Oscillator neurons in crustacean ganglia.

The motor rhythm of ventilation in hermit crabs and lobsters appears to be controlled by a pair of neurons, one in each half of the subesophageal ganglion. Their membrane potentials oscillate and upon depolarization and hyperpolarization elicit spiking in two pools of motor neurons on each side, without spikes in the oscillator neurons themselves. The fact that higher order (command) interneurons can control the rate of the oscillator by means of a smoothly graded input lends support to the idea that oscillator neurons respond periodically to a constant ionic stimulus.