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Dr. Gilmore and Dr. Semyon Slobounov, associate professor
of Kineseology, are working with Elena Slobounov and George Otto of
the CAC Visualization Group to use the CAC Immersadesk and
attached motion capture devices to study relationships between
visual perception of space and motion and postural stability. |
Dr. Rick Gilmore, assistant professor of Psychology and Dr. Sam Slobounov, associate professor of Kinesiology, have been working with Elena Slobounov, lead applications programmer, CAC Visualization Group, and George Otto, manager, CAC Visualization Group, on utilizing pilot research into virtual reality techniques to study the relationship between visual perception of motion and postural response in special populations. The project has been funded by a seed grant from the Children, Youth and Families Consortium, and in-kind facilities and staff support from the CAC and the Department of Kineseology and the Department of Psychology.
Dr. Slobounov describes the research tradition from which this work derives as follows. There is ongoing debate in neuroscience literature regarding the role of various sources of information used in regulation of upright postural stances. It was traditionally thought that the vestibular and neuro-muscular systems play unique and exclusive role in postural control (Sherrington, 1906). This notion has been challenged by a number of research groups who claim a dramatic contribution of vision to posture and postural control. In 1976, David Lee proposed a "moving room" experimental design, examining the effect of physical manipulations of front and/or side walls on human postural sway. The moving room experiments involved the construction and manipulation of a physical structure, the moving room, to surround and fill a subject's visual field with motion stimuli. Perception of wall motion induced postural movement in the subjects. Such motion has been called "ego-motion" which is considered a direct indication of effect of vision on postural control.
Continuing lines of research using Lee's design have varied the properties of wall motion and rigorously studied any accompanying postural movement. Virtual reality technologies, coupled with electronic instrumentation for the accurate measurement of subject motion, offers tremendous advantages over existing "moving room" designs. By substituting computer graphics for physical visual stimuli, various scenes can be created that otherwise may be extremely difficult, if not impossible, to reproduce in the physical environment.
The frequency and range of motion of the virtual room can be variously and accurately programmed and displayed on the VR display, in this case, the CAC's Immersadesk virtual reality display system. Subject postural sway can be accurately measured using a force platform, a device on which subjects stand and which measures changes in their center of pressure over time, and Flock of Birds motion sensors that are attached to key body positions on the subject for directly recording relative changes in those positions for the duration of the trial. All devices are computer controlled. The multiple data streams representing scene position, subject center of mass, and subject body positions are synchronized and time stamped for off-line statistical analyses to determine correlations between apparent motion of the scene and subject postural response.
The virtual reality approach requires multidisciplinary expertise in subject areas including psychology, motion control, neuroscience and computer programming. In addition to Dr. Gilmore, Dr. Slobounov, Ms. Slobounov, and Mr. Otto, our team includes Tim Benner, computer and technology specialist, Department of Kineseology; Alejandro Lleras, graduate student in Psychology; and Huai-Hsiao "Hudson" Chiang, graduate student in Kinesiology.
Pilot studies have begun using the combined system and apparatus. The partnership has been beneficial for the researchers, in that they have gained an extremely adaptable methodology for current and future work, as well as for the CAC Visualization Group, in that the project has provided a test case for working out issues of ongoing utility including the correspondence of measurement between virtual space and physical space, integration and synchronization of multiple systems and data streams, and dealing comfortably with human subjects within the VR facility.
According to Dr. Gilmore, "The CAC Immersadesk Environment provides us with an incredibly flexible and powerful tool for studying how children use visual information to control posture. Thanks to the expertise and hard work of the Visualization Group, we are beginning studies that will answer fundamental questions about the development of visual perception and action planning in the first years of life. These studies would be impossible without access to the Immersadesk and the expertise of the Visualization Group."
Adds Dr. Slobounov, "Personally, I was extremely pleased to work with highly professional individuals from the CAC and the Psychology Department. I really believe that this is just a start for future productive work."
For information on the Immersadesk or other services of the CAC Visualization Group, contact george-otto@psu.edu or vizgroup@psu.edu.
