Multi-species studies of vestibular implants
Event details
| Date | 16.05.2013 |
| Hour | 10:00 |
| Speaker | Prof. Daniel M. Merfeld, Jenks Vestibular Physiology Laboratory, Otology and Laryngology, Harvard Medical School |
| Location |
SV 1717A
|
| Category | Conferences - Seminars |
Disorders of the peripheral vestibular system are relatively common and often result in severely impaired mobility, blurred vision and debilitating attacks of vertigo and motion sickness. Presently, little can be done to resolve these symptoms when they are chronically present. Early research in the area of vestibular neuroprosthetics alongside the success of the cochlear implant, provides hope that providing motion cues via electrical stimulation may eventually help some patients suffering severe vestibular impairment. Conceptually, vestibular prostheses are similar to cochlear implants and consist of 4 principal elements: a power source, motion sensors, a microcontroller, and an electrode. We have developed and tested a vestibular prosthesis that senses yaw angular head velocity and uses this information to modulate the rate of current pulses applied to the vestibular nerve via an electrode chronically.
This device has been tested in three species. In squirrel monkeys, the lateral canals were plugged bilaterally and our prosthesis was secured to the head with the angular velocity sensor parallel to the axis of the lateral canals. The stimulating electrode was placed near the ampullary nerve of one lateral canal. When rotated in the dark, the animals responded with an appropriate horizontal vestibulo-ocular reflex (VOR), which adapted over time, providing evidence that the CNS was utilizing the information provided electrically. Data also show that the artificial rotational cue provided by the prosthesis is combined with normal sensory cues measuring the relative orientation of gravity. In another experiment, guinea pigs were provided chronic constant-rate stimulation and responded with a brisk nystagmus that adapted away after about a day.
When the stimulation was removed, a brisk nystagmus in the opposite direction was measured, again lasting about a day. These findings demonstrate adaptation to constant-rate stimulation. When the stimulation was alternately turned on and off weekly, the nystagmus response began to decay more rapidly, eventually decaying just a few seconds after the device was turned on or off. This indicates that, with repetitive application of chronic stimulation, the animal learned to adapt rapidly to the present state (on or off) of stimulation. Such “switching” will be important for users of vestibular prosthetics so they don’t feel disoriented when they remove the device to sleep, shower, etc. In studies with rhesus monkeys, we inserted an electrode into the right posterior canal. We have found that that the application of prosthetic stimulation to a posterior canal yields perceived tilt illusions consistent with predictions for normal semicircular canal stimulation. While all of this preliminary work suggests clinical potential, many questions remain unanswered, and many challenges must be addressed prior to clinical use.
This device has been tested in three species. In squirrel monkeys, the lateral canals were plugged bilaterally and our prosthesis was secured to the head with the angular velocity sensor parallel to the axis of the lateral canals. The stimulating electrode was placed near the ampullary nerve of one lateral canal. When rotated in the dark, the animals responded with an appropriate horizontal vestibulo-ocular reflex (VOR), which adapted over time, providing evidence that the CNS was utilizing the information provided electrically. Data also show that the artificial rotational cue provided by the prosthesis is combined with normal sensory cues measuring the relative orientation of gravity. In another experiment, guinea pigs were provided chronic constant-rate stimulation and responded with a brisk nystagmus that adapted away after about a day.
When the stimulation was removed, a brisk nystagmus in the opposite direction was measured, again lasting about a day. These findings demonstrate adaptation to constant-rate stimulation. When the stimulation was alternately turned on and off weekly, the nystagmus response began to decay more rapidly, eventually decaying just a few seconds after the device was turned on or off. This indicates that, with repetitive application of chronic stimulation, the animal learned to adapt rapidly to the present state (on or off) of stimulation. Such “switching” will be important for users of vestibular prosthetics so they don’t feel disoriented when they remove the device to sleep, shower, etc. In studies with rhesus monkeys, we inserted an electrode into the right posterior canal. We have found that that the application of prosthetic stimulation to a posterior canal yields perceived tilt illusions consistent with predictions for normal semicircular canal stimulation. While all of this preliminary work suggests clinical potential, many questions remain unanswered, and many challenges must be addressed prior to clinical use.
Practical information
- General public
- Free
Organizer
- Prof. S. Micera