[Neuroscience] Basic question about electrical currents in EEG

Konstantin Kouptsov via neur-sci%40net.bio.net (by konstantin from kouptsov.com)
Mon Nov 30 12:29:12 EST 2009


Look at displacement current:

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

particularly, note that there are two parts: one resulting from the change
of the electric field, and another from polarization.




cwenhoo wrote:
>>From Luck's book, p.32:
> 
> "When a dipole is present in a conductive medium such as the brain,
> current is conducted throughout that medium until it reaches the
> surface...Electricity does not just run directly between two poles of
> a dipole in a conductive medium, but instead spreads out through the
> conductor."
> 
> "Another important point is that electricity travels at nearly the
> speed of light. For all practical purposes, the voltages recorded at
> the scalp reflect what is happening in the brain at the same moment in
> time."
> 
> My question is, what generates this current flow? I mean I can
> understand if the conductive medium is a piece of metal, then a dipole
> results in direct movement of electrons.
> 
> But what about the brain? What is even more confusing to me is that
> action potentials are not even near the speed of light, so how can
> this current resulting from the dipoles in the brain travel that fast?
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