Imagining is not seeing: lower insight-driven memory reconfiguration when imagining the link between separate events.

Gaining insight into the relationship between previously separate events allows us to combine these events into coherent episodes. This insight may occur via observation or imagination. Although much of our reasoning occurs in the absence of direct sensory stimuli, how mnemonic integration is accomplished via imagination has remained completely unknown. Here, we combined fMRI with representational similarity analysis and a real-life-like narrative-insight task (NIT) to elucidate the behavioral and neural effects of insight through imagination (vs. observation). Healthy participants performed the NIT in the MRI scanner and underwent memory testing one week later. Crucially, participants in the observation group gained insight through a video, while participants in the imagination group gained insight through an imagination instruction. Although we show that insight via imagination was weaker than insight via direct observation, the imagination group showed better detail memory. Moreover, the imagination group showed no representational change in the anterior hippocampus or increases in frontal and striatal activity for the linked events, as was the case in the observation group. However, the hippocampus and striatum were more activated during linking via imagination, which might indicate that their increased recruitment during imagination impedes concurrent mnemonic integration but may facilitate long-term memory.