[FieldTrip] How can I use DICS to get the waveforms?

["Jörn M. Horschig"]

Dear Xiao,

the DICS algorithm computes power of a certain frequency band of *one 
*time window (it works in the frequency domain with the cross-spectral 
density matrix, i.e. no time axis anymore). The source.avg.pow field 
contains thus the power value of this one time-frequency bin. I assume 
you want to get time-spectral evolution information? In that case it 
might be best to use the LCMV beamformer in the time-domain, extract the 
spatial location (voxel) of interest and apply the whatever-Fourier 
transform (short time, wavelet, welch, taper) on that. Please have a 
look at our various tutorials, for example:

http://fieldtrip.fcdonders.nl/tutorial/beamformer (on DICS)
http://fieldtrip.fcdonders.nl/tutorial/beamformingextended (appendix for 
LCMV)
http://fieldtrip.fcdonders.nl/tutorial/connectivity (also includes LCMV)

And here for the DICS paper:
http://www.ncbi.nlm.nih.gov/pubmed/11209067

Best regards,
Jörn


On 4/1/2013 4:05 PM, ?? wrote:
> Dear all,
>  I use DICS-beamformer to get the source,as follow:
> cfg                   = [];
> cfg.frequency         = freqP.freq;
> cfg.elec              = grid.cfg.elec;
> cfg.method            = 'dics';
> cfg.keeptrials        = 'yes';
> cfg.grid              = grid;
> cfg.vol               = vol;
> cfg.dics.lambda       = '5%';;
> cfg.dics.realfilter   = 'yes';
> source                = ft_sourceanalysis(cfg, freqP);
> source =
>
>           dim: [19 25 19]
>          freq: 17.9481
>     cumtapcnt: 3
>           pos: [9025x3 double]
>        inside: [1x4686 double]
>       outside: [1x4339 double]
>        method: 'average'
>           avg: [1x1 struct]
>           cfg: [1x1 struct]
>
> source.avg
>
>     pow: [1x9025 double]
> is it right?  if I want to get the waveforms in order to do the 
> correlation,how can I do ?
> thanks,
> best
> xiao
>
>
> _______________________________________________
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> fieldtrip at donders.ru.nl
> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip


-- 
Jörn M. Horschig
PhD Student
Donders Institute for Brain, Cognition and Behaviour
Centre for Cognitive Neuroimaging
Radboud University Nijmegen
Neuronal Oscillations Group
FieldTrip Development Team

P.O. Box 9101
NL-6500 HB Nijmegen
The Netherlands

Contact:
E-Mail: jm.horschig at donders.ru.nl
Tel:    +31-(0)24-36-68493
Web: http://www.ru.nl/donders

Visiting address:
Trigon, room 2.30
Kapittelweg 29
NL-6525 EN Nijmegen
The Netherlands

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