PROJECT SUMMARY/ABSTRACT From an early age, episodic memory supports critical functions such as decision-making in the present, future thinking, development of the self, and social interaction. Episodic memory is not only highly vulnerable to neurological insult, impairments are also prevalent in various neurodevelopmental disorders and neuropsychiatric conditions. There are profound negative consequences for later academic outcomes and socioemotional well-being associated with early disruption of episodic memory function but effective interventions in are scarce. Given that structural and functional brain maturation provides key constraints on memory function and their malleability to interventions, the neural basis of episodic memory development has become an increasingly important field of study in recent years. However, pediatric neuroimaging studies that bridge the gap between the highly controlled laboratory environment and real-life memory function are virtually absent, thereby failing to provide guidance for effective interventions. Recent neuroimaging work in adults shows great promise to overcome this limitation by utilizing novel tools to extract neural activity patterns from electroencephaolographic (EEG) and functional magnetic resonance imaging (fMRI) signals elicited during perception and recall of complex, dynamic, and multi-sensory naturalistic events, such as filmed, written, or spoken stories. The overall objective of the proposed project is to validate this new approach for the study of naturalistic memory in the transition from early to middle childhood—an age period that is characterized by rapid improvement in episodic memory function. Fifty 5-8-year-old children will view a 33-min movie clip and then verbally recount its content. Capitalizing on the high temporal resolution of scalp EEG, this study aims to replicate 3 key findings from previous work in adults: (1) Show that continuous experience is divided into discrete events by identifying perceived boundaries between events as rapid shifts in the stability of EEG activity patterns. Representational similarity analyses will be used to compare the stability of children’s brain activity patterns within events vs. across event boundaries. Pattern similarity is predicted to be higher within the same event than across different events. (2) Test whether boundary detection triggers rapid replay of just- encoded events. Event reinstatement upon boundary detection will be quantified by comparing across- boundary similarity for pre-boundary events that are later remembered vs. those that are later forgotten. Relatively greater similarity is expected between pre- and post-boundary EEG patterns if the pre-boundary event is later successfully recalled. (3) Establish to which extent movie viewing and later spoken recall elicit similar patterns of event-specific EEG activity. Viewing-to-recall correlations of EEG patterns should be greater for matching than nonmatching events. This res...