We recently received a revise-and-resubmit for a paper submission. One of the reviewers made a couple of comments regarding our contrasts. I am hoping to get some help from fellow SPM users here so I can adequately address these comments.

In a go/nogo task, we used Go>Nogo contrast to get activation to response (contrast 1), and Nogo>Go to get activation to response inhibition (contrast 2). Next, we performed 2 multiple regressions, each using a different clinical measure from our participants as the independent variable and activation from the contrast as the dependent variable. The two multiple regressions showed significant activations which partially overlapped. We explored this overlapping regions in an ROI analysis afterward. Regarding our choice of contrasts and the overlap, the reviewer said "the response contrast and the response inhibition contrast are the opposite of the same contrast" and listed this as one of the issues. I don't really see a problem with this as response and response inhibition are the opposite actions. I acknowledge that the brain activity for the overlapping region in one contrast is exactly as the other contrast with the sign reversed. Does anyone see a methodological/theoretical issue with this contrast selection?

Since we have overlapping activation, the reviewer also suggested doing a dysjunction analysis, presumably the opposite of the overlap. I'm not sure how to do this dysjunction analysis. I'd appreciate any suggestions you may have.

Thank you!

Miranda