Figure 4.

Development of alternans. Steady-state restitution curve for rate-dependent excitation threshold (β = 1 × 10^-3 and α = 0.346). Inserts A and B show T_h response to a 5% perturbation in stimulation rate, for initial T_m = 50.40 (v_r = 0.30). The adaptation constant for insert A is τ = 144 and for insert B is τ = 576. Inserts C and D show T_h alternans for the same two adaptation constants (τ = 144 for C and τ = 576 for D) with initial T_m = 37.94 (v_r = 0.31). The horizontal dashed line near the end of the restitution curve marks the critical duration of a solitary pulse, .