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Memory Mechanics

Ian Goddard igoddard at erols.mom
Wed Mar 27 09:54:01 EST 2002


Scientists Enhance Fruit Fly Memory Using Mouse Protein: 
New Clue To Fundamental Brain Mechanism

Date Posted:    Wednesday, March 27, 2002

Researchers have found that they can enhance memory in fruit flies
by boosting the level of a protein called PKM. The scientists could
trigger memory enhancement in the flies by using either a fly or a
mouse version of PKM. The study, published in the April issue of
Nature Neuroscience, provides an important new clue about a
fundamental mechanism of memory common to flies, humans, and most
other animals.

It is widely believed that memories are stored as changes in the
number and strength of the connections between brain neurons, called
synapses. A typical brain neuron makes thousands of synapses with
other neurons. However, only a subset of those synapses is involved
in a particular memory or learned skill.

Neuroscientists are interested in determining how molecules that
strengthen synapses are targeted to some synapses but not to others.

"We believe that PKM may be involved in a process that 'tags'
synapses during memory formation," says Jerry Yin, a scientist at
Cold Spring Harbor Laboratory and the principle investigator in the
new study. "In this way, those synapses and only those synapses
corresponding to a particular memory are strengthened in response to

To explore the role of PKM in memory, Yin and his colleagues used a
method (pioneered by another CSHL researcher, Tim Tully) for
training fruit flies to avoid a particular odor. The method involves
pairing an odor with a mild electric shock, training the flies to
avoid the odor, and subsequently measuring the flies's ability to
remember to avoid the odor.

Depending on the training regimen, fly memories based on this type
of "associative" learning (made famous by Pavlov's Dogs) are
initially robust, but fade away completely over one to seven days
(the lifespan of a fruit fly is 30-40 days). However, when Yin and
his colleagues used a genetic trick to boost the level of PKM in the
flies, a substantial proportion of flies retained the "avoid that
odor" memory at times after training when the memory would normally
be long gone.

According to Thomas Carew, Professor and Chair of the Department of
Neurobiology and Behavior at the University of California, Irvine,
"Much of what we know about memory processing comes from studies in
which memory is disrupted. This study takes on added significance
because it is a rare example that demonstrates actual enhancement 
of memory formation."



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