Integrate-and-fire neurons coupled by excitatory pulses self-organize into synchrony. Each neuron charges until threshold, fires a pulse advancing all others, and resets. Mirollo-Strogatz (1990) proved all-to-all coupling always synchronizes.
Mirollo-Strogatz (1990): N all-to-all coupled integrate-and-fire oscillators synchronize in finite time from almost all initial conditions. Firefly synchronization, cardiac pacemakers, neural circuits.