Effect of Vestibular Perceptual Learning on Vestibular Thresholds and Balance

Sponsor

Ohio State University (Other)

Overall Status

Not yet recruiting

CT.gov ID

NCT05818787

Collaborator

National Institute on Aging (NIA) (NIH)

Enrollment

Location

Arms

Anticipated Duration (Months)

1.4

Patients Per Site Per Month

Study Details

Study Description

Brief Summary

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.

Condition or Disease	Intervention/Treatment	Phase
Healthy Aging	Behavioral: Vestibular Perceptual Learning Behavioral: Placebo Intervention	N/A

Detailed Description

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:

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).
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.
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).

Intervention-First arm:
Day 1: Pre-test assessment
Days 2-5: Active perceptual learning intervention
Day 6: Post-test assessment
Day 13: One-week retention assessment
Day 36: One-month retention assessment
Days 37-40: Control intervention
Day 41: Post-test assessment
Control-First arm:
Day 1: Pre-test assessment
Days 2-5: Control intervention
Day 6: Post-test / Pre-Test assessment
Days 7 to 10: Active perceptual learning intervention
Day 11: Post-test assessment
Day 18: One-week retention assessment
Day 41: One-month retention assessment

Study Design

Study Type:

Interventional

Anticipated Enrollment :

40 participants

Allocation:

Randomized

Intervention Model:

Crossover Assignment

Intervention Model Description:

Four training paradigms will be evaluated in 4 cohorts of older 10 adults; each subject will complete only one training task. In addition to the active perceptual learning task, each subject will complete a control (i.e., placebo) intervention. Half of each cohort will begin with the perceptual learning protocol, and half will begin with the placebo; assignment will be randomized. One of the training protocols 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 that will be completed prior to enrollment begins in the present clinical trial.Four training paradigms will be evaluated in 4 cohorts of older 10 adults; each subject will complete only one training task. In addition to the active perceptual learning task, each subject will complete a control (i.e., placebo) intervention. Half of each cohort will begin with the perceptual learning protocol, and half will begin with the placebo; assignment will be randomized. One of the training protocols 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 that will be completed prior to enrollment begins in the present clinical trial.

Masking:

Single (Outcomes Assessor)

Masking Description:

Statistical analysis at the conclusion of the trial will be completed using de-identified data, masking the outcomes assessor from the identity and group assignment of each individual.

Primary Purpose:

Basic Science

Official Title:

Effect of Vestibular Perceptual Learning on Vestibular Thresholds and Balance

Anticipated Study Start Date :

Jan 1, 2024

Anticipated Primary Completion Date :

Dec 31, 2025

Anticipated Study Completion Date :

