Dear Colleagues

I have a seamingly simple question for the second level seed2voxel analysis, where we are interested inthe effects of a treatment in relation to a numeric symptom score. So we have two groups: treatment & placebo. For each subject there is a score i.e. from 0-30.

we would first calculate:

(A) the contrast for the main effect of treatment: Treatment > Placebo [1-1]. Using the same seed we then calculate
(B) the contrast for the interaction: Treatment, Placebo, Scores for only the Treatment Group, Scores for only the Placebo Group [0 0 1 -1].

With the Rex toolbox, we then load the main effect results (from contrast (A)). Then in order to see, weather there is an effect of interaction (treatment x symptoms) we would load the SPM file of the interaction statistics (the spm.mat from (B)) and extract the results on a cluster level. As such, we then are able to interpret whether the aberrant connectivity due to treatment is affected by the sypmtomscores.

Is this procedure a valid approach?

Warm regards,
Julian