Dear Alfonso,
(thanks for your previous answer)
I'm trying to run a gPPI analysis (6 experimental conditions) with 4 groups scanned two-times (pre/post).
I defined 2 sessions per subject for pre / post, added the corresponding functional and anatomical images and used the SPM.mat of each session to define the conditions.
Everything works well until the second-level analysis where I was not able to define between-sessions contrasts. Indeed, I only get the 6 experimental conditions concatenated across the sessions and not the 6 conditions for each session (which I'd like to compare for specific conditions).

Should I define the different sessions as different subject? (in that case, how can I define within-subject contrasts and be sure that covariance effects are removed?)

Thank you very much for your help,
Best wishes,

Pauline