I have questions about a modeling process related to my experimental design.
The experiment consists of three runs.
The first run is composed of 12 condition A blocks and 12 fixation blocks.
The second run is composed of 6 condition B blocks, 6 condition C blocks, and
12 fixation blocks.
The third run is equal to the second run.
Subjects performed the identical tasks in every conditions, but the contexts
provided with the tasks were manipulated differently depending on condition
A, B, and C. During the fixation blocks, subjects were instructed to see the
cross placed in the middle of the screen.
Here, I would like to make all the comparisons among given conditions such as,
A-B/ A-C/ A-fixation/ B-C, etc..
Is it possible to consider all the combinations among conditions in a one fMRI
modeling? Or should I seperate it into two fMRI modelings (one for run 1, the
other one for run2 and run3)?
And if the first case of modeling is plausible, how can I make a contrast among
conditions? if you look at the contrasts below, which case is the right one?
A Fix B C Fix B C Fix
1. A-B 2 0 -1 0 0 -1 0 0
2. A-B 1 0 -1 0 0 -1 0 0
Best regards,
Yoonkyung Chung
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