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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Hi Eric,<o:p></o:p></span></p>
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<span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Did you reduce the rank of your data by 1 before running ICA? I would do Matlab rank(EEG.data(:,:)) and check it is not 1 less than the number of your channels
in ICA. If it is the same and you are not rank deficient. If you are then you can perform channel rejection to match EEG.nbchan with rank(EEG.data(:,:)).<o:p></o:p></span></p>
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<span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Average referencing reduces the rank of the data by 1. When you rereference to average, the sum of all your channels is 0 at each time point. One channel
is therefore a linear combination of the others, which implies statistical dependence, therefore the dimensionality of your data is reduced by one after averaging. I always average reference after ICA.
<o:p></o:p></span></p>
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<span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Average referencing before means you can only extract N-1 independent components after this. This is fine as long as you remember to extract 1 component
less than you would have before average reference.<o:p></o:p></span></p>
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<span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Best wishes,<o:p></o:p></span></p>
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<span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Jumana
</span><span style="font-size:9.5pt;font-family:"Arial",sans-serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif"> eeglablist-bounces@sccn.ucsd.edu [mailto:eeglablist-bounces@sccn.ucsd.edu]
<b>On Behalf Of </b>Eric HG<br>
<b>Sent:</b> 08 December 2016 00:39<br>
<b>To:</b> eeglablist <eeglablist@sccn.ucsd.edu><br>
<b>Subject:</b> [Eeglablist] Artifacts after removal of ICA component<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-size:9.5pt">Hi everybody,</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:9.5pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.5pt">I've had some trouble with removal of components using ICA (I'm currently using ICA infomax). After I remove a component there seems to be induced high frequency noise in the dataset. <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.5pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.5pt">The data is referenced to average before applying ICA. <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.5pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.5pt">Does anyone know why that is happening? <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.5pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.5pt">Best,<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.5pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.5pt">Eric<o:p></o:p></span></p>
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