Dear all,
I have used SPM12 to create a flexible-factorial model (2nd Level-analysis). The model includes one group factor (2 levels; within-subject factor) and a condition factor (also 2 levels; within-subject factor). I did not model any interactions.
As long as I include not more than 9 subjects I get very moderate to no activation for the main effect contrasts. However, as soon as I include 10 or more subjects I suddenly get very strong activation in the whole brain (clusters up to 60.000 voxels, uncorrected).
I first thought this might be a problem of the subjects I selected. But it does not matter which subject I select as tenth subject, I will always get a jump from almost no activity to very high activation.
Is there anyone who has an idea about this problem? If you need further information I would be happy to give it to you.
Kind regards
Jonas
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