FIG. 4.
Effects of changes in drives Di to each neuron in the 3-phase rhythm-generating state, in (mAD2, mAD3) space. As in Fig. 2C, solid curves are trajectories, dashed curves denote I-to-E transitions, and dash-dotted curves denote E-to-I transitions. As in Fig. 3, changes were produced by changes in total drives to the pre-I neuron (D1, A), the early-I neuron (D2, B), the post-I neuron (D3, C), and the aug-E neuron (D4, D). Note that each trajectory evolves in a counterclockwise direction, with mAD2 increasing during inspiration and decreasing during expiration. Also, each E-to-I transition curve includes 2 components, as in Fig. 2C. Different levels of drives are color-coded as indicated in the figure panels.