Hi,
> What I've done was a task-control first level analysis for each subject and
> the created contrast was used in a one sample ttest for each group, one for
> group A and one for group B. In this case is it ok to pool all the data for
> group A + group B and create the ROIs?
You would need to create a map that reflects the average of [(average
group A) and (average group B)]. You can use this to define ROIs
which look for differences between A and B, This average is not so
straightforward in the SPM machinery as I remember it though - you
will either have to do the averaging and ROI extraction by hand
(imcalc or something) or use a two-sample model without constant (see
the list for suggestions) or - if you are lucky - your groups are the
same size, and you can just use the one sample t test model pooling
across groups.
Best,
Matthew
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