Timothy Hain, M.D. - US grants

The long term objective of our research is to better understand the mechanisms underlying both normal and abnormal vestibulo-ocular function. The aim of the present proposal is to develop new ways of testing and analyzing the vestibulo-ocular reflex (VOR). The research strategy is to make quantitative measurements of vestibulo-ocular function in humans using paradigms suggested by the results of both recent neurophysiological studies as well as mathematical analyses of VOR function. In particular, we will choose rotational vestibular and optokinetic stimuli that exceed the capabilities of or circumvent the compensatory mechanisms which normally make vestibular diagnosis so difficult. We will begin by applying the new methodology to the detection of unilateral peripheral vestibular disease (UPVD) -- first in patients with complete loss, then those with partial loss -- with the ultimate plan to extend our results to patients with central vestibular disorders. We plan to 1) use brief, high-velocity head-on-body movements to expose UPVD, 2) determine (with the magnetic field search coil technique) if inappropriate directly slow phase eye movements during high-velocity vertical or horizontal head rotations are a reliable index to UPVD, 3) develop a new test to measure vertical semicircular canal function by using their contribution to the horizontal (eye in head) VOR, 4) use the initial slow phase velocity profile (plateau effect), in response to a constant velocity head rotation, to detect UPVD and 5) examine the usefulness of optokinetic afternystagmus (OKAN) in assessment of UPVD. Our results will provide new information useful in the assessment of the large number of patients with nystagmus, visual blurring and oscillopsia, and vertigo and dizziness.

The long term objective of our research is to better understand the mechanisms underlying both normal and abnormal vestibulo-ocular function. The aim of the present proposal is to develop new ways of testing and analyzing the vestibulo-ocular reflex (VOR). The research strategy is to make quantitative measurements of vestibulo-ocular function in humans using paradigms suggested by the results of both recent neurophysiological studies as well as mathematical analyses of VOR function. In particular, we will choose rotational vestibular and optokinetic stimuli that exceed the capabilities of or circumvent the compensatory mechanisms which normally make vestibular diagnosis so difficult. We will begin by applying the new methodology to the detection of unilateral peripheral vestibular disease (UPVD)--first in patients with complete loss, then those with partial loss--with the ultimate plan to extend our results to patients with central vestibular disorders. We plan to 1) use brief, high-velocity head-on-body movements to expose UPVD, 2) determine (with the magnetic field search coil technique) if inappropriately directed slow phase eye movements during high-velocity vertical or horizontal head rotations are a reliable index to UPVD, 3) develop a new test to measure vertical semicircular canal function by using their contribution to the horizontal (eye in head) VOR, 4) use the initial slow phase velocity profile (plateau effect), in response to a constant velocity head rotation, to detect UPVD and 5) examine the usefulness of optokinetic afternystagmus (OKAN) in assessment of UPVD. Our results will provide new information useful in the assessment of the large number of patients with nystagmus, visual blurring and oscillopsia, and vertigo and dizziness.

Our long-term goal is to improve mobility and decrease injury due to falls in persons with balance disorders. Our specific aim is to determine if eight weeks of daily practice of an alternative health care exercise, T'ai Chi, can significantly improve balance of persons with "high-level" (mild) balance disorders. We propose to study 30 persons with stable mild balance disorders, with imbalance defined by their score on the Duke Mobility Skills protocol. We will recruit 10 persons in each of 3 age groups: 20-44, 46-60, and 61 and beyond. Prospective subjects will undergo a set of pre-training assessment instruments including a Dizziness Handicap Inventory (Jacobson et al, 1990), a falls self-report questionnaire, the Duke Mobility Skills Protocol, the Mini Mental screen (Folstein et al, 1975), and have their postural sway measured using a posture platform (Smart BalanceMaster). They will then undergo 8 weeks of daily T'ai Chi practice, after which they will again undergo assessment. Three months after the course, they will return for a final set of assessments and an ascertainment of continued practice of T'ai Chi. Scores from the assessments instruments will be collated, and we will determine if there is a significant change between start and end of the course. For simple comparisons, looking for changes in measures, we will use paired t-tests, each subject being their own control. We will use analysis of variance (ANOVA), including a nonparametric form when required, to determine if age or degree of compliance with exercises has a significant effect on changes in scores. This study will determine whether T'ai Chi can improve balance in persons with mild balance disorders. It will also provide information as to whether there is a difference in effect between younger and older persons. These data may be used to justify a study of a larger number of subjects, as well as determine whether a study comparing results from traditional physical therapy to T'ai Chi should be undertaken.

The aim of this project is to determine how intentional mechanisms contribute to head stabilization in the pitch (sagittal) plane during voluntary trunk movements in persons with intact and bilaterally impaired vestibular (BVL) systems. One set of studies will quantify the contributions made by intentional mechanisms beyond reflex and mechanical processes. A second set of studies will evaluate what subtypes of intentional strategies are used to stabilize the head under different conditions. Empirical and computer modeling approaches will test the hypotheses that intentional mechanisms contribute significantly to head stabilization in the BVL as well as intact subject, and that these groups use different subtypes of strategies to stabilize their heads. In the empirical studies, subjects will sit on a sled that can translate in the anterior-posterior direction. They will voluntarily control translation of the sled by a hand-held joystick, and have some sled motions imposed on them. The sled translations generate forces that destabilize the head in the pitch plane. Analyses of head motion and torques and of electromyographic activity in the neck and trunk muscles will reveal how well subjects counteract the head-destabilizing forces during sled translation. The data also will reveal whether subjects stabilize their heads by avoiding the disturbance (reducing trunk subjects motion), anticipating and predictively cancelling the disturbance, by stiffening their neck through muscle cocontraction, or by relying on reflexes and passive mechanics. An analytical model of the head-neck control system will be used to run simulations that will determine how much intentional mechanisms contribute to head stabilization, and that will establish how combinations of intentional, mechanical and reflex strategies could work together to stabilize the head. This project is the first to evaluate intentional head-stabilizing mechanisms during voluntary trunk movements. The project also will add to basic knowledge of head control mechanisms by evaluating intentional processes during voluntary movements that are similar to activities of daily life, which generally involve voluntary rather than imposed motion of the trunk. The comparison of intact and BVL populations will elucidate why some persons with BVL recover relatively high functional levels, and others do not.

[unreadable] DESCRIPTION (provided by applicant): This proposal requests support for an Optotrak Motion Analysis system. Its purpose is to update equipment and provide greater access to motion analysis equipment for investigators working in the department of Physical Therapy/Human Movement Sciences. Motion analysis equipment is critical to all of our research faculty, and we have also recently added investigators to the department who need motion analysis capabilities. [unreadable] [unreadable]