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.