US scientists perfect targeted memory erasure in mice

US researchers said Wednesday they are able to selectively erase memories from mice in a laboratory, raising hopes human memory afflictions like post-traumatic stress syndrome can one day be cured.

"Targeted memory erasure is no longer limited to the realm of science fiction," the research team headed by Joe Tsien, from the Brain and Behavior Discovery Institute at the Medical College of Georgia, said in Thursday's issue of Cell Press magazine.

The new technique, which the team stress is at a very early stage, could be applied one day to the human brain to erase traumatic memories or deep-set fears, and leave all other memories unaffected.

Memory is generally separated into four different stages: acquisition, consolidation, storage, and retrieval. Earlier research identified specific molecules that appear to play a role in the various phases of the memory process.

But Tsien said his team found a way to quickly manipulate the activity of the "memory molecule," the protein CaMKII (calcium/calmodulin-dependent protein kinase II) that plays a key role in brain cell communication, and so is linked to many aspects of learning and memory.

Researchers developed a "chemical genetic strategy," which made it possible to manipulate the protein in transgenic mice, which had been bred to overproduce the molecule.

"Using this technique, we examined the manipulation of transgenic CaMKII activity on the retrieval of short-term and long-term fear memories and novel object recognition memory" in transgenic mice, Tsien said.

The team figured out they could manipulate the protein in the mice's brain as the animal was stimulated, and observe the brain's ability to recall memory of the stimulation.

Through the protein manipulation, researchers then found a way to not just block the mice's memory of the stimulation, but erase them without impacting the brain's ability to recall other memories.

Tsien became famous in 1999 for his creation of Doggie, the smart transgenic mouse with enhanced learning and memory abilities.

In the recent findings, Tsien's team found that transient excessive activity of CaMKII at the time of recall impaired retrieval of short- and long-term fear memories, as well as memories formed as recently as one hour.

They also showed that recall deficits linked to excessive CaMKII activity were not caused by a blockade of the recall process but instead seemed to be due to rapid erasure of the stored memories.

In addition, they found that the erased memories were limited to those being retrieved, while others remained intact.

"The results demonstrate a successful genetic method for rapidly and specifically erasing specific memories, such as new and old fear memories, in a controlled and inducible manner without doing harm to the brain cells," the researchers said.

Tsien said the technique might one day be applied to war veterans who "often suffer from reoccurring traumatic memory replays after returning home."

However, he warned that it was premature to expect a such a miracle cure.

"No one should expect to have a pill do the same in humans any time soon, we are barely at the foot of a very tall mountain," he said.