Chronic vestibulo-ocular reflexes evoked by a vestibular prosthesis.

We are developing prosthetics for patients suffering from peripheral vestibular dysfunction. We tested a sensory-replacement prosthesis that stimulates neurons innervating the vestibular system by providing chronic pulsatile stimulation to electrodes placed in monkeys' lateral semicircular canals, which were plugged bilaterally, and used head angular velocity to modulate the current pulse rate. As an encouraging finding, we observed vestibulo-ocular reflexes that continued to be evoked by the motion-modulated stimulation months after the nystagmus evoked by the constant-rate baseline stimulation had dissipated. This suggests that long-term functional replacement of absent vestibular function is feasible.