[FieldTrip] Source fitting with template MRI/Headmodel

[Julian Keil]

Hi Tommy,

did you do some sort of contrast (e.g. with the noise estimate or a baseline) after your source analysis?
Right now, it's not clear what you are looking at. Could you paste your code not only of the sourceanalysis, but the rest after which got you to the plot?
It might also be the case that the automatic scaling in the source plot throws you off - maybe try setting it by hand.

Good luck,

Julian

Am 23.01.2017 um 22:00 schrieb Tommy Wilson:

> Hi all,
> 
> I'm working with EEG data and I'm trying to get some basic source fitting up and running. Unfortunately, I don't have individual subject MRIs, so I'm using the templates provided by fieldtrip. I've co-registered my 160 Biosemi electrodes to the standard_bem template (see attached picture). For the sourcemodel, I'm using the standard_sourcemodel3d5mm grid (picture attached, overlaid on standard_bem). I can prepare the leadfield from there with ft_prepare_leadfield (cfg.normalize = 'yes'), as per the LCMV tutorial.
> 
> To test this configuration, I've selected a time window in my data and averaged across it (the covariance matrix was also calculated); the topography of this averaged data is attached. I then attempted a source fit with the LCMV beamformer:
> 
> cfg                     = [];
> cfg.method              = 'lcmv';
> cfg.grid                = leadfield;
> cfg.vol                 = vol;
> cfg.elec                = elec;
> cfg.lcmv.lambda         = '15%';
> cfg.lcmv.keepfilter     = 'yes';
> cfg.lcmv.fixedori       = 'yes';
> cfg.lcmv.projectnoise   = 'yes';
> 
> sourceA = ft_sourceanalysis(cfg,A);
> 
> After interpolating to the single_subj_T1.nii provided with ft_sourceinterpolate and plotting with ft_sourceplot, I am given a sourceplot that is highly focal in nature (see attached picture).
> 
> I'd find it very surprising if this topography were generated primarily by a source that isn't even inside the brain (as the sourceplot indicates). So, I'm not sure exactly where/how I'm going wrong with this one, nor am I sure how to trouble shoot it. Any guidance you might provide would be greatly appreciated.
> 
> Thanks so much,
> 
> Tommy
> 
> <Grid.PNG><Electrode localization.PNG><Topo.PNG><Source.PNG>_______________________________________________
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