Dear SPM experts,
I thought that perhaps you could help me with one 2nd level analysis. In the 1st level, I specified 2 conditions (C1,C2) and a Baseline (exhaling). I want to remove the effects of exhaling in C2 from the C2>C1 contrast and for that I think I could use as an exclusive mask the contrast baseline>C2 in the results from the 1st Level.
The difficulty arises when trying to implement the exclusive masking at the 2nd level. I think one way to go could be to save the thresholded image for each subject of the C2>C1 contrast with an exclusive mask of the baseline>C2 contrast. Then create a binary mask for each subject and add the masks of all subjects to create a new mask that can be used as an explicit mask in the 2nd level.
Which threshold should be used in ImCalc to get the binary mask of the thresholded image from each subject? Would this procedure be statistically correct?
Thank you in advance for your assistance.
Best wishes,
Noelia
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