afni.nimh.nih.gov

> I want to model the amplitude of the BOLD response, but not the duration.

Could you clarify a little bit? It's not clear to me exactly what your goal is at group level. If you just want to model the BOLD response amplitude, one possibility is to ignore the derivative part and run group analysis only one the effect from the 1st basis function. And this is what most people do.

Gang