I have a question about my fmri design and I need some help.
My experiment had two runs per subject. In the first run, subjects listened in blocks feedback of the own heart, either in sync with the actual heartbeat or asynchronously. At the end of each block, they responded whether this was their own heart or someone else’s. This yield 4 regressors for the first run: Sync (block) Async(block) Mine(Event) Other(Event).
In the second run, the subjects listened to feedback again, either sync or async and responded whether their attention was shifted internally or externally. This yield 4 regressors for the first run: Sync (block) Async(block) Internal(Event) External(Event).
Is it possible to create a design matrix for each subject, such that I can estimate the effect of mine/other responses from one run, the effect of internal/external attention in the other run, and then I can substract the effect of attention from mine/other responses.