In the present study, we combined resting-state and task-based fMRI to assess the internal orienting and hippocampal coupling hypotheses regarding DMN involvement in episodic encoding and retrieval. To ensure regional overlap between the DMN and episodic memory activations, we first identified the DMN based on a resting-state coherence analysis in one group of participants. Next, we probed the identified DMN regions for their involvement in episodic encoding and retrieval in a different group of participants. To test the internal orienting and hippocampal coupling hypotheses, we used a memory task including encoding and retrieval of both internally-generated (internal condition—Int) and externally-presented (external condition—Ext) events (Figure 1). During Int-Enc, subjects imagined sounds or pictures associated with a cue word (e.g., “duck”). During Ext-Enc, they listened to sounds (e.g., the “quack” sound of a duck) or observed pictures (e.g., picture of a duck) associated with the cue word. The next day, participants' retrieval of the events was tested unexpectedly with a source memory task. This paradigm allows the comparison of successful memory activations for internal and external events during both encoding and retrieval phases, and thereby, for a direct test of the internal orienting and hippocampal coupling accounts.
