to homogenous magnetic fields up to 300 Hz, and 70 mT. EEG alpha power was calculated during each exposure.

Results:Magnetophosphene thresholds were found to be lowest (16.92 mTrms) at 35 Hz. Thresholds established at powerline frequencies. Magnetophosphene perception was not accompanied by a change in EEG activity.

Conclusions:Magnetophosphenes frequency dependence is consistent with previous studies involving magnetic stimuli. Occipital EEG alpha power is not an appropriate biomarker of magnetophosphene perception.