title: Vestibular prosthesis tested in rhesus monkeys.
abstract: We are studying the effectiveness of a semicircular canal prosthesis to improve postural control, perception of spatial orientation, and the VOR in rhesus monkeys with bilateral vestibular hypofunction. Balance is examined by measuring spontaneous sway of the body during quiet stance and postural responses evoked by head turns and rotation of the support surface; perception is measured with a task derived from the subjective visual vertical (SVV) test during static and dynamic rotation in the roll plane; and the angular VOR is measured during rotation about the roll, pitch, and yaw axes. After the normal responses are characterized, bilateral vestibular loss is induced with intratympanic gentamicin, and then multisite stimulating electrodes are chronically implanted into the ampullae of all three canals in one ear. The postural, perceptual, and VOR responses are then characterized in the ablated state, and then bilateral, chronic electrical stimulation is applied to the ampullary nerves using a prosthesis that senses angular head velocity in three-dimensions and uses this information to modulate the rate of current pulses provided by the implanted electrodes. We are currently characterizing two normal monkeys with these paradigms, and vestibular ablation and electrode implantation are planned for the near future. In one prior rhesus monkey tested with this approach, we found that a one-dimensional (posterior canal) prosthesis improved balance during head turns, perceived head orientation during roll tilts, and the VOR in the plane of the instrumented canal. We therefore predict that the more complete information provided by a three-dimensional prosthesis that modulates activity in bilaterally-paired canals will exceed the benefits provided by the one-dimensional, unilateral approach used in our preliminary studies.
authors.affiliation: Jenks Vestibular Physiology Laboratory, Massachusetts Eye and Ear Infirmary, Department of Otology and Laryngology at the Harvard Medical School, Boston, MA 02114, USA. richard_lewis@meei.harvard.edu
authors.forename: Richard F
authors.initials: RF
authors.lastname: Lewis
authors.forename: Csilla
authors.initials: C
authors.lastname: Haburcakova
authors.forename: Wangsong
authors.initials: W
authors.lastname: Gong
authors.forename: Daniel
authors.initials: D
authors.lastname: Lee
authors.forename: Conrad
authors.initials: C
authors.lastname: Wall
authors.forename: Lara
authors.initials: L
authors.lastname: Thompson
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Merfeld
mesh_terms: D000818:Animals; D004599:Electric Stimulation Therapy / Q000295:instrumentation* / Q000379:methods; D019544:Equipment Failure Analysis; D008253:Macaca mulatta; D004856:Postural Balance; D019736:Prostheses and Implants; D011474:Prosthesis Design; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016896:Treatment Outcome; D015837:Vestibular Diseases / Q000503:physiopathology* / Q000534:rehabilitation*