Volume 5, Number 6, Article 1, Pages 493-503 doi:10.1167/5.6.1 http://journalofvision.org/5/6/1/ ISSN 1534-7362
Timing and velocity randomization similarly affect anticipatory pursuit
Stephen J. Heinen
The Smith-Kettlewell Eye Research Institute, San Francisco, CA, USA
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Jeremy B. Badler
The Smith-Kettlewell Eye Research Institute, San Francisco, CA, USA
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William Ting
Camino Medical Center, Sunnyvale, CA, USA
Abstract

Smooth pursuit eye movements are guided largely by retinal-image motion. To compensate for neural conduction delays, the brain employs a predictive mechanism to generate anticipatory pursuit that precedes target motion (E. Kowler, 1990). A critical question for interpreting neural signals recorded during pursuit concerns how this mechanism is interfaced with sensorimotor processing. It has been shown that the predictor is not simply turned-off during randomization because anticipatory eye velocity remains when target velocity is randomized (E. Kowler & S. McKee, 1987; G. W. Kao & M. J. Morrow, 1994). This study was completed to compare pursuit behavior during randomized motion-onset timing with that occurring during direction or speed randomization. We found that anticipatory eye velocity persisted despite motion-onset randomization, and that anticipation onset time was between that observed in the different constant-timing conditions. This centering strategy was similar to the bias of eye velocity magnitude away from extremes observed when direction or speed was randomized. Such a strategy is comparable to least-squares error minimization, and could be used to facilitate acquisition of a target when it begins to move. Centering was in some observers accounted for by a shift of eye velocity toward that generated in the preceding trial. The results make unlikely a model in which the predictor is disengaged by randomizing stimulus timing, and suggest that predictive signals always interact with those used in sensorimotor processing during smooth pursuit.

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History
Received June 30, 2004; published June 8, 2005
Citation
Heinen, S. J., Badler, J. B., & Ting, W. (2005). Timing and velocity randomization similarly affect anticipatory pursuit. Journal of Vision, 5(6):1, 493-503, http://journalofvision.org/5/6/1/, doi:10.1167/5.6.1.
Keywords
smooth pursuit, visual motion, prediction, anticipation, timing, human
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