[Neuroscience] Re: Explaination of the direction of field potentials

Bill connelly.bill at gmail.com
Thu Jun 8 17:06:57 EST 2006

Matthew Kirkcaldie wrote:
> It's positive ions entering the cell.  If you're near the dendrite, but
> not in it, since dendrites are tiny, the charges are leaving the
> electrode region to enter the dendrite, so the electrode region is
> negative. If you're in the soma, the ions are entering the region around
> the electrode, so it looks positive.
> However I would love someone with a better answer to chime in.
>          MK.

So are you saying that the EPSP invading the soma is sensed by the
extracellular electrode (even though there are 100s of mega-Ohm
resistors between that voltage change and the electrode, i.e. the cell
membrane), or are you saying the extracellular electrode is sensing the
leakage of current out of the cell (probably potassium efflux)?

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