Milivojevic, B. | bioRxiv Science

bioRxiv2023

Causal role of the angular gyrus in insight-driven memory reconfiguration

Maintaining an accurate model of the world relies on our ability to update memory representations in light of new information. Previous research on the integration of new information into memory mainly focused on the hippocampus. Here, we hypothesized that the angular gyrus, known to be involved in episodic memory and imagination, plays a pivotal role in the insight-driven reconfiguration of memory representations. To test this hypothesis, participants received continuous theta burst stimulation (cTBS) over the left angular gyrus or sham stimulation before gaining insight into the relationship between previously separate life-like animated events in a narrative-insight task. During this task, participants also underwent EEG recording and their memory for linked and non-linked events was assessed shortly thereafter. Our results show that cTBS to the angular gyrus decreased memory for the linking events and reduced the memory advantage for linked relative to non-linked events. At the neural level, cTBS targeting the angular gyrus reduced centro-temporal coupling with frontal regions and abolished insight-induced neural representational changes for events linked via imagination, indicating impaired memory reconfiguration. Further, the cTBS group showed representational changes for non-linked events that resembled the patterns observed in the sham group for the linked events, suggesting failed pruning of the narrative in memory. Together, our findings demonstrate a causal role of the left angular gyrus in insight-related memory reconfigurations.

neuroscience↗

bioRxiv2021

Hippocampal reconfiguration of events in mnemonic networks

It is widely assumed that episodic memories are not stored in isolation but rather in dynamic event networks. However, the mechanisms of the underlying dynamic of these representations, in particular how such networks are updated, remain elusive. In this study, we investigated the reconfiguration of events into event networks in the hippocampus by presenting new events that could update either one of two competing narratives. During the first session, participants viewed four animated movies, each representing a distinct narrative; two distinct narratives from the Jones family and two distinct narratives from the Smith family. During the second session, we re-exposed participants to snapshots of these narratives along with snapshots of new events from one of the two families, allowing updating of the acquired event networks of that family. Our findings show that the hippocampus integrated new events that relate to the old family, and then integrated these new events with the corresponding old events. Furthermore, hippocampal representations of the events within a narrative became better integrated after updating. Our results shed new light on the neural mechanisms underlying flexible mnemonic updating with realistic events and further advance our understanding of the structured reconfiguration of event networks in memory.

neuroscience↗