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Episodic memory is a type of long-term memory that allows individuals to recall specific personal experiences tied to a particular time and place. While episodic memories have traditionally been studied in isolated contexts, emerging models suggest that social interactions play a critical role in shaping memory formation, consolidation, and retrieval, highlighting the need to investigate memory processes within interpersonal and dynamic social environments. To examine the neural basis of social interactions in real-life, recent advances in neuroscience propose that assessment of neural activity should not confined to individual brains but extend to the coupling between the brains of interacting partners. Measuring inter-brain coupling offers a promising measure of the strength of social connections and has been shown to predict social learning outcomes. However, despite its importance, there is a notable lack of research exploring the relationship between inter-brain coupling and episodic memory within authentic, emotionally charged interpersonal contexts. To address this gap, this study investigated inter-brain coupling during memory sharing. We focused on inter-brain coupling in the Dorsolateral Prefrontal Cortex (dlPFC), a region associated with emotion regulation, and the Inferior Frontal Gyrus (IFG), a key component of the Mirror Neuron System involved in empathy and social cognition and tested their association with the retrieval of memories recounted in social interactions.
Using functional near-infrared spectroscopy (fNIRS), we examined inter-brain coupling in 26 dyads during an emotional memory-sharing task, in which one participant recounted a personal emotional experience while the other listened. To assess memory retention, listeners were asked to recall details of the shared memory three days post-interaction. Given that inter-brain coupling is thought to reflect the degree of social and cognitive alignment between interacting individuals, we hypothesized that greater inter-brain coupling during the interaction would predict enhanced memory retention of the shared narratives. Results revealed that compared to pseudo dyads, real dyads showed higher inter-brain across all regions. Critically, inter-brain coupling in the right dlPFC (particularly BA46) was positively associated with memory recall, while no significant association was found in the IFG. Despite the small sample size, this study highlights the role of inter-brain coupling in the dlPFC in episodic memory during real-world social interactions. It provides new insights into the neural mechanisms of memory sharing in naturalistic settings, emphasizing how social interactions shape memory processes.