<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Dear Makoto<div class=""><br class=""></div><div class="">Thank you very much for your reply. That makes all sense. However, I don’t understand why performing average referencing after ICA is not recommended? Do you mean by this that you should not re-reference data after preprocessing with ICA at all? Or do I misunderstand this point? Thank you!</div><div class=""><br class=""></div><div class="">All the best</div><div class="">Andreas</div><div class=""><br class=""></div><div class="">
<br class=""><div><blockquote type="cite" class=""><div class="">Am 31.07.2018 um 19:16 schrieb Makoto Miyakoshi <<a href="mailto:mmiyakoshi@ucsd.edu" class="">mmiyakoshi@ucsd.edu</a>>:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class="">Dear Andreas,<div class=""><br class=""></div><div class="">
<span style="font-size:small;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline" class="">> Is there a particular reason for this? Is there anything wrong in doing ICA on EEG referenced to a single channel?</span>
<br class=""></div><div class=""><br class=""></div><div class="">Average referencing is to impose zero-sum assumption to channel data. ICA result does not get affected by this, except DC differences. In other words, if you don't apply average reference, some of your IC scalp topographies could be all read or all blue.</div><div class=""><br class=""></div><div class="">Overall, I would rate the importance of average referencing before ICA not very high. It's just a minor issue even if you forgot to do so, most of your IC scalp topos are fine. However, if you perform average referencing after ICA, that may cause various problems so not recommended. If you forgot to perform average reference and finished lengthy ICA process which you can't do again for short of time, just forget it and proceed with what you have.</div><div class=""><br class=""></div><div class="">
<span style="font-size:small;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline" class="">> my idea was to compute the ICA on 1 Hz filtered (and average referenced) data and apply the selection of ICs to the same unfiltered (and average referenced) data.</span>
<br class=""></div><div class=""><br class=""></div><div class="">If you mean you copy the ICA weight matrices to do so, yes it is a common practice.</div><div class=""><br class=""></div><div class="">Makoto</div><div class=""><br class=""></div><div class=""><br class=""></div><br class=""><div class="gmail_quote"><div dir="ltr" class="">On Thu, Jul 26, 2018 at 2:29 AM Andreas Pedroni <<a href="mailto:andreas.pedroni@uzh.ch" class="">andreas.pedroni@uzh.ch</a>> wrote:<br class=""></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word" class="">Dear Makoto, dear EEGLAB list<div class=""><br class=""></div><div class="">I came across several sources where it is suggested to use average referenced data to perform ICA (including your very helpful discussion about preprocessing <a href="https://sccn.ucsd.edu/wiki/Makoto's_preprocessing_pipeline" target="_blank" class="">https://sccn.ucsd.edu/wiki/Makoto%27s_preprocessing_pipeline</a>). Is there a particular reason for this? Is there anything wrong in doing ICA on EEG referenced to a single channel?</div><div class=""><br class=""></div><div class="">In addition, I have the goal to apply ICA on (1 Hz filtered) data with the purpose to get rid of artifacts (using MARA), but apply the clean ICs on unfiltered data to keep lower frequencies than 1 Hz. Based on your comments, my idea was to compute the ICA on 1 Hz filtered (and average referenced) data and apply the selection of ICs to the same unfiltered (and average referenced) data. Is that the way to go, or are there other suggestions? </div><div class=""><br class=""></div><div class="">Thanks and all the best</div><div class=""><br class=""></div><div class="">Andreas</div><div class=""><br class=""></div><div class=""><div class=""><div class="">
<div style="letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; word-wrap: break-word;" class="">Andreas Pedroni<br class="">Psychologisches Institut<br class="">Methoden der Plastizitätsforschung<br class="">Andreasstrasse 15, AND 4.58<br class="">CH-8050 Zürich<br class=""><a href="mailto:andreas.pedroni@uzh.ch" target="_blank" class="">andreas.pedroni@uzh.ch</a><br class=""><br class=""><br class=""></div>
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