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<p>Dear all,</p>
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<p>The previous messages largely answer my query, but I'd like just to make sure I understand correctly. The results of ICA decomposition should be similar whether the data is epoched or not- is that correct? Obviously the results will be different if the data
itself is different, but does ICA essentially treat epoched data as a continuous section?</p>
<p> </p>
<p>I would also really appreciate it if someone could approve, or otherwise, my pre-processing order. My pre-processing order is the following: resample, filter, epoch, remove baseline, interpolate bad channels and remove bad epochs (based on visual inspection),
re-reference to average, and (finally) run ICA to detect artefacts. One thing I wasn't sure about was re-referencing- am i doing that at the right point?</p>
<p> </p>
<p>Many thanks in advance,</p>
<p>katherine</p>
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<div style="DIRECTION: ltr" id="divRpF872502"><font color="#000000" size="2" face="Tahoma"><b>From:</b> eeglablist-bounces@sccn.ucsd.edu [eeglablist-bounces@sccn.ucsd.edu] on behalf of Mikołaj Magnuski [imponderabilion@gmail.com]<br>
<b>Sent:</b> 06 June 2013 19:13<br>
<b>Cc:</b> eeglablist@sccn.ucsd.edu<br>
<b>Subject:</b> Re: [Eeglablist] Epoching eeg data<br>
</font><br>
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<div>Dear Karlo,
<div><br>
</div>
<div>there is a case when dividing your whole 15 min. into smaller epochs (say 1 or 2 seconds long)</div>
<div>is quite convenient with respect to ICA:</div>
<div>--> cleaning data before ICA is easy if you just have to click bad epochs instead of marking</div>
<div>bad periods in continuous data - although this is just my personal feeling. </div>
<div>Nevertheless, you can also use automatic artifact rejection methods</div>
<div>available in EEGlab this way. These methods require epoched data. </div>
<div>(it is also easy to reconstruct your rejections later if you do them</div>
<div>on epochs - you can just <span class="Apple-style-span">save the indices of windows that you removed [by </span></div>
<div>coping relevant field in EEG <span class="Apple-style-span">structure after marking bad epochs</span><span class="Apple-style-span">,</span></div>
<div><span class="Apple-style-span">but before rejecting them]).</span></div>
<div><span class="Apple-style-span">--> Then, after your first IC decomposition, if you are not satisfied with its results and observe that</span></div>
<div><span class="Apple-style-span">some parts of your data may be responsible for poor results - you can remove</span></div>
<div><span class="Apple-style-span">epochs containing these data easily and perform ICA again.</span></div>
<div><span class="Apple-style-span"><br>
</span></div>
<div><span class="Apple-style-span">So, just as Makoto wrote, ICA does not care whether data are epoched<span></span> but you may -</span></div>
<div><span class="Apple-style-span">because in some cases it is conven</span><span class="Apple-style-span">ient in preprocessing or 'postprocessing' (correcting</span></div>
<div></div>
<div><span class="Apple-style-span">ICA decomposition).</span></div>
<div><span class="Apple-style-span">If you need any extra help with this - let me know (I have some scripts and functions to do this).</span></div>
<div><span class="Apple-style-span"><br>
</span></div>
<div><span class="Apple-style-span">Mikolaj</span></div>
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<div><br>
W dniu środa, 5 czerwca 2013 użytkownik Makoto Miyakoshi napisał:<br>
<blockquote style="BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8ex; PADDING-LEFT: 1ex" class="gmail_quote">
<div dir="ltr">Dear Karlo,
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<div>If you want to epoch your data into 3-min blocks, for example, put event markers every 3 minutes then epoch the data.</div>
<div><br>
</div>
<div>ICA does not care temporal continuity of the data since it shuffles them up differently for every iteration as a preprocess. That means, if the total number of datapoints are the same before and after the epoching, the ICA results should be the same.</div>
<div><br>
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<div>Makoto</div>
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<div class="gmail_extra"><br>
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<div class="gmail_quote">2013/6/3 karlo gonzales <span dir="ltr"><<a href="https://dbxprd0111.outlook.com/owa/UrlBlockedError.aspx" target="_blank">thats_karlo@yahoo.com</a>></span><br>
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<div><font face="arial, helvetica, sans-serif">Dear EEGlab experts,</font></div>
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<div style="BACKGROUND-COLOR: transparent"><font face="arial, helvetica, sans-serif">I need you help regarding an</font><span style="BACKGROUND-COLOR: transparent"><font face="arial, helvetica, sans-serif"> eeg data files which was recorded during eye closed
state (15 min long). Thus, there is no event to epoch the data. 1) How do you epoch such data</font></span><span style="BACKGROUND-COLOR: transparent; FONT-STYLE: normal; FONT-FAMILY: arial,helvetica,sans-serif; FONT-SIZE: small">? 2) should we epoch data
before running ica (dose more epoch means better results?)</span></div>
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<font face="arial, helvetica, sans-serif">Thanks in advance</font></div>
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<br>
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</blockquote>
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-- <br>
<div dir="ltr">Makoto Miyakoshi<br>
Swartz Center for Computational Neuroscience<br>
Institute for Neural Computation, University of California San Diego<br>
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-- <br>
Pozdrawiam,<br>
Mikołaj Magnuski<br>
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