Excitatory autapse with short time delay can lower the firing frequency of spiking behaviors near subcritical Hopf bifurcation, which is interpreted with type II phase response curve wherein an excitatory impulse current applied at the phase following a spike can induce the next spike delayed. Such a nonlinear phenomenon is different from the common viewpoint that excitatory effect typically induces enhancement of neuronal firing activities. In this paper, more cases of reduction of firing activities induced by excitatory autapse than the one mentioned above are simulated in the Hodgkin-Huxley model with relatively short time delay, and the dynamical mechanism is provided with phase trajectories modulated by excitatory autaptic current and bifurcations. For the monostable spiking near the subcritical Hopf bifurcation, one novel case is induced. The delayed autaptic current pulse evoked by a spike induces the trajectory moved to the neighborhood of the unstable focus, and after the pulse, the subthreshold oscillations with ascending amplitude appear until they evolve to the next spike, which results in mixed subthreshold oscillations and a single spike. For the spiking coexisting with the resting state, which locates between the subcritical Hopf bifurcation and saddle-node bifurcation of limit cycles, two novel cases are induced. One is the mixed-mode oscillations, and the trajectory of subthreshold oscillations begins from the neighborhood outside of the unstable limit cycle, which is induced by the delayed autaptic current pulse. The other is induced by the autaptic current pulse that can cause the trajectory to run into the unstable limit cycle, which leads to the appearance of subthreshold oscillations with descending amplitude after the pulse, and finally evolves to the resting state corresponding to the coexisting stable focus. The results present novel cases that excitatory effects can suppress rather than enhance firing activities and the corresponding dynamical mechanism related to bifurcations, which enrich the study of nonlinear dynamics and neurodynamics, and provide the potential functions of excitatory autapse.

具有短时间延迟的兴奋性自发可以降低亚临界霍普夫分叉附近的尖峰行为的触发频率，这可以通过II型相位响应曲线来解释，其中在尖峰之后的阶段施加的兴奋性脉冲电流可以引起下一个尖峰延迟。这种非线性现象不同于通常的观点，即兴奋作用通常引起神经元放电活动的增强。本文在Hodgkin-Huxley模型中以相对较短的时延模拟了比上述情况更多的由兴奋性自发突触引起的射击活动降低的情况，并且动力学机制提供了由兴奋性自发突触电流和分叉调节的相轨迹。 。对于亚临界Hopf分叉附近的单稳态尖峰，引发了一种新情况。由尖峰引起的延迟的自发电流脉冲诱导轨迹移动到不稳定焦点附近，并且在脉冲之后，出现幅度上升的亚阈值振荡，直到它们发展到下一个尖峰为止，这导致混合的亚阈值振荡和单个穗。对于与静止状态共存的尖峰，它位于极限环的次临界Hopf分叉和鞍形节点分叉之间，引发了两种新情况。一种是混合模式振荡，亚阈值振荡的轨迹从不稳定极限循环之外的附近开始，这是由延迟的自发电流脉冲引起的。另一个是由自给电流脉冲引起的，它可能导致轨迹进入不稳定的极限周期，在脉冲之后，这会导致亚阈值振荡的出现，并出现幅度下降的趋势，最终演变为与并存稳定焦点相对应的静止状态。结果表明，兴奋作用可以抑制而不是增强射击活动以及与分叉有关的相应动力学机制，这丰富了非线性动力学和神经动力学的研究，并提供了兴奋性自发的潜在功能。