[FieldTrip] Source Reconstruction using Openmeeg method

["Jörn M. Horschig"]

Dear Mushfa,

I think you have to compute two leadfield matrices, one for EEG (elec) 
and one for MEG (grad), and then concatenate these (and make sure that 
the order of sensors won't get mixed up anywhere, because  
sourceanalysis just expects the leadfield matrix to be ordered like your 
data. If that's not the case, you either encounter the previous error 
you described or (if the number of channels matches, but order is mixed 
up) it will just return wrong source estimated activity.

Best,
Jörn

On 5/6/2013 2:47 PM, Mushfa Yousuf wrote:
> Hello;
>
> Yes you were right. I have defined the wrong sensors i.e 'grad' 
> instead of 'elec' while calculating the Leadfield.
>
> Actually I am trying to calculate Combined source reconstruction from 
> both EEG and MEG sensors.
>
> Do you have any idea, how to define both elec and grad definition  
> while calculating first forward then inverse solution.
>
> Because in a fieldtrip either you can defined elec or grad at one time.
>
>
> Regards;
>
>
> Mushfa Yousuf
>
> Neurozentrum,
> Universitätsklinikum Schleswig-Holstein,
> Campus Kiel (UKSH), Deutschland
>
>
> On Tue, Apr 30, 2013 at 6:23 PM, Johanna Zumer 
> <johanna.zumer at gmail.com <mailto:johanna.zumer at gmail.com>> wrote:
>
>     Hi Mushfa,
>
>     My guess is that the channels that have you used to compute
>     .csdspctrm are not the same as the channels in cfg.elec.    If you
>     set cfg.channel = freqPost.label, does that solve it?
>
>     Cheers,
>     Johanna
>
>
>     2013/4/30 Mushfa Yousuf <mushfa.yousuf at googlemail.com
>     <mailto:mushfa.yousuf at googlemail.com>>
>
>         Hello Fieldtrippers,
>
>         I am doing source reconstruction using EEG channels on a
>         fieldtrip.
>
>         I have computed Forward solution i.e head model using
>          'Openmeeg' and lead field successfully.
>
>         For the inverse solution using 'dics' method, I wrote the
>         following syntax
>
>
>
>
>
>          cfg              = [];
>          cfg.method       = 'dics';
>          cfg.frequency    = 130;
>          cfg.elec         = dataFIC12.hdr.elec;
>          cfg.grid         = grid;
>          cfg.vol          = vol;
>
>          sourcePost = ft_sourceanalysis(cfg, freqPost);
>
>
>         and I have received the following error:
>
>
>         ??? Error using ==> mtimes
>         Inner matrix dimensions must agree.
>
>         Error in ==> beamformer_dics at 314
>                 filt = pinv(lf' * invCf * lf) * lf' * invCf;          %
>                 Gross eqn. 3, use PINV/SVD to cover rank deficient
>                 leadfield
>
>         Error in ==> ft_sourceanalysis at 595
>               dip(i) = beamformer_dics(grid, sens, vol, [],
>         squeeze(Cf(i,:,:)), optarg{:});
>
>         Error in ==> newCode at 214
>         sourcePost = ft_sourceanalysis(cfg, freqPost);
>
>
>
>
>         Any help would be appreciated.
>
>
>         Regards;
>
>
>         Mushfa Yousuf
>
>         Neurozentrum,
>         Universitätsklinikum Schleswig-Holstein,
>         Campus Kiel (UKSH), Deutschland
>
>
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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
NL-6500 HB Nijmegen
The Netherlands

Contact:
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