Magnetic field exposure and behavioral monitoring system

Thomas, Alex; Drost, Dick J.; Prato, Frank S.

doi:10.1002/bem.67

Cited by 9 publications

(27 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Each Helmholtz pair was driven by a Techron constant-current amplifier (CCA) (model 7780EI6, Crown International, Elkhart, IN, USA) via digital to analogue (D/A) converter. A 9 pole Bessel low-pass filter (LPF, 1 kHz corner frequency) before the amplifier input removed high-frequency noise from the D/A converter signal (Thomas et al 2001). The magnetic field was monitored with a 3D fluxgate magnetometer through an analogue to digital (A/D) converter (MAG-03MS 1000 T ± 50 nT offset, 12 pT rms resolution; Bartington Instruments Ltd, Oxford, UK).…”

Section: (C) Magnetic Exposure Conditionsmentioning

confidence: 99%

Shielding, but not zeroing of the ambient magnetic field reduces stress-induced analgesia in mice

Choleris

Seppia

Thomas

et al. 2002

Proc. R. Soc. Lond. B

View full text Add to dashboard Cite

Magnetic field exposure was consistently found to affect pain inhibition (i.e. analgesia). Recently, we showed that an extreme reduction of the ambient magnetic and electric environment, by -metal shielding, also affected stress-induced analgesia (SIA) in C57 mice. Using CD1 mice, we report here the same findings from replication studies performed independently in Pisa, Italy and London, ON, Canada. Also, neither selective vector nulling of the static component of the ambient magnetic field with Helmholtz coils, nor copper shielding of only the ambient electric field, affected SIA in mice. We further show that a pre-stress exposure to the -metal box is necessary for the anti-analgesic effects to occur. The differential effects of the two near-zero magnetic conditions may depend on the elimination (obtained only by -metal shielding) of the extremely weak time-varying component of the magnetic environment. This would provide the first direct and repeatable evidence for a behavioural and physiological effect of very weak time-varying magnetic fields, suggesting the existence of a very sensitive magnetic discrimination in the endogenous mechanisms that underlie SIA. This has important implications for other reported effects of exposures to very weak magnetic fields and for the theoretical work that considers the mechanisms underlying the biological detection of weak magnetic fields.

show abstract

Section: (C) Magnetic Exposure Conditionsmentioning

confidence: 99%

Shielding, but not zeroing of the ambient magnetic field reduces stress-induced analgesia in mice

Choleris

Seppia

Thomas

et al. 2002

Proc. R. Soc. Lond. B

View full text Add to dashboard Cite

show abstract

“…No causal relationship between EMF and symptoms has yet been proven, but sensitivity to specific frequencies has been suggested [1]. The frequency dependent non-thermal effects of ELF magnetic fields and microwaves on the conformation of chromatin in lymphocytes have been described and individual variability has been observed [3,4]. OBJECTIVE: Here, we used specific conditions of exposure to ELF to investigate if the response of lymphocytes from hypersensitive persons is different as compared to healthy subjects.…”

Section: Introductionmentioning

confidence: 99%

“…There was no doseresponse relationship between the extent of vasomotion changes and power levels of SMF (1, 5, 10, 100 mT). One mT of SMF for 10 min modulated the vascular tone biphasically 1,4) . Sub-chronic exposure of SMF (180 mT) for several weeks induced enhancement of vasomotion and dilatation of arterioles 3) .…”

mentioning

confidence: 99%

“…In this study we investigated the possible synergistic effects of 60 Hz EPMFs on the gene-locus mutations that triggers point mutation, deletion, and/or translocation of the thymidine kinase (TK) locus causing the anti-cancer drug to damage DNA in the human lymphoblastoid cell lines, WTK-1 cells (tk +/-, p53 mutation). METHOD: We used the EES-002, the multifunctional exposure system, manufactured by Electric Research and Management [4]. WTK-1 cells, mid log-phase growth (5 x 10 5 cells / ml, grown in RPMI medium 1640 supplemented with 10 % v/v heat inactivated FBS) were treated for 1 h with doxorubicin (Dox: anti-cancer drug, 0, 0.02, 0.05 µg / ml).…”

mentioning

confidence: 99%

“…Effects of local or whole body exposures of static magentic fields (SMF) on cutaneous microcirculation within a rabbit ear chamber under conscious conditions [1][2][3][4] 9) and skeletal muscle microcirculation under anesthetized conditions in mice 7) were studied intravitalmicroscopically. Concurrent with intravital-microscopic study, blood pressure and heart rate were also monitored 2, 5, 6, 8,[9][10][11] .…”

