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<p><span style="font-size:9.0pt; font-family:"Verdana",sans-serif">Dear all,<br>
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<p><span style="font-size:9.0pt; font-family:"Verdana",sans-serif">I am using ICA to clean my EEG data for eye-movement related artifacts. I’ve already done some testing in the past to see how certain pre-processing steps affect the quality of my decomposition
(e.g. filter settings). In most cases, it took approximately 1-2 hours to run ICA for single subjects (62 channels: 59 EEG, 3 EOG channels).<br>
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<p><span style="font-size:9.0pt; font-family:"Verdana",sans-serif">Now that I run ICA on my final datasets it suddenly takes hours over hours to do only a few steps. It still works fine in some subjects but in others runica takes up to 50 hours. I observed
that in some cases the weights blow up (learning rate is lowered many times); in others it starts right away without lowering the learning rate but every step takes ages.</span></p>
<p><span style="font-size:9.0pt; font-family:"Verdana",sans-serif">I’ve done some troubleshooting to see if a specific pre-processing step causes this behavior but I cannot find a consistent pattern. It seems to me though that (at least in some cases) the high-pass
filter played a role – can anyone explain how this is related? Could a high-pass filter potentially be too strict?<br>
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<p><span style="font-size:9.0pt; font-family:"Verdana",sans-serif">On the eeglablist I could only find discussions about rank deficiency (mostly due to using average reference) as a potential reason. I re-referenced to linked mastoids – does this also affect
the rank? When I check with <em><span style="font-family:"Verdana",sans-serif">rank(EEG.data(:, :))
</span></em>it returns 62 though, which is equal to the number of channels. For some of the “bad” subjects I nonehteless tried without re-referencing – no improvement. Also, reducing dimensionality with pca ("pca, 61") didn’t help.<br>
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<p><span style="font-size:9.0pt; font-family:"Verdana",sans-serif">Any advice would be very much appreciated!<br>
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<p><span style="font-size:9.0pt; font-family:"Verdana",sans-serif">Many thanks in advance,</span></p>
<p><span style="font-size:9.0pt; font-family:"Verdana",sans-serif">Hannah</span></p>
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<div class="PlainText">Hannah Hiebel, Mag.rer.nat.<br>
Cognitive Psychology & Neuroscience</div>
<div class="PlainText">Department of Psychology, University of Graz</div>
<div class="PlainText">Universitätsplatz 2, 8010 Graz, Austria </div>
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