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</font>Dear Stan,</div>
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<div>Regarding your first question, you should check out Truccolo et al., Clinical Neurophysiology 2002 113:206-226. In this study they demonstrated that subtraction of the ERP from single trials actually leaves residual activity on the single trials which
distorts estimates of single-trial activity. This is highly relevant for both coherence and single-electrode analyses.</div>
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<div>While subtracting the ERP from the single trials before subsequent analyses is not a good idea, if you're doing time-frequency analyses, you can subtract evoked power/coherence from total power/coherence (average of single-trial power/coherence).</div>
<div> </div>
<div>Kevin</div>
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<div><font size="2" face="Tahoma">Kevin M. Spencer, Ph.D. </font></div>
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<div><font size="2"><font size="2"><font size="2"><font size="2"><font face="Tahoma">Director, Neural Dynamics Laboratory (</font><a href="http://ndl.hms.harvard.edu/"><font face="Tahoma">http://ndl.hms.harvard.edu</font></a><font face="Tahoma">)</font></font></font></font></font></div>
<div><font size="2"><font size="2"><font size="2"><font size="2" face="Tahoma">Research Health Scientist, VA Boston Healthcare System</font></font></font></font></div>
<div><font size="2"><font size="2"><font size="2"><font size="2" face="Tahoma">Assistant Professor of Psychiatry, Harvard Medical School</font></font></font></font></div>
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</font><font color="#000000" size="2"><font face="Tahoma"><b>From:</b> eeglablist-bounces@sccn.ucsd.edu [eeglablist-bounces@sccn.ucsd.edu] On Behalf Of Stanley Klein [sklein@berkeley.edu]<br>
<b>Sent:</b> Saturday, May 29, 2010 5:40 AM<br>
<b>To:</b> eeglablist@sccn.ucsd.edu<br>
<b>Subject:</b> [Eeglablist] improving coherence estimates<br>
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<div>Dear EEGlab,</div>
<div> In three days we'll be presenting a poster at a brain-computer </div>
<div>interface (BCI) conference in Monterey, CA on the topic of how to </div>
<div>reduce noise in coherence estimates for BCI purposes. I would</div>
<div>like to ask EEGlab whether the two approaches of the poster have</div>
<div>already been published or discussed. I'm not familiar with prior</div>
<div>work on it and I would really like to know before I make a fool of</div>
<div>myself. </div>
<div> </div>
<div>1) The usefulness of removing the ERP before calculating coherence.</div>
<div>Our simulations are the main topic of the poster.</div>
<div> </div>
<div>2) The usefulness of using Cauchy wavelets as filters for time-frequency</div>
<div>analysis when one wants high resolution in time (like 1 to 1.5 cycles). </div>
<div>These filters have rapid falloff at low temporal frequencies so they are</div>
<div>appropriate for the 1/f nature of EEG noise. </div>
<div> </div>
<div>Again, I'd be grateful for any leads to articles on either of this items.</div>
<div>And I look forward to seeing some of you in Monterey. </div>
<div> </div>
<div>thanks,</div>
<div>Stan</div>
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