The vestibular system produces a variety of compensatory responses to
accelerations of the head, which include reflex responses recorded fro
m respiratory muscle nerves of the thorax and abdomen. In order to bet
ter understand the functional significance of vestibulo-respiratory re
flexes, we investigated the extent to which such responses are also pr
esent on muscle nerves of the upper airway. Experiments were conducted
on adult cats that were decerebrated, paralyzed, and artificially ven
tilated. Electrical stimulation of the vestibular nerve using short tr
ains of current pulses evoked reflex responses on the following nerves
: recurrent laryngeal, superior laryngeal, pharyngeal branch of the va
gus, glossopharyngeal, and hypoglossal. The responses were bilateral a
nd occurred on average within about 15 ms after stimulus onset. The me
dial and inferior vestibular nuclei wore shown to be essential for the
reflex, since the responses were abolished by injections of the neuro
toxin kainic acid into these nuclei. The widespread presence of vestib
ular-evoked responses recorded from respiratory muscle nerves of the u
pper airway, as well as from those of the thorax and abdomen, suggests
that one function of vestibulo-respiratory reflexes is to provide adj
ustments in breathing and airway patency during movements and changes
in posture.