Schedule of Events | Symposia

Representation of spatial boundary-dependent episodic memory segmentation in the human subiculum

Poster Session C - Sunday, March 30, 2025, 5:00 – 7:00 pm EDT, Back Bay Ballroom/Republic Ballroom

Hye Ja Kang¹ (piotwo412@snu.ac.kr), Jung Han Shin¹, Yu Jin Rah¹, Sang Ah Lee¹; ¹Seoul National University

To efficiently remember long and complex episodes, it is useful to segment them into smaller chunks. Previous studies have shown that sharp contextual changes mark event boundaries that are processed by the hippocampus. Here we investigated the change in hippocampal representations across a spatial boundary within a single context (without a sharp contextual shift) and its potential role in the adaptive segmentation and organization of episodic memory. 61 participants in the fMRI scanner watched as five objects were placed into baskets scattered around a virtual room; after a delay, they re-enacted the episode using a controller. In the boundary condition, a low spatial boundary divided the room into two sides, with half of the event sequence occurring on one side and the other half on the other. First, we found that the event immediately following boundary crossing was better remembered compared to an event in the same temporal position in the no-boundary condition. During encoding, activation in the subiculum was significantly higher in the boundary than in the no-boundary condition. Furthermore, boundary and no-boundary trials showed different neural pattern similarity dynamics upon“crossing” the boundary. The difference between pre-and post-boundary event representations across conditions was positively correlated with the degree to which the spatial boundary improved memory. These findings suggest that crossing a spatial boundary induces representational changes in the subiculum that signify the organization of experience into discrete segments in episodic memory.

Topic Area: LONG-TERM MEMORY: Episodic