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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Darren,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I recommend reading this paper:<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:black'>Junghöfer M,
Elbert T, Tucker DM & Braun C. (1999) The polar average reference effect: a
bias in estimating the head surface integral in EEG recording. Clinical
Neurophysiology 110(6): 1149-1155 <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Basically, the best “practical” reference would
cover the whole body evenly, or at least the whole head evenly, in order to
approach the “reference-at-infinity” used in physics. The more
channels, the better. The only reason to exclude any channel is if it is known
to have noise on it.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>The only subtle catch is that one should include the original reference
electrode in the calculation, if its location is known. It just gives one a
little extra information.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>-Jeff Eriksen<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
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<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> eeglablist-bounces@sccn.ucsd.edu
[mailto:eeglablist-bounces@sccn.ucsd.edu] <b>On Behalf Of </b>Darren Weber<br>
<b>Sent:</b> Wednesday, February 06, 2008 5:13 PM<br>
<b>To:</b> eeglablist@sccn.ucsd.edu<br>
<b>Subject:</b> [Eeglablist] EGI data re-reference (reref)<o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><br>
Hi,<br>
<br>
I have an EGI dataset loaded into EEGLAB. It was acquired using an EGI
HydroCel Geodesic Sensor Net (128 channels). I would appreciate advice
about re-referencing the data to average reference. I've never done this
before and I'm wondering if there are any important or subtle catches. I
am concerned that some of the channels should not be included in the average
reference.<br>
<br>
Regards, Darren<o:p></o:p></p>
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