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Anna Montagnini, Miriam Spering, Guillaume S. Masson; Combining 1D visual motion and 2D predictive signals to control smooth pursuit eye movements. Journal of Vision 2006;6(6):5. doi: https://doi.org/10.1167/6.6.5.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Pursuit of a tilted bar has a complex dynamics: tracking is initiated in the direction orthogonal to the bar (1D motion signals) before slowly converging on the actual 2D object motion trajectory. We investigated how 1D and 2D motion signals are combined with internal signals (eye velocity memory or object velocity prediction) related to 2D object motion.
Methods: Eye movements were recorded in 4 subjects using the scleral search coil technique. Subjects were asked to track a single oblique line (length: 10°) moving horizontally (rightward/leftward) at 10°/s.
Results: In a first experiment, the tilted line was transiently blanked (200ms) during steady-state tracking. The decrease of eye speed during target blanking was corrected shortly after target reappearance, using 2D target velocity and not 1D edge velocity. However, when the line was rotated by 90° at reappearance, a small but significant tracking direction error in the (new) 1D motion direction was observed. Corrective saccades were directed in the same direction. To test the contribution of visual and predictive signals we presented blocks of line motion (400ms duration) always with same orientation/direction. We found strong anticipatory eye movements in the global (2D) motion direction of the bar. However, ∼100ms after target motion presentation, a consistent tracking error in the oblique direction was again observed. Stimulus predictability had very small effect on the amplitude of 1D-driven responses.
Conclusion: Pursuit is driven by independent visual and internal signals related to object motion that do not interact to resolve ambiguity in the visual inflow.
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