[FieldTrip] Antw: plv and sourceanalysis

[Gregor Volberg]

Dear Sybille, 

the plv option is now within ft_connectivityanalysis. I was successful with the code given below (ft_freqanalysis changed a bit in newer versions of fieldtrip so there might be some small corrections necessary). As much as I know, a plv analysis on source activity is not implemented as one of fieldtrip's high-level functions, but could be done by hand. One possibility is to use source analysis to identify regions of interest, which can then be used as "virtual electrodes" for ft_freqanalysis and ft_connectivityanalysis, just as the real electrodes in sensor space data. In order for that to work, you need to reconstruct single trial source activity at your ROIs. How this is done depends on the method you use for source analysis. There are some recent postings where a method is described for an LCMV beamformer. 
Hope this helps, 
Gregor 


cfg_tfr                    = []; 
cfg_tfr.output             = 'fourier'; 
cfg_tfr.channel            = 'all'; 
cfg_tfr.method             = 'mtmconvol' 
cfg_tfr.taper              = 'hanning' 
cfg_tfr.toi                = -0.6:0.02:1 
cfg_tfr.foi                = [8 9 10 11 12]; 
cfg_tfr.t_ftimwin          = 7./cfg_tfr.foi; 
cfg_tfr.channelcmb         = {'EEG', 'EEG'} 
freq_output = ft_freqanalysis(cfg_tfr,data); 

cfg_con = []; 
cfg_con.method = 'plv'; 
plv = ft_connectivityanalysis(cfg_con, freq_output); 






-- 
Dr. rer. nat. Gregor Volberg <gregor.volberg at psychologie.uni-regensburg.de> ( mailto:gregor.volberg at psychologie.uni-regensburg.de )
University of Regensburg
Institute for Experimental Psychology
93040 Regensburg, Germany
Tel: +49 941 943 3862 
Fax: +49 941 943 3233
http://www.psychologie.uni-regensburg.de/Greenlee/team/volberg/volberg.html


>>> sibylle <s.mohr at psy.gla.ac.uk> 4/7/2011 12:55 PM >>>
Dear Fieldtrippers,

I have a couple of question and I hope someone can help me:
How is it possible to compute plv (for freq data)?
As far as I can remember there used to be an option within 
ft_sourcedescriptives, which seems to have disappeared.
How can one use plv to determine connectivity in source space?

Thanks a lot & best wishes,

Sibylle


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