Hi experts,
I have a decision making paradigm with some basic questions and hope someone to clarify my concept. You can just answer yes or no and it would be better if you can tell me why.
Suppose in a single trial, subjects have to watch a picture for 4 seconds (STIM) and, after 6-sec interval(INT), see a cue for 4 sec (DECISION) and then press one of the two response buttons. That is, each trial equals to 4+6+4=14 sec. We're interested in STIM- and DECISION-related activations.
Herein I have several questions:
(a). Suppose my TR is 2 sec and ITI is always 6 sec. In this case, a trial plus an ITI is 20 sec, which equals to 10 times the TR. This setting is inappropriate because, with a TR of 2 sec, the scans will always capture the same time points of each trials and can not depict the whole hemodynapic pictures. Am I right?
(b). Suppose my TR is 2 sec but I let my ITI jitters between 6 and 8 sec (6, 6.5, 7, 7.5, or 8 sec). Now it is acceptable. Am I right?
(c). Suppose my TR is 3 sec and the ITI is always 6 sec. Identical to (a), a trial plus an ITI is 20 sec, but now it is not a multiple of the TR. Then it is also acceptable. Am I right?
(d). Suppose my TR is 2 sec but I let my INT jitters between 6 and 8 sec (6, 6.5, 7, 7.5, or 8 sec). It is also acceptable. Am I right?
(e). Compared with (c), we can say that (b) and (d) is better because there is jittering. Am I correct? (To be honest I'm not sure if jittering is a must in a paradigm) Moreover, any difference between (b) and (d)?
Thank you.
Mark
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