[Neuroscience] Basic question about electrical currents in EEG

cwenhoo via neur-sci%40net.bio.net (by ilangobi from yahoo.com)
Mon Nov 30 03:38:42 EST 2009

>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

"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

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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