What is the intensity and frequency of the brain's electromagnetic field?

[termina]

"Electromagnetic" brain?

Hello there!

It's a fact that our brain emits an (weak) electromagnetic field.
But do you know its precise intensity and its frequency (in Hertz)?

 

[berkeman]

Hello there!

It's a fact that our brain emits an (weak) electromagnetic field.
But do you know its precise intensity and its frequency (in Hertz)?

Our brain does not really "emit" anything (unless you have a mainstream journal reference for that "fact"). You can monitor the brain's electrical activity in a primitive fashion using the EEG:

http://en.wikipedia.org/wiki/Eeg

You can also gain other insights into brain function using PET scans:

http://en.wikipedia.org/wiki/Neuroimaging

.

 

[nismaratwork]

Hello there!

It's a fact that our brain emits an (weak) electromagnetic field.
But do you know its precise intensity and its frequency (in Hertz)?

Berkeman is right; it's a common misconception that we have some kind of organized emmisions. Remember, the heat we emit (waste heat) is in the EM spectrum too. We emit a wide variety of waste, but much in the form of heat (IR).

It should be noted that this is like any other waste heat; disorganized, adding to the entropy of a given system.

 

[Lievo]

It's a fact that our brain emits an (weak) electromagnetic field.
But do you know its precise intensity and its frequency (in Hertz)?

~10^-12T ~10 Hz

Our brain does not really "emit" anything (unless you have a mainstream journal reference for that "fact")

http://scholar.google.com/scholar?q=magnetoencephalography&hl=fr&btnG=Rechercher&lr="

Berkeman is right; it's a common misconception that we have some kind of organized emmisions.

I really don't understand your point. Of course the brain emits electromagnetic fields. Of course it's organized enough to reflect the organization of the underlying brain activity. What's the problem exactly?

 

[Evo]

I really don't understand your point. Of course the brain emits electromagnetic fields. Of course it's organized enough to reflect the organization of the underlying brain activity. What's the problem exactly?

Posting a google search with nothing specific is not acceptable. Make a specific stance and back it up with a specific peer reviewed study so we have some idea of what you are referencing.

 

[berkeman]

~10^-12T ~10 Hz


http://scholar.google.com/scholar?q=magnetoencephalography&hl=fr&btnG=Rechercher&lr="


I really don't understand your point. Of course the brain emits electromagnetic fields. Of course it's organized enough to reflect the organization of the underlying brain activity. What's the problem exactly?

Sigh. What kind of radiated EM field intensity does a uV 10Hz oscillator emit from a 0.1m antenna. Nada.

You need galvanic contact for EEG measurements, right?


EDIT -- beat out by Evo, yet again!

 

[berkeman]

~10^-12T ~10 Hz


http://scholar.google.com/scholar?q=magnetoencephalography&hl=fr&btnG=Rechercher&lr="

Jeeze Lievo, please make your points more clear next time. It took me multiple reads to finally find the link you had in your "Well" comment. Yes, magnetoencephalography is an interesting technology, but it is only practical in highly shielded and instrumented rooms, not in the real world. The OP implied that there were detectable "emissions" in the real world. MEG is not practical outside of highly shielded and instrumented rooms, AFAIK.

Detecting pT signals at 10Hz is incredibly non-trivial.

 

[Lievo]

Posting a google search with nothing specific is not acceptable. Make a specific stance and back it up with a specific peer reviewed study so we have some idea of what you are referencing.

My specific stance is that there is several tenth thousands of peer reviewed papers that have analysed a signal Bekerman said does not exist. My answer was deliberatly not too explicit as a mean to not be too rude. I'll be more explicit next time.

You need galvanic contact for EEG measurements, right?

A signal expressed in Tesla is not something you can collect from EEG, right?

magnetoencephalography is an interesting technology, but it is only practical in highly shielded and instrumented rooms

This was true and it's false for maybe 10-15 years. The need for shielding dramatically decreased since the devices rely on paired sensors so as to cancel far-coming emission. It's still better to shield, but you can remove the highly now.

