(A) study on the differential roles of hippocampal subregions in memory integration

Abstract

the CA3 / DG mainly processed the direct associations between objects, while CA1 mainly processed the integration information between indirectly associated objects. Additionally, there was greater correspondence between the representation of the dorsolateral prefrontal cortex (dlPFC) and the representations of the CA1 compared to the representations of the dlPFC and the CA3 / DG. These results demonstrate the differential roles of the hippocampal subregions during memory integration and suggest that the interaction between the CA1 and the dlPFC mainly subserves memory integration based on inference processes.

The memory integrating process, in which new information is integrated into prior knowledge, is critical for our adaptive behaviors. Previous studies have shown that the hippocampus is involved in memory updating processes and have suggested that the hippocampal subregions might have different roles during memory integration processes. However, the neural information processing underlying the memory integration between prior and newly learned memories in the hippocampus remains unclear. To address this, we monitored the neural representational changes during memory integration using event-related functional magnetic resonance imaging (fMRI) and multi-variate analyses. In the experiment, participants were asked to conduct two consecutive learning sessions and one retrieval session. During the first learning session, they learned the first set of common object pairs. Following the first learning session, they learned the second set of the object pairs, which partially overlapped with the first set of object pairs. Using trial-by-trial similarity analysis, we found that the hippocampal representations of associative information dynamically changed during the memory integration process. Moreover, the hippocampal subregions supported different associative information