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Title: Clinical application of magnetic stimulation of focal epilepsy and the influence of low frequency magnetic fields on brain electrical activity
Author: Verschueren, Sarah B. F.
ISNI:       0000 0001 3546 7047
Awarding Body: University of Keele
Current Institution: Keele University
Date of Award: 2006
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The question of whether or not extremely low frequency (ELF) electromagnetic fields can have any influence on the human body has sparked heated debate over the last few decades. While several plausible theories on possible transduction mechanisms for these ELF fields (such as ferromagnetic transduction or shifts in the probability distribution of ion channel states) have been put forth, experimental research into such ELF effects has been widely overlooked. The work presented here aims to examine the effects of two forms of ELF exposure on the human brain. Our work investigates the influence of weak-field magnetic stimulation on the brain electrical activity for the purpose of defining a magnetic stimulation protocol that elicits most response, with an eye on potential future use of such protocol as a diagnostic or therapeutic tool in the treatment of focal epilepsy. We also establish for the first time the effects of exposure to the 60jlT 2Hz magnetic field associated with the discontinuous transmission (DTX) feature used in present-day mobile phones. Because of the widespread use of mobile phones and the nature of the exposure (i.e. close proximity to the head), the investigation of any potential health effects of such exposure is of vital importance. Seven patients suffering from mesial temporal lobe epilepsy and eight healthy volunteers were exposed to weak DC magnetic fields (l-4mT) as well as 60jlT 2Hz DTX magnetic fields. The brain electrical activity was recorded with semi-invasive (foramen ovale) and scalp electrodes for the epileptic subject group and scalp electrodes for the healthy subject group. Analysis of the data consisted of quantifying the average spectral power density pre- and post field exposure, as recorded by EEG. Results indicate significant alterations in the EEG's spectral power as a direct consequence of the exposure to weak DC magnetic fields in all of the individuals studied. The field combination that elicited most response was found to be the 0.55Hz frequency at 2-3mT field strengths for the healthy subject group and 0.1 Hz frequency at 2-3 mT field strengths for the epileptic subject group. Results show significant alterations in the EEG's spectral power content following exposure to the DTX mobile phone field for 9 of the 14 individuals studied. A statistically significant difference was found between both subject groups: while the DTX field altered the power density by an average of 55.5% in the healthy subject group, a much smaller change of 30.9% was found for the epileptic subject - 4 - group (P=0.003). The influence of the DTX-field seems to peak lOs after removal of the field. Overall, most changes to the spectral power density were found in the Alpha and Beta bands.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available