Pattern integration and differentiation: Dual process model of episodic memory

The role of precise timing in episodic memory remains obscure. We showed 139 participants episodes consisting of objects, and tested subsequent memory for the precise timing and order of the objects and episodes. Temporal compression of the episode enhanced memory for relative but not absolute timing of the objects' presentation and their order. Conversely, temporal expansion between neighboring episodes was associated with successful memory for episode order. fMRI in 36 participants revealed that temporal compression of the episode was associated with more similar activation patterns within episodes in several brain regions including the posterior hippocampus. However, the activation pattern in the anterior hippocampus and other brain regions became more unique with temporal expansion between neighboring episodes. We propose that human episodic memory relies on two fundamentally opposite processes: pattern integration helps strengthen the relationship between the items that make up an episode and pattern differentiation keeps different episodes apart.