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Paul K. Mitchell, Jay A. Edelman; The effect of presaccadic and postsaccadic visual information on saccade endpoint error and velocity. Journal of Vision 2006;6(6):502. doi: 10.1167/6.6.502.
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© ARVO (1962-2015); The Authors (2016-present)
We measured how the saccadic system's ability to get on target depends upon the visual information available before and after the saccade. We were particularly interested in whether postsaccadic visual information was sufficient to program subsequent saccades orthometrically. Using variants of visual and memory-guided saccade tasks we measured saccade endpoint error and peak velocity. Tasks varied with regard to the information available presaccadically: 1) visually-guided (VG); 2) memory-guided (MG) - target appeared for 250ms then disappeared 750 ms before saccade; 3) target invisible before saccade (NVG). Tasks also varied with regard to whether targets appeared postsaccadically: 1) visible immediately postsaccade (Tvis); 2) invisible postsaccade (Tnot). Tnot trial blocks began with 5 Tvis trials. Stimuli were presented using a CRT projector (Barco) on a large (54″×71″) screen in a darkened environment. A thin white frame was visible at the screen's edge. EMs of 3 Ss were recorded at 500Hz using an EyelinkII eye tracker. Saccade amplitude ranged from 30–40°. NVG endpoint error was surprisingly small. In the Tvis condition errors were: VG-1.34°, MG-1.60°, NVG-2.00°. In the Tnot condition NVG error increased but was still quite small. Errors in the Tnot condition were VG-1.00°, MG-1.47°, NVG-2.27°. VG peak velocity was larger than that of MG and NVG (VG-485°/sec, MG-426°/sec, NVG-413°/sec). Target visibility after the saccade had little effect on peak velocity. Our results suggest that information obtained after a saccade is sufficient to maintain saccade accuracy and precision, even across several movements in which the target is invisible both pre and postsaccadically.
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