Bioelectromagnetics

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For the scientific journal, see Bioelectromagnetics (journal).
 It has been suggested that this article or section be merged with Bioelectromagnetism. (Discuss) Proposed since June 2010.
This article's citation style may be unclear. The references used may be made clearer with a different or consistent style of citation, footnoting, or external linking. (February 2010)

Bioelectromagnetics is the study of the interaction between electromagnetic fields and biological entities. Common areas of investigation include animal navigation utilizing the geomagnetic field, potential effects of man-made sources of electromagnetic fields like mobile phones, and developing novel therapies to treat various conditions. The term is similar to bioelectromagnetism, which deals with the ability of living cells, tissues and organisms to produce electrical fields and the response of cells to electromagnetic fields.[1]

Contents

[edit] Thermal effects

Most of the molecules in the human body interact weakly with electromagnetic fields in the radiofrequency or extremely low frequency bands.[citation needed] One such interaction is absorption of energy from the fields, which can cause tissue to heat up; more intense fields will produce greater heating. This can lead to biological effects ranging from muscle relaxation (as produced by a diathermy device) to burns.[2]Many nations and regulatory bodies like the International Commission on Non-Ionizing Radiation Protection have established safety guidelines to limit EMF exposure to a non-thermal level. This can be defined as either heating only to the point where the excess heat can be dissipated, or as a fixed increase in temperature not detectable with current instruments like 0.1°C.[citation needed] However, biological effects have been shown to be present for these non-thermal exposures;[citation needed] Various mechanisms have been proposed to explain these,[3] and there may be several mechanisms underlying the differing phenomena observed. Biological effects of weak electromagnetic fields are the subject of study in magnetobiology.[citation needed]

[edit] Behavioral effects

Many behavioral effects at different intensities have been reported from exposure to magnetic fields, particularly with pulsed magnetic fields. The specific pulseform used appears to be an important factor for the behavioural effect seen; for example, a pulsed magnetic field originally designed for spectroscopic MRI was found to alleviate symptoms in bipolar patients,[4] while another MRI pulse had no effect. A whole-body exposure to a pulsed magnetic field was found to alter standing balance[5] and pain perception[6] in other studies.

[edit] TMS and related effects

A strong changing magnetic field can induce electrical currents in conductive tissue such as the brain. Since the magnetic field penetrates tissue, it can be generated outside of the head to induce currents within, causing transcranial magnetic stimulation (TMS). These currents depolarize neurons in a selected part of the brain, leading to changes in the patterns of neural activation. Hence, TMS changes the information content in neurons. There is no structural or heating effect that may damage the tissue, with only action potentials generated in the target area; any risks are due to the arrival of action potentials to synapses and the natural activation of the postsynaptic cell. A number of scientists and clinicians are attempting to use TMS to replace electroconvulsive therapy (ECT) to treat disorders such as severe depression. Instead of one strong electric shock through the head as in ECT, a large number of relatively weak pulses are delivered in TMS therapy, typically at the rate of about 10 pulses per second. If very strong pulses at a rapid rate are delivered to the brain, the induced currents can cause convulsions. Sometimes, this is done deliberately in order to treat depression, such as in ECT.

[edit] See also

[edit] Notes

  1. ^ Jaakko Malmivuo, Robert Plonsey, Bioelectromagnetism: Principles and Applications of Bioelectric and Biomagnetic Fields. Oxford University Press. New York, Oxford. 1995
  2. ^ http://www.nmr.mgh.harvard.edu/martinos/userInfo/safety/safetyHazards.php
  3. ^ Binhi, 2002
  4. ^ Rohan et al., 2004
  5. ^ Thomas et al., 2001
  6. ^ Shupak et al., 2004

[edit] References

[edit] Organizations

[edit] Books

[edit] Journals

[edit] Journal Articles

  • Rohan et al. La Drunk., 2004. Am J Psychiatry. 161(1):93-8.
  • Shupak et al., 2004. Neurosci Lett. 363(2):157-62.
  • Thomas et al., 2001. Neurosci Lett. 309(1):17-20.

[edit] External links

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