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<div style="direction: ltr;font-family: Tahoma;color: #000000;font-size: 10pt;">Dear Subbu,<br>
<br>
PDC seems to be influenced by filtering, see <a href="http://www.ncbi.nlm.nih.gov/pubmed/20026279" target="_blank">
http://www.ncbi.nlm.nih.gov/pubmed/20026279</a> by Florin et al., 2010, Neuroimage.
<br>
I would not recommend therefore applying PDC to source data. <br>
Other views are much welcome.<br>
Best,<br>
Carlo<br>
<br>
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<div style="direction: ltr;" id="divRpF693373"><font color="#000000" face="Tahoma" size="2"><b>Von:</b> fieldtrip-bounces@science.ru.nl [fieldtrip-bounces@science.ru.nl]" im Auftrag von "Subramaniam Iyer [eeguser@hotmail.com]<br>
<b>Gesendet:</b> Mittwoch, 27. Februar 2013 00:07<br>
<b>An:</b> FieldTrip<br>
<b>Betreff:</b> Re: [FieldTrip] Preprocessing before connectivity analysis and model order<br>
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<div dir="ltr">Dear Jan-Mathjis
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<div>Thanks for your reply. So if I understand correctly, performing PDC on EEG data can still be affected due to volume conduction, hence I will have to do source localization first.</div>
<div>I have never done source localization before, but I will try it by going through the extensive FT documentation.</div>
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<div>However, is performing ICA before computing inverse solution recommended or is it better to simply reject artifactual sections as you mentioned even in this case ?</div>
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<div>Regards</div>
<div>Subbu</div>
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From: jan.schoffelen@donders.ru.nl<br>
Date: Tue, 26 Feb 2013 21:52:37 +0100<br>
To: fieldtrip@science.ru.nl<br>
Subject: Re: [FieldTrip] Preprocessing before connectivity analysis and model order<br>
<br>
Dear Subbu,
<div><br>
</div>
<div>In general I would discourage people to perform connectivity analysis on (non-invasively obtained) sensor-level data, with or without ICA cleaning. If, however, you are bold enough to try, I'd recommend to discard epochs that are contaminated by eye-blinks/EMG
activity etc., rather than using ICA for cleaning. The main reason is that removing topographies of artifactual components may actually inject correlations onto the recordings. I don't know the wikipedia article myself, but I would say that DTF and PDC are
not immune for volume conduction. Also, it is important to keep in mind that your choice of reference is important when interpreting results. </div>
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<div><br>
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<div>Best,</div>
<div><br>
</div>
<div>Jan-Mathijs</div>
<div><br>
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<div><br>
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<div>On Feb 25, 2013, at 10:52 PM, Subramaniam Iyer wrote:</div>
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<div dir="ltr">Dear FieldTrip users<br>
<br>
I am trying to compute PDC from a set of EEG data from 10 subjects. I have three questions regarding connectivity analysis.<br>
<br>
1) Since the data has artifacts (EOG,EMG) , would it be alright to preprocess the data using for ex. ICA ? This wikipedia article says, its not advisable :<a href="http://en.wikipedia.org/wiki/Brain_connectivity_estimators#DTF_and_PDC_are_not_influenced_by_volume_conduction" target="_blank">http://en.wikipedia.org/wiki/Brain_connectivity_estimators#DTF_and_PDC_are_not_influenced_by_volume_conduction</a>.
What would be your opinion ? Is there any article that would shed some light on this ?<br>
2) How do I compute the model order in FieldTrip ? Before that, how can I check if the data is stable and stationary before computing the MVAR model in FieldTrip ?<br>
3) How do I compute the threshold for PDC above which I can safely assume, a link exists between two regions ?<br>
<br>
Thanks in advance.
<div>Subbu</div>
</div>
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<div>Jan-Mathijs Schoffelen, MD PhD </div>
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<div>Donders Institute for Brain, Cognition and Behaviour, <br>
Centre for Cognitive Neuroimaging,<br>
Radboud University Nijmegen, The Netherlands</div>
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<div>Max Planck Institute for Psycholinguistics,</div>
<div>Nijmegen, The Netherlands</div>
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<div><a href="mailto:J.Schoffelen@donders.ru.nl" target="_blank">J.Schoffelen@donders.ru.nl</a></div>
<div>Telephone: +31-24-3614793</div>
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