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Edward Justin Modestino, M.Phil. wrote:
<blockquote cite="mid1299.131.91.30.56.1122308286.squirrel@131.91.30.56"
type="cite">
<pre wrap="">Hello,
In the EEGLAB tutorial on artifact rejection, it mentions the default trim
percentage is 5%. Are there any references for using this default of 5%?
Or is this based on general statistics of a 95% confidence, or something
similar?
</pre>
</blockquote>
This percentage correspond to the percentage of epochs the experimenter
judge to be artifactual. If the data quality is bad, you might want to
increase it, but 10% is usually an acceptable value for most datasets.<br>
<blockquote cite="mid1299.131.91.30.56.1122308286.squirrel@131.91.30.56"
type="cite">
<pre wrap="">If I were to perform a amplitude thresholding on a channel by channel
basis, what amplitude in +/- microvolts would be considered an upper
limit?</pre>
</blockquote>
Yes, you may select specific channels for amplitude thresholding
("electrode(s)" edit box).<br>
<blockquote cite="mid1299.131.91.30.56.1122308286.squirrel@131.91.30.56"
type="cite">
<pre wrap="">Should this be dynamic and thus be a different microvolt +/-
amplitude value cutoff for each channel? Are there any reference papers
for this?
</pre>
</blockquote>
Usually the same value is used for different (often eye) channels. <br>
<blockquote cite="mid1299.131.91.30.56.1122308286.squirrel@131.91.30.56"
type="cite">
<pre wrap="">I have one reference Picton et al. (2000), an article about guidelines for
ERPs which includes recording standards and publication criteria. In this
article on page 138, it mentions that a criterion level of +/- 200
microvolts could be used to remove trials. It mentions this may be too
Conservative for sleep studies which may have higher amplitudes. This +/-
200 microvolts sounds far too liberal to me. I believe the eye movements
I have already removed from the data were much less than that!</pre>
</blockquote>
The standard value I use is 50 microvolt although I do not have a
reference
at hand. Eye movement amplitude also varies widely from subject to
subject, from probably 30 microvolt to 300 microvolts. For the purpose
of rejecting eye blink artifacts, I think it is better to adjust this
value on a subject to subject basis.<br>
<br>
Best regards,<br>
<br>
Arno<br>
<div class="moz-signature">-- <br>
<br>
<b><font face="Arial,Helvetica"><font size="+1">Arnaud Delorme, Ph.D.</font></font></b>
<br>
<font face="Arial,Helvetica"><font size="+1"><font color="#3333ff">Swartz
Center for Computational Neuroscience,</font> <font color="#3333ff">INC,
University of San Diego California</font></font></font>
<br>
La Jolla, CA92093-0961, USA
<p><font face="Arial,Helvetica"><b>Tel</b> :<i>(+1)-858-458-1927 ext 15</i></font>
<br>
<font face="Arial,Helvetica"><b>Fax</b> :<i>(+1)-858-458-1847</i></font>
<br>
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href="http://www.sccn.ucsd.edu/%7Earno">sccn.ucsd.edu/~arno</a></font>
<br>
<font face="Arial,Helvetica"><b>To think upon</b>:</font></p>
<blockquote><dt><font face="Arial,Helvetica"> If I try to be like him,
who will be like me?
<font size="-5"><br>
<br>
</font></font></dt>
<dd><font face="Arial,Helvetica"><i>Yiddish proverb</i></font></dd>
</blockquote>
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