Fig. 5.

Simulation of a nonlinear model. (A) Bending activity of a midbody segment. Blue, bending amplitude during normal locomotion; red, when the head and body undulation was decoupled, oscillation with higher frequency and lower amplitude emerged. (B) Nullcline analysis of motor neuron dynamics. The n- and V-nullclines were defined as $dn/dt=0,\hspace{0.17em}\hspace{0.5em}dV/dt=0$, respectively. In the absence of proprioceptive coupling and AVB-B gap junctions ($g_{AVB-B}=0),$ the fixed point of the membrane potential dynamics (green) corresponds to a steady state; in the presence of AVB-B gap junctions, that is, $g_{AVB-B}=100\hspace{0.17em}\mathrm{ps}$, the system undergoes bifurcation, and the new fixed point becomes unstable (red), leading to periodic oscillation. (C) A comparison of bending amplitude along the body, with and without AVB-B gap junctions. All parameters used in the simulation are described in Supporting Information.