US researchers have said they are able to selectively erase memories from mice in a laboratory, raising hopes human memory afflictions like post-traumatic stress disorder 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 Behaviour Discovery Institute at the Medical College of Georgia,
said in Cell Press magazine.
The new technique, which the researchers 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.
How the research was done
Researchers developed a "chemical genetic strategy," which made it
possible to manipulate the protein in transgenic mice 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
The team figured out they could manipulate the protein in the mouse'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 mouse's memory of the stimulation, but erase it
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 previously.
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.
What the findings mean
"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 recurring traumatic memory replays after returning
home." However, he warned that it was premature to expect 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. – (Sapa, October 2008)
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