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Yasunori Hayashi
By focusing the energies of his lab on the
synaptic connections in the hippocampus, Professor Yasunori
Hayashi is helping to build a comprehensive understanding
of how memory is formed at the molecular level. For this purpose,
he employs combinatorial approaches using electrophysiology
and optical imaging as well as molecular biology. Unique to
his laboratory is a technique for observing the dynamics of
individual proteins in single synapses.
How is a memory formed in the brain? This has been a long-standing question but only recently have various methodologies allowed us to investigate this problem in molecular detail. The principal focus of our laboratory is the hippocampus, a small, curvy structure embedded deep in the cerebrum. Although small in size, it plays a critical role in memory formation.
At the cellular level, a phenomenon called "synaptic plasticity" is observed there. Neurons communicate with each other through a structure called the synapse. There, neurotransmitters are released from the presynaptic terminal into the synaptic cleft, ultimately reaching postsynaptic receptors on the soma, dendritic shaft or dendritic spine. On excitatory dendritic spines, a glutamatergic receptor receives the neurotransmitter and converts this chemical signal into an electrical signal. In an in vitro brain slice preparation, when a presynaptic terminal is stimulated intensely (mimicking a situation when a subject tries to remember something), synaptic transmission is enhanced and lasts for hours and days. Since this phenomenon, called long-term potentiation (LTP), was first described almost three decades ago, it has been proposed as a potential cellular correlate of learning and memory. Our laboratory investigates the mechanisms underlying LTP by combining different technologies: we construct recombinant neuronal proteins and express them in neurons using molecular biological techniques. The proteins we are interested in are various glutamate receptors and their binding proteins.
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