Abstract
This tutorial illustrates the use of data assimilation algorithms to estimate unobserved variables and unknown parameters of conductance-based neuronal models. Modern data assimilation (DA) techniques are widely used in climate science and weather prediction, but have only recently begun to be applied in neuroscience. The two main classes of DA techniques are sequential methods and variational methods. We provide computer code implementing basic versions of a method from each class, the Unscented Kalman Filter and 4D-Var, and demonstrate how to use these algorithms to infer several parameters of the Morris–Lecar model from a single voltage trace. Depending on parameters, the Morris–Lecar model exhibits qualitatively different types of neuronal excitability due to changes in the underlying bifurcation structure. We show that when presented with voltage traces from each of the various excitability regimes, the DA methods can identify parameter sets that produce the correct bifurcation structure even with initial parameter guesses that correspond to a different excitability regime. This demonstrates the ability of DA techniques to perform nonlinear state and parameter estimation and introduces the geometric structure of inferred models as a novel qualitative measure of estimation success. We conclude by discussing extensions of these DA algorithms that have appeared in the neuroscience literature.
Highlights
1.1 The Parameter Estimation ProblemThe goal of conductance-based modeling is to be able to reproduce, explain, and predict the electrical behavior of a neuron or networks of neurons
We cannot be cavalier with using as much data with 4D-Var as we did with the Unscented Kalman Filter (UKF), as that would result in a (200,001)2 + 8 = 400,010 dimensional problem
We ran the UKF with initial parameter guesses corresponding to the same bursting regime as the observed data
Summary
1.1 The Parameter Estimation ProblemThe goal of conductance-based modeling is to be able to reproduce, explain, and predict the electrical behavior of a neuron or networks of neurons. Conductancebased modeling of neuronal excitability began in the 1950s with the Hodgkin–Huxley model of action potential generation in the squid giant axon [1]. This modeling framework uses an equivalent circuit representation for the movement of ions across the cell membrane: dV C = Iapp − Iion, (1). The ionic currents arise from channels in the membrane that are voltage- or calcium-gated and selective for particular ions, such sodium (Na+) and potassium (K+). The maximal conductance gion is a parameter that represents the density of channels in the membrane. The gating variable n is the probability that one of four identical subunits of the potassium channel is open. The dynamics of the gating variables are given by dx
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