[FieldTrip] source-level phase coherence (following beamforming extended tutorial)

Vitoria Piai v.piai.research at gmail.com
Wed Jan 1 18:32:41 CET 2014

Dear FT-ers,

Sticking to the Dutch tradition, my best wishes for 2014, first of all!

I'm trying to compute phase coherence between two sources of activity 
that I previously localised with DICS (one anterior and one posterior 
source, see figure if needed).
It was suggested to me I'd use the approach explained in the beamforming 
extended tutorial, in particular "Localization of cortical sources that 
are coherent with the EMG". If I follow that approach (copied here below)

cfg                 = [];
cfg.method          = 'dics';
cfg.refchan         = 'EMGlft';
cfg.frequency       = 20;
cfg.vol             = hdm;
cfg.grid            = sourcemodel;
source_coh_lft      = ft_sourceanalysis(cfg, freq_csd);

I get stuck at the definition of cfg.refchan because I already know my 
sources of interest, so there's no "sensor" I can use for this. So I'm 
wondering whether there is another way to define the refchan or whether 
this specific approach is not the most appropriate.
Intuitively, I myself had first chosen the approach discussed in the 
tutorial connectivity extended, in particular "Source-level 
cortico-cortical connectivity in MEG data". When then computing the 
LCMV, I had the positions in grid.pos for the maximum activity both for 
the anterior and the posterior activity taken from the data shown in the 
figure. Would this be the most appropriate/best way of getting the phase 
coherence between these two sources? Or is there another method I should 

Any thoughts or suggestions are most welcome!
Thanks a lot, Vitória

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