[FieldTrip] PLV on sources

[Robert Oostenveld]

Dear Sheraz, Bob

You are completely right; since the fft and the spatial filter multiplication are both linear operations, their order can be interchanged. If nsource>nchan, this will speed things up. For full brain source reconstructions it will be much faster (and require less memory).

It would be nice to extend the tutorial with a section that explains precisely this.

Best
Robert

Op 28 aug. 2012 om 12:34 heeft Sheraz Khan <sherrykhan78 at gmail.com> het volgende geschreven:

> Dear  Bob,
> 
> Another possible solution is to do wavelet decomposition in sensor space and then multiply it with your imaging kernel, then do PLV in source space, this will save some computational time, but still you have to deal with EEG/MEG point spread function.
> 
> Sheraz Khan
> Martinos Center
> MGH/MIT/Harvard
> 
> On Tue, Aug 28, 2012 at 4:05 AM, Robert Oostenveld <r.oostenveld at donders.ru.nl> wrote:
> Dear Robert and Nayaran,
> 
> The data handling in ft_connectivityanalysis is not yet at the level that it can easily deal with all source representations; that is something that we will improve upon in the future.
> 
> The way we suggest it now is similar to your suggestion and is outlined in detail in the http://fieldtrip.fcdonders.nl/tutorial/connectivity tutorial. Specifically have a look at the second section where as example source (virtual channel) coherence and granger is computed. In that tutorial you would just change cfg.method in plv and you should be rolling.
> 
> Best regards,
> Robert O.
> 
> PS this connectivity tutorial is quite new, so might also be of interest for other people doing connectivity analysis!
> 
> 
> Op 24 aug. 2012 om 14:35 heeft "Narayan Puthanmadam Subramaniyam" <narayan.ps at tut.fi> het volgende geschreven:
> 
> > hi
> >
> > i was thinking of doing the same thing exactly. Computing plv on the eeg inverse solution. technically it should be possible going by the general level concept of phase locking. but i am not sure so let the experts here speak.
> >
> > Thanks&Regards,
> > NPS
> >
> > Sent from my Nokia phone
> > -----Original Message-----
> > From: Robert Brown
> > Sent:  24:08:2012, 11:38
> > To: fieldtrip at science.ru.nl
> > Subject: [FieldTrip] PLV on sources
> >
> >
> > Dear Fieldtrippers,
> >
> > I see (from the ft_connectivityanalysis code) that one cannot run phase
> > locking (PLV) analysis (a la Lachaux et al) on source data.
> >
> > My brain still insisted on trying to do so but unfortunately I am not sure
> > if it is clever enough. Hope you can help!
> >
> > It seems that a way to go would be to do LCMV beamforming on the data, get
> > the virtual electrodes, then run freqanalysis with fourier output on these
> > virtual electrodes and then perform PLV on those data.
> >
> > Before I dig myself very deep into this, maybe some experts here could
> > guide me: Would this approach work? Any possible caveats? Are there maybe
> > other, better and more straightforward ways for achieving the PLV on source
> > level?
> >
> > Any comments would be appreciated. Thank you very much for your time!
> >
> > Kind regards,
> > Bob
> >
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