Hi,

I have a question about the mean adjustment done in gPPI. I set P.contrast to the index of the effects of interest F-contrast (which I defined as [eye(nCondsAllRuns) zeros(nCondsAllRuns,nNuisanceRegr)]).

If you plot a regressor with its PPI regressor counterpart (from SPM.xX.X), should they both have a "zero" baseline? In the attached plot, I'm told that the one on the left looks like how it should be and the plot on the right looks suspicious and as if the adjustment were done over the entire time series rather than only on the events of interest. Is this grounds for concern?

Thanks very much in advance!
Gina