I posted this message last month but since I didn't get a reply I decided to try my luck again and re-post it.
If I include the spatial and temporal derivatives in my design matrix, and tell SPM to generate the contrasts for me (1st level), it shows me two types of contrasts: F-tests, which include condition plus derivatives, and t-tests which are defined separately for a given condition and for its derivatives. Does it make sense to perform t-test on, say, the spatial derivative alone? What would this tell me?
I've also seen some researchers that just include the derivatives in the design matrix but do nothing with them, do we gain anything by doing this, or could we just as well not include the derivatives if they aren't going to be used anyway?
Thank you very much in advance,