The OP implied that there were detectable "emissions" in the real world. MEG is not practical outside of highly shielded and instrumented rooms, AFAIK.

I'm not sure where you see that in OP's question nor what do you mean by real word, but if you think PET is real word and MEG is not I suggest you have a look at the numbers of studies published in the last five years using either MEG or PET.

Detecting pT signals at 10Hz is incredibly non-trivial.

Again I don't know what incredibly non-trivial means for you. In some sense I can agree, but there is no doubts it's both easier and cheaper to experiment with a MEG than with PET, so I don't see your point.

But anyway, so what? The OP asked for the amplitude and frequency of this signal. This is a scientifically sound question and the answer is not controversial, so again what's the problem?

 

[berkeman]

My specific stance is that there is several tenth thousands of peer reviewed papers that have analysed a signal Bekerman said does not exist. My answer was deliberatly not too explicit as a mean to not be too rude. I'll be more explicit next time.


A signal expressed in Tesla is not something you can collect from EEG, right?


This was true and it's false for maybe 10-15 years. The need for shielding dramatically decreased since the devices rely on paired sensors so as to cancel far-coming emission. It's still better to shield, but you can remove the highly now.


I'm not sure where you see that in OP's question nor what do you mean by real word, but if you think PET is real word and MEG is not I suggest you have a look at the numbers of studies published in the last five years using either MEG or PET.


Again I don't know what incredibly non-trivial means for you. In some sense I can agree, but there is no doubts it's both easier and cheaper to experiment with a MEG than with PET, so I don't see your point.

But anyway, so what? The OP asked for the amplitude and frequency of this signal. This is a scientifically sound question and the answer is not controversial, so again what's the problem?

Incredibly non-trivial means electrically and magnetically shielded medical rooms for measurements. What do you think the OP intended with his question?

 

[berkeman]

My specific stance is that there is several tenth thousands of peer reviewed papers that have analysed a signal Bekerman said does not exist. My answer was deliberatly not too explicit as a mean to not be too rude. I'll be more explicit next time.

Out of those tens of thousands, could you please post your top ten links? Remember that links must be from peer-reviewed journals here on the PF.

 

[Pythagorean]

there's a thread by Q Goest in the Medical Sciences forum that implies a role for the brains gobal electric fields.

 

[nismaratwork]

~10^-12T ~10 Hz


http://scholar.google.com/scholar?q=magnetoencephalography&hl=fr&btnG=Rechercher&lr="


I really don't understand your point. Of course the brain emits electromagnetic fields. Of course it's organized enough to reflect the organization of the underlying brain activity. What's the problem exactly?

Go forth and learn:
http://en.wikipedia.org/wiki/Entropy
http://en.wikipedia.org/wiki/Entropy_(information_theory)

 

[Pythagorean]

Nismara, could you include a point/argument with your links? Most of us know about entropy, but we can sill imagine a physical system that produces coherent field effects. (we all know of several intentionally engineered systems that do so).

 

[Lievo]

What do you think the OP intended with his question?

I think he intended to ask the precise intensity and frequency of the (weak) electromagnetic field generated by the brain.

To be completely clear: your initial answer to this was the brain does not emits anything, and it was wrong. Now you've changed to yes but the signal is weak, I do agree. You may wish to notice that the OP himself mentionned it was weak, in the opening post.

Remember that links must be from peer-reviewed journals here on the PF.

It has escaped both your attention and Evo's that the link I posted is a search using scholar.google.com, which is an engine devoted to academic stuff only (mostly peer-reviewed papers, plus some book chapters, abstract and posters). It's quite the same as doing a pubmed search, except it takes 15 seconds instead of 5 minutes. If you didn't know that engine, I recommand you give it a try.

