I am using the gPPI toolbox, but we have a bit of an unconvential fMRI design, and I am not sure how to specify things.
We have an fMRI design in which we model how many stimuli are presented {1,2,3} and have a range of parametric modulators (also including behavioral measures) at different timepoints of a trial.
We are mainly interested in the effects of the parametric modulators and their interactions, and use those as our main 'contrasts' in SPM. We do not have any traditional contrasts comparing conditions.
We would like to check if connectivity differs depending on the parametric modulators (and then especially an interaction term between two parametric modulators), and I am not sure if one can check this with the gPPI Toolbox? And if so, what approach to follow (e.g. how to define the task and contrasts). Would the results be meaningful at all?
Any help is very much appreciated. Thanks a lot in advance.

Hi,

gPPI should be able to generate and estimate the model with parametric modulators. For the contrasts, you want to use contrail to identify the string in the column names that comes after the task, I believe its "x...".

Yes. The results would be meaningful. An example can be found in: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4002228/

Best,
Donald