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Oculomotor responses to gradual changes in target direction
Leigh A Mrotek1, Martha Flanders, John F Soechting
1Department of Neuroscience, University of Minnesota, 6-145 Jackson Hall, Minneapolis, MN 55455, USA.
Experimental Brain Research
|January 19, 2006
Summary
Human eye tracking (smooth pursuit) in two dimensions (2D) shows a lag in direction. Retinal slip, not target direction, drives eye movements, with reduced sensitivity to motion along the pursuit path.
Area of Science:
- Neuroscience
- Vision Science
- Oculomotor Research
Background:
- Smooth pursuit eye movements are crucial for visual tracking.
- Existing models accurately describe one-dimensional (1D) linear tracking.
- These models are insufficient for explaining two-dimensional (2D) target motion tracking.
Purpose of the Study:
- To investigate human smooth pursuit eye movements during two-dimensional (2D) target motion.
- To determine the role of retinal slip in 2D pursuit.
- To analyze how gaze velocity and direction are controlled during curved trajectories.
Main Methods:
- Human subjects performed smooth pursuit eye tracking of targets moving linearly and circularly.
- Eye gaze angular velocity and target angular velocity were recorded.
- Brief perturbations were introduced before directional changes to analyze responses.
Main Results:
- Gaze angular velocity matched target angular velocity, but pursuit direction lagged.
- Pursuit speed transiently decreased during curved trajectories.
- Retinal slip, particularly perpendicular slip, was the primary driver of gaze acceleration, except for a nonspecific transient decrease in velocity.
Conclusions:
- Two-dimensional (2D) smooth pursuit is primarily driven by retinal slip.
- The visual system exhibits differential sensitivity to image motion components during curved pursuit.
- Expectations may influence the gain of pursuit eye movements, reducing sensitivity to motion along the pursuit path.