Perceptual and navigational strategies for obstacle circumvention in a virtual environment

The ability to accurately judge distance and time to collision is an important perceptual determinant in shaping obstacle circumvention strategies for functional locomotion. In addition, deficits in planning and execution, as well as biomechanical constraints imposed by age or neurological insult may lead to avoidance failure in this population. We have designed a closed system in sitting displaying self motion through a virtual environment to evaluate perceptual and navigational strategies for obstacle circumvention. In a pilot study involving six healthy young subjects and one older participant, all subjects perceived collision with a moving obstacle to have occurred almost a meter before the actual collision would have taken place. The older participant consistently under-estimated the distance of collision to a larger extent as compared to the young subjects. In the navigation task using a joystick, the older individual initiated medio-lateral deviations later than the younger individuals. The clearance distance was also observed to be smaller for the older participant thus increasing the risk of collision. Deficits in depth perception as well as motor planning may contribute to increased errors. However, rehabilitation interventions that use VR can be utilized to improve perceptual and planning abilities, such that efficacious avoidance strategies can be facilitated. Moreover, further testing of locomotion in environments may help devise novel interventions for promoting ambulation.