This question is more of a theoretical question than one of the mechanics of AFNI. When IRFs are computed and plotted, what is one to think of (large) significant differences that occur between conditions on the 1st TR? That is - there is a large difference even before "things can get going". I know the shape of an IRF over TRs is identical to what one would get if you just deviated each TR from a baseline image preceding or at stimulus onset, but, when you compute change scores, of course, the data will necessarily be brought together at the baseline. So - I know the IRFs are "modeling" the data, with some sort of correction for baseline, but I guess I don't really trust significant differences that are there on the 1st TR? Any thoughts appreciated, thanks, mb