Schedule of Events | Symposia

Graduate Student Award Winner

Integration and differentiation of object representations based on contextual association across the medial temporal lobe subregions

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

Ji Sun Kim¹ (kimjisun1006@gmail.com), Jae Min Seol¹, Choong-Hee Lee², Inah Lee¹, Sang Ah Lee¹; ¹Seoul National University, ²Institute for Basic Science (IBS), Suwon, Korea

Episodic memory is constructed by binding together the representation of objects with that of the spatial context. While increased neural representational similarity between items sharing the same context is useful for memory integration, differentiating between them is also important for memory precision. To explore how the medial temporal lobe (MTL) balances these complementary processes, 30 participants were trained on object-place associations across four transparent VR houses surrounded by distinct distal landmarks. The next day, they performed an fMRI task in which they saw each object presented on a blank screen and then navigated to the associated house. We compared representational similarity between objects from the same vs. different house (as well as corners and views). Memory performance was correlated with increased representational similarity between objects from the same house in the entorhinal cortex (EC) but with decreased representational similarity in the perirhinal cortex (PRC) and subiculum. These findings suggest complementary roles of integration across shared contexts in the EC and differentiation of objects in the PRC for memory binding in the hippocampus. Differentiation in the PRC, subiculum and CA3DG was also correlated with memory for objects sharing similar landmark views. Conversely, at finer spatial scales (corners within houses), integration in the posterior CA1 facilitated better memory retrieval, consistent with its role in associative memory and fine-grained spatial processing in the posterior hippocampus. These findings demonstrate the importance of both integration and differentiation underlying episodic memory, with distinct MTL subregions specializing in binding objects across contexts at different spatial scales.

Topic Area: LONG-TERM MEMORY: Episodic