[FieldTrip] Fwd: ft_sourceplot stubbornly projects rays beyond the head

Schoffelen, J.M. (Jan Mathijs) jan.schoffelen at donders.ru.nl
Fri Jan 15 14:04:04 CET 2021

Hi and thanks for your suggestions. I'm using mesh based source model prepared with FreeSurfer and downsampled with HCP-workbench. I'm nearly sure that the sources are reconstructed correctly, as they nicely match with Curry results.

The reason I use ft_sourceinterpolate is (if I understand this correctly) to perform group analysis. So I wanted to interpolate sources onto MRI volume and then warp them to a MNI template. After some more investigation I found that my problem is not located in ft_sourceplot, but these strange 'rays' are produced already by ft_sourceinterpolate. I can see high power values outside the brain volume when examining SourceInt.pow variable.

Maybe I'm doing the interpolation wrong, but I couldn't find any appropriate information about required masking in tutorials... If you have any suggestions, I would really appreciate..

All the best,

cfg            = [];
cfg.parameter  = 'pow';
sourceInt      = ft_sourceinterpolate(cfg, source , mri_itab_rars);

cfg              = [];
cfg.method       = 'ortho';
cfg.funparameter = 'pow';
ft_sourceplnt(cfg, sourceInt, mri_itab_rars);

Mirek Wyczesany
Psychophysiology Lab
Jagiellonian University
Kraków, PL

On 08/01/2021 21:22, Schoffelen, J.M. (Jan Mathijs) wrote:
> Mirek,
> I could be amiss, but it sounds as if you are interpolating (or rather extrapolating) a cortical surface based source model into a volume. Although it is not clear why you would want this, because in that case I’d recommend to visualize the source power on the mesh, but if you insist in the extrapolation, you may need to specify an ‘inside’ mask to your volume, so that the what you call rays are masked. On the off chance that you are using a volume-based sourcemodel I think the origin of your problem might also lie in the absence of an ‘inside’ mask.
> Best wishes,
> Jan-Mathijs

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