[FieldTrip] overlaying beamformer results to native/normalized space

jan-mathijs schoffelen jan.schoffelen at donders.ru.nl
Wed May 11 11:02:49 CEST 2011

Dear Akiko,

On May 4, 2011, at 3:17 PM, Akiko Ikkai wrote:

> I sent a below message to the list last night, but it was bounced  
> back. I'm trying from another email account. My apologies if this  
> was duplicate...
> I'm trying to run beamformer analysis on my MEG data, using DICS,  
> and having difficulty visualizing meaningful results.
> I was able to align MRI image to MEG sensors; after segmentation,  
> ft_prepare_singleshell and  ft_prepare_leadfield, plotting  
> ft_data.grad and volume model confirms that they align reasonably.  
> However, using data.grad, grid, and vol to run ft_sourceanalysis,  
> and ft_sourceinterpolate with MRI (in ctf coordinate system and  
> aligned to MEG sensors) somehow distorts the alignment, and the new  
> volume model does not resemble the original.

So, the problem is that ft_sourceinterpolate does not behave as  

> I'm assuming that, after ft_sourceinterpolate, if I segment  
> source_interpolated.anatomy and run ft_prepare_singleshell and  
> ft_prepare_leadfield, it should align with MEG sensors, just as the  
> initial volume model aligned with MEG sensors... or am I making too  
> much of an assumption here?

Why would you want to do this?

> Because of the misalignment, output data of ft_sourceinterpolate  
> with "anatomy" and "avg.pow" does not agree with topoplot (run  
> ft_freqanalysis on the same dataset).
> If anyone could explain why this alignment distortion might be  
> happening during ft_sourceanalysis and/or ft_sourceinterpolate, I'd  
> really appreciate it.

I am afraid you need to be a bit more specific in order for us to  
understand what may be going wrong here.



> Thanks in advance, Akiko
> -- 
> Akiko Ikkai, Ph.D.
> Postdoctoral Fellow
> Department of Psychological and Brain Sciences
> Johns Hopkins University
> Ames Hall, 3400 N. Charles St.
> Baltimore, MD 21218
> _______________________________________________
> fieldtrip mailing list
> fieldtrip at donders.ru.nl
> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip

Dr. J.M. (Jan-Mathijs) Schoffelen
Donders Institute for Brain, Cognition and Behaviour,
Centre for Cognitive Neuroimaging,
Radboud University Nijmegen, The Netherlands
J.Schoffelen at donders.ru.nl
Telephone: 0031-24-3614793

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