Study reveals
process of storing long-term memories is like
dynamic memory machine
Newswise — What happens in
our brains when we learn and remember? Are
memories recorded in a stable physical change,
like writing an inscription permanently on a
clay tablet? Prof. Yadin Dudai, Head of the
Weizmann Institute’s Neurobiology Department,
and his colleagues are challenging that view.
They recently discovered
that the process of storing long-term memories
is much more dynamic, involving a miniature
molecular machine that must run constantly to
keep memories going. They also found that
jamming the machine briefly can erase long-term
memories.
Their findings, which
appear today in the journal Science, may
pave the way to future treatments for memory
problems.
Dudai and research student
Reut Shema, together with Todd Sacktor of the
State University of New York (SUNY) Downstate
Medical Center, trained rats to avoid certain
tastes. They then injected a drug to block a
specific protein into the taste cortex – an area
of the brain associated with taste memory. They
hypothesized, on the basis of earlier research
by Sacktor, that this protein, an enzyme called
PKMzeta, acts as a miniature memory “machine”
that keeps memory up and running.
An enzyme causes
structural and functional changes in other
proteins: PKMzeta, located in the synapses –
the functional contact points between nerve
cells – changes some facets of the structure
of synaptic contacts. It must be
persistently active, however, to maintain
this change, which is brought about by
learning. Silencing PKMzeta, reasoned the
scientists, should reverse the change in the
synapse.
And this is exactly what
happened: Regardless of the taste the rats were
trained to avoid, they forgot their learned
aversion after a single application of the drug.
The technique worked just as successfully a
month after the memories were formed (in terms
of life span, more or less analogous to years in
humans), and all signs so far indicate that the
affected unpleasant memories of the taste had
indeed disappeared. This is the first time that
memories in the brain were shown to be capable
of erasure so long after their formation.
“This drug is a molecular
version of jamming the operation of the
machine,” says Dudai. “When the machine stops,
the memories stop as well.” In other words,
long-term memory is not a one-time inscription
on the nerve network, but an ongoing process
which the brain must continuously fuel and
maintain. These findings raise the possibility
of developing future, drug-based approaches for
boosting and stabilizing memory.
Prof. Yadin Dudai's
research is supported by the Norman and Helen
Asher Center for Brain Imaging; the Nella and
Leon Benoziyo Center for Neurosciences; the Carl
and Micaela Einhorn-Dominic Brain Research
Institute; the Irwin Green Alzheimer's Research
Fund; and the Sylvia and Martin Snow Charitable
Foundation. Prof. Dudai is the incumbent of the
Sara and Michael Sela Professorial Chair of
Neurobiology.
The Weizmann Institute of
Science in Rehovot, Israel, is one of the
world's top-ranking multidisciplinary research
institutions. Noted for its wide-ranging
exploration of the natural and exact sciences,
the Institute is home to 2,600 scientists,
students, technicians, and supporting staff.
Institute research efforts include the search
for new ways of fighting disease and hunger,
examining leading questions in mathematics and
computer science, probing the physics of matter
and the universe, creating novel materials, and
developing new strategies for protecting the
environment.
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