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Clara Bourrelly, Julie Quinet, Laurent Goffart; Evolution of the oculomotor tracking with an accelerating or decelerating target. Journal of Vision 2015;15(12):1016. doi: 10.1167/15.12.1016.
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© ARVO (1962-2015); The Authors (2016-present)
A target that moves smoothly and continuously in the visual periphery triggers interceptive saccades that bring its image within the central field. Thus, the saccades increase the population of neurons (e.g., in the cerebral cortex) whose activity correlates with the visual presence of the object, facilitating its foveal pursuit. This foveation is maintained more or less efficiently by two types of tracking eye movements: low-velocity movements and catch-up saccades. We studied in four head-restrained monkeys the evolution of the oculomotor tracking in response to a small target that moved for less than one second (800 ms) along a horizontal or vertical path, after its sudden appearance at an eccentric position (16°) along the vertical or horizontal meridian, respectively. We tested target motions of different velocity profiles (accelerating or decelerating). During the first trials, the tracking consisted of saccades separated by periods during which gaze moved smoothly in the same direction as the target, but lagging behind its current position. The eye velocity mimicked the target velocity profile, i.e., it accelerated or decelerated. This slow tracking evolved: with the number of trials and training days, the animal developed the ability to match the kinematics of its eye movements with that of the target. This evolution in pursuit was obviously associated with a reduction in the amplitude of catch-up saccades and gaze moved as if it were locked onto the target. Our work shows that the oculomotor tracking is driven by sluggish dynamic signals that evolve to encode the “here-and-now” position of the target. Mostly saltatory at the beginning, the tracking transitions to a continuous mode that mimics the target kinematics, enabling the animal to foveally "grasp" the target where it is and when it is there.
Meeting abstract presented at VSS 2015
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