[FieldTrip] MNI grid alignment in subjects for group comparison

Marco Curado marco.curado at yahoo.com.br
Fri Jan 11 14:00:14 CET 2013

Dear Fieldtrip experts,

I have a question on MNI aligned grids for subjects head prior to source reconstruction.

In my experimental design, there are three experimental conditions (A, B and C) I want to compare in one group of subjects at the source level. To be able to compare source activity (by LCMV beamforming) among them, I use the MNI grid warped in every subject's head (to allow comparison at the source level) as stated in the tutorial "Create MNI-aligned grids in individual head-space": 


Up to now, everything is ok. But as I am naive in beamforming, I am a bit confused on the last sentence of this tutorial, where it is stated:

"You can use these single subjects' MNI grids in source analysis. After that you should put .pos, .xgrid, .ygrid, .zgrid, .dim field from the template_grid onto the subjects's source, which is thereby in MNI coordinates."

My question (indeed very basic) is what is exactly referred as the subject's source? Is it the final source localization after LCMV? I.e., do I need to insert such template_grid parameters in subject's parameter as last step after all source localization?
Summing up: The procedure would be to use the .grid from the subject (already warped with MNI grid) for source localization with LCMV and after it I include these parameters from the template-grid?

Thanks a lot for your comprehension and attention to my question - I hope I was clear in my issue.
My best wishes of an excellent year to everybody,
Marco Curado
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