Robustness of respiratory rhythm generation across dynamic regimes
Fig 2
(A): The Vpre−I-nullcline structure for the pre-I unit in the preBötC depends on its tonic drive parameter, c11. Blue curves denote the Vpre−I-nullcline for several values of c11, with different line patterns used for contrast enhancement. The red curve is the hpre−I-nullcline, which is independent of c11. A fixed point occurs where the two nullclines intersect. (B): Bifurcation diagram for the pre-I unit with respect to c11. Solid (dashed) curve denotes stable (unstable) equilibria. Red curves are max and min voltages along a family of stable periodic orbits; these grow extremely rapidly in amplitude when they first appear, near c11 = −0.060. Pre-I is oscillatory where these orbits exist, on c11 ∈ (−0.060, −0.011). Inset shows dependence of periods on c11; period jumps sharply from 0 at the onset of oscillations, drops abruptly, and then decays more gradually as c11 increases.