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The human brain is said to produce a magnetic field resulting from the action potentials released inside the brain. What's the nature of such a field in terms of size and strength, and what is the potential for manipulation of brain functions by interfering with it by means of electromagnetic radiation?

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There is some good info on this at en.wikipedia.org/wiki/Electroencephalography as far as affecting the brain except for shock therapy I don't think anybody knows as yet. –  Fortunato Jun 23 '11 at 1:44
@Fortunato Please use answers for answers. –  mbq Jun 23 '11 at 13:09

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The human body produces a wide range of bioelectromagnetic signals from various electrical impulses in the brain. The origin of the magnetic field is the charge exchange in the muscular and neural tissues (i.e no magnetic material is usually present in the body with very rare exceptions).

The brain's magnetic field varies from 10s of fT to 100s of fT [1]. The frequency varies from 0.1 Hz to <100 Hz. Measurement of brain magnetism is limited by the complexity of signal due to the overlap of the signals from various parts of the brain. In magentoencephelograpahy this is done using SQUIDS [2].

The second part of your question is about magnetic excitement of brain functions. This is in fact possible and some testing/use is reported with limited clinical success. The strength of the applied magnetic fields are 1-5T for trans-cranial excitation [3].

[1] http://www.bem.fi/book/12/12.htm#02 [2] http://www.scholarpedia.org/article/Magnetoencephalogram [3] http://en.wikipedia.org/wiki/Transcranial_magnetic_stimulation [4] http://www.bem.fi/book/22/22.htm An excellent source for this topic is [1]

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Can the brain's magnetic field be "amplified" by electromagnetic radiation? Is a magnetic field damaging to the brain or human tissue? –  Stein Åsmul Jul 12 '11 at 22:40
It is very hard to sense the fields from the brain. When an MEG is done there is amplification to pick the signal out of noise. I have to say any grand ideas of using the magnified field to do science fiction-styled tricks are just not sensible today. Human brain and tissue are actually quite robust to magnetic fields even up to 10s of Tesla. There is some hallucination/erratic visual fields reported in high field due to nerve end excitation. –  New Horizon Jul 12 '11 at 23:10
This answer is inaccurate regarding the frequency range 0.1-100 Hz. For example, electric median nerve stimulation has been shown to induce high-frequency oscillations near 600 Hz. –  mmh May 16 at 15:31
@NewHorizon Horizon You could also mention that the MEG measurements are done in a magnetically shielded room. –  mmh May 16 at 15:32

protected by Qmechanic Jan 28 '13 at 14:41

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