Dear John,
We are close to finish the analysis and would like to make sure the stat
model that you described:
'Do the stats, with proportional scaling looking for interactions
between modality and group, like (PET_1 - PET_2) - (GM_1 - GM_2)'
For this step, I assume that we need to use 'Multi subj:
interaction&covariates'from stat model, as Example2 in the SPM99 manual ,
then choose '2 subjects' (for PET and GM), enter images of both comparison
groups (PET_1 and PET_2 to subject 1, GM_1 and GM_2 to subject 2) with
conditions 1 or 2, choose 'proportional scaling', and threshold (0 for
GM?). In the stat analysis of Results, make contrasts '1 -1 -1 1'(PET_1,
PET_2, GM_1, GM_2, respectively) or '-1 1 1 -1'. By these contrasts, we can
see the interaction of PET and GM, which is the outcome of this group
comparison (1 vs 2).
I would appreciate your correction if anything wrong.
Best Regards,
Akira Kugaya
|