Hippocampal and Cortical Contributions to Human Episodic Memory

Abstract

Episodic memory refers to our cognitive ability to remember past experiences. The hippocampus (HPC) is hypothesized to be a central hub region that supports both episodic memory encoding and retrieval by acting as an indexing system that points to specific information stored throughout the cortex. This dissertation investigated the neural mechanisms underlying episodic memory, with a focus on the hippocampus (HPC) and its interactions with cortical regions such as the ventromedial prefrontal cortex (vmPFC) and angular gyrus (AG) across three functional neuroimaging studies. Chapter 2 investigates the neural correlates of episodic memory recall and counterfactual thinking, revealing that the HPC and vmPFC are more strongly engaged during memory recall while the AG is more involved in recombining memory elements for mental simulations. Chapter 3 examines how schema knowledge influences encoding in younger and older adults, showing a memory-boosting effect of a vmPFC-HPC interaction present in both age groups and an effect of AG-HPC interaction only in the older age group, reflecting older adults’ compensatory use of sematic knowledge. Chapter 4 demonstrates that hippocampal interactions with cortical representations during encoding predicted conceptual and perceptual memory in a transfer-appropriate manner. These findings support the idea that the HPC acts as a central indexing system with extensive functional connections with the cortex. In addition, this dissertation also presents several methodological advancements for cognitive neuroscience research, such as a trial-level representational similarity analysis and enhanced models for assessing inter-regional interactions. This dissertation research contributes to a deeper understanding of the intricate coordination between the HPC and cortical regions in enabling episodic memory.