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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Hi Natalia,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><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">How are you? I didn’t know you were fieldtripin’, too.<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>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I can’t really tell if your approach is correct, but I have some comments. First, to me it seems that the imaginary part of csd is not enough to
calculate PLV. But then, I don’t know the details of how you compute it. Second, the 3 orientations issue is commonly tackled by singular value decomposition rather than by averaging (see e.g. beamformer_dics.m). One can use svd to compute the orientation
of maximum power, and I think one could adapt the code, e.g. to get the orientation of maximum phase difference.<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>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">One straight-forward alternative I know of, is to extract source level time courses using the LCMV beamfomer. You can set cfg.projectmom=’yes’
to only get the direction of max. power. Then you could use ft_connectivityanalysis with cfg.method=’plv’ to get the phase locking values.<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>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Hope this helps,<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">Jan
<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>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">Von:</span></b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> fieldtrip-bounces@science.ru.nl [mailto:fieldtrip-bounces@science.ru.nl]
<b>Im Auftrag von </b></span><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">Natalia Zaretskaya<br>
<b>Gesendet:</b> Dienstag, 1. April 2014 09:20<br>
<b>An:</b> fieldtrip@science.ru.nl<br>
<b>Betreff:</b> [FieldTrip] PLV with DICS beamformer<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Dear FieldTrip experts,<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I would like to be able to compute the phase-locking value (<span style="font-family:"Arial","sans-serif";background:white">Lachaux, 1999</span>) using source data derived from disc beamformer.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Right now I perform ft_sourceanalysis with <o:p></o:p></p>
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<p class="MsoNormal">cfg.method = ‘dics’;<o:p></o:p></p>
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<p class="MsoNormal">cfg.refdip = [x y z];<o:p></o:p></p>
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<p class="MsoNormal">cfg.rawtrial = ‘yes’; <o:p></o:p></p>
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<p class="MsoNormal">cfg.keepcsd = ‘yes’;<o:p></o:p></p>
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<p class="MsoNormal">cfg.grid.filter = source.avg.filter; % precomputed common filter for two conditions<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">and then use the imaginary part of the single-trial cross-spectral densities to compute PLV “by hand”. Cross-spectra at each position have a 3x3 format, so I compute the PLV for each dipole orientation pair and then average.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I was wondering whether 1) the above procedure is technically correct and 2) whether there is a better, more efficient way to do it (I assume plv can be derived at the same step where source.avg.coh is computed?).<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Many thanks in advance!<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Best regards,<o:p></o:p></p>
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<p class="MsoNormal">Natalia Zaretskaya<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">---<o:p></o:p></p>
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<p class="MsoNormal">Dr. Natalia Zaretskaya<o:p></o:p></p>
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<p class="MsoNormal">Centre for Integrative Neuroscience<o:p></o:p></p>
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<p class="MsoNormal">Vision and Cognition Lab (AG Bartels) <o:p></o:p></p>
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<p class="MsoNormal">72076 Tübingen, Germany<o:p></o:p></p>
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<p class="MsoNormal"><a href="mailto:natalia.zaretskaya@cin.uni-tuebingen.de">natalia.zaretskaya@cin.uni-tuebingen.de</a><o:p></o:p></p>
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<p class="MsoNormal">phone: +49 7071 2989032<o:p></o:p></p>
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