Experience-dependent persistent Arc expression is reduced in the aged hippocampus.

Aging is typically accompanied by both memory decline and changes in hippocampal function. Lasting memory is thought to also require recapitulation of recent memory traces during subsequent rest-a phenomenon termed memory trace reactivation or replay. Replay becomes less synchronized in the CA1 region of aged animals, and while subtle, this deficit may have profound physiological consequences for driving plasticity. Importantly, spike timing changes during replay may impair the induction of plasticity-regulating gene products, such as activity-regulated cytoskeletal protein (Arc). To test this hypothesis, Arc transcription was assessed both during spatial exploration and subsequent memory-related replay in hippocampal CA1 of young and aged animals. A significant age-related difference was observed in the pattern of pyramidal cells expressing Arc during rest, supporting the hypothesis that altered plasticity-related cascade is a major consequence of the changes in coordinated activity that occur during consolidation in older animals.