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Hi Becky,<br>
We exclude the bad channels before average reference, else you add a
small amount of the noise back into all channels. Keep in mind that
average referencing might reduce the rank of your data (compare the
discussions on the maillinglist for details).<br>
To your second question: I think all of these steps should not
interfere with the average referencing.<br>
<br>
Best,<br>
<br>
Benedikt<br>
<br>
<br>
<div class="moz-cite-prefix">Am 26.09.2013 14:28, schrieb Becky
Prince:<br>
</div>
<blockquote
cite="mid:CANd5Z7fv6OnQ+r3UxutDgijmKuRzrN3M7r8QM11ST12zfy1qJg@mail.gmail.com"
type="cite">
<div dir="ltr">Dear Makoto,
<div><br>
</div>
<div>
<div>Thanks for your response!</div>
<div><br>
</div>
<div>I'll be analyzing my data in channel space, so I'll go
with average referencing as you suggest. </div>
<div><br>
</div>
<div>Can you (or anyone else) please tell me whether to
exclude bad channels (including both mastoids and any
others) before or after applying a common average reference
to the data?</div>
<div><br>
</div>
<div>Also, is it ok to re-reference to a common average after
having completed the following processing steps: 1) remove
DC offset, 2) 0.1 high-pass filter, 3) epoch the data? </div>
<div><br>
</div>
<div>Many thanks!</div>
<div>Becky</div>
<div><br>
</div>
</div>
</div>
<div class="gmail_extra"><br clear="all">
<div><span
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">______________________________</span><span
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<br
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
<span
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">Becky
Gilbert (nee Prince)</span><br
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
<span
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">PhD
Researcher</span>
<div><br
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<span
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A109</span>
<div><span
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">Department
of Psychology</span><br
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
<span
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">University
of York</span>
<div><span
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">Heslington,
York, YO10 5DD, UK</span><br>
</div>
</div>
</div>
</div>
<br>
<br>
<div class="gmail_quote">On 25 September 2013 18:46, Makoto
Miyakoshi <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:mmiyakoshi@ucsd.edu" target="_blank">mmiyakoshi@ucsd.edu</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">Dear Becky,
<div class="im">
<div><br>
</div>
<div>> I believe the convention is to use the average
of linked ears or mastoids as the reference for
optimal measurement of these components,<br>
</div>
<div class="gmail_extra">
<br>
</div>
</div>
<div class="gmail_extra">It depends on whether you want to
use ICA to analyze your data in the source-resolved EEG
or not. If you do, re-reference does not affect the ICA
results. If you want to use channel EEG for the final
analysis, I recommend average referencing. If you need
to choose 1 electrode, choose Cz or FCz because that's
another 'convention' I've seen so far (may not specific
to your task though). Cz and FCz are easy to
interpolate.</div>
<div class="gmail_extra"><br>
</div>
<div class="gmail_extra">Makoto</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">2013/9/18 Becky Prince <span
dir="ltr"><<a moz-do-not-send="true"
href="mailto:becky.prince@york.ac.uk"
target="_blank">becky.prince@york.ac.uk</a>></span><br>
<blockquote class="gmail_quote" style="margin:0px 0px
0px
0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<div>
<div class="h5">
<div dir="ltr">Dear EEGLAB list,
<div>
<br>
</div>
<div>I've run an ERP study on auditory
temporal expectations in which I'm
interested in the auditory N2b and P3b
components. I believe the convention is to
use the average of linked ears or mastoids
as the reference for optimal measurement of
these components, but my mastoid channels
are consistently noisy in all of my
participants. The mastoid channels have
higher impedances (~15 KOhms) than the other
sites, probably due to the fact that the
caps we use have built in mastoid sites that
don't fit close enough to the skin. </div>
<div><br>
</div>
<div>I'm guessing it's a bad idea to
re-reference to noisy channels, so I'm
wondering what my options are. Can anyone
explain what they would do in this
situation? Are there any resources that
explain the effects of re-referencing on
specific components? I'm wondering if I'll
be able to see changes in N2b/P3b if I use
another reference, e.g. average of all
electrodes, and how the appearance of the
components (sites/polarities) will be
different from those typically reported with
a linked ear or mastoid reference.</div>
<div><br>
</div>
<div>Apologies for the fact that this isn't
strictly an EEGLAB question - I'm hoping
someone will still offer some advice!</div>
<div><br>
</div>
<div>Thanks,</div>
<div>Becky<br>
<div>
<div><span
style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">______________________________</span><span
style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">______________</span><br
style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">
<br
style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">
<span
style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">Becky
Gilbert (nee Prince)</span><br
style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">
<span
style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">PhD
Researcher</span>
<div><br
style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">
<span
style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">Room
A109</span>
<div><span
style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">Department
of Psychology</span><br
style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">
<span
style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">University
of York</span>
<div><span
style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">Heslington,
York, YO10 5DD, UK</span><br>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
<br>
</div>
</div>
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</blockquote>
</div>
<span class="HOEnZb"><font color="#888888"><br>
<br clear="all">
<div><br>
</div>
-- <br>
<div dir="ltr">Makoto Miyakoshi<br>
Swartz Center for Computational Neuroscience<br>
Institute for Neural Computation, University of
California San Diego<br>
</div>
</font></span></div>
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</blockquote>
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