VESTIBULAR INFLUENCES ON HYPOGLOSSAL NERVE ACTIVITY IN THE CAT

The purpose of the present study was to determine if selective activat ion of vestibular receptors during movement produces changes in hypogl ossal nerve activity. Responses were recorded from the hypoglossal ner ves during trapezoidal and sinusoidal head rotations in cats with exte nsive denervations to eliminate non-labyrinthine inputs that could be produced by the movements. Large (50 degrees) nose-up trapezoidal tilt s produced an increase in nerve discharge; ear-down tilt was also effe ctive in one-fourth of the animals. The responses to nose-up tilt were abolished following Intracranial transections of the VIIIth cranial n erves. Smaller (20 degrees) sinusoidal head rotations in the roll, pit ch and yaw planes were ineffective in producing responses. These data suggest that vestibular inputs elicited by nose-up pitch contribute to tongue protrusion and participate in maintaining airway patency by pr eventing the tongue from falling to the back of the mouth.