原網址：
http://www.sciencedaily.com/releases/2009/06/090618151331.htm
image在網址內就有
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ScienceDaily (June 19, 2009) — The ability to learn and to establish new
memories is essential to our daily existence and identity; enabling us to
navigate through the world. A new study by researchers at the Montreal
Neurological Institute and Hospital (The Neuro), McGill University and
University of California, Los Angeles has captured an image for the first
time of a mechanism, specifically protein translation, which underlies
long-term memory formation.
The finding provides the first visual evidence that when a new memory is
formed new proteins are made locally at the synapse - the connection between
nerve cells - increasing the strength of the synaptic connection and
reinforcing the memory. The study published in Science, is important for
understanding how memory traces are created and the ability to monitor it in
real time will allow a detailed understanding of how memories are formed.
When considering what might be going on in the brain at a molecular level two
essential properties of memory need to be taken into account. First, because
a lot of information needs to be maintained over a long time there has to be
some degree of stability. Second, to allow for learning and adaptation the
system also needs to be highly flexible.
For this reason, research has focused on synapses which are the main site of
exchange and storage in the brain. They form a vast but also constantly
fluctuating network of connections whose ability to change and adapt, called
synaptic plasticity, may be the fundamental basis of learning and memory.
"But, if this network is constantly changing, the question is how do memories
stay put, how are they formed? It has been known for some time that an
important step in long-term memory formation is "translation", or the
production, of new proteins locally at the synapse, strengthening the
synaptic connection in the reinforcement of a memory, which until now has
never been imaged," says Dr. Wayne Sossin, neuroscientist at The Neuro and
co-investigator in the study. "Using a translational reporter, a fluorescent
protein that can be easily detected and tracked, we directly visualized the
increased local translation, or protein synthesis, during memory formation.
Importantly, this translation was synapse-specific and it required activation
of the post-synaptic cell, showing that this step required cooperation
between the pre and post-synaptic compartments, the parts of the two neurons
that meet at the synapse. Thus highly regulated local translation occurs at
synapses during long-term plasticity and requires trans-synaptic signals."
Long-term memory and synaptic plasticity require changes in gene expression
and yet can occur in a synapse-specific manner. This study provides evidence
that a mechanism that mediates this gene expression during neuronal
plasticity involves regulated translation of localized mRNA at stimulated
synapses. These findings are instrumental in establishing the molecular
processes involved in long-term memory formation and provide insight into
diseases involving memory impairment.
This study was funded by the National Institutes of Health, the WM Keck
Foundation and the Canadian Institutes of Health Research.
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