化学自突触的电导扰动诱导相干或随机双共振现象

Coherent or stochastic bi-resonance induced by conductance disturbance of chemical autapse

神经元的自突触结构具有自反馈的作用,神经递质量子形式的释放使得自突触的自反馈作用容易受到扰动,本文重点研究了化学自突触的电导扰动对FHN神经元电生理活动的影响.首先,恰当的化学自突触参数能够产生动力学行为的分岔现象,诱导不同周期峰放电模式之间的转迁.特别地,自突触的自反馈功能会引起从混沌放电状态到周期的峰放电或准周期的簇放电状态的转迁.其次,基于神经递质释放的量子特征,借助放电频率和变异系数两个指标定量地研究自突触电导的随机扰动对神经元放电活动的影响.数值结果表明自突触电导的扰动在自反馈的作用下能够改变离子通道的活性,不仅提高FHN神经元对外加激励信号的编码效率,而且改变神经元放电活动的规则性,诱导显著的相干或随机双共振现象,其内在机制是电导扰动所引起的神经元系统不稳定的动力学分岔.本文的研究进一步揭示了自突触结构对神经元放电活动自我调节的作用,有待为生理操控自突触结构提供理论参考.

The autaptic structure of neurons has the function of self-feedback,which is easily disturbed due to the quantum characteristics of neurotransmitter release.This paper focuses on the effect of conductance disturbance of chemical autapse on the electrophysiological activities of FHN neuron.First,the frequency encoding of FHN neuron to periodic excitation signals exhibits a nonlinear change characteristic,and the FHN neuron without autapse has chaotic discharge behavior according to the maximum Lyapunov exponent and the sampled time series.Secondly,the chemical autaptic function can change the dynamics of FHN neuronal system,and appropriate autaptic parameters can cause the dynamic bifurcation,which corresponds to the transition between different periodic spiking modes.In particular,the self-feedback function of chemical autapse can induce a transition from a chaotic discharge state to a periodic spiking or a quasi-periodic bursting discharge state.Finally,based on the quantum characteristics of neurotransmitter release,the effect of random disturbance from autaptic conductance on the firing activities is quantitatively studied with the help of the discharge frequency and the coefficient of variation of inter-spike interval series.The numerical results show that the disturbance of autaptic conductance can change the activity of ion channels under the action of selffeedback,which not only improves the encoding efficiency of FHN neuron to external excitation signals,but also changes the regularity of neuronal firing activities and induces significant coherent or stochastic bi-resonance.The coherent or stochastic bi-resonance phenomenon is closely related to the dynamic bifurcation of FitzHughNagumo(FHN)neuronal system,and its underlying mechanism is that the disturbance of autaptic conductance leads to the unstable dynamic behavior of neuronal system,and the corresponding neuronal firing activity may transit between the resting state,the single-cycle and the multicycle spike states,thereby providing the occurring possibility for coherent or stochastic bi-resonance.This study further reveals the self-regulatory effect of the autaptic structure on neuronal firing activities,and could provide theoretical guidance for physiological manipulation of autapses.In addition,according to the pronounced self-feedback function of autaptic structure,a recurrent spiking neural network with local self-feedback can be constructed to improve the performance of machine learning by applying a synaptic plasticity rule.