Jun 1, 2026

Arms and Interventions

Arm	Intervention/Treatment
Experimental: Training Protocol 1 - Intervention First Participants will complete a roll tilt training protocol previously shown to reduce roll tilt thresholds. The training stimulus parameters are as follows: 0.5 Hz roll tilt motion, stimulus size will be adjusted based upon subject responses using a 2-down, 1-up (2D/1U) staircase, and only auditory feedback will be provided.The training protocol will be completed first, followed by the placebo intervention.	Behavioral: Vestibular Perceptual Learning The participants will be tilted and asked to indicate their perceived direction of self-motion (e.g., left or right). Feedback will be provided to promote learning (i.e., improved perception of motion). Feedback will only be provided after the subject response, and thus vestibular (i.e., self-motion) perception is required to judge the direction of the tilt stimulus. After each trial, a 3 second period of rest will be given. Each day of training will include three blocks of one-hundred trials each. Testing will take place in the dark (except for aims where a visual cue is provided). Subjects will be seated on a motion platform with a 5-point harness and the head restrained. Noise cancelling earpieces (along with a white noise signal) will be used to reduce external noise. Subjects will always be asked to make a decision (e.g. left versus right) by pressing buttons with their left or right hands. If not certain, subjects are instructed to provide their best guess. Other Names: Vestibular Perceptual Training Vestibular Perceptual Adaptation Behavioral: Placebo Intervention The placebo (or control) task will consist of oculomotor exercises that the subject will complete at home (i.e., outside of the lab). The oculomotor exercises will include saccadic eye movements performed in the horizontal and vertical planes. All movements will be completed within a limited, comfortable range of motion with the head remaining stationary. As the control intervention will be performed with the head stationary and in a seated position, no change in self-motion perception or balance is expected to result from the control (i.e., placebo) task.
Experimental: Training Protocol 1 - Placebo First Participants will complete a roll tilt training protocol previously shown to reduce roll tilt thresholds. The training stimulus parameters are as follows: 0.5 Hz roll tilt motion, stimulus size will be adjusted based upon subject responses using a 2D/1U staircase, and only auditory feedback will be provided. The placebo intervention will be completed first, followed by the roll tilt training intervention.	Behavioral: Vestibular Perceptual Learning The participants will be tilted and asked to indicate their perceived direction of self-motion (e.g., left or right). Feedback will be provided to promote learning (i.e., improved perception of motion). Feedback will only be provided after the subject response, and thus vestibular (i.e., self-motion) perception is required to judge the direction of the tilt stimulus. After each trial, a 3 second period of rest will be given. Each day of training will include three blocks of one-hundred trials each. Testing will take place in the dark (except for aims where a visual cue is provided). Subjects will be seated on a motion platform with a 5-point harness and the head restrained. Noise cancelling earpieces (along with a white noise signal) will be used to reduce external noise. Subjects will always be asked to make a decision (e.g. left versus right) by pressing buttons with their left or right hands. If not certain, subjects are instructed to provide their best guess. Other Names: Vestibular Perceptual Training Vestibular Perceptual Adaptation Behavioral: Placebo Intervention The placebo (or control) task will consist of oculomotor exercises that the subject will complete at home (i.e., outside of the lab). The oculomotor exercises will include saccadic eye movements performed in the horizontal and vertical planes. All movements will be completed within a limited, comfortable range of motion with the head remaining stationary. As the control intervention will be performed with the head stationary and in a seated position, no change in self-motion perception or balance is expected to result from the control (i.e., placebo) task.
Experimental: Training Protocol 2 - Intervention First Participants will complete the training protocol that, after completion of preliminary basic science experiments, is found to most effectively reduce tilt thresholds in young adults. The potential training stimulus parameters are as follows: (1) roll tilt, pitch tilt, LARP tilt, or RALP tilt motion, (2) stimulus size will be adjusted based upon subject responses using either a 2D/1U, three-down, one-up (3D/1U), or six-down, one-up (6D/1U) staircase, and (3) either auditory, visual, or combined auditory+visual feedback will be provided. The training protocol will be completed first, followed by the placebo intervention.	Behavioral: Vestibular Perceptual Learning The participants will be tilted and asked to indicate their perceived direction of self-motion (e.g., left or right). Feedback will be provided to promote learning (i.e., improved perception of motion). Feedback will only be provided after the subject response, and thus vestibular (i.e., self-motion) perception is required to judge the direction of the tilt stimulus. After each trial, a 3 second period of rest will be given. Each day of training will include three blocks of one-hundred trials each. Testing will take place in the dark (except for aims where a visual cue is provided). Subjects will be seated on a motion platform with a 5-point harness and the head restrained. Noise cancelling earpieces (along with a white noise signal) will be used to reduce external noise. Subjects will always be asked to make a decision (e.g. left versus right) by pressing buttons with their left or right hands. If not certain, subjects are instructed to provide their best guess. Other Names: Vestibular Perceptual Training Vestibular Perceptual Adaptation Behavioral: Placebo Intervention The placebo (or control) task will consist of oculomotor exercises that the subject will complete at home (i.e., outside of the lab). The oculomotor exercises will include saccadic eye movements performed in the horizontal and vertical planes. All movements will be completed within a limited, comfortable range of motion with the head remaining stationary. As the control intervention will be performed with the head stationary and in a seated position, no change in self-motion perception or balance is expected to result from the control (i.e., placebo) task.