mentioning

confidence: 99%

See 2 more Smart Citations

Twenty-Fourth Annual Meeting

2001

Journal of Hand Therapy

View full text Add to dashboard Cite

INTRODUCTION:Transcranial magnetic stimulation (TMS) has become an important tool for the study of the functional organization of the human brain as well as for the potential treatment of central nervous system diseases such as depression. The principles of localized magnetic stimulation, field calculations and functional brain mappings obtained by TMS, nerve excitation models, and applications for cognitive neuroscience are reviewed. In addition, the effects of repetitive TMS (rTMS) on the protection or recovery of injured hippocampal neurons in rats are discussed. Localized Magnetic Stimulation: TMS is a technique to stimulate the brain by magnetically induced eddy currents through a coil positioned on the surface of the head [Barker et al., 1985]. Mapping studies are carried out by a method of localized and vectorial magnetic stimulation using a figure eight coil [Ueno et al., 1988]. The basic principle is to concentrate induced eddy currents locally near a target by a pair of opposing pulsed magnetic fields produced by a figure-eight coil. When a transient current flows through a coil exterior to the head, time-varying magnetic fields are generated in the brain. The time -varying magnetic fields induce eddy currents that stimulate nerve fibers. When a single coil is used, the induced eddy currents flow in a concentrated manner. The maximum current density is attained beneath the coil and, in principle, the current density is zero at the center. When a figure-eight coil is used, flow patterns of induced currents create two vortices that merge at the point beneath the intersection of the figure-eight. A computer simulation shows that the current density at the merging point is three times greater than that in the surrounding areas. Hence, localized stimulation is attained. For TMS of the human brain, transient magnetic fields in the order of 1 T and a duration of 0.1-0.2 ms are generally used. These transient magnetic fields contribute to the depolarization of nerve cells in the brain. This method facilitates stimulation of the motor cortex of the human brain within a 5 mm resolution [Ueno et al., 1989; Ueno et al., 1990]. Vectorial stimulation can be attained because the concentrated eddy currents at the target under the intersection of the figure eight coil flow parallel to the tangent of the two circular coils. Based upon this principle, functional maps of the human motor cortex related to the hand, arm, and foot areas were obtained by measuring the motor evoked potentials (MEPs) of the peripheral muscle responses to the TMS. The functional maps showed that an optimal direction of stimulating induced currents for neuronal excitation exists in each functional area of the cortex. These vectorial characteristics in TMS reflect, in part, anatomical and functional organization of the neurons and neuronal fibers of the brain [Ueno et al., 1991]. Nerve Excitation Models: The introduction of nerve excitation models has widened our understanding of the mechanisms of nerve excitation elicited by magnetic stimulation...

show abstract

Resting EEG is affected by exposure to a pulsed ELF magnetic field

Cook

Thomas

Prato

2004

Bioelectromagnetics

106

View full text Add to dashboard Cite

An increasing number of reports have demonstrated a significant effect of extremely low frequency magnetic fields (ELF MFs) on aspects of animal and human behavior. Recent studies suggest that exposure to ELF MFs affects human brain electrical activity as measured by electroencephalography (EEG), specifically within the alpha frequency (8-13 Hz). Here we report that exposure to a pulsed ELF MF with most power at frequencies between 0 and 500 Hz, known to affect aspects of analgesia and standing balance, also affects the human EEG. Twenty subjects (10 males; 10 females) received both a magnetic field (MF) and a sham session in a counterbalanced design for 15 min. Analysis of variance (ANOVA) revealed that alpha activity was significantly higher over the occipital electrodes (O1, Oz, O2) [F(1,16) = 6.858; P =.019, eta2 = 0.30] and marginally higher over the parietal electrodes (P3, Pz, P4) [F(1,16) = 4.251; P =.056, eta2 = 0.21] post MF exposure. This enhancement of alpha activity was transient, as it marginally decreased over occipital [F(1,16) = 4.417; P =.052; eta2 = 0.216] and parietal electrodes [F(1,16) = 4.244; P =.056; eta2 = 0.21] approximately 7 min after MF exposure compared to the sham exposure. Significantly higher occipital alpha activity is consistent with other experiments examining EEG responses to ELF MFs and ELF modulated radiofrequency fields associated with mobile phones. Hence, we suggest that this result may be a nonspecific physiological response to the pulsed MFs.

show abstract

Magnetic field exposure and behavioral monitoring system

Cited by 9 publications

References 28 publications

Shielding, but not zeroing of the ambient magnetic field reduces stress-induced analgesia in mice

Shielding, but not zeroing of the ambient magnetic field reduces stress-induced analgesia in mice

Twenty-Fourth Annual Meeting

Resting EEG is affected by exposure to a pulsed ELF magnetic field

Contact Info

Product

Resources

About