Citation

Ke SR, Lam J, Pai DK, Spering M. Invest. Ophthalmol. Vis. Sci. 2013; 54(6): 4409-4421.

Copyright

(Copyright © 2013, Association for Research in Vision and Ophthalmology)

DOI

10.1167/iovs.12-11369

PMID

23716624

Abstract

PURPOSE: Humans make smooth pursuit eye movements to bring the image of a moving object onto the fovea. Although pursuit accuracy is critical to prevent motion blur, the eye often falls behind the target. Previous studies suggest that pursuit accuracy differs between motion directions. Here, we systematically assess asymmetries in smooth pursuit. METHODS: In experiment 1, binocular eye movements were recorded while observers (n=20) tracked a small spot of light moving along one of four cardinal or diagonal axes across a featureless background. We analyzed pursuit latency, acceleration, peak velocity, gain, and catch-up saccade latency, number and amplitude. In experiment 2 (n=22), we examined effects of spatial location and constrained stimulus motion within the upper or lower visual field. RESULTS: Pursuit was significantly faster (higher acceleration, peak velocity and gain) and smoother (fewer and later catch-up saccades) in response to downward vs. upward motion in both the upper and the lower visual field. Pursuit was also more accurate and smoother in response to horizontal vs. vertical motion. CONCLUSIONS: Our study is the first to report a consistent up-down asymmetry in human adults, regardless of visual field. Our findings suggest that pursuit asymmetries are adaptive responses to the requirements of the visual context: preferred motion directions (horizontal and downward) are more critical to our survival than non-preferred ones.

Language: en