Dear SPMers,

Thanks for reading. I want to ask a question about PPI analysis.

In my experiment, I have two factors A (condition A1 and A2) and B (condition B1 and B2). Using the conjunction analysis, three brain areas were found activated both in the contrast A1>A2, and B1>B2. Now, I want to perform a PPI analysis to find the causal relationship between the three brain areas. But, I’m a little confused about how to construct the GLM of PPI with the conjunction results. Should I first construct two GLMs of factor A and factor B separately, and then do the conjunction analysis in the 2^nd level analysis? Is this doable? Do you have better suggestions?

Thank you very much for your time and consideration. Look forward to your reply!

Best wishes!

                                                       Sincerely yours, Lisa Wong