Spatio-temporal theta pattern dissimilarity in the right centro-parietal area during memory generalization

Generalization across past events may guide our action in novel situations. Although generalization is a fundamental memory process, its neural underpinnings are not fully understood yet. In the present experiment, we combined Electroencephalography (EEG) with multivariate representational similarity analysis (RSA) to examine in particular the role of spatio-temporal patterns of theta oscillations known to be important for associative memory processes, in memory generalization. We recorded EEG while healthy participants (n = 56) performed an acquired equivalence task. In this task, participants first acquired multiple associations among antecedent and consequent stimuli before they were required to transfer the acquired knowledge to novel stimulus pairs, thus probing memory generalization. Our behavioural data indicated that participants learned the initial associations well and transferred these associations successfully to novel test stimuli, demonstrating successful memory generalization. Our neural data revealed that, compared to mere memory retrieval, gener-alization was associated with significantly increased pattern dissimilarity of theta activity in the right centro-parietal area (electrodes P4 and P6). This pattern was specific to theta oscillations and not observed in other frequency bands. Our findings suggest an important role of theta oscillations in memory generalization, potentially serving the reactivation and integration of distinct events that enable the generalization across experiences.