Beamformer of correlated sources

Cristiano Micheli michelic72 at GMAIL.COM
Fri Aug 8 14:05:20 CEST 2008

Dear all
I have some questions about the use of DICS in the case of two correlated
cortical activations.
I am using an isometric contraction protocol and i localized the reference
dipole through cortico-muscular coherence with external myography and
(classic) DICS method. Now I have to calculate cortico-cortical activations
and i use:

cfg               = [];
cfg.grid         = grid;
cfg.method    = 'dics';
cfg.projectnoise = 'yes';
cfg.lambda    = 0; 
cfg.refdip   = ref_dipole_position;
cfg.frequency = 20;
cfg.hdmfile   = 'mymodel.hdm';
sourcecond    = sourceanalysis(cfg, freq);

According to Schoffelen et al. in order to disentangle the sources a
modification of the classic DICS algorithm is necessary. 
Am i supposed to extract the two activations if they are correlated with the
above written lines?
If not, how would it be a FT implementation to get to correlated sources
localization with DICS?
I tried with simulation and apparently the above implemetation is able to
localize only one source with a spread activation.
Attachments show:
'1sourceDICS.png' : simulation with an external reference channel correlated
with a source in the left emisphere
'2sourcesCCCDICS.png': simulation with reference dipole (same as above)
whose activity is correlated to a simmetric one in the right emisphere


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