Dear all,
I have a question about doing 2-by-2 analysis on fMRI data acquired in an experiment with an event-related and a blocked design respectively on 2 groups of subjects. That is, 2 groups of subjects (group A and B) did 2 different tasks, task 1 (event-related task) and task 2 (blocked task). Can I set up a 2-by-2 comparison in order to see the interaction effect between tasks and groups? Will I run into any trouble with the concern that the signal strength obtained in an event-related analysis is intrinsically different from that in a blocked analysis, which may make such a comparison problematic?
If so, I thought of using a combined model to model trials as both single events and epochs [example work refers to "Mechelli et al. (2003). Comparing event-related and epoch analysis in blocked design fMRI. NeuroImage (18) 806-810."]. But unfortunately, my block task is actually a Continuous Performance Task which does not have various ISI, i.e., the ISI is always 1000ms and stimuli presentation time is always 500ms. So I think I cannot use Mechelli et al.'s approach to solve my problem...
Welcome any thoughts and comments! Thank you for your help!
Best wishes,
Meikei
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