Go forth and learn:
http://en.wikipedia.org/wiki/Entropy
http://en.wikipedia.org/wiki/Entropy_(information_theory)

Topsy dopsy you still haven't been rebuted, despite I referred to academic materials and you're not. BTW. To be completely clear this time: your suggestion that magnetic fields from the brain are dissipating processes is wrong, which is demonstrated each time a peer-reviewed paper report results collected using MEG. If you follow the link I posted, you'll realized this happens quite often.

there's a thread by Q Goest in the Medical Sciences forum that implies a role for the brains gobal electric fields.

Yes but it'd hardly applies. In the paper you're talking about it's mentioned that the neuronal electric fields are just intense enough to impact the firing locally. However the induced magnetic field are far less powerfull than the electric fields, so we should not expect it to have any effects. Unless there is a hidden surprise to find, of course.

 

[nismaratwork]

Nismara, could you include a point/argument with your links? Most of us know about entropy, but we can sill imagine a physical system that produces coherent field effects. (we all know of several intentionally engineered systems that do so).

My point was what I made earlier, but I was asked what the hell I meant by "disorganized", and waste heat, so I linked. It wasn't meant for anyone but Lievo... I know for a fact that you don't need it.

That said, are you really impressed by possible non-local correlations in a lab, in DNA cultures, that may or may not be QM related? To go from there, to where Lievo is leading, is a winding road with dead ends at every turn.

 

[nismaratwork]

I think he intended to ask the precise intensity and frequency of the (weak) electromagnetic field generated by the brain.

To be completely clear: your initial answer to this was the brain does not emits anything, and it was wrong. Now you've changed to yes but the signal is weak, I do agree. You may wish to notice that the OP himself mentionned it was weak, in the opening post.


It has escaped both your attention and Evo's that the link I posted is a search using scholar.google.com, which is an engine devoted to academic stuff only (mostly peer-reviewed papers, plus some book chapters, abstract and posters). It's quite the same as doing a pubmed search, except it takes 15 seconds instead of 5 minutes. If you didn't know that engine, I recommand you give it a try.

Ummm... I can't claim this ia friendly, but a bit of advice: don't insult the mentors.

Topsy dopsy you still haven't been rebuted, despite I referred to academic materials and you're not.

Your academic materials are woefully insufficient, and your point diverges from their claims to the point of absurdity. By the way, I didn't know you were Danish; in English it's, "topsy turvy"... and still doesn't work here.

BTW. To be completely clear this time: your suggestion that magnetic fields from the brain are dissipating processes is wrong, which is demonstrated each time a peer-reviewed paper report results collected using MEG. If you follow the link I posted, you'll realized this happens quite often.

Yeah... I've worked with one... BIG... HEAVILY shielded, in a shielded room; it doesn't change the nature of a dissipative process. If you don't think it's that... what do you think our waste heat IS?... how are we alive?

Yes but it'd hardly applies. In the paper you're talking about it's mentioned that the neuronal electric fields are just intense enough to impact the firing locally. However the induced magnetic field are far less powerfull than the electric fields, so we should not expect it to have any effects. Unless there is a hidden surprise to find, of course.

It was informative; nothing applies to the magic you seem to believe in.

 

[Lievo]

possible non-local correlations in a lab, in DNA cultures, that may or may not be QM related? To go from there, to where Lievo is leading, is a winding road with dead ends at every turn. (...) nothing applies to the magic you seem to believe in.

I'm talking about MEG, referring to peer-reviewed material, and you read magic and 'DNA QM related' stuff

Ummm... I can't claim this ia friendly, but a bit of advice: don't insult the mentors.

I think the mentors can recognized when they are wrong and behave as a function of the rules they are supposed to defend. If I'm wrong that will be one professional scientist less on this forum and you'll have more space to discuss your magic DNA QM related thing you seems to see somewhere.

 

[nismaratwork]

I'm talking about MEG, referring to peer-reviewed material, and you read magic and 'DNA QM related' stuff

No, I'm referring to the OP study, your talk of MEG is simply diversion that doesn't have any relevence.

