Program :    Biomedical Research and Countermeasures	Ground Research
Element :    Behavior and Performance
Visual Orientation in Unfamiliar Gravito-Inertial Environments
Principal Investigator:
Charles M. Oman, Ph.D. Center for Space Research Man Vehicle Laboratory Room 37-219 Massachusetts Institute of Technology 77 Massachusetts Avenue Cambridge, MA 02139-4307	Phone: (617) 253-7508 Email: cmo@space.mit.edu Fax: (617) 258-8111 Congressional District: MA-8
Co-Investigator(s):
Beall, A.C. Andrew Liu Howard, I.P. Shebilske, W.L. Taube, J.S. University of California Santa Barbara Massachusetts Institute of Technology York University Wright State University Dartmouth College
Monitoring Center: NSBRI	Solicitation: NSBRI
Initial Funding Date: 1997	Expiration: 2000
Students Funded Under Research: 6	Post-Doctoral Associates: 3
Required Hardware: KC-135 parabolic flight aircraft NASA Virtual Environment Generator
Task Description:
What visual cues do astronauts rely upon to maintain their spatial orientation and sense of where they are relative to other objects and places ? Why is living in a three dimensional structure like the MIR space station disorienting ? What visual cues normally provide us with cues to the gravitational vertical on Earth ? Does inadvertent use of these same cues cause disorientation when astronauts live in weightlessness ? Does 1-G training in simulated 0-G real or virtual environments improve spatial orientation, spatial memory and task performance ? Using tumbling room and mirror bed devices, the group showed that compelling visual scenes can produce much larger illusions of subjective tilt than had previously been thought. For example, many supine subjects feel erect which viewing an environment which is visually upright with respect to their bodies, resulting in an interesting levitation sensation if subjects elevate their arms. The strength of tilt illusions also depends on the gravitational polarity of objects in the scene. This attribute depends both an objects usual orientation in 1-G everyday life, and on its means of apparent physical support. A correlation between tilt illusion susceptibility and age was found. Results on the polarity of objects in a visual scene can be used to update and extend NASA human factors standards on spacecraft visual verticals, and also suggest specific countermeasures. For example, placing pictures of gravitationally polarized objects on walls could make older people less prone to falls, and astronauts less prone to visual reorientation illusions. In a collaborative project with the Cardiovascular team, the investigators found that if a scene is sufficiently polarized and realistic, e.g. produced using an inclined mirror, the resulting tilt illusion can produce transient cardiorespiratory changes, further evidence of visual/vestibular-autonomic coupling. The team has also studied 3D spatial memory in a task analogous to that confronting astronauts in the node module of a space station. Though the experiments were performed in 1-G, spatial memory and learning was not strongly dependent on the gravitational orientation of the subject, nor on whether a virtual or real training environment was used. Instead, performance depended on the mental image and mnemonic strategies used, and correlated with performance on conventional 2 and 3 dimensional mental rotation ability, and visual field dependence. Training the subjects on generic 3D orientation strategies was found to help. Skills acquired were shown to transfer to a second environment, and were retained for at least several weeks. The training method could be used as the basis of a generic preflight spatial orientation training procedure for astronauts. Lastly, this group has studied the limbic coding of 3D orientation in 1-G and in an animal model in parabolic flight. Head direction cells in the anterior thalamic nuclei of rats retained normal visual environment-referenced responses in zero g and hypergravity when on the floor or walls. When crawling on the ceiling, directional specificity was frequently lost. However, when the animal was on the ceiling in 0-G, reversals in cell preferred response direction were found. The investigators believe this phenomenon is the neural correlate of visual reorientation illusions described by humans in analogous situations. The finding helps explain rat place cell results obtained on the Neurolab Spacelab mission. The team has succeeded in defining a scientific basis for preflight visual orientation training, the main goal of the project.
Completed 3rd year of research.
Our research also has potentially important terrestrial applications: An estimated two million American adults summer from chronic impairment of dizziness or difficulty with balance, and one quarter of emergency room visits include a complaint of dizziness. Balance- related falls account for more than one half of accidental deaths in the elderly. Alzheimer's disease patients suffer from impaired spatial memory, which is one of the central research themes of this project. Virtual reality devices are increasingly being used for entertainment, training and mission simulation, and in clinical applications. Understanding how users orient in virtual environments may help improve the design of human computer interfaces
FY00 Publications, Presentations, and Other Accomplishments:
Allison, R., Zacher, J. and Howard, I.P. ''The effect of field size, head motion and rotational velocity on roll vection and illusory self tilt in a tumbling room.'' (abstract) Perception and Psychophysics, in press. Taube, J.S., Stackman, R.W., and Oman, C.M. ''Rat head direction cell responses in 0-G.'' (abstract) Neuroscience Abstracts, V25, Part 2. 557.2, (1999). Jenkin, H., and Howard, I. ''Visually Induced Disorientation as a Function of Age.'' (abstract) Investigative Opthalmology and Visual Science, (40, S801) Association for Research in Vision and Opthalmology, Fort Lauderdate, FL, May, 1999. Richards, J.T. ''Three Dimensional Spatial Learning in a Virtual Space Station Node.'' Massachusetts Institute of Technology (September, 2000). Allison, R., Zacher, J., and Howard, I.P. ''The effect of field size, head motion and rotational velocity on roll vection and illusory self tilt in a tumbling room.'' Perception and Psychophysics, (in press). Taube, J.S., Stackman, R.W., and Oman, C.M. ''Rat head directin cell responses in 0-G.'' Neuroscience Abstracts, V25, Part 2. 557.2, (1999).

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