Stephen Heinen¹, Devashish Singh¹, Arvind Chandna¹, Scott Watamaniuk^1,2; ¹Smith-Kettlewell Eye Research Institute, ²Wright State University

There is evidence that horizontal and vertical smooth pursuit are subserved by different channels. Last year we showed that the eyes were well-aligned during binocular pursuit of a horizontally moving target. However, with one eye covered, the eyes still moved together but the covered eye was horizontally displaced. These results suggest that the eyes are driven by a unitary conjugate controller but have separate independent controllers that use visual feedback to maintain eye alignment. Here we ask if the eyes move equally well together when pursuing vertically-moving targets. Neurotypical observers pursued a small (0.4 deg) spot on a tangent screen that moved vertically with either a predictable sinusoidal profile, or an unpredictable combination of sinusoids (noise condition). Peak target velocity was either 25 or 5 deg/sec. Binocular eye movements were recorded during binocular and monocular viewing with an EyeLink+ at 1000 Hz, and occlusion was implemented with an infra-red pass filter to allow eye recording. We found that during monocular pursuit, while the eyes moved together vertically, the covered eye was again horizontally displaced, but to a greater degree than during horizontal pursuit. Furthermore, the horizontal displacement between the eyes was greater in noise condition. The results suggest that the eyes are driven together vertically using a similar conjugate mechanism as is used to drive them horizontally, but that independent control is less able to maintain alignment during vertical pursuit.

Acknowledgements: Supported by NIH R01EY034626 and Smith-Kettlewell Eye Research Institute