 

[Lievo]

No, I'm referring to the OP study, your talk of MEG is simply diversion that doesn't have any relevence.

The OP did not mentionned any study. MEG is the only device that can detect the magnetic fields emited by the brain -the ones you said does not exist.

 

[nismaratwork]

The OP did not mentionned any study. MEG is the only device that can detect the magnetic field emited by the brain -the ones you said does not exist.

Oh hell... I mixed up this thread with the "non-local effects" thread.

OK... this was my bad.


To MEG: the point remains, it's still a dissipative process, hence the need for immense resolution and shielding to wade through the waste heat and get to the ongoing activity.

 

[Lievo]

To MEG: the point remains, it's still a dissipative process, hence the need for immense resolution and shielding to wade through the waste heat and get to the ongoing activity.

Heat does not affect the magnetic fields recorded in MEG in any way. The shielding is a magnetic shielding, again a small one, that is there only to cancel the far-coming magnetic noise, and this has nothing to do with heat dissipation. The need for resolution is because this kind of signal does not carry a lot of energy -again a reason why this has nothing to do with dissipation- but on the other hand the signal is known to be directly tied to the ongoing activity -which is why it is organized/of low entropy. The main reason for the latter is that neither the tissue nor the skull blur this signal (contrary to EEG signal) so what you get is quite directly what has been produced.

 

[berkeman]

Sigh. What kind of radiated EM field intensity does a uV 10Hz oscillator emit from a 0.1m antenna. Nada.

You need galvanic contact for EEG measurements, right?

Jeeze Lievo, please make your points more clear next time. It took me multiple reads to finally find the link you had in your "Well" comment. Yes, magnetoencephalography is an interesting technology, but it is only practical in highly shielded and instrumented rooms, not in the real world. The OP implied that there were detectable "emissions" in the real world. MEG is not practical outside of highly shielded and instrumented rooms, AFAIK.

Detecting pT signals at 10Hz is incredibly non-trivial.

My specific stance is that there is several tenth thousands of peer reviewed papers that have analysed a signal Bekerman said does not exist. My answer was deliberatly not too explicit as a mean to not be too rude. I'll be more explicit next time.


A signal expressed in Tesla is not something you can collect from EEG, right?


This was true and it's false for maybe 10-15 years. The need for shielding dramatically decreased since the devices rely on paired sensors so as to cancel far-coming emission. It's still better to shield, but you can remove the highly now.


I'm not sure where you see that in OP's question nor what do you mean by real word, but if you think PET is real word and MEG is not I suggest you have a look at the numbers of studies published in the last five years using either MEG or PET.


Again I don't know what incredibly non-trivial means for you. In some sense I can agree, but there is no doubts it's both easier and cheaper to experiment with a MEG than with PET, so I don't see your point.

But anyway, so what? The OP asked for the amplitude and frequency of this signal. This is a scientifically sound question and the answer is not controversial, so again what's the problem?

My posts were from the position of S/N, and to discourage pseudo-scientific beliefs. The brain does not emit anything that is measurable in the real world. In a shielded lab setting, or with galvanic contact EEG, sure, you can measure crude/gross electrical activity. That's what lab setups are for.

I believe it is important to be clear in what we post and say, otherwise folks with less training in science may latch onto what we say, and believe more in pseudo-science. You're not going to be reading somebody's thoughts from "emitted" EM waves if you're not in a highly shielded room and using large detectors, for example. But yes, given the right shielding and instrumentation, we do have some interesting and developing windows into how the brain works, and into people's thoughts...

 

[Lievo]

My posts were from the position of S/N, and to discourage pseudo-scientific beliefs.

Ok I do understand the problem now. However, I don't think it makes any good to hide reality on the basis someone will not understand it properly. So maybe a better way would have been to say:

Yes, there is a magnetic field (~10^-12T ~10 Hz) which can be recorded above the head using our best technology, but beware that the intensity fall as the squared of the distance. That means that even supraconducting sensors -which are several order more sensitive to magnetic field than anything else- will not detect anything if farer than say, 10 cm from the scalp.

