Two OHSU researchers, Fay Horak, Ph.D., professor of neurology, and Robert Peterka, Ph.D., associate professor of biomedical engineering, were recently recognized by the American Physiological Society for having highly cited publications in the Journal of Neurophysiology. Dr. Horak’s paper, “Central programming of postural movements: Adaptation to altered support-surface configurations,” was one of the top ten cited papers from 1980-1989, and Dr. Peterka’s, “Sensorimotor integration in human postural control,” was one of the top ten from 2000 to 2011.
Dr. Peterka’s paper, published in 2002, explores balance and the complex mechanisms that enable us to stand upright.
“This may seem simple, but it’s not,” he said. “Gravity is constantly pulling at us. Gravity would topple us over except for the fact that we use information from sensory systems (mainly proprioception, vision, and vestibular) to determine our body orientation and motion, and then use this orientation information to generate motor actions that correct for deviations from the upright stance position.”
Because we live in a dynamic world with slanted surfaces and moving parts, Dr. Peterka “played tricks” on study participants, like rotating the surface they were standing on or the visual scene they were viewing. He developed a mathematical model that accounted for how humans process orientation information from each sensory system and combine this information for balance control. Using this model, he found that the brain is very flexible and can essentially recalibrate under different environmental conditions. He also found that damage to one of these systems, like the inner ear vestibular sensors, causes a reorganization that increases reliance on other sensory systems for balance.
Since 2002, Dr. Peterka and others have been working to further refine his mathematical model.
“The model in our 2002 paper was relatively simple. It accounted for the motion of the body’s center of mass but not for the motion of individual body segments. We have gone on to develop more complex models that do account for the motion of body segments and how body-segment motion is coordinated. We are still working on this,” he said.
Dr. Peterka has also collaborated with Dr. Horak to test whether sensory contributions to balance are effected by Parkinson’s disease (no, he says) or loss of function in one ear (yes—“one ear is not as good as two.”) With a variety of collaborators across the institution, he continues to study the relationship between the vestibular system and balance. Future research directions include determining whether a “vestibular prosthesis” can be created to restore vestibular contribution, and determining if altered sensory function causes the imbalance and dizziness experienced by chemotherapy patients.