Dear All,

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,