ISI and stim presentation

hello, i’m new in fMRI, designing my first ER-fMRI experiment. but i don’t really know how to calculate the fixed ISI, or how to make it jitted when designing. the ISI used in previous experiments alike varied from 1.5s to quite long ones like 15 to 20s (i wanna make it as short as possible in mine). what i wanna know is how long on earth i should use as ISI if we only consider analysing. and it seems that if i want to design the stimuli presentation, using RSFgen or “”, the ISI need to be known in advance. is that right?
and by the way, which is the better function to design the stimuli presentation, RSFgen or “”?
sorry for bothering and thank u so much if u can answer my questions.
looking forward to hearing you back.

The design can be set up around average ISIs, and can be used to also specify
accompanying minimum and maximum values for that
ISI type, depending on the chosen distribution of
the ISI times. Consider “Advanced Example 2” from -help, which shows defining
timing (stim and/or ISI) classes with min/mean/max

Note that if a uniform distribution is chosen, the
mean should equal the average of the min and max,
if specified.

  • rick