抄録
A distinctive function of the hippocampus is to learn a sequence of places so that animals can recognize the places where they are. In this paper, we will show that theta burst stimulation organizes radial propagation of neuronal activity from the stimulus site in a CA3 network model that contains recurrent excitatory synapses having nature of spike-timing-dependent plasticity (STDP). We will also report that a neuronal assembly coding a temporal sequence of signals may be organized in CA1 through the radial propagation of neuronal activity in CA3 when Schaffer collateral synapses are subject to a STDP rule. When firing of the presynaptic neuron precedes firing of the postsynaptic neuron, the synaptic connection is potentiated by a STDP rule, while the synaptic connection is depressed when the neurons fire in reverse order. Radial propagation of neuronal actvity was therefore produed by theta burst stimulation fed to a local site in CA3. When theta burst signals were successively fed to several local sites in CA3 and CA1, radial propagations of neuronal activity were produced first, like ripples spreading on the surface of water. Since the radius of the ripples depends on the time when signals are fed, the distribution of ripples reflects the sequence of signals. The coincident firing of CA3 pyramidal cells on the ripples then potentiated Schaffer collateral synapses to specific CA1 neurons together with proper perforant path signals. These CA1 neurons may code a sequence of signals fed to the hippocampus. [Jpn J Physiol 55 Suppl:S9 (2005)]
