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Scientists capture the first image of memories
being made
The ability to learn and to establish new memories is essential to
our daily existence and identity; enabling us to navigate through the
world. |
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| 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.
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