Neuronal activity in the vestibular nuclei after trigeminal stimulation

The activity of 131 vestibular neurons was investigated in 40 guinea pigs during trigeminal stimulation. The influence of trigeminal sensory information was tested by means of electrical stimulation of the trunk of the trigeminal nerve and with nonnociceptive cutaneous stimulation of facial areas. The spontaneous activity of vestibular neurons was modified by trigeminal electrical stimulation with an increase or decrease of the discharge rate. Some units underwent rhythmic modulation. Forty-one percent of recorded units responded also to cutaneous trigeminal stimulation. An analysis of vestibular action potentials evoked by trigeminal stimulation revealed latency values from 1.2 to 6.2 ms. The anatomic-functional relationship between the trigeminal and the vestibular systems is discussed in light of the reported results.