When the brain forms a memory, part of the process involves physically moving that memory from a neural network that supports short-term memory to one that holds long-term memories. The researchers, led by Joseph LeDoux, aimed to interrupt the transfer of a fear memory with the overall goal of deleting it. The way the scientists went about deleting the targeting memory implies that the act of recalling a memory involves a physical transfer as well. They were able to erase a memory by recalling it while the rats were under the influence of a drug call U0126, which induces limited memory loss (humans can’t get it — it’s only approved for use in other animals).
The process they used for the study is fascinating. The researchers began with classical fear conditioning to create fear memories in a group of rats. They played two different musical tones, each one accompanied by an electric shock
Pointing to the change in amygdala activity, which is central to the brain’s system of storing and recalling fearful memories (see How Fear Works to learn about this process), the researchers say the memory was not simply disconnected from fear, but that it was actually erased in its entirety. In other words, it was not that the rats learned not to be afraid of the tone; it was as if the rats had never learned to be afraid of the tone in the first place. And the fear of the second tone — the one they’d not recalled while under U0126 — was still active. The rest of the rats’ memories appeared to be unaffected by the process.
This is really amazing to think that just one part of your memory can be erased and the others can remain intact. This has great implications in the field of psychology. Patients that have suffered traumatic stress may be candidates for this type of a drug in the future. Neuroscience research is finding new practical applications every day.
Gene Expression: 10 Questions for Joseph LeDoux – Aug. 7, 2006