"Current theories of memory state that the act of remembering turns a stored memory into something malleable that then needs to be re-encoded," said K. Matthew Lattal, a postdoctoral researcher in Penn's Department of Biology and a co-author of the study. "We show that the act of retrieving an old memory and then putting it back into storage is a different process than creating a memory in the first place. Unfortunately, it could mean that 'erasing' traumatic memories is not as simple as one might hope."
The study will be published in the Proceedings of the National Academy of Science and will be available on the Internet this week in the PNAS Online Early Edition.
Previous studies in rodents had shown that the process of encoding a memory could be blocked by the use of a protein synthesis inhibitor called anisomycin. Experiments with anisomycin helped lead to the acceptance of a theory in which a learned behavior is consolidated into a stored form and that then enters a 'labile' or adaptable state when it is recalled. According to these previous studies, the act of putting a labile memory back into storage involves a reconsolidation process identical to the one used to store the memory initially. Indeed, experiments showed that anisomycin could make a mouse forget a memory if it were given anisomycin directly after remembering an event.
In the PNAS study, however, the Penn researchers showed that disruption of a "re-remembered" memory was not permanent.
"When we looked at mice 21 days after they were treated with anisomycin to block the reconsolidation
Contact: Greg Lester
University of Pennsylvania