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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">jan.schoffelen@donders.ru.nl</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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<td style="font: inherit;" valign="top">
<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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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">J.Schoffelen@donders.ru.nl</a></div>
<div>Telephone: +31-24-3614793</div>
</span></div>
</span></div>
</span></span>
</div>
<br>
</div>
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<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">jm.horschig@donders.ru.nl</a>
Tel: +31-(0)24-36-68493
Web: <a class="moz-txt-link-freetext" href="http://www.ru.nl/donders">http://www.ru.nl/donders</a>
Visiting address:
Trigon, room 2.30
Kapittelweg 29
NL-6525 EN Nijmegen
The Netherlands</pre>
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