I am running into some difficulties when determining which regress_basis_multi option to use for our analysis. The data is from a social incentive delay (SID) task where people anticipate varying levels of social reward or no reward, and depending on a successful response to a cue, receive that reward or not. Because there are individual differences in response timing, we used dmBLOCK. However, after extracting activation in our primary ROI, we are getting negative beta values in all conditions of interest (when based on our past samples/SID literature we would expect to get positive values). In a previous sample using the same task, we ran into this same issue and found that when WAV was used (outside of proc) the values were positive but were negative when using dmBLOCK, which made us wonder whether there was some sort of scaling issue when using dmBLOCK.
I am wondering if/why dmBLOCK could be contributing to negative values and if you have any recommendations for how to possibly correct this?