Experimental: Training Protocol 2 - Placebo First Participants will complete the training protocol that, after completion of preliminary basic science experiments, is found to most effectively reduce tilt thresholds in young adults. The potential training stimulus parameters are as follows: (1) roll tilt, pitch tilt, left anterior/right posterior (LARP) tilt, or right anterior/left posterior (RALP) tilt motion, (2) stimulus size will be adjusted based upon subject responses using either a 2D/1U, 3D/1U, or 6D/1U staircase, and (3) either auditory, visual, or combined auditory+visual feedback will be provided. The placebo intervention will be completed first, followed by the roll tilt training intervention.	Behavioral: Vestibular Perceptual Learning The participants will be tilted and asked to indicate their perceived direction of self-motion (e.g., left or right). Feedback will be provided to promote learning (i.e., improved perception of motion). Feedback will only be provided after the subject response, and thus vestibular (i.e., self-motion) perception is required to judge the direction of the tilt stimulus. After each trial, a 3 second period of rest will be given. Each day of training will include three blocks of one-hundred trials each. Testing will take place in the dark (except for aims where a visual cue is provided). Subjects will be seated on a motion platform with a 5-point harness and the head restrained. Noise cancelling earpieces (along with a white noise signal) will be used to reduce external noise. Subjects will always be asked to make a decision (e.g. left versus right) by pressing buttons with their left or right hands. If not certain, subjects are instructed to provide their best guess. Other Names: Vestibular Perceptual Training Vestibular Perceptual Adaptation Behavioral: Placebo Intervention The placebo (or control) task will consist of oculomotor exercises that the subject will complete at home (i.e., outside of the lab). The oculomotor exercises will include saccadic eye movements performed in the horizontal and vertical planes. All movements will be completed within a limited, comfortable range of motion with the head remaining stationary. As the control intervention will be performed with the head stationary and in a seated position, no change in self-motion perception or balance is expected to result from the control (i.e., placebo) task.
Experimental: Training Protocol 3 - Intervention First Participants will complete the training protocol that, after completion of preliminary basic science experiments, is found to most effectively improve balance in young adults. The potential training stimulus parameters are as follows: (1) roll tilt, pitch tilt, LARP tilt, or RALP tilt motion, (2) stimulus size will be adjusted based upon subject responses using either a 2D/1U, three-down, one-up (3D/1U), or six-down, one-up (6D/1U) staircase, and (3) either auditory, visual, or combined auditory+visual feedback will be provided. The training protocol will be completed first, followed by the placebo intervention.	Behavioral: Vestibular Perceptual Learning The participants will be tilted and asked to indicate their perceived direction of self-motion (e.g., left or right). Feedback will be provided to promote learning (i.e., improved perception of motion). Feedback will only be provided after the subject response, and thus vestibular (i.e., self-motion) perception is required to judge the direction of the tilt stimulus. After each trial, a 3 second period of rest will be given. Each day of training will include three blocks of one-hundred trials each. Testing will take place in the dark (except for aims where a visual cue is provided). Subjects will be seated on a motion platform with a 5-point harness and the head restrained. Noise cancelling earpieces (along with a white noise signal) will be used to reduce external noise. Subjects will always be asked to make a decision (e.g. left versus right) by pressing buttons with their left or right hands. If not certain, subjects are instructed to provide their best guess. Other Names: Vestibular Perceptual Training Vestibular Perceptual Adaptation Behavioral: Placebo Intervention The placebo (or control) task will consist of oculomotor exercises that the subject will complete at home (i.e., outside of the lab). The oculomotor exercises will include saccadic eye movements performed in the horizontal and vertical planes. All movements will be completed within a limited, comfortable range of motion with the head remaining stationary. As the control intervention will be performed with the head stationary and in a seated position, no change in self-motion perception or balance is expected to result from the control (i.e., placebo) task.
