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Joost C. Dessing, J. Douglas Crawford, W. Pieter Medendorp; Spatial updating across saccades during manual interception. Journal of Vision 2011;11(10):4. doi: 10.1167/11.10.4.
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We studied the effect of intervening saccades on the manual interception of a moving target. Previous studies suggest that stationary reach goals are coded and updated across saccades in gaze-centered coordinates, but whether this generalizes to interception is unknown. Subjects (n = 9) reached to manually intercept a moving target after it was rendered invisible. Subjects either fixated throughout the trial or made a saccade before reaching (both fixation points were in the range of −10° to 10°). Consistent with previous findings and our control experiment with stationary targets, the interception errors depended on the direction of the remembered moving goal relative to the new eye position, as if the target is coded and updated across the saccade in gaze-centered coordinates. However, our results were also more variable in that the interception errors for more than half of our subjects also depended on the goal direction relative to the initial gaze direction. This suggests that the feedforward transformations for interception differ from those for stationary targets. Our analyses show that the interception errors reflect a combination of biases in the (gaze-centered) representation of target motion and in the transformation of goal information into body-centered coordinates for action.
*Fitting Error = a + bAD + c(IP − FP1) + d(IP − FP2) to the horizontal interception errors of each subject. Significant regression coefficients (first four columns) and correlation coefficients (R, last column) are depicted in boldface.
*Fitting Errorfix = a fix + b fixAD + c fix(IP − FP1) to the interception errors in the fixation condition and Errorsac = a sac + b sacAD + c sac(IP − FP1) + d sac(IP − FP2) to those in the saccade condition for each subject. Significant regression coefficients (first seven columns) and correlation coefficients (R fix and R sac) are depicted in boldface.
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