Figure 2.

The dynamics of a burst-generator module has 3 phases. (A) The half-center organization consists of modules: flexor (F) and extensor (E) modules, which generate rhythmic bursting activity and these are reciprocally connected via inhibitory modules to ensure F/E alternation. (B,C) The F/E modules are composed of excitatory neurons with pacemaker properties, which are recurrently connected. The module has three phases: (a) When a neuron fire action potentials (arrows) these quickly activate other neurons, since it is supercritical, resulting in an exponential increase in the network activity. More activity leads to more spikes activating more neurons. Once the activity has propagated to the whole network, the neurons reach their max firing rate the network reach saturation (phase b). Shortly there after the adaptation/pacemaker property turns off the firing in the adaptation phase c, and the activity decay back toward quiescence. During the adaptation phase the quiescence also cease the inhibition to the opposite module, allowing a similar cycle to take place there with a delay. Hence, the population alternates between quiescence and maximal firing rates for all the cells in the module.