Researchers led by New York University neuroscientist Joseph LeDoux recently claimed to be the first scientists to erase a single memory. Working with rats, LeDoux’s team first taught the animals to fear both a beep and a siren by giving them an electric shock every time either of the tones sounded. Then LeDoux gave half the rats the drug U0126, which is known to interfere with memory storage, and replayed the beep without electric shocks.
A day later, when LeDoux played back both tones to the rats, the animals that hadn’t been given the drug were still fearful of both sounds. But the rats that had been given the memory-blocking drug weren’t afraid of the beep, which they had last heard while under the influence of U0126.
Exactly how U0126 exerts its amnesiac effect is unknown, but it may block the synthesis of proteins that help strengthen connections between neurons and establish memories. The opportunity for erasure occurs during the act of retrieving a memory because that’s when the memory is being updated and stabilized again for long-term storage. “Only those memories that are activated are vulnerable,” LeDoux says.
Drugs like U0126 may someday help sufferers of traumatic memories. A small group of human studies have been done on a drug called propranolol, which blocks the action of stress neurotransmitters that help cement memories in the brain, but LeDoux’s work shows the potential for greater precision. “You might be able to reduce the traumatic impact of memories in people with PTSD,” says LeDoux. “The good news is you wouldn’t be erasing their memory bank.”