The power of one’s social environment to modulate cognition is well documented, but the processes by which social experiences impact the cellular substrates of memory remain unknown. We show that social experience, but not physical stress, causes reactivation of fear engrams in the dentate gyrus of the hippocampus, and optogenetic stimulation of social ensembles containing these reactivated cells is sufficient to drive fearful behavior. This endogenous reactivation in the dentate gyrus during social stress is followed by a context-specific enhancement of fear recall and reinstatement. Our findings suggest that social interactions can reactivate pre-existing engrams and thereby strengthen discrete memories.
bioRxiv Subject Collection: Neuroscience