Selectively Removing Memories Now Possible

Changing the Structure of Memory

To produce a memory, a lot has to happen, including the alteration of the structure of nerve cells via changes in the dendritic spines—small bulb-like structures that receive electrochemical signals from other neurons. Normally, these structural changes occur via actin, the protein that makes up the infrastructure of all cells.

In the new study, the scientists inhibited actin polymerization—the creation of large chainlike molecules—by blocking a molecular motor called myosin II in the brains of mice and rats during the maintenance phase of methamphetamine-related memory formation.

Behavioral tests showed the animals immediately and persistently lost memories associated with methamphetamine—with no other memories affected.

In the tests, animals were trained to associate the rewarding effects of methamphetamine with a rich context of visual, tactile and scent cues. When injected with the inhibitor many days later in their home environment, they later showed a complete lack of interest when they encountered drug-associated cues. At the same time, the response to other memories, such as food rewards, was unaffected.

While the scientists are not yet sure why powerful methamphetamine-related memories are also so fragile, they think the provocative findings could be related to the role of dopamine, a neurotransmitter involved in reward and pleasure centers in the brain and known to modify dendritic spines. Previous studies had shown dopamine is released during both learning and drug withdrawal. Miller adds, “We are focused on understanding what makes these memories different. The hope is that our strategies may be applicable to other harmful memories, such as those that perpetuate smoking or PTSD.”

The first author of the study, “Selective, Retrieval-Independent Disruption of Methamphetamine-Associated Memory by Actin Depolymerization,” is Erica J Young; other authors include Massimiliano Aceti, Erica M Griggs, Rita A Fuchs, Zachary Zigmond and Gavin Rumbaugh of TSRI. For more information, seehttp://www.biologicalpsychiatryjournal.com/article/S0006-3223(13)00727-0/abstract

The research was supported by the National Institute on Drug Abuse (grant numbers R00 DA024761 and R01DA034116) and the National Institute for Neurological Disorders and Stroke (R01NS064079).

Eric Sauter