Advanced Techniques for Assessment of Postural and Locomotor Ataxia, Spatial Orientation, and Gaze Stability
Principal Investigator: Conrad Wall, III, Ph.D.
PROJECT OVERVIEW
Major problems of space flight, in addition to adapting to microgravity, include postflight difficulties with standing, walking, turning corners, and other activities that require stable upright posture and gaze stability. These difficulties inhibit astronauts' ability to stand up, bail out or escape from their vehicle during emergencies. The overall goal of this project is to develop quantitative, parametric approaches for assessing gaze stability, and spatial orientation during normal gait and when gait is perturbed. Compared to assessments of the vestibuo-ocular reflex, analysis of vestibular effects on locomotor function is relatively less well developed and quantified. We plan to improve this situation by applying the methodology of nonlinear orbital stability to quantify responses in a single variable and by using multivariate statistical approaches to link together the responses across separate tests. In this way we will exploit the information available and increase the "resolving power" to discriminate between normal and pathological responses. Responses will be studied with, and without, interactive visual environments. Measures of stability and orientation will be compared and assessed with measures of dynamic visual acuity and with other vestibular function tests. The responses of normal human subjects and of subjects having well documented pathophysiologies will be characterized. When these studies are completed, we should have a clearer idea about normal and abnormal patterns of eye, head, and body movements during locomotion and their stability in a wide range of environments. We will then use this information to characterize and validate neurovestibular rehabitative approaches being developed in other projects.
Other photos/info expected to be presented on this
page soon:
Photo of CUNY circular treadmill
Data showing application of Floquet multipliers to asses repeatability
of human gait.
Team members at Baylor, JSC
and CUNY employ a Dynamic Visual Acuity test (DVA) for its
sensitivity to measure recovery from a change in vestibular function
(the inner ear). Our study will determine if DVA will be
useful for evaluating the effectiveness of future countermeasures
and readiness to return to duty. (Click on the picture to
view an enlarged version).
Boston University BALDER moving platform. The subject is stepping onto the platform which can be programmed to make a controlled displacement at a known time. This will introduce a perturbation in the regular gait pattern. One aim of Dr. Wall's project will be to characterize quantitatively the response of subjects to these controlled perturbations.
PROJECT 3 REFERENCES
JOURNAL ARTICLES
Raphan, T. Modeling control of eye orientation in three dimensions (I): Role of muscle pulleys in determining saccadic trajectory, J. Neurophysiol., 79:2653-2667, 1998.
Hirasaki, E., Moore, S., Raphan, T. Cohen, B. Effects of walking velocity on vertical head and body movements during locomotion. Exp. Brain Res. (Submitted, 1998)
Moore, S.T., Hirasaki, E., Cohen, B., Raphan, T. Generation of vertical eye movements by the vor during locomotion. Soc. For Neuroscience (submitted, 1998).
Moore, S.T., Hirasaki, E., Cohen, B., Raphan, T.
Role of the VOR in the Generation of Vertical Eye Movements During
Locomotion, (In Preparation, 1998).
ABSTRACTS
Imai, T., Hirasaki, E. Moore, S., Raphan, T. Cohen, B. Stabilization of gaze when turning corners during overground walking. Soc. For Neuroscience (Submitted, 1998).
Hirasaki, E., Moore, S., Raphan, T., Weinberger, J., Cohen, B. Head movements during circular locomotion in normal subjects. Soc. For Neuroscience (Submitted, 1998).