[FieldTrip] ft_sourcegrandaverage & grid computation

Konstantina Kalogianni K.Kalogianni at tudelft.nl
Fri Aug 9 09:59:18 CEST 2013

Dear fieldtripers,
I have experienced a problem with ft_sourcegrandaverage and the calculation of my grid and I want to ask for help.
The error I get is the following :different grid locations in source reconstructions.

I will describe briefly the processing to give you a better idea about my error.

For every subject I have 6 conditions and I want to average all subjects per condition.
After preprocessing I calculate the covariance matrix and then  I use the MUSIC algorithm for my sources.
For  the grid calculation I use a default MRI a default VOL and a default electrodes' positions.
However  for every subject the grid is not identical since  cfg.channel in ft_prepare_leadfield is dependent on the channels I've discarded as noisy during the preprocessing.
By the way for the grid calculation I had to change the order  of cfg.elec because it didn't agree with the order of cfg,channel in my data.
So apparently I end up with a different grid for every subject but still I want to average all of them per condition.

Do I have to use another function to average my sources in this case?
Because the grid would never be identical among subjects.

I hope somebody out there experienced that before and can probably help me.
Thank you.

Konstantina [Nadia] Kalogianni
PhD candidate, TU Delft

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