[FieldTrip] Problem in calculating connectivity from PCC beamformed data

[Davide Tabarelli]

Dear all,

I'm currently trying to calculate various spectral based connectivity
metrics starting from the results of a partial canonical coherence
beamfomer as in this tutorial:

http://www.fieldtriptoolbox.org/tutorial/chieti/wholebrain?s[]=connectivity

but I'm facing with the following problems:

1) Despite I specify a seed location in cfg.refindx,
ft_connectivityanalysis is calculating the coherence spectrum for all the
possible grid point combinations (24024 x 24024 values)
2) I cannot calculate WPLI (seems this method is not supported for source
data).

Below the code I'm using. Fieldtrip version is 20170522.

Any help will be appreciated ! Thank you !


% Here I compute full Fourier spectrum from "data"
cfg = [];
cfg.keeptrials = 'yes';
cfg.channel = '{ft_channelselection({'MEGGRAD'}, data);
cfg.method='mtmfft';
cfg.output = 'fourier';
cfg.pad = 'nextpow2';
cfg.foi = 5.5;
cfg.taper='dpss';
cfg.tapsmofrq = 1.5;
frc = ft_freqanalysis(cfg, data);

% Compute the PCC beamformer
cfg = [];
cfg.method = 'pcc';
cfg.headmodel = vol;
cfg.grad = grad;
cfg.grid = sourcemodel;
cfg.frequency = 5.5;
cfg.pcc.lambda = lambda;
cfg.pcc.fixedori = 'yes';
cfg.pcc.feedback = 'no';
cfg.pcc.normalize = 'yes';
cfg.pcc.keepfilter = 'yes';
cfg.channel = ft_channelselection({'MEGGRAD'}, data);
source = ft_sourceanalysis(cfg, frc);

% Compute connectivity
cfg = [];
cfg.refindx = seedIndex;
% cfg.method = 'wpli_debiased";  % Not supported?
cfg.method = 'coh';
cfg.complex = 'imag';
conn = ft_connectivityanalysis(cfg, source);


D.

-- 
Davide Tabarelli, Ph.D.
Center for Mind Brain Sciences (CIMeC)
University of Trento,
Via delle Regole, 101
38123 Mattarello (TN)
Italy
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