I would like to compare the strength of the correlation of brain activation with a behavioral variable in two groups of subjects (ie group A's activation with their behavioral scores vs group B's activation with their behavioral scores). I can see two ways this may be doable, and would love input/thoughts etc.
1. Run an independent sample t-test including covariates for each group (behavioral measure) and then in the GLM contrast covariate for A minus covariate for B. Problem is that this would be looking at different correlation strengths after accounting for group main effects, which isn't necessarily what I want.
2. Separately normalize the behavioral scores for each group and then run a multiple regression model with all scans put in, and then two regressors, corresponding to group A's normalized behavioral scores followed by zeros for group B, and zeros for group A followed by group B's normalized behavioral scores.