Intrahippocampal anisomycin infusions disrupt previously consolidated spatial memory only when memory is updated

Reconsolidation has proven to be a common phenomenon relevant to memory processing. However, the functional significance of this process is still a matter of debate. Previous work has shown that reconsolidation is indeed a process by which updated information is integrated, through the synthesis of proteins, to a memory trace. To further analyze the role that updated information plays in retrieved spatial memory susceptibility to disruption, we injected anisomycin bilaterally in the dorsal hippocampus of Wistar rats. Implanted animals were trained for 5 days on the Morris water maze (MWM) task and injected with anisomycin before the third or fifth training session. When memory was assessed a week later, only animals injected on the third training session showed disruption of long-term memory. Furthermore, when animals were trained for either 3 (middle-trained) or 5 (well-trained) days and a week later anisomycin was infused before a reminder session, only middle-trained rats infused with anisomycin showed reduced performance when tested for long-term memory. Finally, animals trained for 5 days and injected with anisomycin 7 days later on an extinction session showed impaired long-term extinction when tested. These results suggest that for spatial memory tasks acquisition of updated information is a necessary feature to undergo this process. We propose that reconsolidation is not an accurate term because it implies that consolidation happens again. This conception does not fit with the evidence; hence, we suggest that updating consolidation is a more descriptive term to refer to this process. (C) 2007 Elsevier Inc. All rights reserved.