afni.nimh.nih.gov

Assuming you centered your covariates properly, the answer for your first question is a).

> we assume that sub-brick [2], described as "difference of slopes wrt
> covariate" shows us the areas that are correlated with the first > covariate
> (i.e. an increase in the covariate is associated with an increase in the BOLD).

Yes, that's right if you only have one group of subjects.

Gang