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Name |
Email |
Telephone |
| Professor |
YAMAMOTO, Nobuhiko, Ph.D. |
 |
+81-6-6879-4636 |
| Associate Prof. |
SHIRASAKI,Ryuichi, Ph.D. |
 |
+81-6-6879-4635 |
| Assistant Prof. |
SUGO, Noriyuki , Ph.D. |
 |
+81-6-6879-4635 |
We are interested in how neuronal connections are formed during
development of the brain. It has been suggested that fundamental
patterns of neuronal circuits are established by a precise developmental
program whereas fine connections are modified by electrical activity
including spontaneous firing. We are exploring cellular and molecular
mechanisms that underlie these processes, focusing on neocortical
connections.
| 1 |
Laminar specific connections |
 One of the characteristic features in cortical
connections is layer specificity. The neocortex is composed
of six cell layers, by which extrinsic and intrinsic cortical
connections are organized. In particular the thalamocortical
projection is well characterized in terms of laminar specificity
and development. During development sensory thalamocortical
axons travel through the specific pathways, enter the cortical
plate, pass through the deep cortical layers and finally
project to layer 4. How thalamocortical axons recognize
the target layer? Previous in vitro studies with organotypic
coculture preparations have demonstrated that thalamic
axons exhibit stopping and branching behavior in the target
layer. Moreover, evidence indicates that stopping is attributable
to the inhibitory activity (partly due to glycosylphosphatidylinositol-linked
molecules) in the upper cortical layers, whereas lamina-specific
branching is regulated by a positive factor (unknown) in
the target layer and an inhibitory component (polysialylated
neural cell adhesion molecule) in all cortical layers.
To reveal the molecular mechanisms that are responsible
for axonal stopping and branching behaviors, we attempt
to identify the genes that are expressed specifically in
layer 4 or in the upper layers. |
| 2 |
Intrinsic cortical connections |
| ICortical neurons in the upper layers are known to project
axons to the same layers as well as the contralateral hemisphere.
This horizontal projection has been shown to contain additive
and retractive processes of axonal growth and branching.
Evidence further suggests that electrical activity of cortical
neurons are involved in these processes. We recently began
to study how horizontal axon behaviors are regulated by
electrical activity in organotypic slice cultures, by monitoring
and manipulating neuronal activity in vitro. |
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