[Eeglablist] p300 convention

[Teresa Hawkes]

Dear List,

I was under the impression that positive deflections reflect dipoles moving
toward an electrode and negative deflections reflect dipoles moving away
from an electrode. I would be interested in seeing the evidence correlating
negative potentials with cortical activation and positive potentials with
cortical inhibition.

Cheers,
Teresa Hawkes
University of Oregon

On Thu, Jun 16, 2011 at 6:55 PM, Geert van Boxtel <G.J.M.vBoxtel at uvt.nl>wrote:

> **
> Dear list,
>
> The historical "accidents" that Steve describes actually had a sound basis
> in neurophysiology in that negativity measured at the scalp was supposed to
> reflect cortical activation, whereas positivity measured at the scalp was
> thought to reflect cortical inhibition, both at the level of postsynaptic
> potentials (EPSPs and IPSPs, respectively). Much research in the 1960s
> focused on three types of ERPs: the negative Contingent Negative Variation
> (CNV) and Readiness Potential (RP), and the positive P300. For the CNV and
> RP, an increase in negativity meant an increase in cortical activity, so it
> made perfect sense to plot these potentials negative-up.
>
> Nowadays, the convention originating from physics to plot positivity
> upwards is becoming more and more current. Of course, polarity depends on
> the reference used in the recording, so it should be considered good science
> to be able to think both negative-up and positive-up.
>
> Best regards,
> Geert
>
>
>
> Op 16-6-2011 21:42, Steve Luck schreef:
>
> Mehmet-
>
>  The polarity conventions in ERP research are arbitrary and partially
> reflect historical accidents.  You can plot negative upward if you mainly
> want to communicate your results to people who are used to looking at ERPs
> with negative upward.  You should plot positive upward if you mainly want to
> communicate your results to the 99.999999% of scientists who use the
> Cartesian convention of plotting positive upward.
>
>  Steve
>
>
>
> *From: *mehmet ali <theretinaguy at gmail.com>
>  *Date: *June 16, 2011 5:29:38 AM PDT
>  *To: *eeglablist at sccn.ucsd.edu
>  *Subject: **[Eeglablist] p300 convention*
>
>
> Hi all,
>
> p300 is conventionally plotted on an inverted axis( positive potentials to
> down), is there a reason to end up with this convention?
>
> Best,
>
>
>
>
> _______________________________________________
> eeglablist mailing list eeglablist at sccn.ucsd.edu
> Eeglablist page: http://www.sccn.ucsd.edu/eeglab/eeglabmail.html
> To unsubscribe, send an empty email to eeglablist-unsub at sccn.ucsd.edu
> To switch to non-digest mode, send an empty email to
> eeglablist-nodigest at sccn.ucsd.edu
>
>
>      --------------------------------------------------------------------
> Steven J. Luck, Ph.D.
> Director, Center for Mind & Brain
> Professor, Department of Psychology
> University of California, Davis
> Room 109
> 267 Cousteau Place
> Davis, CA 95618
> (530) 297-4424
> E-Mail: sjluck at ucdavis.edu
> Web: http://mindbrain.ucdavis.edu/people/sjluck
> Calendar:
> http://www.google.com/calendar/embed?src=stevenjluck%40gmail.com&ctz=America/Los_Angeles<http://www.google.com/calendar/embed?src=stevenjluck@gmail.com&ctz=America/Los_Angeles>
> --------------------------------------------------------------------
>
>
>
>
>
>
>
>
>
>
>
> _______________________________________________
> Eeglablist page: http://sccn.ucsd.edu/eeglab/eeglabmail.html
>
> To unsubscribe, send an empty email to eeglablist-unsubscribe at sccn.ucsd.edu
> For digest mode, send an email with the subject "set digest mime" to eeglablist-request at sccn.ucsd.edu
>
>
> _______________________________________________
> Eeglablist page: http://sccn.ucsd.edu/eeglab/eeglabmail.html
> To unsubscribe, send an empty email to
> eeglablist-unsubscribe at sccn.ucsd.edu
> For digest mode, send an email with the subject "set digest mime" to
> eeglablist-request at sccn.ucsd.edu
>



-- 
Teresa D. Hawkes, B.F.A.
Ph.D. Candidate
Department of Human Physiology
University of Oregon
348 Gerlinger Hall,
1240 University of Oregon
Eugene, Oregon 97403-1240
Phone: 541-337-9443 (cell) or 541-346-0275 (laboratory)
thawkes at uoregon.edu
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://sccn.ucsd.edu/pipermail/eeglablist/attachments/20110617/d019b856/attachment.html>