Hi Michael,

When you select the "PPI interaction with other sources" and select the M1 ROI you are performing a Physio-Physiological interaction where the M1 region acts as the interaction term, and this will be performed for each of the ROIs in your "sources" list. When, in your second-level analyses you select another source X, your will be exploring whether M1 modulates the connectivity between X and every voxel (for seed-to-voxel results) or between X and every other ROI (for ROI-to-ROI analyses). 

If, instead, what you intended to do was exploring whether the connectivity between M1 and other regions/areas is being modulated by your task condition (Psycho-Physiological interaction) then simply select the "PPI interaction with task effects" option, and then in your second-level analyses simply select the M1 source, and your desired task/condition.  That will be exploring whether the chosen task effect modulates the connectivity between M1 and every voxel (for seed-to-voxel results) or between M1 and every other ROI (for ROI-to-ROI analyses).

Hope this helps
Alfonso

Originally posted by Michael King: