Linking new information to a short-lasting memory trace induces consolidation in the hippocampus

Novelty often influences the retention of nearby weak and transient memory traces, yet its precise role in shaping long-term memory storage remains elusive. Here, we demonstrate that a short-lasting memory is stabilized into a long-lasting one when new information is linked to the weak mnemonic trace in rats, resulting in the formation of long-term memories that are recalled together. An increased overlap between neuronal ensembles and <i>de novo</i> protein synthesis in the dorsal CA1 region of the hippocampus (dCA1) mediates this process. This intricate interconnectedness relies on both temporal and contextual relations between experiences, enhancing the adaptive value of memory consolidation. Finally, this phenomenon is negatively affected by aging, which is associated with reduced ensemble size after novelty exposure and diminished overlap between ensembles in aged dCA1. These findings provide valuable insights into the selectivity and malleability of memory consolidation and its decline during aging.