[FieldTrip] EEG Source Reconstruction - Interpolation by Trial?

"Jörn M. Horschig" jm.horschig at donders.ru.nl
Tue Sep 3 12:46:04 CEST 2013

Dear Roey,

of course there is a way, actual several. I don't see a reason why you 
would want to do that though :) The interpolation purpose is mainly for 
plotting, not for performing fancy statistics or other analyses. In case 
you want to go to a finer spatial resolution, I'd do the reconstruction 
on a finer grid (and there, you will be faced with just physical and 
mathematical constraints in terms of spatial accuracy). That way, your 
reconstruction will be at least based on a physical model, not on some 
'weird' linear interpolation.

Anyway, to answer your question:
First, there is a cfg.parameter field, with which you can specify the 
parameter. If that does not work, the easiest way for you would be to go 
to the code of ft_sourceinterpolate at line 171, copy the lines up to 
184 and put these into your own function. You would need to change them 
appropriately, so that you loop over trials. As I said, there are other 
ways, but that would be the most elegant, fastest (computationally) and 
easiest to understand.


On 9/2/2013 4:54 PM, Roey Schurr wrote:
> Hi all,
> We are interested in comparing two source reconstruction calculated 
> using EEG records taken in two different conditions (not ERP), from 
> different subjects, across the group.
> As we see it, what we must do is the following:
> 1) ft_sourceanalysis (for each condition in each subject, in all trials)
> 2) ft_sourceinterpolate (the same)
> 3) ft_volumenormalise (the same)
> 4) ft_sourcegrandaverage
> 5) ft_sourcestatistics
> The problem is ft_sourceinterpolate will not interpolate each trial 
> individually, as there is no way to give it the "pow" field per trial.
> Is there a way to performd the interpolation over the anatomycal MRI 
> per trial?
> Thank you so much!
> Aia and Roey
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Jörn M. Horschig
PhD Student
Donders Institute for Brain, Cognition and Behaviour
Centre for Cognitive Neuroimaging
Radboud University Nijmegen
Neuronal Oscillations Group
FieldTrip Development Team

P.O. Box 9101
NL-6500 HB Nijmegen
The Netherlands

E-Mail: jm.horschig at donders.ru.nl
Tel:    +31-(0)24-36-68493
Web: http://www.ru.nl/donders

Visiting address:
Trigon, room 2.30
Kapittelweg 29
NL-6525 EN Nijmegen
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