Dear forum members,

while I looked at the gPPI analysis results for an N-back block paradigm, I also checked the condition-specific gPPI contrasts versus baseline, which should be valid according to previous postings in this forum.

To my surprise, the negative contrast (i.e. Baseline > Condition) produced extensive effects in ventricular areas.

Therefore, I suspect that I misspecified my model, but I do not see where: The model included three regressors for the active task conditions, as well as an additional regressor for the instruction phases before each task block, while fixation cross phases between task blocks  were treated as implicit baseline. . Accordingly, the gPPI model additionally included 4 PPI terms and the seed time course.

Any ideas?

Thanks in advance,

Marcel