The classic FN equations model the spike potentials of neurons, where system components \(X = (V,R)\) represent the voltage and recovery variables, respectively.
\(V\) and \(R\) are governed by the following differential equations:
$$ \frac{dV}{dt} = c(V-\frac{V^3}{3}+R) $$
$$ \frac{dR}{dt} = -\frac{1}{c}(V-a+bR) $$
where \(\theta = (a,b,c)\) are system parameters.