We must point the eyes directly at an object to observe the fine detail of its features. This is because only a small region of the retina of the eye called the fovea can "see" with high resolution. When an object that is being viewed moves, the eyes must also move to keep the fovea and that object together. The type of eye movement used to follow moving objects is called smooth pursuit, the study of which is the central focus of our laboratory. We measure directly how the brain controls smooth pursuit and assess the ability of people to use smooth pursuit eye movements to follow different patterns of object motion and from the results of these studies we infer neural processing. These experiments can show us which areas of the brain are involved in smooth pursuit, and the strategy that the brain uses to generate different patterns and speeds of eye movements. A major emphasis of our work is how expectations about where an object will move next alters activity in the brain and hence the eye movements. These expectations are strong, sometimes to the extent that they can override the visual signal produced by a moving object and control the response.

We also measure eye movements with a device that senses the reflections of an invisible infra-red light projected on the fovea and the lens of the eye. As the eye rotates, the reflections change their positions on the sensors, and this change of position is measured at high speed. We can record accurately where the eye is looking at any given time. Experiments assess how an observer's perception of a moving object changes when alterations are made to the visual texture or features of the moving objects. We then measure smooth pursuit eye movements to objects during the same texture and feature manipulations. From the results of these studies we infer how the brain converts our perception of the motion of an object into an eye movement response.

The goal of our work is to understand how the brain controls eye movements and the regions of the brain that participate in specific aspects of eye movement control. This knowledge can be used to help develop treatment for diseases that affect the motility of the eyes. Furthermore, information about how the brain coordinates the muscles of the eye could eventually be used to fashion prosthetic devices that can be implanted to replace defective neural tissue in patients that cannot effectively move their eyes.

For more information, visit Steve Heinen's lab web pages.

Collaborators: Jeremy Badler, Scott Watamaniuk, Anca Velisar, Sarah Pilkington. Edward Keller, Marcus Missal.