Memory-Erasing Drugs
Could Result from New Brain Discovery
Charles Q. Choi
LiveScience Contributor
Yahoo! News
Thu Feb 18, 12:05 pm ET
A newfound brain mechanism erases memories on purpose to
help make way for new ones. Scientists suggest it could lead to the development
of memory-erasing drugs that make a person forget certain things.
Researchers have often debated about the reasons we forget -
for instance, why newly acquired short-term memories are fleeting. One theory
suggests that such memories are simply unstable, fading over time. Others
contend interference causes short-term memories to be overridden as new data
comes in.
Both notions suggested that forgetting is a passive
mechanism, but now it seems "it's not that at all - it's an active system
to erase memory, completely independent from the mechanisms to form
memories," researcher Yi Zhong, a neurogeneticist at
Zhong and his colleagues made
their discovery by training fruit flies with two odors, one of which was paired
with a foot shock to the insects as they smelled it. That experience normally
leads flies to avoid the shocking odor in favor of the alternative.
In the first set of experiments, the researchers left the
flies alone after their training session was over, later testing them at
specific points in time as their memory weakened. In a second experiment, the
researchers disrupted the odor-shock memories by exposing flies to a new pair
of odors. Finally, they reversed the flies' lesson, delivering the foot shock
in conjunction with the opposite odor.
In all cases, the flies forgot what they learned previously,
which the researchers suspect was due to a small protein known as Rac that switched on with the passage of time. This
molecule switched on faster when the insects either got distracted by new
experiences or confused by conflicting information.
When Rac was blocked, flies held
on to newly acquired memories for longer than they otherwise would have,
extending their life from a few hours to more than a day. When the researchers
artificially increased Rac in fly neurons, new
memories were erased more rapidly.
Scientists have yet to deeply understand what molecules are
involved in the formation of memories. "By studying what is being erased
or altered with this new mechanism, we may be able to identify the material basis
of memory," Zhong said.
Zhong suspected the forgetting
mechanism they uncovered would apply to other animals, with some hints in that
direction in mice. Intriguingly, he noted mutations in other molecules involved
with Rac have been linked to mental retardation in
humans.
"We're now developing experiments to see if this also
works on long-term memory," Zhong said.
Rac or molecules linked with it
"could serve as targets for drugs to erase memory," Zhong added. Although such amnesia drugs could serve
nefarious purposes, they could also help treat disorders where people remember
trauma against their will, such as post-traumatic stress disorder.
The scientists detail their findings in the Feb. 19 issue of
the journal Cell.
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