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Zhenlan Jin, Scott Watamaniuk, Aarlenne Khan, Stephen Heinen; Integration of motion information for smooth pursuit during multiple object tracking (MOT). Journal of Vision 2010;10(7):542. doi: 10.1167/10.7.542.
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Previously, we showed that observers could simultaneously perform multiple object tracking (MOT) and pursue the array of MOT targets without loss of performance on either task (Watamaniuk et al., 2009). We proposed that local motion information is maintained for MOT, while pursuit uses a velocity signal obtained by integrating the local motion of the MOT elements. However, in that work, the MOT array always moved at the same constant velocity, and therefore, a predictive pursuit movement could maintain eye velocity without requiring integration. Here, we test this, by changing the speed of the array at a random time. The MOT stimulus was composed of nine dots (0.2 deg diameter) that moved randomly within a virtual region measuring 8 by 8 deg for 3 sec. Observers were initially cued as to which four of the dots to remember by a brief color change. All dots returned to the same color until the end of the trial, when one dot again changed color and had to be identified as a member of the cued set or not. The array began moving from left to right at 7deg/sec. In 60% of trials, the array speed was randomly increased to 11.5 deg/sec or decreased to 2.3 deg/sec for 500 msec, beginning 700-2000 msec after motion onset. Observers pursued the array either with or without performing the MOT task. We found that eye velocity changed in response to the array speed change after a normal latency (112 msec mean) regardless of whether the MOT task was performed, and MOT performance was unimpaired. The results suggest that local motion information is continuously integrated for pursuit even when individual, non-consistent motion signals are attended, supporting simultaneous access of global and local motion signals for pursuit and MOT tasks.
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