Thalamo-Cortico-Hippocampal Connectivity Signatures of Durable Memory Formation for Complex Narrative Events

Recent frameworks of naturalistic memory encoding emphasize coordinated interactions between the hippocampus and the default mode network (DMN), especially at event boundaries that segment continuous experience. Notably absent from these accounts, however, is the thalamus—now increasingly recognized as an integrative hub with wide-ranging relevance for memory. Here, we expand existing hippocampal-DMN models of event cognition by explicitly incorporating thalamic circuitry and dynamics, with a focus on functional connectivity (FC). We reanalyzed a previously acquired fMRI dataset in which participants viewed two animated movies and subsequently recalled them either immediately or after a 2-day delay. Combining naturalistic event-based analytic approaches with contemporary Bayesian multilevel modeling, we quantified how FC among the thalamic subnuclei (anterior, mediodorsal, and lateral geniculate), hippocampus, and DMN relates to subsequent event memory. Our analyses revealed robust thalamic connectivity signatures predictive of durable memory encoding. Hippocampal–anterior thalamic FC at event boundaries was associated with better recall at 2-day delay. Conversely, thalamo–DMN FC at those boundaries generally corresponded to poorer delayed recall performance. Weaker but convergent patterns also emerged across the full encoding period: hippocampal FC with the anterior thalamus and lateral geniculate nucleus covaried positively with the richness of retrieved event details, whereas mediodorsal thalamus–DMN FC selectively predicted reduced detail following delayed retrieval. These findings identify thalamo-hippocampal and thalamo-cortical dynamics as candidate contributors to the formation and longer-term stability of episodic memories. More broadly, they position the thalamus as an active participant in shaping how complex real-world experiences are transformed into lasting mnemonic representations.