Cluster-size for subtraction condition

Hello,

I have two group activation maps at two different conditions. 3dClustSim was used to obtain cluster-size for the individual group maps. How can I calculate the cluster-size for the difference map (activation map 1 minus activation map2)?

Thank you for your help and suggestions.

How can I calculate the cluster-size for the difference map (activation map 1 minus activation map2)?

What is your intention to show the difference map? Making inference regarding the difference between the two conditions?

Yes.

In your original population-level analysis, directly obtain the contrast between the two conditions and then make inference.

Sorry, I may not have explained my query clearly. Two scans were performed in which subjects performed the same task. The condition was ON during one scan, and OFF during the other. We used 3dClustSim to calculate cluster size for the ON and OFF scans separately. Now we want to calculate the cluster size for on minus off activation map and am looking for some advice on that.