<html><body bgcolor="#FFFFFF"><span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26, 0.296875); -webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469); ">Dear Jörn,</span><div><span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26, 0.292969); -webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469);"><br></span><div>Thanks for you helping.</div><div><br></div><div>Weina</div><div><br></div><div><br><br><br></div><div><br>在 2011-9-26,17:45,"Jörn M. Horschig" <<a href="mailto:jm.horschig@donders.ru.nl">jm.horschig@donders.ru.nl</a>> 写道:<br><br></div><div></div><blockquote type="cite"><div>
    Dear Weina,<br>
    <br>
    Basically, any montage will cause signal characteristics from the
    sensors used for re-referencing to show up in all other sensors. If
    you use a common average, the signal from any sensor will depend to
    some degree to any other sensor (because common average uses all
    sensors for rereferencing). If you use only Cz, you will obtain a
    high granger causality for any sensors to Cz. This would of course
    not reflect a real brain process, but is just the consequence of
    substracting the signal from Cz from all other sensors. Best would
    be to use a sensor that you will not include in computing granger
    causality (e.g. a mastoid, or choose Cz but then exclude this sensor
    for further analyses).<br>
    <br>
    Best,<br>
    Jörn<br>
    <br>
    On 9/25/2011 7:48 PM, lwn_07 wrote:
    <blockquote cite="mid:396096E2-923B-48D7-9201-A041A4F22571@yahoo.com.cn" type="cite">
      <div>
        <div style="-webkit-tap-highlight-color: rgba(26, 26, 26,
          0.296875); -webkit-composition-fill-color: rgba(175, 192, 227,
          0.230469); -webkit-composition-frame-color: rgba(77, 128, 180,
          0.230469); font-size: medium; ">Thanks <span class="Apple-style-span" style="-webkit-tap-highlight-color:
            rgba(26, 26, 26, 0.292969); -webkit-composition-fill-color:
            rgba(175, 192, 227, 0.230469);
            -webkit-composition-frame-color: rgba(77, 128, 180,
            0.230469); ">Jan-Mathijs.  Does it mean if I selected my
            data segment from mono montage (reference to mastoid), i'd
            better  calculate the granger causality in mono montage?
             Some paper selected Cz as reference, is that OK?</span></div>
        <div style="-webkit-tap-highlight-color: rgba(26, 26, 26,
          0.296875); -webkit-composition-fill-color: rgba(175, 192, 227,
          0.230469); -webkit-composition-frame-color: rgba(77, 128, 180,
          0.230469); font-size: medium; "><span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26,
            0.292969); -webkit-composition-fill-color: rgba(175, 192,
            227, 0.230469); -webkit-composition-frame-color: rgba(77,
            128, 180, 0.230469); "><br>
          </span></div>
        <div style="-webkit-tap-highlight-color: rgba(26, 26, 26,
          0.296875); -webkit-composition-fill-color: rgba(175, 192, 227,
          0.230469); -webkit-composition-frame-color: rgba(77, 128, 180,
          0.230469); font-size: medium; "><span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26,
            0.292969); -webkit-composition-fill-color: rgba(175, 192,
            227, 0.230469); -webkit-composition-frame-color: rgba(77,
            128, 180, 0.230469); ">Best regards.</span></div>
        <div style="-webkit-tap-highlight-color: rgba(26, 26, 26,
          0.296875); -webkit-composition-fill-color: rgba(175, 192, 227,
          0.230469); -webkit-composition-frame-color: rgba(77, 128, 180,
          0.230469); font-size: medium; "><span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26,
            0.292969); -webkit-composition-fill-color: rgba(175, 192,
            227, 0.230469); -webkit-composition-frame-color: rgba(77,
            128, 180, 0.230469); ">Weina   </span></div>
        <br>
        发自我的 iPad</div>
      <div><br>
        在 2011-9-25,23:36,jan-mathijs schoffelen <<a moz-do-not-send="true" href="mailto:jan.schoffelen@donders.ru.nl"><a href="mailto:jan.schoffelen@donders.ru.nl">jan.schoffelen@donders.ru.nl</a></a>>
        写道:<br>
        <br>
      </div>
      <blockquote type="cite">
        <div>Hi Weina,
          <div><br>
          </div>
          <div>Yes, granger causality results will for sure change when
            you use different montages. When you replace each
            measurement (what you call 'mono-montage') with that
            measurement minus the average across the whole recording
            array (what you call 'average montage') the amount with
            which signals can be explained in terms of their own and the
            other signals' past will change as well. This most likely
            leads to 'granger causality' estimates which just reflect
            spurious interactions.</div>
          <div><br>
          </div>
          <div>Best wishes,</div>
          <div><br>
          </div>
          <div>Jan-Mathijs</div>
          <div><br>
            <div>
              <div>On Sep 25, 2011, at 1:42 PM, 李卫娜 wrote:</div>
              <br class="Apple-interchange-newline">
              <blockquote type="cite">
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                        <div>Dear all,</div>
                        <div>  Is anyone knows about that wether
                          different EEG motages (such as mono-motage or
                          average montage) have effect on the result of
                          granger connectivity?</div>
                        <div> </div>
                        <div>                                                                                                        
                          Weina</div>
                      </td>
                    </tr>
                  </tbody>
                </table>
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                        after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; color:
                          rgb(0, 0, 0); font-family: Helvetica;
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                          <div style="word-wrap: break-word;
                            -webkit-nbsp-mode: space;
                            -webkit-line-break: after-white-space; ">Jan-Mathijs
                            Schoffelen, MD PhD </div>
                          <div>Donders Institute for Brain, Cognition
                            and Behaviour, <br>
                            Centre for Cognitive Neuroimaging,<br>
                            Radboud University Nijmegen, The Netherlands</div>
                          <div><a moz-do-not-send="true" href="mailto:J.Schoffelen@donders.ru.nl"><a href="mailto:J.Schoffelen@donders.ru.nl">J.Schoffelen@donders.ru.nl</a></a></div>
                          <div>Telephone: +31-24-3614793</div>
                        </span></div>
                    </span></div>
                </span></span>
            </div>
            <br>
          </div>
        </div>
      </blockquote>
      <blockquote type="cite">
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      <pre wrap="">_______________________________________________
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    </blockquote>
    <br>
    <br>
    <pre class="moz-signature" cols="72">-- 
Jörn M. Horschig
PhD Student
Donders Institute for Brain, Cognition and Behaviour 
Centre for Cognitive Neuroimaging
Radboud University Nijmegen 
Neuronal Oscillations Group

P.O. Box 9101
NL-6500 HB Nijmegen
The Netherlands

Contact:
E-Mail: <a class="moz-txt-link-abbreviated" href="mailto:jm.horschig@donders.ru.nl"><a href="mailto:jm.horschig@donders.ru.nl">jm.horschig@donders.ru.nl</a></a>
Tel:    +31-(0)24-36-68493
Web: <a class="moz-txt-link-freetext" href="http://www.ru.nl/donders"><a href="http://www.ru.nl/donders">http://www.ru.nl/donders</a></a>

Visiting address:
Trigon, room 2.30
Kapittelweg 29
NL-6525 EN Nijmegen
The Netherlands</pre>
  

</div></blockquote><blockquote type="cite"><div><span>_______________________________________________</span><br><span>fieldtrip mailing list</span><br><span><a href="mailto:fieldtrip@donders.ru.nl">fieldtrip@donders.ru.nl</a></span><br><span><a href="http://mailman.science.ru.nl/mailman/listinfo/fieldtrip">http://mailman.science.ru.nl/mailman/listinfo/fieldtrip</a></span></div></blockquote></div></body></html>