The paper by Fischmeister et al. 2016 (Cortex) analysed fMRI task-related connectivity patterns, for two tasks that relied vs did not rely on recursive reasoning. Namely, they found "increased connectivity within Default Mode Network (DMN) related brain areas during the representation of recursion, while non-recursive representations yielded increased connectivity within the Fronto-Parietal Control-Network".
This sounds to me a lot like a Psychophysiological Interactions (PPI) analysis, although the authors do not identify it as such. PPI can be defined as a technique that "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" (O’Reilly et al., 2012)
Could anyone explain whether the analysis reported in Fischmeister et al. is in a fact (a flavour of) PPI, and if not, how exactly it differs?