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Questions on brain function

  1. Aug 10, 2011 #1
    I'm new to this forum, and I'm not very educated in biology, although i have recently grown extremely interested. I have gathered bits and pieces of information over the years on how the brain works and have some questions. I understand that the brain is still like the depths of space when it comes to understanding exactly how it all works. in fact i think we could know more about space. but there are a few questions i have that i think there is some what of an answer to. please bare with me.

    does the brain function completely on electrical or electron flow through the nervous system, or is more of a chemical reaction between cells?

    is there such a thing as cell to cell communication in a kind of alien like data stream that can be partially or completely decoded?

    i know there is voltage present in the brain, but how is it measured? how is it measured externally and at what frequency is it measured?

    what kind of shielding does the brain have from outside electrical interference? you would think sitting too close to a powerful processor would interfere with normal brain function?

    and finally, how is the brain manipulated electrically or with magnetics without intrusive probing?

    if there is a link to the answers I'm looking for it would probably be easier than dealing with my barrage of questions. i would probably just have questions for your answers anyway. lol...
     
  2. jcsd
  3. Aug 10, 2011 #2

    Pythagorean

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    Welcome to PF, dyce.

    neurons do have electric action potentials, but they are not caused by electron flow, they are caused by the flow of ions (mostly, Na+, K+, and Ca-). And a lot of information does flow this way, but there's a lot of modulatory information at the molecular/chemical level as well (protein interactions) that tune and regulate the neurons.

    not sure how technically you mean alien. Assuming you just mean different from normal human communication. In that case, there's a lot of work that goes into understanding how cells communicate. Besides electrical communication, there's chemical signaling pathways. Again, protein interactions.

    You are measuring a population of neural activity when you measure externally. A more descriptive, reduced method is intracellular recording, so that you get the potential difference (the voltage) from the inside of the membrane to the outside of the membrane.

    The external measurements rely on electric and/or magnetic fields (depending on the technology). Even some invasive electrodes are still only listening to near field potentials (not actually getting the voltage across the membrane). So it's hard to deconstruct that signal into its component parts without knowledge of the component neural circuitry.

    I'm not really sure. The interference has to be on the same order of frequency as the brain's functional frequencies. Too slow or too fast of an electromagnetic wave wouldn't interfere with the brain at all (except maybe to cook it if there was enough power... but realize this is a highly unlikely event, the most radiative power you expose yourself to is the sun for the average american, and it's known to be dangerous, but only to your skin).

    If people sit really still and push the machine right up against their head, the magnetic sensor technology just barely detects the weak magnetic fields from the neurons.

    MRI senses blood flow and makes assumption about neural activity based on blood demand.

    electrical sensors work too, but they have to be so sensitive that they pick up noise and 60 Hz signal from the wall (which you have to filter out, but now are you losing any significant information around the 60 Hz band?)
     
  4. Aug 10, 2011 #3

    MRIs do not "sense" blood flow.

    It is magnetic resonance imaging, an intuitive name for the process.
     
  5. Aug 10, 2011 #4
  6. Aug 11, 2011 #5

    Pythagorean

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    MRI relies on the zeeman effect, but it does so in a way that requires a plane of cooperating particles. The easiest place to find this plane is in water based mixtures in the human body since polar water molecules have a high ratio (2:1) of one of the least shielded atoms: hydrogen..

    Individual neural events happen on a much faster scale than fMRI. All that fMRI detects is population demand based on the flow of blood (or specifically, the hydrogen atoms within the blood). Specifically, it detects the spatiotemporal change in volumes of blood in the brain.

    the fMRI can also detect activity in a dead salmon: :)

    http://www.wired.com/wiredscience/2009/09/fmrisalmon/
     
  7. Aug 11, 2011 #6

    Mk

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    The brain needs both to communicate, and I don't think either one could really be said to be dominant. It's part of one, cohesive, electrochemical system.

    The data streams are still working on being decoded, and I am not aware of any efforts right now that have gone very far in this field.

    Some people study connectomes:
    http://www.ted.com/talks/sebastian_seung.html
    http://en.wikipedia.org/wiki/Connectome

    Here are two articles with links to the original papers on biophotonic communication; the second one is research on neural systems:
    http://www.technologyreview.com/blog/arxiv/24425/
    http://www.technologyreview.com/blog/arxiv/26151/

    This would be a very rough (and fun and highly esoteric!) way to study input/output of neural signals and muscles. The people that developed this were undergraduate electrical engineering students at Michigan University and are a couple of very smart guys!


