Biomedicine Seminar

Abstract:
The hippocampus plays a crucial role in memory processing. Recent studies in both humans and rodents have revealed that the hippocampus is a heterogeneous structure, with distinct gene expression patterns, circuit organization, and functions along its longitudinal axis. However, how different hippocampal regions—including the dorsal, intermediate, and ventral hippocampus in rodents (corresponding approximately to the posterior, intermediate, and anterior hippocampus in humans)—communicate and cooperate to support memory remains poorly understood.

In this seminar, I will present our investigation of intra-hippocampal circuit organization and its role in aversive episodic-like memory using a mouse model. Episodic-like memory refers to memory for events that contain contextual information about place, time, and the individual involved. Our circuit analysis identified a population of CA3 neurons in the intermediate hippocampus (iCA3) that connects the dorsal and ventral hippocampus. In vivo calcium imaging revealed that iCA3 neurons were strongly activated during re-exposure to the context associated with an aversive event. Moreover, suppressing their activity weakened the defensive response induced by aversive memory during extinction phase, suggesting that iCA3 activity contributes to the persistence of the aversive memory. Together, our findings demonstrated that iCA3 neurons play a crucial role in maintaining aversive memory and may serve as a functional link between distinct hippocampal regions, supporting their contributions to stabilize episodic-like memory.