Psycho-physiological interaction (PPI) is a functional brain imaging analysis method. It estimates context-specific changes in effective connectivity (coupling) between a region of interest (seed) and other brain regions. Thus, PPI analysis identifies brain regions whose activity depends on an interaction between psychological context (the task) and physiological state (the time course of brain activity) of the seed region.
References
Psychophysiological Interaction Wikipedia(Text) CC BY-SA