抑制性自突触诱发耦合Morris-Lecar神经元电活动的超前同步

Anticipated synchronization of electrical activity induced by inhibitory autapse in coupled Morris-Lecar neuron model

超前同步(anticipated synchronization,AS)是一种普遍存在的违反直觉的非线性行为:被驱动系统的响应会早于驱动出现,在神经系统的实验中也被发现.本研究揭示了抑制性自突触诱发Morris-Lecar神经元模型产生AS,给出了产生AS的条件.在单向兴奋性驱动的双神经元耦合系统,无论神经元是I型兴奋性还是II型兴奋性,都只会产生驱动行为在响应之前的滞后同步(delayed synchronization,DS).在被驱动神经元引入抑制性自突触,II型兴奋性神经元构成的耦合系统会表现出驱动在响应之后的AS;随着自突触电导的增大,DS会转迁到AS;而I型兴奋性神经元构成的耦合系统则只会产生DS.进一步,提示了AS产生与不产生分别与II型和I型兴奋性神经元的放电响应特性有关:II型神经元在抑制性脉冲刺激下放电提前而I型兴奋性神经元不易产生放电提前.研究结果给出了抑制性自反馈诱发AS的神经元的兴奋性类型,有助于理解违反直觉的动力学行为—AS,给出了调控AS的可能手段,为进一步研究AS提供了方向.

Anticipated synchronization,the response of the driven subsystem which appears earlier than the stimulation from the driving subsystem,is a universally counterintuitive nonlinear behavior.This behavior is also observed in the experiment on the nervous system in different brain regions.In the present paper,the anticipated synchronization phenomenon evoked by the inhibitory autapse is simulated in the coupled system composed of Morris-Lecar model,and the condition of excitability of single neurons and parameter ranges for the anticipated synchronization is presented.For a coupled system composed of two neurons,whether both neurons are either type-I excitability/Hopf bifurcation or type-II excitability/saddle-node bifurcation on an invariant cycle,in a driven neuron unidirectionally receiving the excitatory synaptic current from a driving neuron the delayed synchronization(the response of the driven neuron appears after the drive of the driving neuron)instead of the anticipated synchronization is simulated.After the inhibitory autapse is introduced into the driven neuron,the anticipated synchronization can be simulated in the coupled neurons when both neurons are of type-II excitability.With the increase of the conductance of the inhibitory autapse,the transition from delayed synchronization to anticipated synchronization is simulated.The time interval between spike of the driving and driven neuron is acquired,and the parameter ranges of anticipated synchronization in the plane of conductance of the inhibitory autapse and excitatory synapse are obtained.However,if both neurons are of type-I excitability,only delayed synchronization is simulated for the driven neuron with inhibitory autapse.Furthermore,the appearance of anticipated synchronization for type-II neurons and no anticipated synchronization for type-I neurons are suggested to have a relationship between the different responses of firing to external inhibitory stimulation for neurons with type-II excitability and type-I excitability.For spiking of type-II neuron,when an inhibitory pulse stimulation is applied,the spike following the pulse appears earlier than the one in the absence of stimulation in a wide range of the stimulation phase.However,for spiking behavior of type-I excitability,the spike following an inhibitory pulse stimulation appears later than the spike in the absence of stimulation.The results present the condition of single neurons for the appearance of anticipated synchronization induced by the inhibitory self-feedback mediated by autapse,which is helpful for understanding the dynamics of the counter-intuitive behavior,anticipated synchronization,presenting possible measures to modulate the anticipated synchronization,and proving directions for further study of anticipated synchronization.