Spontaneous excitability in the Morris--Lecar model with ion channel noise

TL;DR

This paper investigates how ion channel noise induces spontaneous firing in Morris-Lecar neurons, revealing a unified mechanism underlying excitability despite differences in deterministic dynamics.

Contribution

It develops asymptotic approximations of stationary densities and most probable paths to explain channel noise effects on spontaneous excitability in type I and II neurons.

Findings

Ion channel noise can induce spontaneous firing in Morris-Lecar neurons.

A single mechanism explains excitability in both neuron types despite different deterministic behaviors.

Asymptotic methods reveal the role of channel noise in spontaneous action potentials.

Abstract

Noise induced excitability is studied in type I and II Morris-Lecar neurons subject to constant sub threshold input, where fluctuations arise from sodium and potassium ion channels. Ion channels open and close randomly, creating current fluctuations that can induce spontaneous firing of action potentials. Both noise sources are assumed to be weak so that spontaneous action potentials occur on a longer timescale than ion channel fluctuations. Asymptotic approximations of the stationary density function and most probable paths are developed to understand the role of channel noise in spontaneous excitability. Even though the deterministic dynamical behavior of type I and II action potentials differ, results show that a single mechanism explains how ion channel noise generates spontaneous action potentials.