    Neurons electrically "talk" in binary. The signals (called "action potentials") are not known to vary in voltage or current, but it seems to be the patterns of the pulsing of these single signals is meaningful. The action potential is sent up or down a neuron's axon (mainly down), and when it reaches the tip, a tiny space (on the order of 20 nm) called a synaptic cleft is shared by two tips of neurons. The neurons emit and absorb particular combinations of chemicals and the signal is regenerated. People have simplified this down to "calcium channels" or "sodium channels", but in my understanding it is actually extremely complex, with most things unknown.

    Hope one of these answers your question.

    Two ways. You can measure individual neurons with microelectrodes placed inside and outside the neuron, or you can place general transcranial (inside head) or supercranial (outside head) electrodes under the skin or on the scalp. Voltages on the outside of the scalp are on the order of 10 µV (microvolts) and inside the scalp I recall as perhaps 40-100 µV (not sure). Frequencies range anywhere from infra- (1.5-10 Hz) to ultra-, but the brain's strongest activity seems to be going on between 10 and 80 Hz.

    If you want to build your own device for measuring brainwaves, here's a good site to explore:
    http://openeeg.sourceforge.net/doc/modeeg/modeeg.html

    You're right! The strongest brain activity seems to be going on right around the mains hum frequency (50 or 60 Hz). I don't know what this means. I have personally found that the human body works as an excellent antenna, and that an EEG without a right leg driver (something to deconstructively interfere with artificial electrical noise) is very muddy. The scalp and skull are good enough shielding to make it difficult to read electrical fields coming out of the brain, but all is relative to whatever strengths we are talking about.

    This is precisely what you are looking for:
    http://en.wikipedia.org/wiki/Transcranial_magnetic_stimulation
    http://en.wikipedia.org/wiki/Transcranial_direct_current_stimulation

    welcome to PF, as was said, and hope we got your interests piqued and served :)
     
    Last edited by a moderator: Sep 25, 2014
  8. Aug 11, 2011 #7
    Are you disagreeing Magnetic Resonance Imaging is an intuitive name or that it does not "sense" blood flow.
     
  9. Aug 11, 2011 #8

    Mk

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    Am I not mistaken that it MRI registers the density of hydrogen atoms crossing a given two dimensional plane? So, this is correlated to water, which is correlated to blood.
     
  10. Aug 11, 2011 #9
    Which is not sensing the blood is it?

    Perhaps you would define that an MRI works by sensing blood.

    I think that is too far from the truth.
     
  11. Aug 11, 2011 #10

    Pythagorean

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    It seemed to me that you didn't understand what I meant, so I was explaining what I meant. I had good faith in your misunderstanding, I didn't think you were pedantically splitting hairs. I'm beginning to have bad faith in your motivation.
     
  12. Aug 12, 2011 #11
    wow!! that is some extremely educational information...thank you all... this will keep my mind going the right direction.

    i have been interested in bio mechanical technology for an extremely long time. but my thoughts in the subject always bring me to a control device that would be able to manipulate something of the nature. i understand a PC is pretty close to good enough, but as far as the learning ability us humans possess goes, a PC only does what its told to do. this always brings me to the brain and how it functions. this has always drawn a blank area.

    then there is the ever present mobile, light weight, long lasting, power source needed to provide energy for such a device. this always complicates things.

    but then there is known ability to easily create static electricity. this always adds a spark of light to my ideas. i understand that static electricity is a high voltage low amperage power source, but if the human brain uses such a low voltage/amperage then a small Wimshurst machine could provide more than enough energy. and i know from experience that it can control muscle function.

    the chemical side of the brain is now the show stopper. i do understand that alternate methods can be used, but the brain is so perfect, an attempt to replicate it should stay consistent in my opinion. not that i would ever posses the know how or technology to do so. but brewing thoughts without facts are just childhood fantasy.

    thanks again. it will take me some time to absorb the info already here. but feel free to add more. i like knowledge.
     
  13. Aug 12, 2011 #12
    Saying "MRI senses blood flow and makes assumption about neural activity based on blood demand." and then clarifying by explaining that MRIs detect magnetism of atoms is hardly splitting hairs.

    My motivation was that an MRI not be past off as a device the merely "senses blood flow".

    Does an xray machine sense bones?
     
  14. Aug 13, 2011 #13
    This is a purely semantic argument and is irrelevant to the topic. Mk and Pythagorean have explained it quite clearly.

    For further clarification (since you never cared to read the article I linked to);
    An MRI works by detecting the rotating magnetic fields generated by nuclei of atoms while fMRI or Functional MRI is a specialized technique that specifically designed to measure changes in blood flow.
    So if you don't like the "sensing blood flow", you can freely call it "measuring change in blood flow".
     
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