Hello Y'all,
I'm doing a pain experiment in the scanner in block design. The subject first rates his resting pain, then experiences an external pain eliciting stimulus, then rates that pain on a 0 to 10 scale, then he rests, and then rates this resting pain and so on. So, the design looks like this:
rest rate1 pain rate2
rest rate1 pain rate2 ...
The problem is that a small residual pain lasts beyond the task and extends into the rest period. And this residual pain seems to increase after each block. So, the pain rating right after 'rest' keeps increasing with the blocks.
What will be the best way to control for the residual pain in the fMRI analysis? I can covary out the rating during rate1 but is there a simpler or better way?
Thanks and regards,
G
