Fig. 4
From: Phase-Amplitude Descriptions of Neural Oscillator Models

Typical trajectory of the ML model of the transformed system. Left: Time evolution of θ and ρ. Right: Trajectory plotted in the phase plane. We see that when ρ has a local maximum, the evolution of θ slows down, corresponding to where trajectories pass near to the saddle node. Parameter values as in Appendix B.1