X-Message-Number: 13757
From: "Gary Tripp" <>
Subject: New finding on memory
Date: Sat, 20 May 2000 13:01:23 -0400

Source:   Brown University (http://www.brown.edu)

Date:   Posted 5/19/2000

Memory Mechanism Found At Nerve Cell Connections In The Brain

PROVIDENCE, R.I. - Scientists have identified a novel mechanism behind
 the decrease in strength of synapses in the brain, a process that leads to
the
creation of memories and their long-term storage. The increase or decrease
in
strength among synapses, and subsequent changes in memory, are based on
sensory-driven experiences. Synaptic strengthening or weakening also occurs
during the brain's development. Synapses are the connections between
neurons,
or nerve cells.

Reporting in today's Science, researchers from the Howard Hughes Medical
Institute (HHMI) and Brown University describe machinery at the synapse for
the synthesis of new proteins that depress synaptic strength. The study was
conducted in rats.

The finding suggests that experience or activity in the mammalian brain can
regulate individual synapses, said lead investigator Kimberly Huber, a
post-doctoral researcher at Brown.

"The study shows that synaptic depression actually relies on the manufacture
of
proteins at the synapses," she said. "This is the first demonstration in
mammals
that when synapses change, the modification depends on new proteins created
specifically at the site."

This synaptic chemical activity is an efficient way for the brain to make
new proteins
and change existing ones rapidly, Huber said. "The mechanism appears to be a
viable
way for the brain to express its changes. We think this activity also may be
a way that
the structure, or shape, of synapses can be altered."

The findings hint that connections in the brain can be modified on an
individual basis,
facilitating long-term memory storage.

"It is important to understand the mechanism by which connections are
weakened - not
only because such understanding may yield insight into long-term memory, but
also
because this is a fundamental part of normal brain development," said senior
investigator
Mark Bear, an HHMI investigator and professor of neuroscience at Brown.

Although synapses have the machinery to make proteins, there had not been
evidence that
this machinery can function to change synapses.

Huber and colleagues worked with tissue from the hippocampus region of the
brain,
separating synapses from their cell bodies. Even after the cells and
synapses were cut
apart, the synapses continued to be modified by local protein activity,
indicating that
synaptically synthesized proteins are involved.

This led the researchers to introduce specific inhibitors of the protein
synthetic machinery
directly to the synapses. The synaptic depression was blocked, providing
further evidence
that the proteins are made at the synapse. Follow-up experiments, in which
the activation
of genes at the cell body was blocked, reinforced that the new proteins are
synthesized
directly at the synapses.

The Howard Hughes Medical Institute and a grant from the National Eye
Institute funded
the study. The other researcher involved was Matthew Kayser, a graduating
senior who
conducted the work as part of his honors thesis.

At Brown, the researchers are based in the Department of Neuroscience in the
School
of Medicine. They are currently studying what types of proteins are being
made at the
synapses and how experience rapidly regulates synapses through local protein
synthesis.

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