Prof. Yadin Dudai, Head of the Weizmann Institute's Neurobiology Department, and his colleagues discovered that the memory storing process involves a miniature molecular machine that runs constantly to keep memories going. The team, which also found that jamming the machine briefly can erase long-term memories, suggests that their findings may pave the way to future treatments for memory problems.
Prof. Dudai said that their study challenges the idea that long-term memories stabilize after maturing from short-term memories.
In the study, the U.S. and Israeli researchers fed the rats with saccharine, which made them sick and taught them to associate the taste with feeling unwell.
They then injected an enzyme inhibitor called ZIP into the rats' brains that blocked a protein, PKMzeta, which controls the flow of information involving memory between brain cells.
After the injection, the rats did not remember the association with saccharine, no matter how long the researchers had trained them to do so, said Dudai, a researcher at the Weizmann Institute of Science in Israel.
This suggests a key mechanism in the brain works like a piece of machinery to store long-term memory, Dudai said. Once the machinery stops, memory shuts down.
The technique worked as successfully a month after the memories were formed (in terms of life span, more or less analogous to years in humans) and all signs so far indicate that the affected unpleasant memories of the taste had indeed disappeared. This is the first time that memories in the brain were shown to be capable of erasure so long after their formation.
"This drug is a molecular version of jamming the operation of the machine. When the machine stops, the memories stop as well. This research is important because it casts light on the mechanisms of memory. It also shows that long-term memory is not a permanent change and can be edited," Dudai said.
In other words, long-term memory is not a one-time inscription on the nerve network, but an ongoing process which the brain must continuously fuel and maintain. These findings raise the possibility of developing future, drug-based approaches for boosting and stabilizing memory.
The findings of the study are published in the journal Science.