title: Spike-Threshold Variability Originated from Separatrix-Crossing in Neuronal Dynamics.
abstract: The threshold voltage for action potential generation is a key regulator of neuronal signal processing, yet the mechanism of its dynamic variation is still not well described. In this paper, we propose that threshold phenomena can be classified as parameter thresholds and state thresholds. Voltage thresholds which belong to the state threshold are determined by the 'general separatrix' in state space. We demonstrate that the separatrix generally exists in the state space of neuron models. The general form of separatrix was assumed as the function of both states and stimuli and the previously assumed threshold evolving equation versus time is naturally deduced from the separatrix. In terms of neuronal dynamics, the threshold voltage variation, which is affected by different stimuli, is determined by crossing the separatrix at different points in state space. We suggest that the separatrix-crossing mechanism in state space is the intrinsic dynamic mechanism for threshold voltages and post-stimulus threshold phenomena. These proposals are also systematically verified in example models, three of which have analytic separatrices and one is the classic Hodgkin-Huxley model. The separatrix-crossing framework provides an overview of the neuronal threshold and will facilitate understanding of the nature of threshold variability.
authors.affiliation: Institute of Theoretical Physics, Lanzhou University, Lanzhou, Gansu 730000, China.
authors.forename: Longfei
authors.initials: L
authors.lastname: Wang
authors.affiliation: College of Physics and Information Technology, Shaanxi Normal University, Xi'an 710062, China.
authors.forename: Hengtong
authors.initials: H
authors.lastname: Wang
authors.affiliation: Institute of Theoretical Physics, Lanzhou University, Lanzhou, Gansu 730000, China.
authors.forename: Lianchun
authors.initials: L
authors.lastname: Yu
authors.affiliation: Center of Soft Matter Physics and its Application, Beihang University, Beijing 100191, China.|School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Chen
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000465:Algorithms; D000818:Animals; D003198:Computer Simulation; D004558:Electric Stimulation; D006801:Humans; D008564:Membrane Potentials / Q000502:physiology; D008959:Models, Neurological; D009474:Neurons / Q000502:physiology*