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</o:shapelayout></xml><![endif]--></head><body lang=NL-BE link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Dear Tarik<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Thank you for your quick response.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>I will look into the ADJUST plugin and the other points you mention.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Best Veerle<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'><p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> Tarik S Bel-Bahar [mailto:tarikbelbahar@gmail.com] <br><b>Sent:</b> woensdag 20 februari 2013 2:01<br><b>To:</b> Veerle ROSS<br><b>Cc:</b> eeglablist@sccn.ucsd.edu<br><b>Subject:</b> Re: [Eeglablist] running ICA a second time<o:p></o:p></span></p></div><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal><span style='color:#333399'>Greetings Ross:</span><o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal><span style='color:#333399'>Some brief responses to your questions below, I hope they are helpful. I've numbered the responses according to your questions.</span><o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal><span style='color:#333399'>0. if you have note please search eeglab list archives where you will definitely find some past discussions.</span><o:p></o:p></p></div><div><p class=MsoNormal><span style='color:#333399'>PLease read through the articles about cleaning with eeglab, which you can easily find on Google Scholar.</span><o:p></o:p></p></div><div><p class=MsoNormal><span style='color:#333399'>Check out the eeglab tutorial and wiki, particular guidelines. </span><o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal><span style='color:#333399'>1a. You can use PCA (see post within last 2 months on this subject based on a "should I PCA and if so what is best method")</span><o:p></o:p></p></div><div><p class=MsoNormal><span style='color:#333399'>Reducing by PCA may decrease the "validity" or "truthfullness" of your ICs. </span><o:p></o:p></p></div><div><p class=MsoNormal><span style='color:#333399'>Check Joseph Dien's PCA toolkit for some principled methods to do PCA.<span class=apple-style-span> </span></span><o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal><span style='color:#333399'>1c. You should find similar ICs after 2 ICAs, as the second ICA decomposition. The ones in the second ICA should be cleaner and more accurate.</span><o:p></o:p></p></div><div><p class=MsoNormal><span style='color:#333399'>Some people just publish their first ICA results, as it is not always the case that you gain much from a second ICA.</span><o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal><span style='color:#333399'>2a. I assume you have properly cleaned your data before the first ICA. </span><o:p></o:p></p></div><div><p class=MsoNormal><span style='color:#333399'>My recommendation is, if you want to do a second ICA, first consider doing what eeglab documentation recommend: </span><o:p></o:p></p></div><div><p class=MsoNormal><span style='color:#333399'>after your first ICA, then do artifactual epoch rejection using ICA-based rejection, then do a second ICA.</span><o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal><span style='color:#333399'>2b. it's not clear what your question is, perhaps there is a word missing in your question.</span><o:p></o:p></p></div><div><p class=MsoNormal><span style='color:#333399'>You could remove noisy or blink or other artifactual components if you want to, go ahead</span><o:p></o:p></p></div><div><p class=MsoNormal><span style='color:#333399'>and do a second ICA, and compare the results to doing it via the method suggested in the response to 2a above.</span><o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal><span style='color:#333399'>also:</span><o:p></o:p></p></div><div><p class=MsoNormal>Check out the the ADJUST plugin (amongst others for a variety of cleaning techniques). <o:p></o:p></p></div><div><p class=MsoNormal>&<o:p></o:p></p></div><div><p class=MsoNormal>Note there are least three camps:<o:p></o:p></p></div><div><p class=MsoNormal>a. those who use ICA just to deblink or otherwise clean their data, and then they reconstruct the EEG and do their analyses outside of ICA space. [ergo, ICA is a cleaning tool]<o:p></o:p></p></div><div><p class=MsoNormal>b. those who use ICA to get ICs that reflect brain dynamics and (often) established ERP components, they do their analyses on ICs [ergo, ICA gives real brain dynamics]<o:p></o:p></p></div><div><p class=MsoNormal>c. those who use PCA (with or without ICA) to decompose ERPs into spatial (and/or) temporal components, they do their analyses on PCs<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div></div></body></html>