We have conducted an fMRI study in which each trial corresponds to the
viewing of two categories of 12 sec video clips, immediately followed by a
memory decision to make based on what has been seen at the very end of
each clip. We have constructed a statistical model including our two
categories of stimuli, in which each phase is modeled separately: activity
related to the viewing phase was modeled as an extended event of 12s
duration, whereas the response phase was modeled with a canonical hrf
(i.e. without specifying any duration) applied at the very end of the
video clip presentation.
In order to see which regions were more active during each of the two
phases, we performed a paired t test between contrasts related to each of
them. The results we have obtained are consistent with what we were
expecting, but we are still wondering if this comparison (between extended
events and more transient activity) is correct from a statistical point of
view. Does anyone know if this is a valid comparison to make?
Thanks a lot in advance,