[FieldTrip] MNE: sourcespace and volume aligned?

Magyari, Lilla Lilla.Magyari at mpi.nl
Tue Feb 28 14:52:55 CET 2012

hi Sara,

I think the alignment looks just good. The volume conductor is made from 
the (inside) skull surface, so it is a bit bigger indeed than the 
For me, it seems that there is also space between the vol and the 
sourcespace on the picture in the tutorial, but it is more difficult to 
see because it is colored. Probably, it wasn't plot with exactly the 
same piece of code than what is indicate above it.

About the error message. I am wondering which version of Fieldtrip are 
you using? Because I had similar problems with my units when I used an 
earlier version of FieldTrip where the ft_convert_unit function worked a 
bit differently than now.

In any case, we are simplifying this anatomical preprocessing pipeline 
(all things that you do in FieldTrip before using FreeSurfer) right now, 
so you can see the new version of the tutorial in a few days.


Sara Bögels wrote:
> Hi all,
> I am working my way through the MNE tutorial and plotted the mesh and 
> vol on top of each other at the end of the Freesurfer and MNE suite 
> steps to check whether they are aligned. The volume seems to fit quite 
> well into the mesh but is a bit smaller (see attached figures), but 
> definitely not a factor 10. However, from the figure (5) in the 
> tutorial, it seems as if the mesh has to be exactly on top of the 
> volume. Does my plot show that the two are misaligned? If so, what might 
> be the problem?
> I tried to use ft_determine_coordsys on the vol, but that gives me the 
> error message: 'unknown units (dm)'. If I use it on the sourcespace I 
> get the output that the units are 'cm'.
> Any help is appreciated.
> Thank you,
> Sara Bögels
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