Effect of Vestibular Perceptual Learning on Vestibular Thresholds and Balance

The intervention being studied is a minimal risk perceptual learning protocol delivered in an academic laboratory setting; the goal of the intervention is to improve the perception of passive whole-body tilts, as well as balance, by providing feedback during passive tilts of the body. The protocol lasts a total of 6 days: Day 1 includes a pre-test assessment of perception and balance, as well as 100 repetitions of training, Days 2-5 each include 300 repetitions of training, and Day 6 includes only post-test assessments of perception and balance.

Four training paradigms will be evaluated in 4 cohorts of older 10 adults (N=40; Ages 60 to 89). The first training protocol will be a roll tilt training protocol previously shown to reduce roll tilt thresholds. The remaining three training protocols will include the parameters (i.e., plane of tilt, feedback schema, and difficulty level) found most effective following a series of basic science human subject experiments. As such, each cohort will perform perceptual training using a combination of the following training parameters:

1. Tilt Plane: training stimuli will either be in (A) the roll plane, (B) the pitch plane, (C) in the anatomical plane of vertical semi-circular canals (i.e., 45 degrees between the roll and pitch planes).
2. Difficulty Level: As was done in a published study of roll tilt perceptual training, the training stimuli will be adjusted during each training session using an adaptive staircase procedure. Older adults will train using either a (A) 2-Down/1-Up (i.e., the size of the tilt stimulus decreases after 2 consecutive correct responses and increases after each incorrect response), (B) 3-Down/1-Up, or (C) 6-Down/1-Up staircase. The respective staircases target a stimulus that, on average, should yield an accuracy level of 70.7%, 79.4%, and 89.1%, and thus represent a progressive decrease in difficulty level.
3. Feedback Method: During training, the accuracy of perceptual judgement (e.g., recognizing a left vs. right tilt motion) will be provided to the subject using one of three feedback schema: (A) an auditory stimulus indicating when an answer is correct, as well as incorrect, (B) a visual stimulus provided after the subject responds (i.e., chooses left or right) during the return of the chair to an upright position (i.e., tilting back to the start), or (C) a combination of auditory feedback and visual feedback.

Specifically, one cohort of older adults will use the training protocol that, after completion of pilot experiments, is found to most effectively reduce tilt thresholds in young adults, another cohort will use the training protocol that yields the best change in balance in young adults, and the last cohort will use the remaining training protocol judged to best reduce thresholds AND yield the best sway changes. A training protocol may be repeated in more than one older adult cohort (e.g., if best threshold and best balance change are achieved via the same protocol in young adults) however each older adult participant recruited will only be randomly assigned to a single test condition. All other elements of the training not outlined above, (e.g., 6 days for testing/training visits, etc.) will mimic the published protocol.

The targeted dates for each assessment and intervention period are shown, however, to permit greater adherence to the study protocol, tests of retention will be accepted if they occur within 7 to 10 days after the post-test (for the one-week follow-up) or 30 to 40 days after the post-test (for the one-month follow-up).

1. Intervention-First arm:

   1. Day 1: Pre-test assessment
   2. Days 2-5: Active perceptual learning intervention
   3. Day 6: Post-test assessment
   4. Day 13: One-week retention assessment
   5. Day 36: One-month retention assessment
   6. Days 37-40: Control intervention
   7. Day 41: Post-test assessment
2. Control-First arm:

   1. Day 1: Pre-test assessment
   2. Days 2-5: Control intervention
   3. Day 6: Post-test / Pre-Test assessment
   4. Days 7 to 10: Active perceptual learning intervention
   5. Day 11: Post-test assessment
   6. Day 18: One-week retention assessment
   7. Day 41: One-month retention assessment

Eligibility Criteria:
Inclusion Criteria:

* Must be able to stand
* No leg or foot amputations
* No lower limb braces
* Not currently feeling dizzy/lightheaded
* Not currently pregnant by self-report
* Weight \<= 275 pounds

Exclusion Criteria:

* Severe head trauma or traumatic brain injury
* Any vestibular disorder (e.g., Meniere's Disease, Vestibular Migraine, Unresolved benign paroxysmal positional vertigo (BPPV), Vestibular hypofunction, except that due to aging, PPPD) as assessed by a Vestibular OtoNeurologist and Neurotologist using clinical diagnostic tests described in proposal plus any additional clinical evaluations they identify
* History of seizures
* Neurologic illness or condition determined by an Otoneurologist known to impact vestibular or balance function(e.g., stroke, neurodegenerative disorders, demyelinating illness)
* Major psychiatric (e.g., panic disorder, psychosis, etc.) disorder
* 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, or any other eye condition that limits vision to worse than 20/40
* Recent (\<6 months) orthopedic injuries of the lower extremities (e.g., plantar fasciitis, ankle, knee or hip injury, back strain/herniated disc, ...).
* Upper extremity injuries requiring current sling immobilization
* Recent surgery
* Any other severe health problem (heart disease, pulmonary disease, cancer, etc.).
* Vision in both eyes must be better than 20/40 with best correction
* Due to the potential for nausea with some of the motion stimuli, and to protect fetus and mother, pregnant women will also be excluded from this study
* Since every possible exclusionary factor cannot be predicted, additional exclusion criteria may be required