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

[Eelke Spaak]

Dear Xiao,

In addition to Jörn's excellent tips, specifically refer to the
appendix of the beamformingextended tutorial
(http://fieldtrip.fcdonders.nl/tutorial/beamformingextended#appendixcomputation_of_virtual_meg_channels_in_source-space),
where the steps needed to extract a waveform from a specific grid
point (in this case, the peak voxel after a DICS beamformer) are
explained.

Best,
Eelke

On 2 April 2013 09:32, "Jörn M. Horschig" <jm.horschig at donders.ru.nl> wrote:
> 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, 陈雪 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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>
> --
> 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
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>
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>
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