Periodically reactivated context memory retains its precision and dependence on the hippocampus

Hippocampus is hypothesized to play a temporary role in the retrieval of context memories. Similarly, previous studies have reported that the expression of context memories becomes more generalized as memory ages. We report, first, that contextual fear memory expression changes from being sensitive to dorsal hippocampus inactivation by muscimol at 2 days post-conditioning, to insensitive at 28 days, and second, that over the same period rats lose their ability to discriminate between a novel and conditioned context. Furthermore, we show thatrepeated brief memory reactivation sessions prevent memory from becoming both hippocampus-independent and generalized. (C) 2011 Wiley Periodicals, Inc.