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Jeremy B. Wilmer, Ken Nakayama; Two components of oculomotor pursuit isolated by covariance based methods. Journal of Vision 2005;5(8):584. doi: 10.1167/5.8.584.
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© ARVO (1962-2015); The Authors (2016-present)
We assessed covariation in performance between 55 individuals on various psychophysical tasks as well as an oculomotor pursuit task to a ramped stimulus. This analysis isolated two pursuit components of particular interest: 1) an early “latency” component consisting of latency to both presaccadic pursuit and the initial saccade, and 2) a later “accuracy” component consisting of accuracy of eye velocity during the 120ms following the first saccade. The early pursuit component was associated with three dynamic psychophysical tasks: motion detection (“Newsome” paradigm), velocity discrimination, and counterphase flicker identification. However, it was not associated with our two static psychophysical tasks: form detection and orientation discrimination. We propose that this pattern of results may reflect the presence of a high-level, temporal resolution of attention mechanism. It cannot reflect an entirely motion based mechanism because the counterphase flicker identification task does not evoke a motion percept, and moreover its thresholds are quite slow, ranging from 2 to 6 hz. It is unlikely that it reflects a generalized visual or temperamental mechanism because then one would expect the static psychophysical tasks to covary as well with this early stage of pursuit. The later, “accuracy” pursuit component was associated only with psychophysical velocity discrimination. Since this component was not associated with psychophysical motion detection, we propose that it reflects the presence of a mechanism devoted specifically to motion magnitude estimation, distinct from mechanisms devoted to the detection of motion.
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