Final seminar: Zhenghao Liu – Temporal dynamics of memory-integration processes

Commentator: Prof. Lluís Fuentemilla, Universitat de Barcelona

Abstract

Episodic memories can extend beyond direct experience. For example, seeing a woman walking a dog and later seeing a man walking the same dog, you may infer that the man and the woman are connected. These inferences, which are crucial for making novel decisions and extending knowledge to new situations, are thought to rely on memory integration mechanisms. Two mechanisms have been proposed to support memory integration. The integrative encoding account suggests that novel experiences can trigger the reactivation of past events, promoting the integration of new information within pre-existing knowledge structures. A complementary view holds that memory integration can be accomplished on demand as needed. Memory integration is thus accomplished by flexibly retrieving and recombining information from distinct memory representations.

The present thesis employed time-resolved multivariate pattern analysis and representational similarity analysis to measure memory reactivation during new learning and tests of associative inference. This approach allows us to uncover the temporal dynamics of the processes involved in memory integration and examine its boundary conditions. Study 1 investigates the temporal dynamics of integrative encoding and shed light on inter-individual differences in the capacity to integrate memories across events.

Study 2 examines how memory-integration processes are influenced by the encoding context and Study 3 the role of both context and semantic schema in memory integration. Finally, Study 4 investigates how memory is supported by both integrated and separated memory representations.

With the completion of these four studies, the present thesis provides novel evidence for the processes supporting memory integration and elucidates potential boundary conditions integrating memories across different events. In conclusion, memory integration is a multifaceted phenomenon that is affected by processing at several mnemonic stages and by different boundary conditions. The resulting integrated and separated representations are adaptively used to support goal-relevant behaviour, highlighting the flexibility and complexity of memory functions.