dics method for coherence analysis

[Rong, Feng (NIH/NIDCD) [V]]

Dear all,

I have a question regarding the comparison of coherence between virtual
channels with the dics method, following is my script:

 

cfg = [];

cfg.method='mtmfft';

cfg.ouput='powandcsd';

cfg.keeptrials='yes';

cfg.taper='dpss';

cfg.tapsmofrq=4;

cfg.foilim =[8 12];

cfg.sgncmb = channelcombination({'MEG','MEG'},bldata.label);

blfreq = freqanalysis(cfg,bldata);

clear bldata

 

cfg = [];

cfg.method='mtmfft';

cfg.ouput='powandcsd';

cfg.keeptrials='yes';

cfg.taper='dpss';

cfg.tapsmofrq=4;

cfg.foilim =[8 12];

cfg.sgncmb = channelcombination({'MEG','MEG'},eoidata.label);

eoifreq = freqanalysis(cfg,eoidata);

clear eoidata

 

load(datafile,'ldf');

 

cfg = [];

cfg.grid = source2sparse(ldf);  % Only consider gridpoints within head
volume 

cfg.method = 'power'; 

cfg.refdip=refdip; 

cfg.numrandomization = 100; 

cfg.randomization = 'yes'; 

cfg.projectnoise = 'yes'; 

cfg.lambda = 0; 

cfg.hdmfile = headmodel; 

cfg.frequency = (foi(1)+foi(2))/2; 

cfg.keepleadfield = 'no';

cfg.feedback = 'none'; 

[sourceRand] = sourceanalysis(cfg, eoifreq, blfreq);

 

cfg=[];

cfg.comparestat = 'relchange' ;

cfg.method = 'randomization' ;

cfg.parameter = 'coh'  ;

cfg.approach = 'parametric';

sourcestat = sourcestatistics(cfg,sourceRand);

 

In which bldata and eoidata are from the same dataset epoched with two
windows, ldf is the grid which has been computed based on the same
dataset. The purpose of this analysis is to compare the coherence
between the selected seed channel and other virtual channels within
alpha band between the two time windows. 

 

I found in the output variable sourceRand subfield 'pow' and 'coh',
which one shall I use for statistical analysis? I assume it should be
'coh', then what does 'pow' stand for? Is it the psd with the target
frequency range for each virtual channel? Then will the 'pow' values be
different from the computation without specifying reference virtual
channel in the script?

 

Best,

Feng

 

 


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