神経細胞のカオス-周期発火状態の切り替え機構

抄録

Research into the brain's switching circuitry between its chaotic and non-chaotic activities is a topic of brain science. In this paper, the neuron's switching circuitry of its chaotic firing state is estimated using a neuron model. The model, which is carefully tuned up for the properties of emergence of chaos, was obtained from modifications of the McCulloch-Pitts and Nagumo-Sato models. On the modifications, two neuronal properties of the axon's refractoriness and soma's cable property were especially paid attention to. The former is crucial to cause many types of neuron's firing states, including the chaotic firing state. The other has relevance to switch the types. Computer simulation of the switching circuitry was performed under hypothesis that one kind of neuron receives steady stimulation inside the range to activate its chaotic firing. The results suggest that the neuron's chaotic firing state is stable under noisy stimulation, that synaptic transmission even of a few times triggers a bifurcation process to the periodic firing state of a higher firing-rate, and that the bifurcated periodic firing state lasts for a while stably. Such a circuitry may be not only a guide to find out brain's chaos-working circuitry but also a hint to invent a new kind of neural network.