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> rf emissions from the brain
Dan
post Feb 22, 2012, 06:04 PM
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Shawn, what is the known RF spectrum resulting from charge motion during neural activity?
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lucid_dream
post Feb 22, 2012, 09:46 PM
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to my knowledge, RFs have not been observed in the brain. The relevant frequencies for neural activity are lower; i.e., EEG frequencies. If you find anything let me know.
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Dan
post Feb 23, 2012, 09:21 AM
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I am aware of EEG stuff, these consist of measuring electric fields on the scalp resulting from net charge motion during brain activity. However, I am thinking that the charge motion associated with neuronal activities may also generate broadband electromagnetic radiation at relatively short wavelengths. This type of radiation signature is common in physical systems where charge motion is not sinusoidal.
There would be two important questions to deal with:

1. What is the spectrum of the emitted energy, and
2. Can the energy be detected in spite of the background thermal noise?

If it is the case that the signals are weaker than the background thermal noise, I wonder if DSP tactics could be applied in order to identify them. I suppose it might be interesting to isolate a single (or small group of) neurons and trigger individual pulses in order to answer these questions.
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Flex
post Feb 23, 2012, 09:43 AM
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Doesn't seem very likely to me that you could get to RF levels without alternating current in the brain?

Direct current has a frequency of 0hz no? How does stimulating the brain differ when direct current is applied vs alternating current?
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Dan
post Feb 23, 2012, 10:39 AM
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All you need for excitation of the electromagnetic field is the acceleration of charge. The onset or cessation of a DC current contains ac components, and must therefore radiate. I doubt there is much activity at short wavelengths, though, but I don't know enough to be sure. One process that comes to mind is the voltage-gated ion channel. Also, any charge acceleration due either to ion translation or chemical redistribution of bound electrons.
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lucid_dream
post Feb 23, 2012, 01:50 PM
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no-one has recorded RFs from neural activity, to my knowledge. There are no known oscillatory charge motions in the brain in the range of RF, so I think it unlikely that the brain is generating these. If there were weak RFs being generated somehow (though the mechanism is not clear), then they would be causally inefficacious, so they would not be relevant for understanding neural computation and brain function.
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Dan
post Feb 23, 2012, 02:56 PM
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It does seem very unlikely given that known mechanisms operate at much lower frequencies. I am sure a few bored people have given a peek and found nothing interesting in the noise.
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KoolK3n
post Feb 23, 2012, 03:04 PM
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QUOTE(Dan @ Feb 23, 2012, 04:56 PM) *

It does seem very unlikely given that known mechanisms operate at much lower frequencies. I am sure a few bored people have given a peek and found nothing interesting in the noise.


Like binaural beats?
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