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| Volume 5, Number 5, Article 6, Pages 455-465 |
doi:10.1167/5.5.6 |
http://journalofvision.org/5/5/6/ |
ISSN 1534-7362 |
Effects of contrast on smooth pursuit eye movements
Miriam Spering |
Psychologisches Institut, Justus-Liebig-Universität, Gießen, Germany |
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Dirk Kerzel |
Faculté de Psychologie, Université de Genève, Genève, Switzerland |
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Doris I. Braun |
Psychologisches Institut, Justus-Liebig-Universität, Gießen, Germany |
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Michael J. Hawken |
Center for Neural Science, New York University, New York, NY, USA |
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Karl R. Gegenfurtner |
Psychologisches Institut, Justus-Liebig-Universität, Gießen, Germany |
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Abstract
It is well known that moving stimuli can appear to move more slowly when contrast is reduced (P. Thompson, 1982). Here we address the question whether changes in stimulus contrast also affect smooth pursuit eye movements. Subjects were asked to smoothly track a moving Gabor patch. Targets varied in velocity (1, 8, and 15 deg/s), spatial frequency (0.1, 1, 4, and 8 c/deg), and contrast, ranging from just below individual thresholds to maximum contrast. Results show that smooth pursuit eye velocity gain rose significantly with increasing contrast. Below a contrast level of two to three times threshold, pursuit gain, acceleration, latency, and positional accuracy were severely impaired. Therefore, the smooth pursuit motor response shows the same kind of slowing at low contrast that was demonstrated in previous studies on perception.
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