閾値未満の興奮性シナプス刺激が与えられた海馬ニューラルネットワークモデルにおける不規則なシナプスノイズによるθ-γ 位相振幅結合の生成

抄録

θ-γ phase-amplitude coupling (PAC) is observed in neural networks of the hippocampus, in which the amplitude of high-frequency oscillations, γ wave, is modulated by the phase of low-frequency oscillations—θ wave. Several studies have shown that the degree of PAC is closely related to memory formation. In contrast, the stochastic resonance (SR) phenomenon, in which the addition of random synaptic noise can enhance the transmission of sub-threshold synaptic stimuli, is also observed in the hippocampus. Although PAC reportedly appears in a specific status of brain activity, it is still unclear if and how random synaptic noise could contribute to generating θ-γ PAC. In this study, we investigated whether or not θ-γ PAC could be generated by an addition of random synaptic noise in a hippocampal neural network model with sub-threshold excitable synaptic stimuli using the modulation index (MI) through computer simulations. The results of computer simulations showed that the typical resonance curve of resonance phenomena, i.e., MI was maximized at a specific amplitude of synaptic noise. Therefore, it is concluded that θ-γ PAC can be generated by the vibrational mode transition, induced by the random synaptic noise, in the hippocampal neural network model with mixed sub-and supra-threshold stimuli.