Paradoxical phase response at late expiration by superior laryngeal nerve stimulation.

Superior laryngeal nerve (SLN) stimulation during expiration prolongs the respiratory cycle in decerebrate, vagotomized and paralysed cats. In a few animals, however, the cycle can be terminated prematurely by the same stimulus. We developed a mathematical model of the respiratory neural network to stimulate these responses. The model contained inspiratory decrementing (I-DEC), and augmenting (I-AUG) and expiratory decrementing (E-DEC), and augmenting (E-AUG) neurones. Connections were based on published findings. SLN stimulation during late expiration prolonged the cycle when it was assumed to excite principally E-DEC neurones, whereas it terminated the cycle prematurely when it was assumed to excite both I-DEC and E-DEC neurones. Therefore, phase-resetting depends on the differential strength of afferent connections on the network's elements.