非表示:
キーワード:
hippocampus, trisynaptic circuit, neuronal network dynamics, filter, theta, voltage-sensitive dye imaging, CA1 LTP
要旨:
Decades of brain research have identified various parallel loops linking
the hippocampus with neocortical areas, enabling the acquisition of
spatial and episodic memories. Especially the hippocampal trisynaptic
circuit [entorhinal cortex layer II dentate gyrus (DG) cornu ammonis
(CA)-3 CA1] was studied in great detail because of its seemingly simple
connectivity and characteristic structures that are experimentally well
accessible. While numerous researchers focused on functional aspects,
obtained from a limited number of cells in distinct hippocampal
subregions, little is known about the neuronal network dynamics which
drive information across multiple synapses for subsequent long-term
storage. Fast voltage-sensitive dye imaging in vitro allows real-time
recording of activity patterns in large/meso-scale neuronal networks
with high spatial resolution. In this way, we recently found that
entorhinal theta-frequency input to the DG most effectively passes
filter mechanisms of the trisynaptic circuit network, generating
activity waves which propagate across the entire DG-CA axis. These
"trisynaptic circuit waves" involve high-frequency firing of CA3
pyramidal neurons, leading to a rapid induction of classical NMDA
receptor-dependent long-term potentiation (LTP) at CA3-CA1 synapses (CA1
LTP). CA1 LTP has been substantially evidenced to be essential for some
forms of explicit learning in mammals. Here, we review data with
particular reference to whole network-level approaches, illustrating how
activity propagation can take place within the trisynaptic circuit to
drive formation of CA1 LTP.
