Adaptation of catch-up saccades during the initiation of smooth pursuit eye movements |
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Authors: | Alexander C Schütz David Souto |
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Institution: | 1.Abteilung Allgemeine Psychologie,Justus-Liebig-Universit?t Giessen,Giessen,Germany;2.Faculté de Psychologie et Sciences de l’éducation,Université de Genève,Geneva,Switzerland;3.Department of Cognitive, Perceptual and Brain Sciences,University College London,London,UK |
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Abstract: | Reduction of retinal speed and alignment of the line of sight are believed to be the respective primary functions of smooth
pursuit and saccadic eye movements. As the eye muscles strength can change in the short-term, continuous adjustments of motor
signals are required to achieve constant accuracy. While adaptation of saccade amplitude to systematic position errors has
been extensively studied, we know less about the adaptive response to position errors during smooth pursuit initiation, when
target motion has to be taken into account to program saccades, and when position errors at the saccade endpoint could also
be corrected by increasing pursuit velocity. To study short-term adaptation (250 adaptation trials) of tracking eye movements,
we introduced a position error during the first catch-up saccade made during the initiation of smooth pursuit—in a ramp-step-ramp
paradigm. The target position was either shifted in the direction of the horizontally moving target (forward step), against
it (backward step) or orthogonally to it (vertical step). Results indicate adaptation of catch-up saccade amplitude to back
and forward steps. With vertical steps, saccades became oblique, by an inflexion of the early or late saccade trajectory.
With a similar time course, post-saccadic pursuit velocity was increased in the step direction, adding further evidence that
under some conditions pursuit and saccades can act synergistically to reduce position errors. |
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Keywords: | |
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