question- field potential & population spike

Matt Jones jonesmat at
Mon Sep 25 11:39:14 EST 1995

In article <43v217$g9t at> Hannah Dvorak,
hdvorak at writes:
>I think this is just a matter of convention in deciding whether 
>positive-going potentials are depicted as moving up or down.  In the
>vast majority of papers I've read, EPSPs are shown as downward
>deflections, and the pop. spikes go upwards.  Electrically speaking,
>the extracellular field at the dendritic site of an EPSP is definitely
>negative with respect to ground at a distant point in the bath.


You are quite right. I neglected to specify the recording configuration
in my earlier post. I was referring to field recordings in CA1
pyramidale, where pop spikes can be recorded at high resolution. Here,
EPSPs are positive to ground because the dendritic current is distant,
whereas pop spikes are negative to ground because the current sink is
local. Sorry for the confusion.


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