The process by which reactivated long-term memory becomes temporarily sensitive to amnestically active agents that effectively consolidate memory. This phenomenon was first described more than 50 years ago, but it did not fit into the dominant paradigm that consolidation occurs only once for each element of long-term memory. Learning and memory are usually described as going through a set of phases. There is a learning or coding phase in which information is acquired, a stabilization phase in which certain mechanisms are involved to stabilize initially unstable new information (called synaptic consolidation), a “storage” or maintenance phase in which other mechanisms are involved to maintain memory, and a retrieval phase in which certain mechanisms allow the memory to be retrieved. For a long time, from a neurobiological point of view, only the acquisition and stabilization of memory were considered active phases in the sense that neurons had to perform certain calculations or synthesize new RNA and proteins for these phases of memory processing in order for them to perform successfully. Once acquired and stabilized, it was thought that all other phases represented passive reading of changes in neural circuits mediating long-term memory. However, now the picture has changed, and memory maintenance is seen as an active process. One reason for this change is the demonstration that consolidated long-term memory can become susceptible to destruction and restoration, a process called “reconsolidation.”