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J. Danckert, N. Sharif, M. A. Goodale; Intercepting moving targets in the upper and lower visual fields. Journal of Vision 2001;1(3):319. doi: 10.1167/1.3.319.
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Using a task with a well defined speed-accuracy trade-off function we recently demonstrated that visually guided movements made in the lower visual field (loVF) showed a stronger relationship to target size than the same movements made in the upper visual field (upVF). That is, peak velocity increased as target size increased only for movements made in the loVF. In addition, movements made in the loVF were more accurate than their counterparts in the upVF. Monkey neurophysiology has demonstrated an over-representation of the loVF in area MT, an area known to be critical in the processing of motion. This led us to investigate whether or not healthy individuals would demonstrate differences in the ability to intercept moving targets in the loVF and upVF. Targets were small filled squares moving from right to left or vice versa at a constant speed but starting from random positions along the x-axis. Movements were measured at 100 Hz with conventional OPTOTRAK recording. Peak velocity was higher for targets moving from right to left. In addition, subjects spent more time decelerating when targets appeared in the upVF, suggesting that subjects required more time to intercept targets accurately in the upVF. The majority of subjects also reported that subjectively, targets moving from left to right within the loVF were the easiest to intercept. There was a general tendency to overshoot the target in the y-direction. For the x-direction, subjects intercepted targets earlier when they were moving from left to right in both the upper and the lower visual fields. Overall, the data suggest that the interception of targets is more efficient in the lower rather than the upper visual field.
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