Neural Control of Divergence Eye Movements

One of the most sophisticated motor systems is the oculomotor system. Viewing objects in depth is supported by vergence eye movements which controls the inward (convergence) and outward (divergence) turning of the eyes. There are two main aims to this study. One compares converging responses (stimuli approaching the subject) to diverging responses (stimuli moving away from the subject) from 6o/s ramp stimuli. Results show that similar to convergence, divergence may be governed by a twocomponent control system consisting of a transient and sustained component. However, the dynamics of divergence shows a dependency on initial stimulus position which is not apparent for convergent responses. Next this research quantified divergence movements stimulated by 10, 6, 4, and 2o/s ramp stimuli. Results show that for fast moving divergent responses, high-velocity components were present lending further evidence that a transient component similar in form and function to that found in convergence also exists for divergence. Responses to slow moving responses exhibit smoother tracking where the dynamics of the movement were more uniform throughout the range of the visual field. This implies that the transient component is more prominent in faster responses thus showing a strong dependency on initial stimulus position whereas with slower moving responses, the transient component did not dominant the movement leading to more homogeneous dynamic responses where a dependency on initial stimulus position was not as apparent.