Experimental: Training Protocol 3 - Placebo First Participants will complete the training protocol that, after completion of preliminary basic science experiments, is found to most effectively improve balance in young adults. The potential training stimulus parameters are as follows: (1) roll tilt, pitch tilt, LARP tilt, or RALP tilt motion, (2) stimulus size will be adjusted based upon subject responses using either a 2D/1U, 3D/1U, or 6D/1U staircase, and (3) either auditory, visual, or combined auditory+visual feedback will be provided. The placebo intervention will be completed first, followed by the roll tilt training intervention.	Behavioral: Vestibular Perceptual Learning The participants will be tilted and asked to indicate their perceived direction of self-motion (e.g., left or right). Feedback will be provided to promote learning (i.e., improved perception of motion). Feedback will only be provided after the subject response, and thus vestibular (i.e., self-motion) perception is required to judge the direction of the tilt stimulus. After each trial, a 3 second period of rest will be given. Each day of training will include three blocks of one-hundred trials each. Testing will take place in the dark (except for aims where a visual cue is provided). Subjects will be seated on a motion platform with a 5-point harness and the head restrained. Noise cancelling earpieces (along with a white noise signal) will be used to reduce external noise. Subjects will always be asked to make a decision (e.g. left versus right) by pressing buttons with their left or right hands. If not certain, subjects are instructed to provide their best guess. Other Names: Vestibular Perceptual Training Vestibular Perceptual Adaptation Behavioral: Placebo Intervention The placebo (or control) task will consist of oculomotor exercises that the subject will complete at home (i.e., outside of the lab). The oculomotor exercises will include saccadic eye movements performed in the horizontal and vertical planes. All movements will be completed within a limited, comfortable range of motion with the head remaining stationary. As the control intervention will be performed with the head stationary and in a seated position, no change in self-motion perception or balance is expected to result from the control (i.e., placebo) task.
Experimental: Training Protocol 4 - Intervention First Participants will complete the training protocol that, after completion of preliminary basic science experiments, is found to most effectively reduce tilt thresholds AND improve balance in young adults. The potential training stimulus parameters are as follows: (1) roll tilt, pitch tilt, LARP tilt, or RALP tilt motion, (2) stimulus size will be adjusted based upon subject responses using either a 2D/1U, 3D/1U, or 6D/1U staircase, and (3) either auditory, visual, or combined auditory+visual feedback will be provided. The training protocol will be completed first, followed by the placebo intervention.	Behavioral: Vestibular Perceptual Learning The participants will be tilted and asked to indicate their perceived direction of self-motion (e.g., left or right). Feedback will be provided to promote learning (i.e., improved perception of motion). Feedback will only be provided after the subject response, and thus vestibular (i.e., self-motion) perception is required to judge the direction of the tilt stimulus. After each trial, a 3 second period of rest will be given. Each day of training will include three blocks of one-hundred trials each. Testing will take place in the dark (except for aims where a visual cue is provided). Subjects will be seated on a motion platform with a 5-point harness and the head restrained. Noise cancelling earpieces (along with a white noise signal) will be used to reduce external noise. Subjects will always be asked to make a decision (e.g. left versus right) by pressing buttons with their left or right hands. If not certain, subjects are instructed to provide their best guess. Other Names: Vestibular Perceptual Training Vestibular Perceptual Adaptation Behavioral: Placebo Intervention The placebo (or control) task will consist of oculomotor exercises that the subject will complete at home (i.e., outside of the lab). The oculomotor exercises will include saccadic eye movements performed in the horizontal and vertical planes. All movements will be completed within a limited, comfortable range of motion with the head remaining stationary. As the control intervention will be performed with the head stationary and in a seated position, no change in self-motion perception or balance is expected to result from the control (i.e., placebo) task.
Experimental: Training Protocol 4 - Placebo First Participants will complete the training protocol that, after completion of preliminary basic science experiments, is found to most effectively reduce tilt thresholds AND improve balance in young adults. The potential training stimulus parameters are as follows: (1) roll tilt, pitch tilt, LARP tilt, or RALP tilt motion, (2) stimulus size will be adjusted based upon subject responses using either a 2D/1U, 3D/1U, or 6D/1U staircase, and (3) either auditory, visual, or combined auditory+visual feedback will be provided. The placebo intervention will be completed first, followed by the roll tilt training intervention.	Behavioral: Vestibular Perceptual Learning The participants will be tilted and asked to indicate their perceived direction of self-motion (e.g., left or right). Feedback will be provided to promote learning (i.e., improved perception of motion). Feedback will only be provided after the subject response, and thus vestibular (i.e., self-motion) perception is required to judge the direction of the tilt stimulus. After each trial, a 3 second period of rest will be given. Each day of training will include three blocks of one-hundred trials each. Testing will take place in the dark (except for aims where a visual cue is provided). Subjects will be seated on a motion platform with a 5-point harness and the head restrained. Noise cancelling earpieces (along with a white noise signal) will be used to reduce external noise. Subjects will always be asked to make a decision (e.g. left versus right) by pressing buttons with their left or right hands. If not certain, subjects are instructed to provide their best guess. Other Names: Vestibular Perceptual Training Vestibular Perceptual Adaptation Behavioral: Placebo Intervention The placebo (or control) task will consist of oculomotor exercises that the subject will complete at home (i.e., outside of the lab). The oculomotor exercises will include saccadic eye movements performed in the horizontal and vertical planes. All movements will be completed within a limited, comfortable range of motion with the head remaining stationary. As the control intervention will be performed with the head stationary and in a seated position, no change in self-motion perception or balance is expected to result from the control (i.e., placebo) task.

