Causal network structure predicts memory organization and neural reinstatement across events

Causality appears to play a central role in narratives, but how it influences later memory and how the brain creates causal structure is unclear. Here, participants watched and recalled a TV show featuring five temporally interleaved storylines during fMRI, and different participants determined cause-effect relationships between each pair of events. Behaviorally, causality significantly influenced recall organization, with the top cause-effect relationship predicting recall transitions best among several predictors. Neurally, across-event patterns in regions of the default mode network (DMN) reflected causal structure, and DMN patterns at event boundaries specifically reactivated prior, causally related events, suggesting causality predicts our ability to stitch together related events across temporal gaps. Additionally, causal network distance between successive events predicted the strength of DMN pattern changes across event boundaries, suggesting causality also predicts stronger representational switching between unrelated events. Together, these findings suggest that DMN regions perform the mechanisms required to build the complex network of causal associations underlying the comprehension and recall of real-world memories.