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SUMMARY:Multi-species studies of vestibular implants
DTSTART:20130516T100000
DTSTAMP:20260916T081640Z
UID:cc5826fbb409655e7e4b8a879c052d27afff56a8e0322f69c1596be6
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Daniel M. Merfeld\, Jenks Vestibular Physiology Laborato
 ry\, Otology and Laryngology\, Harvard Medical School\nDisorders of the pe
 ripheral vestibular system are relatively common and often result in sever
 ely impaired mobility\, blurred vision and debilitating attacks of vertigo
  and motion sickness.  Presently\, little can be done to resolve these sy
 mptoms when they are chronically present. Early research in the area of ve
 stibular neuroprosthetics alongside the success of the cochlear implant\, 
 provides hope that providing motion cues via electrical stimulation may ev
 entually help some patients suffering severe vestibular impairment.  Conc
 eptually\, vestibular prostheses are similar to cochlear implants and cons
 ist of 4 principal elements:  a power source\, motion sensors\, a microco
 ntroller\, and an electrode.  We have developed and tested a vestibular p
 rosthesis 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.\nThis device has been tested in three species.
   In squirrel monkeys\, the lateral canals were plugged bilaterally and o
 ur prosthesis was secured to the head with the angular velocity sensor par
 allel to the axis of the lateral canals.  The stimulating electrode was p
 laced near the ampullary nerve of one lateral canal.  When rotated in the
  dark\, the animals responded with an appropriate horizontal vestibulo-ocu
 lar reflex (VOR)\, which adapted over time\, providing evidence that the C
 NS was utilizing the information provided electrically.  Data also show t
 hat the artificial rotational cue provided by the prosthesis is combined w
 ith normal sensory cues measuring the relative orientation of gravity.  I
 n another experiment\, guinea pigs were provided chronic constant-rate sti
 mulation and responded with a brisk nystagmus that adapted away after abou
 t a day. \nWhen the stimulation was removed\, a brisk nystagmus in the op
 posite direction was measured\, again lasting about a day.  These finding
 s demonstrate adaptation to constant-rate stimulation.  When the stimulat
 ion was alternately turned on and off weekly\, the nystagmus response bega
 n to decay more rapidly\, eventually decaying just a few seconds after the
  device was turned on or off.  This indicates that\, with repetitive appl
 ication of chronic stimulation\, the animal learned to adapt rapidly to th
 e present state (on or off) of stimulation.  Such “switching” will be
  important for users of vestibular prosthetics so they don’t feel disori
 ented when they remove the device to sleep\, shower\, etc.  In studies wi
 th rhesus monkeys\, we inserted an electrode into the right posterior cana
 l.  We have found that that the application of prosthetic stimulation to 
 a posterior canal yields perceived tilt illusions consistent with predicti
 ons for normal semicircular canal stimulation.  While all of this prelimi
 nary work suggests clinical potential\, many questions remain unanswered\,
  and many challenges must be addressed prior to clinical use.
LOCATION:SV 1717A
STATUS:CONFIRMED
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