Contralateral two-CPG models. Two contralateral two-CPG models were tested: 1) contralateral flexor-flexor/extensor-extensor (f-f/e-e) and 2) contralateral flexor-extensor/extensor-flexor (f-e/e-f). "Max" label indicates maximal enhancement due to excitatory interlimb coupling, where enhancement equalled the maximum amplitude observed within a single excitatory sensory feedback gain minus the amplitude observed with no interlimb coupling gain (i.e. hc = 0). Other figure details are the same as in Figure 3.