Dear SPMers:
I have a question regarding the appropriate ISI for a jittered event-related design. While scanning
with a TR of 2000ms I will be presenting visual stimuli for 1000ms that do not require an overt
response from my subjects. There are 66 unique visual stimuli that will each be presented one time
per run. The condition membership of each stimulus will be determined by behavioral ratings
acquired after scanning is complete.
My ISIs are drawn from a random exponential distribution with a minimum ISI of 1500ms (500ms
between trials) and a mean ISI of 3000ms. Does this sound reasonable or is there anything that I'm
missing?
Any help would be greatly appreciated as this my the first time I've used a jittered design.
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Andrew Engell
Human Neural Systems Laboratory
Princeton University
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