NSF Award
0719639
As a person walks on a sidewalk or drives down a street, he or she detects optic flow that informs of the speed and direction of movement, as well as the distances of objects in the environment. Unlike a viewer looking down from above, who would see the person as moving through a fixed environment, the moving person sees objects in the visual field expand as they are approached, or move off to the side as they are passed. Using this flow to sense and control one's own movement might appear to be a difficult computational problem, and yet people still do it all the time. The visual system does have help, though; in particular, the vestibular system, with its acceleration sensors in the inner ear, detects the directions of rotations and translations of the head independently of vision. Having some redundancy between the two types of sensors is a good thing, because both are subject to errors, and because the two are effective at sensing different types of movements. A major issue is to understand how the visual and vestibular senses work together in sensing and controlling the body's motion through the environment. While each sense has been heavily studied on its own, how they fit together has received relatively little attention, at least for translational movement through a natural environment.<br/><br/>With funding from the National Science Foundation, Dr. Douglas Hanes will begin to address the processes by which visual and vestibular signals together inform about self-motion. The focus of his work will be on mathematically modeling the optimal integration of visual and vestibular information in the central nervous system. It is known that visual signals associated with a rotation of the head?the global flow on the retina in a direction opposite to head or eye rotations?converge with vestibular signals for the same head rotation in movement centers of the brain. Understanding a similar convergence for translational motion is harder, because the visual flow that results is much more complex, and successful modeling of this convergence will require the use of more sophisticated mathematical techniques. By elucidating the ways in which these senses complement one another, and by proposing a specific model of integration, the research will help bring together knowledge from independent research carried out on the visual and vestibular systems. The results should shed light on vexing questions about how humans can estimate distances traveled or trajectories of motion with only one sense or the other, or what happens when the two senses conflict. The results of this work will not only help us better understand multi-sensory function, but will have implications about how problems may arise in the perception and control of self motion while flying or driving.
