Dear Donald and other gPPI users,

I am planning to investigate the relationship between 3 ROIs during a block designed task. I was thinking about using physio-physiological interaction or psycho-physio-physiological interaction analyses, but I am a bit confused by the exact way to handle this with gPPI, and by the interpretation of such analyses. I am using the PPPI_v2012_1_22 version of gPPI.

To be sure I am on the good track, can anyone confirm my thoughts about these?

1) Conceptual questions:

a- The physio-physiological interaction analysis will constrain my PPI analysis to the relationship between 2 (or more?) defined ROIs. Am I right?

b- The psycho-physio-physiological interaction analysis will explain how two regions interact (A and B) to affect a third region C, right? In that case, are all possible interactions between these 3 regions valid? i.e. the relationship between A and B to affect C, but also the relationship between B and C to affect A, and the relationship between A and C to affect B?

2) Methodological questions:

a- For these analyses, I understand I need to introduce a second (and a third?) VOI in the wrapper, introduce their names in ‘Region’, choose the appropriate analysis ('psy' or ‘psyphy’). However, while it seems clear for the physio-physiological interaction analysis, I am confused about the VOI2 option for the psycho-physio-physiological interaction analysis. Should I create a VOI3 field? 

b- For both analyses, how to feed the wrapper correctly?

c- Once everything is set, what would be the outputs, and how should they be used? To be more clear, in the classic psycho-physiological interaction analysis the toolbox creates a contrast that can be used in a new GLM analysis for within/between groups investigations. But what will happen with the physio-physiological interaction and with the psycho-physio-physiological interaction analysis?

d- in the case of the psycho-physio-physiological interaction analysis, if any possible interaction (see question 1b) is possible, how do I know which one is which one?

I am sorry for these questions, but I could not figure out how to do it with the PPPI_Manual_v7_12 and want to be sure of what Im doing. Is there an updated version of the Manual that I missed somewhere?

Thanks for your time!

Cheers,

Yann