Outcome Measures

Primary Outcome Measures

Change in Vestibular Roll Tilt Perceptual Thresholds [Intervention First Group: Days 1, 6, 13, 36, 41; Placebo First Group: Days 1, 6, 11, 18, 41]
Vestibular perceptual thresholds will be measured using forced-choice methodologies; such methods have been used extensively. Passive, whole body tilts will delivered using a Moog motion platform. Subjects will be tilted in one of two directions (e.g., towards the left or right) in complete darkness and asked to report the perceive direction of motion. All subjects will be seated in a chair with a 5-point harness. The head will be restrained by a standard motorcycle helmet. Noise cancelling headphones will be worn, reducing external noise by about 20 decibel (dB); to mask potential auditory directionality cues, auditory "noise" - uncorrelated with motion (amplitude, direction, or type) - will be applied at 60 dB sound pressure level (SPL). Motion stimuli will consist of single cycles of sinusoidal acceleration. using published methods.
Change in the Postural Sway During the Modified Romberg Balance Test [Intervention First Group: Days 1, 6, 13, 36, 41; Placebo First Group: Days 1, 6, 11, 18, 41]
Static stance will be measured using a tri-axial force plate; postural sway will be measured in response to balance challenges including: (1) standing either on a foam or firm surface, (2) with the eyes either open or closed, and (3) with the feet together or in tandem. The center of pressure (COP) root-mean-square-distance will serve as the primary outcome measure describing postural sway.
Change in Postural Sway during the Sensory Organization Test [Intervention First Group: Days 1, 6, 13, 36, 41; Placebo First Group: Days 1, 6, 11, 18, 41]
The Sensory Organization Test (SOT) is a standard clinical and research assessment used to quantify quiet stance postural sway in the presence of unreliable visual and proprioceptive feedback. The conditions of the test include (1) eyes open firm surface, 2) eyes closed firm surface, 3) sway referenced vision firm surface, 4) eyes open sway referenced platform, 5) eyes closed sway referenced platform, 6) sway referenced visual surround and platform. Sway-referencing describes a technique used to alter the reliability of proprioceptive and/or visual inputs by tilting the support surface or visual surround to follow the displacement of the CoP. Center of pressure data will be collected in each condition using a tri-axial force plate; each condition will be repeated 3 times, for 20 seconds each. The root mean square displacement of the center of pressure (CoP) will be calculated for each trial, using the median of 3 trials as the primary outcome.

Secondary Outcome Measures

Change in the Time to Failure During the Modified Romberg Balance Test [Intervention First Group: Days 1, 6, 13, 36, 41; Placebo First Group: Days 1, 6, 11, 18, 41]
Static stance will be measured using a tri-axial force plate; postural sway will be measured in response to balance challenges including: (1) standing either on a foam or firm surface, (2) with the eyes either open or closed, and (3) with the feet together or in tandem. If a trial cannot be completed due to a loss of balance, the time at which the loss of balance occurs will be recorded for each condition.
Change in Pass/Fail Performance on the Modified Romberg Balance Test [Intervention First Group: Days 1, 6, 13, 36, 41; Placebo First Group: Days 1, 6, 11, 18, 41]
Static stance will be measured using a tri-axial force plate; postural sway will be measured in response to balance challenges including: (1) standing either on a foam or firm surface, (2) with the eyes either open or closed, and (3) with the feet together or in tandem. The ability to complete the test (i.e., without a loss of balance) will be recorded.

Eligibility Criteria

Criteria

Ages Eligible for Study:

65 Years to 89 Years

Sexes Eligible for Study:

All

Accepts Healthy Volunteers:

Yes

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