Respiratory rhythmicity in a split medulla preparation of the cat.

Splitting the medulla in the cat resulted in the disappearance of inspiratory activity in the phrenic but not in the recurrent laryngeal nerves with minor changes in respiratory cycle duration. In one animal a complete desynchronization of respiratory rhythms was observed in the opposite recurrent laryngeal nerves. We conclude that each half of the cat's brain stem has its own respiratory phase-switching mechanism. Commissural connections are involved in the bilateral synchronization of activity and the mutual excitatory interactions between medullary respiratory neurons.