 

[berkeman]

Ok I do understand the problem now. However, I don't think it makes any good to hide reality on the basis someone will not understand it properly. So maybe a better way would have been to say:

Yes, there is a magnetic field (~10^-12T ~10 Hz) which can be recorded above the head using our best technology, but beware that the intensity fall as the squared of the distance. That means that even supraconducting sensors -which are several order more sensitive to magnetic field than anything else- will not detect anything if farer than say, 10 cm from the scalp.

I like that.

 

[nismaratwork]

Ok I do understand the problem now. However, I don't think it makes any good to hide reality on the basis someone will not understand it properly. So maybe a better way would have been to say:

Yes, there is a magnetic field (~10^-12T ~10 Hz) which can be recorded above the head using our best technology, but beware that the intensity fall as the squared of the distance. That means that even supraconducting sensors -which are several order more sensitive to magnetic field than anything else- will not detect anything if farer than say, 10 cm from the scalp.

Now that is something we can agree on.

 

[Pythagorean]

I guess I had good faith in the OP's question, myself. I didn't have the slightest notion of QM or mind-reading when I read the OP.

By the by, what's the difference between a changing electric field and an electromagnetic field?

I guess I can imagine a mechanism for coupled fields that isn't coupled through the magnetic field when they're being coupled through concentration gradients... hrm.

 

[nismaratwork]

I guess I had good faith in the OP's question, myself. I didn't have the slightest notion of QM or mind-reading when I read the OP.

By the by, what's the difference between a changing electric field and an electromagnetic field?

I guess I can imagine a mechanism for coupled fields that isn't coupled through the magnetic field when they're being coupled through concentration gradients... hrm.

The QM thing was me mixing up two threads... Lievo was right to be baffled. That was purely my error.

 

[berkeman]

By the by, what's the difference between a changing electric field and an electromagnetic field?

I guess I can imagine a mechanism for coupled fields that isn't coupled through the magnetic field when they're being coupled through concentration gradients... hrm.

An example of a changing electric field that does not launch an EM wave is the E-field between the plates of a capacitor. You can vary that field to moderate frequencies, and not launch an EM wave that propagates away from the capacitor.

I think the term "electromagnetic field" or wave would normally refer to a self-propagating EM wave, and sometimes to the energy in the near field region of an antenna (before the EM wave is truly self-propagating...there's a lot of reactance in the near field).

 

[Pythagorean]

An example of a changing electric field that does not launch an EM wave is the E-field between the plates of a capacitor. You can vary that field to moderate frequencies, and not launch an EM wave that propagates away from the capacitor.

hrm... I guess this seems like a geometry trick to me: because you're still moving charge around the circuit (even if not through the capacitor). So the wires conducting the shuffling charges is where the magnetic field would be expected.

I think the term "electromagnetic field" or wave would normally refer to a self-propagating EM wave, and sometimes to the energy in the near field region of an antenna (before the EM wave is truly self-propagating...there's a lot of reactance in the near field).

Ok, I think I see what the convention is: utility and application (particularly with respect to communications).

 

[Proton Soup]

"field" doesn't imply self-propagating to me, but then, i was never a radio guy. "wave" implies self-propagating to me. "changing electromagnetic field" i would interpret as something like a rotating magnetic field in a motor. thus, a changing magnetic field in a conductor could generate cross-talk in other conductors if they run parallel. but I'm not sure what effect this would have in a biological system. i think to set another nerve off and generate an action potential, you've got to trigger a voltage-gated channel. but cells work pretty hard to maintain a voltage gradient and the fluid between them is a conductor. won't the interstitial fluid act as a kind of faraday cage?

so what is the reason we don't emit radio? I'm guessing it's that our antenna is too short for all the low-frequency electrical activity we generate.