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    Dear Teresa,<br>
    <br>
    Scalp potentials were usually not related to dipoles at the time the
    convention originated.<br>
    <br>
    Early texts are, for instance, Caspers H Speckmann EJ Lehmenkuehler
    A (1987, Rev Physiol Biochem Pharmacol 106:127-178), and Birbaumer
    N, Elbert T Canavan AGM Rockstroh B (1990, Psysiol Rev 70:1-41)<br>
    <br>
    Later texts (e.g. the PIzzagalli chapter in the Handbook of
    Psychophysiology 3rd Ed) are usually less explicit on this issue.<br>
    <br>
    Best,<br>
    Geert<br>
    <br>
    Op 17-06-11 22:03, Teresa Hawkes schreef:
    <blockquote
      cite="mid:BANLkTimowVrSbwsk23+enit_YJvHm7ja5A@mail.gmail.com"
      type="cite">
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      Dear List,
      <div><br>
      </div>
      <div>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.</div>
      <div><br>
      </div>
      <div>Cheers,</div>
      <div>Teresa Hawkes</div>
      <div>University of Oregon<br>
        <br>
        <div class="gmail_quote">On Thu, Jun 16, 2011 at 6:55 PM, Geert
          van Boxtel <span dir="ltr"><<a moz-do-not-send="true"
              href="mailto:G.J.M.vBoxtel@uvt.nl">G.J.M.vBoxtel@uvt.nl</a>></span>
          wrote:<br>
          <blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt
            0.8ex; border-left: 1px solid rgb(204, 204, 204);
            padding-left: 1ex;">
            <div text="#000000" bgcolor="#ffffff"> Dear list,<br>
              <br>
              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.<br>
              <br>
              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.<br>
              <br>
              Best regards,<br>
              Geert<br>
              <br>
              <br>
              <br>
              Op 16-6-2011 21:42, Steve Luck schreef:
              <blockquote type="cite">
                <div>
                  <div class="h5">
                    <div>Mehmet-</div>
                    <div><br>
                    </div>
                    <div>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.</div>
                    <div><br>
                    </div>
                    <div>Steve</div>
                    <div><br>
                    </div>
                    <div><br>
                      <blockquote type="cite"><br>
                        <div style="margin: 0px;"><span
                            style="font-family: 'Helvetica'; font-size:
                            medium; color: rgb(127, 127, 127);"><b>From:
                            </b></span><span style="font-family:
                            'Helvetica'; font-size: medium;">mehmet ali
                            <<a moz-do-not-send="true"
                              href="mailto:theretinaguy@gmail.com"
                              target="_blank">theretinaguy@gmail.com</a>><br>
                          </span></div>
                        <div style="margin: 0px;"><span
                            style="font-family: 'Helvetica'; font-size:
                            medium; color: rgb(127, 127, 127);"><b>Date:
                            </b></span><span style="font-family:
                            'Helvetica'; font-size: medium;">June 16,
                            2011 5:29:38 AM PDT<br>
                          </span></div>
                        <div style="margin: 0px;"><span
                            style="font-family: 'Helvetica'; font-size:
                            medium; color: rgb(127, 127, 127);"><b>To: </b></span><span
                            style="font-family: 'Helvetica'; font-size:
                            medium;"><a moz-do-not-send="true"
                              href="mailto:eeglablist@sccn.ucsd.edu"
                              target="_blank">eeglablist@sccn.ucsd.edu</a><br>
                          </span></div>
                        <div style="margin: 0px;"><span
                            style="font-family: 'Helvetica'; font-size:
                            medium; color: rgb(127, 127, 127);"><b>Subject:
                            </b></span><span style="font-family:
                            'Helvetica'; font-size: medium;"><b>[Eeglablist]
                              p300 convention</b><br>
                          </span></div>
                        <br>
                        <br>
                        Hi all,<br>
                        <br>
                        p300 is conventionally plotted on an inverted
                        axis( positive potentials to down), is there a
                        reason to end up with this convention?<br>
                        <br>
                        Best,<br>
                        <br>
                        <br>
                        <br>
                        <br>
                        _______________________________________________<br>
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                                                          <div
                                                          style="margin:
                                                          0px;">Steven
                                                          J. Luck, Ph.D.</div>
                                                          <div
                                                          style="margin:
                                                          0px;">Director,

                                                          Center for
                                                          Mind &
                                                          Brain</div>
                                                          <div
                                                          style="margin:
                                                          0px;">Professor,

                                                          Department of
                                                          Psychology</div>
                                                          <div
                                                          style="margin:
                                                          0px;">University

                                                          of California,
                                                          Davis</div>
                                                          <div
                                                          style="margin:
                                                          0px;">Room 109</div>
                                                          <div
                                                          style="margin:
                                                          0px;">267
                                                          Cousteau Place</div>
                                                          <div
                                                          style="margin:
                                                          0px;">Davis,
                                                          CA 95618</div>
                                                          <div
                                                          style="margin:
                                                          0px;">(530)
                                                          297-4424</div>
                                                          <div
                                                          style="margin:
                                                          0px;">E-Mail: <a
moz-do-not-send="true" href="mailto:sjluck@ucdavis.edu" target="_blank">sjluck@ucdavis.edu</a></div>
                                                          <div
                                                          style="margin:
                                                          0px;">Web: <a
moz-do-not-send="true" href="http://mindbrain.ucdavis.edu/people/sjluck"
target="_blank">http://mindbrain.ucdavis.edu/people/sjluck</a></div>
                                                          <div
                                                          style="margin:
                                                          0px;">Calendar: <a
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href="http://www.google.com/calendar/embed?src=stevenjluck@gmail.com&ctz=America/Los_Angeles"
target="_blank">http://www.google.com/calendar/embed?src=stevenjluck%40gmail.com&ctz=America/Los_Angeles</a></div>
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                <pre><fieldset></fieldset>
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        <br>
        <br clear="all">
        <br>
        -- <br>
        Teresa D. Hawkes, B.F.A.<br>
        Ph.D. Candidate<br>
        Department of Human Physiology<br>
        University of Oregon<br>
        348 Gerlinger Hall,<br>
        1240 University of Oregon<br>
        Eugene, Oregon 97403-1240<br>
        Phone: 541-337-9443 (cell) or 541-346-0275 (laboratory)<br>
        <a moz-do-not-send="true" href="mailto:thawkes@uoregon.edu"
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