Bilateral Vestibular Hypofunction, Healthy Controls, Presbyvestibulopathy, Vestibular Hypofunction
Conditions
Keywords
Bilateral Vestibular Hypofunction, Vestibular Rehabilitation
Brief summary
The nervous system responds to changes in external or internal conditions by altering the behavior of neurons through multiple forms of neural plasticity. A specific form of plasticity, "homeostatic plasticity", stabilizes neural activity by driving the excitability of neurons toward a "set-point" level of activity. Over the last six years, new data have come to light showing that the vestibular system also possess a robust capacity to modulate sensitivity to self-motion cues in response to prolonged periods of motion. Collectively, these studies have demonstrated a capacity to use motion perturbations (i.e., low, or high levels of vestibular stimulation) to dynamically adjust the sensitivity of the vestibular system on both the single neuron and behavioral levels. The ability to use subthreshold motion stimuli to drive plasticity in the vestibular system motivates this study. The investigators aim to determine the impact of subthreshold motion on (a) balance performance and (b) balance training in individuals with peripheral vestibular hypofunction.
Detailed description
The investigators aim to test (1) if sub threshold motion improves motion perception, (2) if sub threshold motion improves balance performance, and (3) if sub threshold motion prior to balance training leads to improved balance performance. Twenty-four subjects with peripheral vestibular hypofunction (12 with bilateral and 12 with unilateral hypofunction) and twenty-four healthy control participants will complete the study. Each participant will complete four visits to the laboratory. Day 1 will measure the capacity to modify balance and self-motion perception after a single block of subthreshold motion, including any retention effects after a washout period. Days 2-4 will be performed in random order and will test changes in balance and self-motion perception after (a) repeated balance training, (b) repeated subthreshold motion, and (c) balance training combined with sub threshold motion.
Interventions
BEHAVIORALSubthreshold Vestibular Conditioning
Subthreshold vestibular conditioning will be performed while seated on a motion platform and blindfolded. The stimulus will consist of a pseudorandom sum-of-sinusoids roll tilt motion (\~0.08 to 1 Hz) delivered at a peak velocity equal to 57.4% of the measured baseline roll tilt perceptual threshold (e.g., 0.574°/s for a 1 °/s threshold). The participant will be informed that while the chair may vibrate or move slightly, the motion will not occur in any particular direction.
BEHAVIORALBalance Training
Balance training will consist of progressive exposure to continuous one-dimensional roll pseudorandom platform perturbations delivered using a 6DoF motion platform. Participants will stand on a MOOG hexapod motion platform and will be secured using a safety harness tethered to the ceiling and a full enclosure of safety rails. Roll tilt perturbations will be progressed by gradually increasing the displacement/velocity/acceleration of the platform motion.
OTHERBalance Training Plus Subthreshold Conditioning
Subthreshold vestibular conditioning will be performed while seated on a motion platform and blindfolded prior to each bout of balance training. Subthreshold conditioning will consist of a pseudorandom sum-of-sinusoids roll tilt motion (\~0.08 to 1 Hz) delivered at a peak velocity equal to 57.4% of the measured baseline roll tilt perceptual threshold (e.g., 0.574°/s for a 1 °/s threshold). The participant will be informed that while the chair may vibrate or move slightly, the motion will not occur in any particular direction. Balance training will consist of progressive exposure to continuous two-dimensional (2D) pseudorandom platform perturbations delivered using a 6DoF motion platform. 2D perturbations (roll and pitch tilt) will be progressed by gradually increasing the displacement/velocity/acceleration of the motion stimulus.
Sponsors
Creighton University
National Institute on Deafness and Other Communication Disorders (NIDCD)
Study design
Allocation
NA
Intervention model
SINGLE_GROUP
Primary purpose
BASIC_SCIENCE
Masking
NONE
Masking description
All participants will complete all elements of the study. However, they will be blinded to the nature of each day of the study (i.e., will be unaware of participation in a "sham" vs. "motion" stimulus).
Intervention model description
Each participant will complete all four days of the study.
Eligibility
Sex/Gender
ALL
Age
19 Years to 89 Years
Healthy volunteers
Yes
Inclusion criteria
for Bilateral Vestibular Hypofunction: 1\. Bilateral lateral canal VOR gain of \< 0.8 on video head impulse testing OR bilateral positive bedside head impulse test Inclusion Criteria for Unilateral Vestibular Hypofunction: 1\. Unilateral yaw aVOR gain of \< 0.8 on video head impulse testing OR unilateral positive bedside head impulse test Inclusion Criteria for all Participants: 1. Must be able to stand for 5 minutes unassisted 2. No leg or foot amputations 3. No lower limb braces 4. Not currently pregnant by self-report 5. Weight \<= 300 pounds (due to limitations of testing equipment)
Exclusion criteria
for all participants: 1. Severe head trauma or traumatic brain injury 2. History of seizures 3. Alternative neurologic illness or condition known to impact vestibular or balance function (e.g., stroke, neurodegenerative disorders, demyelinating illness) 4. Major psychiatric (e.g., panic disorder, psychosis, etc.) disorder 5. Any of the following eye diseases or conditions: amblyopia (or "lazy eye") or history of amblyopia, diagnosis of age- related macular degeneration, retina dystrophy, glaucoma, cataracts, 6. Recent (\<6 months) orthopedic injury that may affect test performance 7. Recent surgery (\< 6 months) that may impact test performance. 8. Other severe health problems (heart disease, pulmonary disease, cancer, etc.) that may affect test performance 9. Due to potentially nauseogenic nature of some motions and to protect fetus and mother, pregnant women will also be excluded from this study * Since the investigators cannot address every possible potential individual recruit in advance, additional
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Perturbed Stance Postural Control | At each of the 4 visits, outcome measures will be captured at (1) beginning of the visit (i.e., baseline), (2) post-intervention (20 minutes after baseline), and (3) post-washout (20 minutes after the post-intervention assessment). | The RMSD of mediolateral (ML) and anteroposterior (AP) postural sway will be measured in response to pseudorandom two-dimensional mediolateral and anteroposterior tilts of the support surface delivered using a 6DoF motion platform. Participants will stand with eyes closed and feet at a standardized distance on top of the motion platform. The platform will tilt simultaneously in both the roll and pitch planes, with each plane of tilt having independent frequency spectra (\~0.08 to 1 Hz). The perturbation test will last approximately 2 minutes. |
| Vestibular Perceptual Thresholds - 0.5Hz Roll Tilt | At each of the 4 visits, outcome measures will be captured at (1) beginning of the visit (i.e., baseline), (2) post-intervention (20 minutes after baseline), and (3) post-washout (20 minutes after the post-intervention assessment). | Vestibular perceptual thresholds will be measured using a forced-choice direction recognition task using methods that the investigators have used extensively. Subjects will be tilted in the coronal plane (i.e., roll tilt) in one of two directions (e.g., towards the left or right) in complete darkness while seated on a 6DoF platform. To mask potential auditory directionality cues, auditory "noise" - uncorrelated with motion (amplitude, direction, or type) - will be applied at approximately 60 dB SPL. Motion stimuli will consist of single cycles of sinusoidal acceleration. After each motion, the participant will be asked to judge the direction of the tilt stimulus, with the threshold being defined as the smallest velocity of tilt that can be accurately perceived. |
Countries
United States
Contacts
CONTACTAndrew R Wagner, PhD
Outcome results
None listed