Episodic memories contain information not only about the content of an event, but about the temporal context in which the event occurred. Although the neural mechanisms responsible for encoding temporal information are poorly understood, several computational models have proposed that items are associated at encoding with a slowly evolving contextual representation and that this temporal context supports memory for item order at retrieval. We provided evidence for this hypothesis in a recent fMRI experiment, showing that multi-voxel activation patterns in the prefrontal cortex changed gradually over time during an encoding task, and that the degree of pattern change associated with a particular stimulus predicted subsequent memory for temporal context. The experiments proposed here apply this method of analyzing multi-voxel pattern change to the study of temporal context in two novel paradigms. In the first experiment, participants are scanned while encoding words in a verbal free recall task, with the aim of using PFC multi-voxel pattern change at encoding to predict temporal and semantic clustering at recall. In the second experiment, participants are scanned while encoding a series of pictures, and PFC multi-voxel pattern change is used to predict performance on a subsequent recency test. Understanding the mechanisms by which the brain represents and integrates contextual information over time is critical to understanding episodic memory, and the information to be gained from these experiments could eventually prove very useful in diagnosing and treating memory disorders.
The proposed project investigates the role of the prefrontal cortex in encoding temporal context information. The results of this project will have a direct impact on current models of episodic memory and may be useful for developing interventions targeting episodic memory deficits.