Dear Vladimir,
I found that the solutions of source localization (SPM8) for grandmean data (not group inversion) were different according to the number of contrasts that should be inverted. In my 2*2 designed ERP experiment, signals of 4 conditions averaged across subjects were gotten by using 'Grand mean' in the 'other' option. I would like to investigate the source information of the difference between conditions, therefore, contrasts were made by using 'contrast' in the 'other' option. However, I found that the solution of contrast file containing only one contrast (e.g. a1b1 - a1b2) was different from the solutions containing several contrasts (e.g. a1b1 - a1b2; a1b1 - a2b1; ....). I am confused about how many and what contrasts should be inverted simultaneously. I am looking forward to your reply.
Bests,
Sun Delin
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