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Zhenlan Jin, Scott Watamanuik, Adam Reeves, Stephen Heinen; Peripheral motion enhances target selection during smooth pursuit. Journal of Vision 2008;8(6):667. doi: 10.1167/8.6.667.
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Performance on a detection task during smooth pursuit is improved by peripheral motion which is consistent with the motion of the task stimulus (Watamaniuk and Heinen, 2007). Here, we ask whether consistent peripheral motion can also facilitate saccade target selection during pursuit. The target stimulus comprised five, small (0.2 deg) bright spots arranged in a ‘X’ configuration with a 7.4 deg diagonal extent. At the beginning of each trial, the target appeared and the observer fixated the center spot. After a random period, the five-spot target began to move at a constant speed (10–30 deg/sec). At a randomly selected time between 100–500 msec, one of the 4 surrounding spots became larger. The observer's task was to saccade to the spot that enlarged. The five-spot target was presented either on a homogeneous, dark background, or in a field of 500 dots of the same diameter, but with slightly lower luminance, moving at the same velocity as the target. Background dots were randomly positioned within a large rectangular aperture but excluded from the target area. The presence of the dot background decreased the latency of saccades in the task, answering our initial question affirmatively. But why? Since shorter latency saccades were not due to improved image stabilization by the dot background, we hypothesized that instead the dot background (when present) controlled pursuit, releasing attention for the saccadic system from the pursuit spot. We asked in particular if attention was completely released by the dot background during pursuit by introducing a temporal gap with the pursuit dot disappearing before target selection. The gap decreased saccade latency whether the dot background was present or not. The results suggest that the dot background releases attention to perform target selection, but that some attention is still used to pursue the spot when it is present.
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